KR102719101B1 - Ankle arthroplasty system and method - Google Patents

Abstract

An ankle arthroplasty system may have a talar prosthesis and a tibial prosthesis, each of which includes an articular surface and a bone-engaging surface. Each of the bone-engaging surfaces may include an anterior-posterior curvature and a medio-lateral curvature having a convex shape. A burr including a rotatable cutting member may be used to form a prepared surface on the talus or tibia to receive a corresponding prosthesis. A cutting guide may be used to guide movement of the burr; the cutting guide may include a base and an arm movably coupled to the base. Either the base or the arm may include a guide surface, and the other may include a follower that slides along the guide surface to limit movement of the burr such that the prepared surface has at least one concave curvature and one convex curvature.

Description

Ankle arthroplasty system and method

The present invention relates to surgical systems and methods. More particularly, the present invention relates to implants for ankle joint arthroplasty and related methods.

Joint arthroplasty is a surgical procedure in which at least one articular surface of a joint is replaced with a prosthetic articular surface. This procedure is becoming more common. In particular, ankle arthroplasty may be necessary due to trauma or degeneration of the natural articular surfaces of the tibia and talus.

For successful ankle arthroplasty, it is important that the postoperative mobility characteristics of the ankle joint mimic the mobility characteristics of the natural ankle as much as possible. It is also desirable that the ankle implants remain in place while the joint continues to function. Furthermore, it is desirable that the ankle arthroplasty procedure be performed quickly and smoothly, without error. Many existing ankle arthroplasty implants and methods are biomechanically inaccurate, time-consuming to implant, or do not form sufficient attachment to the underlying bone.

Korean Patent No. 10-0764974 (Ankle joint internal artificial insert)

The present invention aims to provide implants and related methods for ankle arthroplasty which can provide improved biomechanics, superior bone fixation, and/or streamlined implants.

In one embodiment, an ankle arthroplasty system can be designed to replace a natural talar articular surface of a talus and a natural tibial articular surface of a tibia. The ankle arthroplasty system can include a talar prosthesis and a tibial prosthesis, each of which has an articular surface and a bony articulation surface. At least one of the bony articulation surfaces can include a first anterior-posterior curvature and a medial-lateral curvature having a convex shape.

The first anterior-posterior bend can extend substantially the entire length of the bone joint surface in the anterior-posterior direction. Additionally, the bone joint surface can include a keel projecting from the first anterior-posterior bend and extending along the anterior-posterior direction. The keel can include a base portion that is secured or integrally formed with the remainder of the bone, and a penetrating portion that extends from the base portion to penetrate a talar prepared surface or a tibial prepared surface. The penetrating portion can include a generally semicircular perimeter.

The talar joint surface can include two convex talar curvatures extending in a mediolateral direction and a concave talar curvature extending in a mediolateral direction between the two convex talar curvatures. The tibial joint surface can include two concave tibial curvatures extending in a mediolateral direction and a convex tibial curvature extending in a mediolateral direction between the two concave tibial curvatures. The talar joint surface and the tibial joint surface can be formed such that when the tibial joint prosthesis is positioned at the center of the talar joint prosthesis, the two concave tibial curvatures are substantially coplanar with the two convex talar curvatures.

The bone engagement surface having the first anterior-posterior curvature can be a talar bone engagement surface, and the first anterior-posterior curvature can be a concave curvature. The talar bone engagement surface can include a second mediolateral curvature having a convex shape and extending in a mediolateral direction, and a central extension extending substantially straight along the mediolateral direction between the first mediolateral curvature and the second mediolateral curvature. The talar bone engagement surface can further include a keel protruding from the first anterior-posterior curvature and extending along the anterior-posterior direction.

The bone engagement surface having the first anterior-posterior curvature can be a tibial bone engagement surface, and the first anterior-posterior curvature can be a convex curvature. The tibial bone engagement surface can include a second mediolateral curvature having a convex shape and extending in a mediolateral direction, and a central extension extending substantially straight along the mediolateral direction between the first mediolateral curvature and the second mediolateral curvature. The tibial bone engagement surface can additionally include a keel protruding from the first anterior-posterior curvature and extending along the anterior-posterior direction.

In one embodiment, a talar joint prosthesis can include a talar joint surface configured to replace a natural talar joint surface, and a talar bone engagement surface configured to mate with a prepared talar surface of the talus. The talar bone engagement surface can include a first anterior-posterior curvature having a concave shape and extending in an anterior-posterior direction, and a first medio-lateral curvature having a convex shape and extending in a medio-lateral direction.

The first anterior-posterior curvature can extend substantially the entire length in the anterior-posterior direction of the talar bone joining surface. The talar bone joining surface can include a second mediolateral curvature having a convex shape and extending in the mediolateral direction, and a central extension extending substantially straight along the mediolateral direction between the first mediolateral curvature and the second mediolateral curvature. The talar bone joining surface can further include a keel protruding from the first anterior-posterior curvature and extending in the anterior-posterior direction. The keel can include a base portion that is secured or integrally formed with the remainder of the talar bone joining surface, and a penetration portion extending from the base portion for penetrating the prepared talar surface. The penetration portion can include a generally semicircular perimeter.

In one embodiment, a tibial joint prosthesis can include a tibial joint surface configured to replace a natural tibial joint surface, and a tibial bone engagement surface configured to mate with a tibial preparation surface of a tibia. The tibial bone engagement surface can include a first anterior-posterior curvature having a convex shape and extending in an anterior-posterior direction, and a first medio-lateral curvature having a convex shape and extending in a medio-lateral direction.

The first anterior-posterior curvature can extend substantially the entire length in the anterior-posterior direction of the tibial bone engagement surface. The tibial bone engagement surface can include a second mediolateral curvature having a convex shape and extending in the mediolateral direction, and a central extension extending substantially straight along the mediolateral direction between the first mediolateral curvature and the second mediolateral curvature. The tibial bone engagement surface can further include a keel projecting from the first anterior-posterior curvature and extending in the anterior-posterior direction. The keel can include a base portion that is secured or integrally formed with the remainder of the tibial bone engagement surface, and a penetration portion extending from the base portion for penetrating the tibial preparation surface. The penetration portion can include a generally semicircular perimeter.

According to one embodiment, a system for preparing bone for arthroplasty can include a burr having a rotatable cutting member having a shape selected from the group consisting of concave shapes and convex shapes and extending along a length of the rotatable cutting member. The system can further include a cutting guide having a bone attachment interface anchorable to the bone and a bur attachment interface anchorable to the burr, and a guide mechanism configured to limit relative movement between the bur attachment interface and the bone attachment interface to facilitate formation of a prepared surface on the bone with the burr. The prepared surface can include at least one concave curvature or a convex curvature.

The cutting guide may further include a foundation and a bur holder. The foundation may include a bone attachment interface and a bur holder interface. The bur holder may include a foundation interface that is coupled to the bur attachment interface and the bur holder interface.

The guide mechanism can allow motion of the burr attachment interface along a first direction perpendicular to the length of the rotatable cutting member. The guide mechanism can guide motion of the burr attachment interface along a straight line perpendicular to the length of the rotatable cutting member. The shape of the rotatable cutting member can be a convex shape having a maximum radius perpendicular to the length. The prepared surface can include a cross-sectional shape having a first convex curvature having a first radius of curvature substantially equal to the maximum radius, a second convex curvature having a second radius of curvature substantially equal to the maximum radius, and a central extension extending substantially in a straight line between the first convex curvature and the second convex curvature.

The guide mechanism can also allow movement of the burr attachment interface along a second direction parallel to the length of the rotatable cutting member. The guide mechanism can allow movement of the burr attachment interface along the second direction by allowing rotation of the burr attachment interface about an axis perpendicular to the rotatable cutting member. The shape of the rotatable cutting member can be a concave shape having a maximum radius perpendicular to the length. The prepared surface can include a cross-sectional shape having a first convex curvature having a first radius of curvature substantially equal to the maximum radius, a second convex curvature having a second radius of curvature substantially equal to the maximum radius, and a central extension extending substantially in a straight line between the first convex curvature and the second convex curvature. The cross-sectional shape can be swept along the convex curvature.

According to one embodiment, a method of preparing a bone for arthroplasty includes the steps of positioning a cutting guide near the bone; the cutting guide can include a bone attachment interface, a bur attachment interface, and a guide mechanism. The method can further include the steps of securing the bone attachment interface to the bone, and securing a bur to the bur attachment interface. The bur can include a rotatable cutting member having a shape selected from the group consisting of concave shapes and convex shapes and extending along a length of the rotatable cutting member. The method can further include the step of guiding movement of the bur relative to the bone using the guide mechanism to facilitate formation of a prepared surface on the bone with the bur. The prepared surface can include at least one concave curvature or a convex curvature.

The cutting guide may further include a foundation having a bone attachment interface and a bur holder interface. Additionally, the cutting guide may include a bur holder having a bur attachment interface and a foundation interface. The method may further include a step of coupling the foundation interface of the bur holder to the bur holder interface of the foundation.

The step of guiding movement of the burr relative to the bone may include allowing movement of the burr along a first direction perpendicular to the length of the rotatable cutting member with the guide mechanism. The step of guiding movement of the burr relative to the bone may further include guiding movement of the burr attachment interface along a straight line perpendicular to the length of the rotatable cutting member with the guide mechanism. The shape of the rotatable cutting member may be a convex shape having a maximum radius perpendicular to the length. The prepared surface may include a cross-sectional shape having a first convex curvature having a first radius of curvature substantially equal to the maximum radius, a second convex curvature having a second radius of curvature substantially equal to the maximum radius, and a central extension extending substantially in a straight line between the first convex curvature and the second convex curvature.

The step of guiding movement of the burr relative to the bone may further comprise the step of allowing movement of the burr attachment interface along a second direction parallel to the length of the rotatable cutting member. The step of guiding movement of the burr relative to the bone may further comprise allowing rotation of the burr attachment interface about an axis perpendicular to the rotatable cutting member. The shape of the rotatable cutting member may be a concave shape having a maximum radius perpendicular to the length. The prepared surface may comprise a cross-sectional shape having a first convex curvature having a first radius of curvature substantially equal to the maximum radius, a second convex curvature having a second radius of curvature substantially equal to the maximum radius, and a central extension extending substantially in a straight line between the first convex curvature and the second convex curvature. The cross-sectional shape may be swept along the convex curvature.

According to one embodiment, a system for preparing a talus or tibia for ankle arthroplasty can include a first burr and a first cutting guide. The first burr can include a first rotatable cutting member having a first shape extending along a length of the first rotatable cutting member. The first shape can be selected from the group consisting of concave shapes and convex shapes. The first cutting guide can include a first bone attachment interface affixable to the talus or tibia, a first burr attachment interface affixable to the first burr, and a first guide mechanism configured to limit relative movement between the first burr attachment interface and the first bone attachment interface by allowing movement of the first burr attachment interface along a first direction perpendicular to the first length of the first rotatable cutting member to facilitate formation of a first prepared surface on the tibia or talus with the first burr. The first prepared surface can include at least one concave curvature or a convex curvature.

The first bone attachment interface can be secured to the talus such that the first prepared surface is on the talus. The first guide mechanism can further allow movement of the first burr attachment interface along a second direction parallel to the first length of the first rotatable cutting member by allowing rotation of the first burr attachment interface about an axis perpendicular to the first rotatable cutting member. The first shape can be a concave shape such that the first prepared surface has a cross-sectional shape swept along a convex curvature.

The system can further include a second burr having a second rotatable cutting member having a convex shape and a second cutting guide. The second cutting guide can include a second bone attachment interface anchorable to the tibia, a second burr attachment interface anchorable to the second burr, and a second guide mechanism configured to limit relative movement between the second burr attachment interface and the second bone attachment interface by allowing movement of the second burr attachment interface along a third direction perpendicular to a second length of the second rotatable cutting member to facilitate formation of a second prepared surface on the tibia with the second burr. The second prepared surface can include at least one concave curvature.

The first cutting guide can further include a first foundation having a first bone attachment interface and a first bur holder. The first foundation can further include a first bur holder interface. The first bur holder can include the first bur attachment interface and a first foundation interface coupleable to the first bur holder interface. The second cutting guide can further include a second foundation and a second bur holder. The second foundation can include the second bone attachment interface and the second bur holder interface. The second bur holder can include the second bur attachment interface and a second foundation interface coupleable to the second bur holder interface. The system can further include an alignment block having a third foundation interface attachable to the first foundation and a fourth foundation interface attachable to the second foundation to facilitate positioning of the second foundation relative to the first foundation.

According to one embodiment, a method of performing ankle arthroplasty may include the steps of exposing the anterior aspect of the ankle joint, securing a first cutting guide to a first bone, the talus or the tibia, inserting a first cutting tool into the ankle joint along an anterior approach, and using the first cutting guide to guide movement of the first cutting tool relative to the first bone such that the first cutting tool forms a first prepared surface on the first bone. The first prepared surface may include a first anterior-posterior curvature extending anterior-posteriorly. The method may further include the step of placing a first prosthesis on the first prepared surface. The first prosthesis may include a first articular surface configured to replace a first natural articular surface of the first bone.

The first prosthesis may be a keel. The method may further include the steps of inserting a second cutting tool into the ankle joint along an anterior approach, and using a first cutting guide to guide movement of the second cutting tool relative to the first bone such that the second cutting tool forms a slot in the first bone, the slot being oriented in an anterior-posterior direction. The step of placing the first prosthesis on the first prepared surface may include the step of inserting the keel into the slot.

The first bone may be the tibia. The first anterior-posterior curvature may be a concave curvature extending anterior-posteriorly. The first prosthesis may include a convex bone-engaging surface. The step of placing the first prosthesis on the first prepared surface may include inserting the convex bone-engaging surface into the concave curvature.

The first bone may be the talus. The first anterior-posterior curvature may be a convex curvature extending in an anterior-posterior direction. The first prosthesis may include a concave bone-engaging surface. The step of positioning the first prosthesis on the first prepared surface may include the step of positioning the convex curvature on the concave bone-engaging surface.

The method may further include the steps of exposing the anterior aspect of the ankle joint, securing a second cutting guide to the tibia, and inserting a first cutting tool or a second cutting tool into the ankle joint along the anterior approach. Furthermore, the method may include the step of guiding movement of the first cutting tool or the second cutting tool relative to the tibia with the second cutting guide, such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curvature, the second prepared surface including a concave curvature extending anterior-posteriorly. The method may further include the step of placing a second prosthesis on the second prepared surface. The second prosthesis may include a second articular surface configured to replace a convex bone engagement surface and a second natural articular surface of the tibia. The step of placing the second prosthesis on the second prepared surface may include the step of inserting the convex bone engagement surface into the concave curvature.

The first cutting guide may include a talus foundation including a talus bone attachment interface and a talus tool holder interface; and a talus tool holder including a talus tool attachment interface and a talus foundation interface. The step of securing the first cutting guide to the first bone may include the step of securing the talus bone attachment interface to the talus. The method may further include the step of coupling the talus foundation to the talus tool holder by coupling the talus tool holder interface to the talus foundation interface prior to guiding movement of the first cutting tool with the first cutting guide; and the step of attaching the first cutting tool to the talus tool attachment interface.

The method may further include a step of positioning the specimen on the talus prior to securing the talus foundation to the talus. The specimen may be coupled to a distal end of the column. The method may further include a step of aligning the specimen and the talus using the column by aligning a proximal end of the column with a landmark on a proximal portion of the patient's leg, and a step of aligning the specimen and the talus foundation.

The method may further include the steps of attaching a talus foundation interface of the alignment block to the talus foundation, and the steps of attaching a tibial foundation interface of the alignment block to the tibial foundation. The tibial foundation may include a tibial bone attachment interface and a tibial tool holder interface. The method may further include the steps of fixing the tibial bone attachment interface to the tibia, and the steps of attaching the tibial tool holder to the tibial foundation by attaching the tibial tool holder interface to the tibial foundation interface of the tibial tool holder. The tibial foundation and the tibial tool holder may form a second cutting guide.

The method may further include the steps of attaching a first cutting tool or a second cutting tool to a tibial tool attachment interface of a tibial tool holder, inserting the first cutting tool or the second cutting tool into the ankle joint along an anterior approach, and guiding movement of the first cutting tool or the second cutting tool relative to the tibia in a medio-lateral direction with a second cutting guide such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia. The second prepared surface may include a second anterior-posterior curvature including a concave curvature extending in the anterior-posterior direction.

The step of guiding movement of the first cutting tool relative to the first bone to form the first prepared surface may include the step of moving the first cutting tool in a medio-lateral direction. The step of guiding movement of the first cutting tool relative to the first bone to form the first prepared surface may further include the step of rotating the first cutting tool relative to the first bone about an axis extending in the medio-lateral direction so that the first cutting tool moves in a forward-backward direction.

In one embodiment, a method of performing arthroplasty on an ankle joint including a talus and a tibia can include the steps of exposing the anterior aspect of the ankle joint, securing a talus cutting guide to the talus, and inserting a first cutting tool into the ankle joint along an anterior approach. The method can further include the step of guiding movement of the first cutting tool relative to the talus about an axis extending in a mediolateral direction with the talus cutting guide, such that the first cutting tool moves in an anterior-posterior direction to form a first prepared surface on the talus. The first prepared surface can include a first anterior-posterior curvature extending in the anterior-posterior direction. The method can further include the step of placing a talus prosthesis on the first prepared surface. The talus prosthesis can include a talus articular surface configured to replace a natural articular surface of the talus.

The talus prosthesis may include a keel. The method may further include the steps of inserting a first cutting tool or a second cutting tool into the ankle joint along an anterior approach, and guiding movement of the first cutting tool or the second cutting tool relative to the talus with a talus cutting guide such that the first cutting tool or the second cutting tool forms a slot in the talus, wherein the slot is oriented in an anterior-posterior direction. The step of placing the talus prosthesis on the first prepared surface may include the step of inserting the keel into the slot.

The step of guiding movement of the first cutting tool relative to the talus to form a first prepared surface may further include the step of moving the first cutting tool in a mediolateral direction. The method may further include the step of securing a tibial cutting guide to the tibia and the step of inserting the first cutting tool or the second cutting tool into the ankle joint along an anterior approach. The method may further include the step of guiding movement of the first cutting tool relative to the tibia with the tibial cutting guide to move the first cutting tool or the second cutting tool in a mediolateral direction to form a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curvature including a concave curvature extending anterior-posteriorly. The method may further include the step of placing a tibial prosthesis on the second prepared surface. The tibial prosthesis may include a tibial articular surface configured to replace a natural articular surface of the tibia.

The talus cutting guide may include a talus foundation including a talus bone attachment interface and a talus tool holder interface; and a talus tool holder including a talus tool attachment interface and a talus foundation interface. The step of securing the talus cutting guide to the talus may include the step of securing the talus bone attachment interface to the talus. The method may further include the steps of coupling the talus foundation to the talus tool holder by coupling the talus tool holder interface to the talus foundation interface prior to guiding movement of the first cutting tool with the talus cutting guide, and the steps of attaching the first cutting tool to the talus tool attachment interface.

The method may further include the steps of attaching the talus foundation interface of the alignment block to the talus foundation and attaching the tibial foundation interface of the alignment block to the tibial foundation. The tibial foundation may include a tibial bone attachment interface and a tibial tool holder interface. The method may further include the steps of fixing the tibial bone attachment interface to the tibia and attaching the tibial tool holder interface to the tibial foundation interface of the tibial tool holder, thereby attaching the tibial tool holder to the tibial foundation. The tibial foundation and the tibial tool holder may form a second cutting guide.

In one embodiment, a method of performing arthroplasty on an ankle joint including a talus and a tibia may include the steps of exposing the anterior of the ankle joint, securing a talus cutting guide to the talus, inserting a first cutting tool into the ankle joint along an anterior approach. With the talus cutting guide, movement of the first cutting tool relative to the talus is guided such that the first cutting tool forms a first prepared surface on the talus, the first cutting tool including a first anterior-posterior bend extending in an anterior-posterior direction. The method may include the steps of securing a tibial cutting guide to the tibia, inserting a second cutting tool into the ankle joint along an anterior approach, and guiding movement of the first cutting tool or the second cutting tool relative to the tibia, the first cutting tool or the second cutting tool forming a second prepared surface on the tibia, the second cutting tool including a second anterior-posterior bend extending in an anterior-posterior direction. The method may further comprise the steps of placing a talar prosthesis on a first prepared surface and placing a tibial prosthesis on a second prepared surface. The talar prosthesis may comprise a talar articular surface configured to replace a first natural articular surface of the talus, and the tibial prosthesis may comprise a tibial articular surface configured to replace a second natural articular surface of the tibia.

The talar prosthesis may include a talar keel, and the tibial prosthesis may include a tibial keel. The method may further include a step of guiding movement of a first cutting tool, a second cutting tool, or a third cutting tool relative to the talus with a talar cutting guide to form a first slot within the talus, wherein the first slot may be oriented in an anterior-posterior direction. The method may further include a step of guiding movement of the first cutting tool, the second cutting tool, the third cutting tool, or a fourth cutting tool relative to the tibia with a tibial cutting guide to form a second slot within the tibia, wherein the second slot is oriented in an anterior-posterior direction. The step of placing the talar prosthesis on the first prepared surface may include a step of inserting the talar keel into the first slot. The step of placing the tibial prosthesis on the second prepared surface may include a step of inserting the tibial keel into the second slot.

The talus cutting guide may include a talus foundation and a talus tool holder, and the tibial cutting guide may include a tibial foundation and a tibial tool holder. The step of securing the talus cutting guide to the talus may include the step of securing the talus foundation to the talus. The method may include, prior to guiding movement of the first cutting tool or the second cutting tool with the tibial cutting guide, the step of attaching the talus foundation interface of the alignment block to the talus foundation, and the step of attaching the tibial foundation interface of the alignment block to the tibial foundation. The step of securing the tibial cutting guide to the tibia may include the step of securing the tibial foundation to the tibia with the talus foundation interface attached to the talus foundation and the tibial foundation interface attached to the tibial foundation.

According to one embodiment, a bone preparation system for arthroplasty can include a cutting tool and a guide assembly secured to the bone. The guide assembly can include a base including a first engagement feature and the first guide feature, an arm including a second engagement feature movably coupled to the first engagement feature, a tool attachment interface attached to the cutting tool, and a second guide feature. One of the first guide feature and the second guide feature can include a guide surface having a predetermined shape. The other of the first guide feature and the second guide feature can include a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base.

The first guide feature and the second guide feature can be coupled together such that the arm can rotate about the base about the axis of rotation of the arm. The guide surface can be oriented toward the axis of rotation of the arm or away from the axis of rotation of the arm. The guide surface can include a planar shape configured to prevent movement of the cutting tool axis of the cutting tool over the planar boundary to prevent excessive penetration of the bone by the cutting tool. The cutting tool can include a burr having a cutting member that rotates about the cutting tool axis.

The guide surface may be on the base and the follower may be on the arm. The follower may include a cylindrical post protruding from the remainder of the arm.

The arm may include a first arm member including at least a portion of a second engagement feature, a tool attachment interface and a second guide feature slidably coupled with the first arm member. The system may further include an elastic member urging the follower toward the guide surface and urging the cutting tool toward the bone.

The guide assembly can further include a foundation including a bone attachment interface attachable to a bone and a base attachment interface attachable to the foundation attachment interface of the base. The foundation can include a fixation member including the bone attachment interface and a movable member coupled to the fixation member to be rotatable about a foundation axis that is perpendicular to the arm rotational axis with respect to the fixation member, the movable member including the base attachment interface.

The bone may be the talus or the tibia. The bone attachment interface is configured to attach the foundation to the talus or the tibia and is proximal to the ankle joint formed by the talus and the tibia.

In one embodiment, a method for preparing a bone for arthroplasty can include securing a guide assembly to a bone. The guide assembly can include a base comprising a first engagement feature and the first guide feature, a second engagement feature movably coupled to the first engagement feature, and an arm comprising a tool attachment interface and a second guide feature. The method can further include attaching a cutting tool to the tool attachment interface, and moving the arm relative to the base to guide movement of the cutting tool relative to the bone, such that the cutting tool forms a prepared surface on the bone. One of the first guide feature and the second guide feature can include a guide surface having a predetermined shape. The other of the first guide feature and the second guide feature can include a follower. Moving the arm relative to the base can include sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base.

The step of moving the arm relative to the base may include the step of rotating the arm relative to the base about the arm rotation axis. The guide surface may be directed toward or away from the arm rotation axis.

The guide surface may have a planar shape, and the cutting tool may include a burr having a cutting member that rotates about a cutting tool axis. The step of sliding the follower along the guide surface to limit movement of the tool attachment interface to the base may include the step of preventing movement of the cutting tool axis over the planar boundary to prevent excessive penetration of the bone by the burr.

The arm can include a first arm member including at least a portion of a second engagement feature, and a second arm member slidably coupled with the first arm member and including a tool attachment interface and a second guide feature. The step of sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base can include the step of sliding the second arm member relative to the first arm member. The guide assembly can include a resilient member. The step of sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base can further include the step of urging the follower toward the guide surface and the cutting tool toward the bone with the resilient member.

The guide assembly can include a foundation including a fixed member including a bone attachment interface, and a movable member rotatably coupled to the fixed member and having a base attachment interface. The step of securing the guide assembly to the bone can include the step of attaching the bone attachment interface to the talus. The method can further include the step of attaching the foundation attachment interface of the base to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone. The step of moving the arm relative to the base to guide movement of the cutting tool relative to the bone can further include the step of rotating the movable member relative to the fixed member about the foundation axis.

The guide assembly can include a foundation having a bone attachment interface and a base attachment interface. The step of securing the guide assembly to the bone can include the step of attaching the bone attachment interface to the tibia. The method can further include the step of attaching the foundation attachment interface of the base to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone.

In one embodiment, a talus or tibia preparation system for arthroplasty can include a burr comprising a cutting member that rotates about a burr axis, and a guide assembly secured to the talus or tibia. The guide assembly can include a base and an arm. The base can include a first engagement feature and a first guide feature. The arm can include a first arm member including at least a portion of a second engagement feature coupled to the first engagement feature to allow the arm to rotate about the base about the arm rotation axis, a second arm member slidably coupled to the first arm member and including a tool attachment interface that attaches to the burr, a second guide feature, and an elastic member. Either the first guide feature or the second guide feature can include a guide surface having a planar shape configured to prevent movement of the burr axis over a planar boundary to prevent excessive penetration of the talus or tibia by the burr. The other of the first guide feature and the second guide feature may include a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base. The elastic member may urge the follower toward the guide surface and urge the burr toward the talus or tibia.

The features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by practice of the systems and methods described hereinafter.

The various systems and methods of the present invention have been developed in response to problems and needs in the art that have not yet been fully addressed by the current state of the art, and particularly by currently available ankle arthroplasty systems and methods. The systems and methods of the present invention can provide ankle implants and devices, including but not limited to talar and tibial prostheses and devices, which can provide improved biomechanics, superior bone fixation, and/or streamlined implantation.

Exemplary embodiments of the present invention will become more fully apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. It is to be understood that these drawings illustrate only exemplary embodiments and are therefore not to be considered limiting the scope of the appended claims, and exemplary embodiments of the present invention will be described with additional specificity and detail using the accompanying drawings.
FIG. 1 is a perspective view illustrating an ankle arthroplasty system according to one embodiment of the present invention.
Figures 2a to 2e are cephalad perspective, caudal perspective, side elevation, side cross-sectional, and anterior cross-sectional views, respectively, of the talar prosthesis.
Figures 3a to 3e are a head perspective view, a tail perspective view, a side view, a side view, and an anterior cross-sectional view, respectively, of a tibial prosthesis.
FIGS. 4A to 4C are perspective views of the head and tail, respectively, of a trial that can be used to position a talus foundation relative to a talus through the use of a column, and FIG. 4C is a perspective view of the head showing the foundation and column assembled with the talus and the trial.
Figures 5a, 5b, and 5c are posterior and anterior head perspective views, respectively, of the talus foundation illustrated in Figure 4c, and Figure 5c is a head perspective view illustrating the talus foundation in a state where it is fixed to the talus.
Figures 6a and 6b are front and rear perspective views, respectively, of a talus burr holder secured to a talus foundation for holding a burr against the talus.
Figures 7a to 7c are a perspective view, a side view, and a cross-sectional view of the burr illustrated in Figures 6a and 6b, respectively.
FIGS. 8A to 8C are side views of a burr according to various embodiments.
FIGS. 9A to 9C are a head perspective view, a tail perspective view, and a front side cross-sectional view, respectively, of the talus burr holder illustrated in FIGS. 6A and 6B.
FIGS. 10A and 10B are an anterior and posterior perspective views, respectively, showing a talus bur holder attached to a talus foundation and a talus foundation attached to the talus, with the bur positioned to cut the anterior portion of the natural articular surface of the talus.
FIGS. 11a and 11b are a side cross-sectional view and an enlarged anterior perspective view, respectively, of a talus foundation, a talus burr holder, and a talus with burr positioned as in FIGS. 10a and 10b.
Figure 12 is a perspective view illustrating the formation of a slot in a prepared surface of a bone using a burr.
Figures 13a to 13c are an anterior perspective view, a plan view, and an anterior head perspective view, respectively, of the tibial foundation, and Figure 13c illustrates a state in which the tibial foundation is provided with an alignment block for fixing the tibial foundation to the tibia and a talus foundation.
Figures 14a, 14b, and 14c are a frontal perspective view, a side view, and a frontal perspective view of a tibial burr holder, respectively, and Figure 14c illustrates a state in which the tibial burr holder is fixed to a tibial foundation and the tibia.
Figure 15 is a cross-sectional side view of the tibial bur holder and tibial foundation fixed to the tibia.
Figure 16 is a cross-sectional view illustrating the talus and tibia, in which the talus prosthesis is fixed to the prepared surface of the talus and the tibial prosthesis is attached to the prepared surface of the tibia.
FIG. 17a is a perspective view of a talus, showing a portion of the specimen shown in FIGS. 4a to 4c with a talus foundation according to an alternative embodiment, positioned on a concave curvature of the talus.
FIG. 17b is a perspective view of the talus foundation illustrated in FIG. 17a, showing the talus foundation (1710) fixed to the talus (420).
FIGS. 18a and 18b are perspective views of the talus foundation illustrated in FIGS. 17a and 17b, with the talus burr holder illustrated in a state of being fixed to a movable member of the talus foundation.
FIG. 19 is a side view of the talus foundation illustrated in FIGS. 17a and 17b, showing the talus burr holder fixed to a movable member of the talus foundation.
FIGS. 20A, 20B, 20C, 20D and 20E are exploded perspective views, rear views, front views, side views and side exploded views, respectively, of an alignment block according to one alternative embodiment.
FIGS. 21a, 21b, 22a, 22b and 22c are perspective, side, front, perspective and cross-sectional views, respectively, of the tibial foundation of FIGS. 17a and 17b attached to the tibia, illustrating the tibial foundation positioned relative to the tibia through the use of an alignment block and a tibial specimen.
FIG. 23 is a perspective view of a tibial burr holder secured to the tibial foundation of FIGS. 17a and 17b to maintain a burr relative to the tibia.
FIGS. 24A, 24B, and 24C are plan, bottom, and side views, respectively, of a patient-specific mounting plate according to one embodiment that may be used as part of a patient-specific guide mechanism for a talus.
FIG. 25a is a perspective view showing the patient-specific mounting plate illustrated in FIGS. 24a through 24c placed on the talus.
FIG. 25b is a perspective view of the patient-specific mounting plate and the talus of FIG. 24a, with a stationary component secured to the patient-specific mounting plate and the stationary member of FIGS. 17a and 17b to form a stationary member having a similar function to the stationary members of FIGS. 5a and 5b.
FIGS. 26A and 26B are plan and side views, respectively, of the talus foundation illustrated in FIGS. 25A and 25B, with the talus bur holder shown secured to a movable member formed by the patient-specific mounting plate and the stationary components of FIGS. 24A to 25B.

The exemplary embodiments of the present invention will best be understood by reference to the drawings, in which like parts are represented by like numerals. It will be readily appreciated that the components of the present invention, as generally described and illustrated in the drawings herein, may be arranged and designed in a wide variety of different configurations. Accordingly, the following more detailed description of the embodiments of the devices, systems, and methods, as illustrated in FIGS. 1 through 16, is not intended to limit the scope of the claimed claims, but is merely representative of exemplary embodiments.

The phrases "connected to", "coupled to", and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interactions. Two components may be functionally coupled to each other even if they are not in direct contact with each other. The term "abutting" refers to items that are in direct physical contact with each other, but the items need not necessarily be attached to each other.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While various aspects of the embodiments are illustrated in the drawings, they are not necessarily drawn to scale unless specifically indicated in the drawings.

FIGS. 1A, 1B, and 1C are perspective, side, and front cross-sectional views of an ankle arthroplasty system or system (100) according to one embodiment. The system (100) may be designed to replace a natural articular surface of an ankle joint and may include a talar prosthesis (102) and a tibial prosthesis (104). In one embodiment, the system (100) may be designed to replace only the talar or tibial articular surface, and thus may include only a talar prosthesis (102) or a tibial prosthesis (104).

The talar prosthesis (102) and the tibial prosthesis (104) may each include an articular surface and a bone-engaging surface. Specifically, the talar prosthesis (102) may include a talar articular surface (110) configured to replace a natural articular surface of the talus, and a talar bone-engaging surface (112) configured to bond to a talar prepared surface of the talus, either by direct contact or via an adhesive layer, such as polymethacrylate (PMMA, or “bone cement”), if the talar bone-engaging surface (112) is a porous growth material. Similarly, the tibial prosthesis (104) may include a tibial articular surface (120) configured to replace a natural articular surface of the tibia, and a tibial bone-engaging surface (122) configured to bond to a tibial prepared surface of the tibia, either by direct contact or via an adhesive layer, such as PMMA, if the tibial bone-engaging surface (122) is a porous growth material.

The system (100) is illustrated with respect to applicable orientations when the system (100) is implanted into an ankle joint. These orientations may include an anterior-posterior direction (130), a medial-lateral direction (132), and a cephalad-caudal direction (134). In this specification, these orientations may be referred to, for example, as "in the anterior-posterior direction (130)," or "anterior-posteriorly." The orientation may refer to movement of an object; for example, an object moving in the anterior-posterior direction (130) is moving in an anterior and/or posterior direction. Alternatively, the orientation may refer to the orientation of an object or feature. For example, an object or feature extending anterior-posteriorly is oriented such that its maximum length is generally parallel to the anterior-posterior direction (130).

The talus prosthesis (102) will be illustrated and described in more detail with respect to FIGS. 2a through 2e. The tibial prosthesis (104) will be illustrated and described in more detail with respect to FIGS. 3a through 3e.

Figures 2a through 2e are a head perspective view, a tail perspective view, a side view, a cross-sectional side view, and an anterior cross-sectional view, respectively, of a talar prosthesis (102). The talar joint surface (110) can be formed to mimic the shape of a natural talar joint surface. In one embodiment, the talar joint surface (110) can include two convex talar curvatures (200) extending mediolaterally. The convex talar curvatures (200) can be separated from each other by a concave talar curvature (202) extending mediolaterally. The convex talar curvature (200) and concave talar curvature (202) are most easily seen in FIG. 2e, with the cross-sectional plane extending medial-laterally and cephalad-caudally, parallel to the convex talar curvature (200) and concave talar curvature (202).

The talar bone engagement surface (112) can be shaped to provide a fixed bond with a prepared surface of the talus using a porous bone growth surface or a surface suitable for bone cement, as described below. In one embodiment, the talar bone engagement surface (112) can include a main portion (210) and a keel (212) extending from the main portion (210). The main portion (210) can have a contour that helps to remain firmly anchored to the talus while leaving much of the adjacent bone of the talus intact. Thus, the talar prosthesis (102) can be a “bone sparing” prosthesis.

In one embodiment, the main portion (210) can include two mediolateral curvatures (220) positioned at the edges of the talus bone interface surface (112) and a central extension (222) extending substantially straight, mediolaterally between the two mediolateral curvatures (220). The mediolateral curvatures (220) and the central extension (222) are most readily visible in FIG. 2e , a cross-section of which extends mediolaterally and craniocaudally parallel to the mediolateral curvatures (220) and the central extension (222). The central extension (222) can be formed slightly concave relative to the mediolateral curvatures (220) forming a wall (224) facing the keel (212). The wall (224) can be arranged circumferentially and can act as a retaining wall for bone cement when the talus prosthesis (102) is implanted. If the bone prosthesis (102) is secured to the bone using a porous interface, the wall (224) can be used to contain a porous material.

The main portion (210) may also include an anterior-posterior curvature (230) extending anteriorly and posteriorly. Accordingly, the cross-sectional shape of the main portion (210) may be generally arched in a concave shape when viewed from the side, as in FIG. 2c, and may be generally straight when viewed from the front, as in FIG. 2e. The main portion (210) may be described as a surface formed when a cross-sectional shape defined by the medio-lateral curvature (220) and the central extension (222) and optionally the wall (224) sweeps along the arcuate passage of the anterior-posterior curvature (230), as illustrated in FIG. 2e. Similarly, the talar articular surface (110) may be described as a surface formed when a cross-sectional shape defined by the medio-lateral curvature (220) and the anterior-posterior curvature (230) sweeps along a similar arcuate passage, as illustrated in FIG.

Additionally, the keel (212) may include a bone-sparing shape. Specifically, the keel (212) may include a base portion (240) formed integrally with the remainder of the talus prosthesis (102) and a penetration portion (242) extending from the base portion (240) to penetrate the talus bone. The penetration portion (242) may include a generally semicircular perimeter (244) at its head end. The semicircular perimeter (244) may assist in preserving bone by providing centrally and laterally facing surface areas that resist central or lateral movement of the talus prosthesis (102). The resistance to central or lateral movement may be equivalent to that provided by a keel having a rectangular cross-sectional shape, without requiring as much bone to be removed as a rectangular perimeter.

In some alternative embodiments (not shown), fixation pegs may be used in addition to or in place of the keel (212). Such fixation pegs may include any size or shape known in the art. In one embodiment, the fixation pegs may be permanently fixed to the remainder of the talar bone-engaging surface (112). In other embodiments, the fixation pegs may be modular and may be affixed to accommodate features in the bone-engaging surface, such as mounting holes. In yet other embodiments, the fixation pegs may be positioned in-situ and may be moveable from a retracted position to a deployed position to facilitate placement of the talar prosthesis and/or to reduce the amount of distraction of the ankle joint required for implantation.

FIGS. 3A through 3E are, respectively, a head perspective, a tail perspective, a side view, a lateral view, and an anterior cross-sectional view of a tibial prosthesis. The tibial joint surface (120) can be formed to mimic the shape of a natural tibial joint surface. In one embodiment, the tibial joint surface (120) can include two concave tibial curves (300) extending mediolaterally. The concave tibial curves (300) can be separated from each other by a convex tibial curve (302) extending mediolaterally. The concave tibial curves (300) and the convex tibial curves (302) are most readily visible in FIG. 3E , a cross-section of which extends mediolaterally and craniocaudally parallel to the concave tibial curves (300) and the convex tibial curves (302).

After the arthroplasty is completed, at a central position in the ankle joint, the convex tibial curvature (200) of the talar prosthesis (102) can remain over the concave tibial curvature (300) of the tibial prosthesis (104), and the convex tibial curvature (302) of the tibial prosthesis (104) can remain over the concave tibial curvature (202) of the talar prosthesis (102). This is the arrangement illustrated in FIG. 1C. As the tibia rotates centrally or laterally relative to the talus, one of the concave tibial curvatures (300) can slide along one of the adjacent convex tibial curvatures (200) such that the other concave tibial curvature (300) displaces one of the adjacent convex tibial curvatures (200). The configuration and operation of the talar articular surface (110) and the tibial articular surface (120) presented herein are merely exemplary; In alternative embodiments, any articular surface and motion path known in the art may be used.

The tibial bone engagement surface (122) may be formed to provide a secure bond with a prepared surface of the tibia, as described below. In one embodiment, the tibial bone engagement surface (122) may include a main portion (310) and a keel (312) extending from the main portion (310). The main portion (310) may have a contour that helps to remain securely anchored to the tibia while leaving much of the adjacent bone of the tibia intact. Thus, the tibial prosthesis (104) may be a “bone sparing” prosthesis.

In one embodiment, the main portion (310) can include two mediolateral curves (320) positioned at the edges of the tibial bone interface surface (122) and a central extension (322) extending substantially straight, mediolaterally between the two mediolateral curves (320). The mediolateral curves (320) and the central extension (322) are most readily visible in FIG. 3e , a cross-section of which extends mediolaterally and cephaladly parallel to the mediolateral curves (320) and the central extension (322). The central extension (322) can optionally be formed slightly concave relative to the mediolateral curves (320) forming a wall (324) facing the keel (312). The wall (324) may be arranged circumferentially and may act as a retaining wall for the bone cement while the tibial prosthesis (104) is implanted. If the talar prosthesis (102) is secured to the bone using a porous interface, the wall (324) may be used to contain the porous material.

The main portion (310) may also include an anterior-posterior curvature (330) extending anteriorly and posteriorly. Accordingly, the cross-sectional shape of the main portion (310) may be generally arched in a convex shape when viewed from the side, as in FIG. 3c, and may be generally straight when viewed from the front, as in FIG. 3e. The main portion (310) may be described as a surface formed when a cross-sectional shape defined by the central-lateral curvature (320) and the central extension (322) and optionally the wall (324) sweeps along the arcuate passage of the anterior-posterior curvature (330), as illustrated in FIG. 3e. Similarly, the tibial articular surface (120) may be described as a surface formed when a cross-sectional shape defined by the central-lateral curvature (320) and the central extension (322) sweeps along the arcuate passage, as illustrated in FIG. 3e.

Additionally, the keel (312) may include a bone-sparing shape similar to the keel (212). Specifically, the keel (312) may include a base portion (340) formed integrally with the remainder of the tibial prosthesis (104) and a penetration portion (342) extending from the base portion (340) to penetrate the talus bone. The penetration portion (342) may include a generally semicircular perimeter (344) at its head end. As described above with respect to the talus prosthesis (102), in one embodiment, anchoring pegs may be used to anchor the tibial prosthesis (104) to an adjacent bone.

A variety of apparatus and methods may be used to prepare the receiving surfaces of the talus and tibia to receive the talus prosthesis (102) and the tibial prosthesis (104), respectively. One exemplary set of apparatus, along with one exemplary method, will be illustrated and described with respect to FIGS. 4 through 15. Those skilled in the art will recognize that each of the implants, apparatuses, and methods described herein may be used independently of the others and/or in conjunction with alternative implants, apparatuses, or methods.

In one embodiment, it may be advantageous to prepare the talus and/or tibia from an anterior approach (i.e., an approach in which the instrument is inserted into the joint space from the anterior direction toward the joint space). An anterior approach is less invasive and may result in less trauma, thereby shortening recovery time. In some known procedures, a lateral approach has been used to create an anterior-posterior curvature in the prepared surface of the talus and/or tibia to preserve more bone underlying the implant. However, known instruments are generally not capable of creating an anterior-posterior curve from other approaches, such as an anterior approach.

In one embodiment, the surgeon may initiate an arthroplasty procedure to gain access to the anterior aspect of the ankle joint. This may be accomplished, for example, by cutting and retracting tissues lying anterior to the joint space (i.e., the anterior surface of the ankle). The joint space may be exposed. The surgeon may then attach at least one guide assembly (also referred to as a guide assembly) to the talus and/or tibia to guide movement of at least one cutting tool.

In one embodiment, the talus guide assembly may first be secured to the talus and used to guide movement of the cutting tool to prepare the talus to receive the talus prosthesis (102). This will be illustrated and described with reference to FIGS. 4A through 12. Next, a portion of the talus guide assembly may be used to properly position the tibial guide assembly, which may then be secured to the tibia after being registered to the talus guide assembly. This will be illustrated and described with reference to FIGS. 13A through 13C. The tibial guide assembly may be used to guide movement of the cutting tool to prepare the tibia to receive the tibial prosthesis (104). This will be illustrated and described with reference to FIGS. 14A through 15. The talus prosthesis (102) and tibial prosthesis (104) may then be inserted and secured into the talus and tibia, respectively. The resulting joint space after the ankle arthroplasty procedure is completed will be illustrated and described with reference to FIG. 16.

FIGS. 4A through 4C are perspective views, respectively, of a head and tail of a trial (400) that may be used to position a talus foundation (410) relative to a talus (420) using a column (430), and FIG. 4C is a perspective view of a head showing the talus foundation (410) and the column (430) assembled into the talus (420) and the trial (400). The talus (420) may include a natural articular surface (422) to be replaced via an arthroplasty procedure.

As illustrated, the specimen (400) can include a cephalad side (440) and a caudal side (442). The cephalad side (440) can include a column mounting feature (444) that interfaces with a corresponding feature (not illustrated) on the column (430). As illustrated, the column mounting feature (444) can include an ovoid shape having an opening that can interface with a corresponding ovoid recess and/or bosses on the column (430). The caudal side (442) can include a talus foundation registration feature (446) that engages with the talus foundation (410) to temporarily couple the specimen (400) to the talus foundation (410) such that the talus foundation (410) rotates due to rotation of the specimen (400). The bone foundation registration feature (446) may include a hole (448) and a rectangular protrusion (450, boss) surrounding the hole (448).

Additionally, the specimen (400) may include an anterior end (460) and a posterior end (462). When the specimen (400) is placed on the talus (420), the anterior end (460) may extend over the anterior portion of the talus (420) and the metacarpal, and the posterior end (462) may rest on a natural articular surface (422) of the talus (420). The anterior end (460) may include an anterior window (464) that may be used to visually align the anterior end (460) with the talus (420) and/or the metacarpal. The posterior end (462) may include a posterior window (456) that facilitates visualization of the natural articular surface (422) and/or alignment of the posterior end (462) with the natural articular surface (422). Additionally, the posterior end (462) may include a concave curvature (458) dimensioned such that the posterior end (462) fits relatively well against the natural joint surface (422).

The column (430) can include a proximal end (not shown) and a distal end (470). The distal end (470) can include a specimen receiver (472) having a specimen mounting feature (not shown) that is secured to the column mounting feature (444) of the specimen (400). Additionally, the specimen receiver (472) can include a hole (474) that aligns with a hole (448) of the talus foundation registration feature (446) when the column (430) is attached to the specimen (400), thereby providing access to the hole (448). The proximal end of the column (430) can include an alignment feature, such as a pin, hole, or marking, that can be readily aligned with landmarks on a patient's leg proximate the talus. In some embodiments, the landmark may be the tibial tuberosity on the proximal end of the tibia. Thus, the column (430) may comprise a length sufficient to span substantially the entire length of the patient's tibia.

When the proximal end of the column (430) is rotated into a desired alignment with the tibial tuberosity, the distal end may also rotate, allowing the specimen (400) to rotate on the talus (420). This rotation may also cause the talus foundation (410) to rotate in a desired direction relative to the talus (420). The talus foundation (410) may then be secured to the talus (420), for example, using a pin (480) inserted through the talus foundation (410) and driven into the talus (420). The pins (480) may be oriented obliquely with respect to one another such that the talus foundation (410) cannot slide toward or away from the talus (420) along the pin (480). After the talus foundation (410) is secured in place relative to the talus (420), the specimen (400) and column (430) can be removed from the talus foundation (410).

FIGS. 5A, 5B, and 5C are posterior and anterior perspective views, respectively, of the talus foundation (410) illustrated in FIG. 4C, and FIG. 5C is a perspective view of the head showing the talus foundation (410) fixed to the talus (420). The talus foundation (410) may be designed as a stable attachment point for positioning and/or moving other devices relative to the talus (420) and/or the tibia. The talus foundation (410) may include a stationary member (500) and a mobile member (502) that may be movably coupled to the stationary member (500).

The fixation member (500) may include a bone attachment interface that facilitates attachment of the fixation member (500) to the talus (420). Any bone attachment feature known in the art may be used; in the embodiments of FIGS. 5A-5C, the bone attachment interface may take the form of a series of passageways (510) through which pins (480) are inserted. The passageways (510) may be oriented obliquely with respect to one another such that the pins (480) are not parallel to one another. Thus, when the pins (480) are in place, the position and orientation of the talus foundation (410) may be substantially fixed with respect to the talus (420). There may be more passageways (510) than are necessary to secure the talus foundation (410); Therefore, the surgeon can insert the pins (480) only through the passages (510) positioned for optimal fixation of the pins (480) in the talus (420).

Additionally, the fixed member (500) may include a movable member interface that provides a movable coupling of the movable member (502) to the fixed member (500). As illustrated in FIGS. 5A-5C , the movable member (502) rotates relative to the fixed member (500). In an alternative embodiment (not shown), instead of pure rotation, the foundation may include a movable member that translates and/or performs some combination of translation and rotation relative to the fixed member. Any movable coupling known in the art may be used, including but not limited to pin joints, sliding joints, links, etc.

In FIGS. 5A-5C, the movable member interface may take the form of a pair of arched slots (512) extending anterior-posteriorly and cephalad-caudally. The arched slots (512) may be centered on an axis (514) extending centrally-laterally. As illustrated in FIG. 5C, the axis (514) may be positioned posteriorly relative to the arched slots (512). From an outwardly facing side of the fixed member (500), the arched slots (512) may be recessed within an arched groove (516) that follows the same arched path. Two or more sets of catches (518) may be formed on each side of the fixed member (500). The catches (518) may extend generally centrally-laterally and may assist in controlling the range of motion of the movable member (502) relative to the fixed member (500), as will be described below.

Additionally, the fixation member (500) may include a specimen interface that couples the fixation member (500) to the specimen (400). It may be desirable for the specimen interface to provide a fixed attachment between the fixation member (500) and the specimen (400) such that the position and orientation of the specimen (400) determines the position and orientation of the fixation member (500) and the position of the talus foundation (410).

As illustrated in FIGS. 5A to 5C, the specimen interface may be a hole (520) present in a rectangular recess (522). A fastener, such as a screw or bolt, may be inserted through the talus foundation registration feature (446) of the specimen (400). The fastener may be inserted through the hole (474) of the specimen receiver (472) and the hole (448) of the talus foundation registration feature (446) and may be secured to the hole (520). To ensure that the fastener (500) cannot rotate relative to the specimen (400) or the column (430) while the column (430) and the specimen (400) are attached to the fastener (500), the rectangular recess (522) may accommodate a rectangular projection (450) of the talus foundation registration feature (446).

The movable member (502) may include a fixed member interface that cooperates with the movable member interface of the fixed member (500) to provide a movable coupling between the fixed member (500) and the movable member (502). The fixed member interface may be selected to provide a rotatable coupling between the fixed member (500) and the movable member (502).

In FIGS. 5A-5C, the fixed member interface may include rollers (530) that are rotatably secured to the body of the movable member (502) through the arched slots (512) and that are present in the arched grooves (516). There may be two rollers (530) in each arched groove (516) to ensure that the movable member (502) is not free to rotate relative to the fixed member (500), but instead is constrained to rotate predictably relative to the fixed member (500) as the rollers move along the arched grooves (516). Thus, the movable member (502) may be constrained to rotate about an axis (514) relative to the fixed member (500).

In addition to the roller (530), the movable member (502) may include a guide knob (540) protruding from the inner or side surface of the movable member (502). In one embodiment, the guide knob (540) is rotatable relative to the remainder of the movable member (502) such that the guide knob (540) can be tightened to frictionally engage the fixed member (500), thereby preventing relative rotation between the fixed member (500) and the movable member (502), or the movable member (502) can be released to rotate relative to the fixed member. Thus, before releasing the guide knob (540) to move the movable member (502) to a new position and orientation, the surgeon can temporarily secure the guide knob (540) to the movable member (502) in place relative to the fixed member (500) in order to cut with the movable member (502) at its current position and orientation.

Additionally, the movable member (502) may include an abutment (not shown) facing the fixed member (500) such that the abutment engages the catch (518) when the movable member (502) is in two or more predetermined positions relative to the fixed member (500). For example, the predetermined positions may be desired anterior and posterior limits of movement of the movable member (502) relative to the fixed member (500). For example, when the movable member (502) is positioned such that the abutment engages the catch (518) forward of the fixed member (500), the engagement of the abutment and the catch (518) may prevent the movable member (502) from moving further anteriorly relative to the fixed member (500). This may be the position illustrated in FIGS. 5A-5C . Similarly, when the movable member (502) is positioned such that the support engages the latch (518) behind the fixed member (500), the engagement of the support and the latch (518) may prevent the movable member (502) from moving further rearwardly relative to the fixed member (500).

Alternatively, the engagement of the support member of the clasp (518) may not define a limit of movement, but may provide a tactile response that indicates to the surgeon that the movable member (502) has reached an anterior or posterior reference position relative to the fixed member (500). Specifically, the engagement of the support member of the clasp (518) may be audible and/or tactile to the surgeon when the support member snaps or clicks into the clasp (518). Thus, the surgeon may recognize that additional anterior or posterior movement of the movable member (502) relative to the fixed member (500) will cause the movable member (502) to pass beyond a predetermined reference point.

Additionally, the moveable member (502) may include a tool holder attachment interface, more specifically a talus burr holder interface that may be attached to a talus burr holder that holds a cutting tool in the form of a burr. The talus burr holder may include a base that may be attached to the talus burr holder interface; thus, the talus burr holder interface may also be referred to as a base attachment interface. The base attachment interface may be designed to secure the base relative to the moveable member (502) so as to carry the base as the moveable member (502) moves relative to the fixed member (500). As described below, the base attachment interface may also be used to attach an alignment block to the moveable member (502) to facilitate positioning of a tibial foundation relative to the tibia.

In FIGS. 5A to 5C, the base attachment interface may take the form of a pair of screw holes (550) formed in the movable member (502). The screw holes (550) may accommodate fasteners, such as screws or bolts, which may be used to secure the base on the movable member (502). The configuration and operation of the talus burr holder will be illustrated and described with respect to FIGS. 6A to 11B.

FIGS. 6A and 6B are front and rear perspective views, respectively, of a talus burr holder (600) secured to a talus foundation (410) to hold a burr (610) relative to a talus (420). The talus foundation (410) and the talus burr holder (600) may be combined to form a talus guide assembly that guides the movement of the burr (610) relative to the talus (420) to form a prepared surface (620) shaped to receive a prosthesis, such as a talus prosthesis (102) of FIGS. 1A to 2E , on the talus (420).

Specifically, the talus burr holder (600) may be secured to the movable member (502) of the talus foundation (410) such that the talus burr holder (600) is pivotable with respect to the fixed member (500) and the talus (420) together with the movable member (502). Additionally, the talus burr holder (600) may allow additional movement of the burr (610) (e.g., in a medio-lateral and dorso-caudal direction) to create a desired contour of the prepared surface (620). The use of the burr (610) is merely exemplary; those skilled in the art will appreciate that a variety of cutting tools may be used to form the prepared surface (620). Such cutting tools may include rotating and/or translating tools, such as burrs, reamers, reciprocating saws, and the like.

As illustrated, the talus burr holder (600) may include a base (630) secured to a movable member (502) of a talus foundation (410) and an arm (640) that moves relative to the base (630). Movement of the arm (640) relative to the base (630) allows the burr (610) to move mediolaterally on the talus (420), and further allows for anterior-posterior rotation provided by movement of the movable member (502) relative to the talus (420). The burr (610), along with additional burrs that may be used in connection with an arthroplasty procedure, will be described in more detail with respect to FIGS. 7A-8C .

FIGS. 7A to 7C are perspective, side, and cross-sectional views, respectively, of a burr (610). The burr (610) may include a body (700), a shaft (710), and a cutting member (720). An adapter (730) may be used to couple the burr (610) and the talus burr holder (600). The body (700) may have a generally cylindrical shape and may include a rotation motor (not shown). The rotation motor may induce the shaft (710) to rotate relative to the body (700); the shaft (710) may also have a cylindrical shape. The cutting member (720) may be carried by the shaft (710); thus, the rotation of the shaft (710) may drive the rotation of the cutting member (720).

The cutting member (720) and shaft (710) can rotate about a cutting tool axis (740) that is parallel to the length of the cutting member (720). The cutting member (720) can include a concave shape that facilitates formation of a convex anterior-posterior curvature from a forward approach. Specifically, the cutting member (720) can include a proximal end (750), a distal end (760), and an intermediate portion (770) between the proximal end (750) and the distal end (760). Both the proximal end (750) and the distal end (760) can extend about the intermediate portion (770) and share a maximum radius (780) that is perpendicular to the cutting tool axis (740). The radius of the intermediate portion (770) can be much smaller. The maximum radius (780) can be substantially equal to the radius of the central-lateral curvature present on the prepared surface (620) to be formed on the talus (420) by the cutting member (720).

Within the cutting tool axis (740) and plane, the cutting member (720) can include an arcuate concave profile having a radius (782) defined by a change in diameter of the cutting member (720) from the proximal end (750) to the middle portion (770) and to the distal end (760), the radius (782) being substantially equal to a radius of anterior-posterior curvature present on a prepared surface (620) to be formed on the talus (420) by the cutting member (720).

The adapter (730) can include a flared proximal end (790), a cylindrical distal end (792), a pair of body attachment holes (794) and a pair of burr holder attachment protrusions (796). The flared proximal end (790) can be hollow and sized to receive the body (700) of the burr (610). Similarly, the cylindrical distal end (792) can be sized to receive the shaft (710) of the burr (610) and/or surrounding material. The body attachment holes (794) can facilitate secure attachment of the adapter (730) to the burr (610). In one embodiment, a fastener, such as a set screw, can be inserted into the body attachment holes (794) to secure the adapter (730) to the burr (610). The attachment protrusion (796) may be used to facilitate attachment of the adapter (730) and the burr (610) to the talus burr holder (600) and/or the tibial burr holder, as will be described below.

In one embodiment, the body (700) may be the body of a standard orthopedic burr or reamer. The cutting member (720) and adapter (730) may be used to customize such a standard orthopedic burr or reamer to form the prepared surface (620) from the anterior approach.

In addition to or as an alternative to the cutting member (720), various other cutting members may be used. Such cutting members may include convex or rectilinear shapes. Embodiments will be illustrated and described with reference to FIGS. 8A through 8C.

FIGS. 8A to 8C are side views of burrs (800, 830, 860) according to various embodiments. The burrs (800, 830, 860) may each be used with an adapter (730) such as FIGS. 7A to 7C, and may include a similar configuration to the burr (610), including a body (700) and a shaft (710). Each of the burrs (800, 830, 860) may be configured to rotate about a cutting tool axis (740) such as the burr (610). However, the cutting members of the burrs (800, 830, 860) may be configured differently.

Specifically, the burr (800) may include a straight, generally cylindrical cutting member (820). The cutting member (820) may have a diameter (822) suitable for cutting a space in a surface (620) prepared for a keel (212) of a talus prosthesis (102). Additionally, the diameter of the cutting member (820) may be suitable for cutting a space for a keel (312) of a tibial prosthesis (104).

Additionally, the burr (830) may include a straight, generally cylindrical cutting member (850). The cutting member (850) may have a diameter (852) suitable for cutting a space in the surface (620) prepared for the shaft (710) of, for example, the burr (610), the burr (800) and/or the burr (860). Thus, the burr (830) may be used as a lead-in to provide space for the shaft (710) to move through in a future bone removal step.

The burr (860) can be used to form a concave anterior-posterior curvature in the tibia. Accordingly, the burr (860) can include a cutting member (880) having a generally convex shape. Specifically, the cutting member (880) can include a proximal end (882), a distal end (884), and an intermediate portion (886) between the proximal end (882) and the distal end (884). The intermediate portion (886) can be enlarged relative to the proximal end (882) and the distal end (884) and can have a maximum radius (888) that is perpendicular to the cutting tool axis (740). The radii of the proximal end (882) and the distal end (884) can be much smaller. The maximum radius (888) can be substantially equal to the radius of the medial-lateral curvature present on the prepared surface to be formed on the tibia by the cutting member (880).

Within the cutting tool axis (740) and plane, the cutting member (880) can include an arcuate convex profile having a radius (890) defined by a change in diameter of the cutting member (880) from the proximal end (882) to the middle portion (886) and to the distal end (884). The radius (890) can be substantially equal to a radius of anterior-posterior curvature present in a prepared surface to be formed on the tibia by the cutting member (880).

Figures 9a to 9c are a top perspective view, a tail perspective view, and a front side cross-sectional view, respectively, of the talus burr holder illustrated in Figures 6a and 6b. The talus burr holder (600) may be designed to hold one or more cutting tools to facilitate formation of a prepared surface (620) within the talus (420).

Specifically, the talus burr holder (600) can be used to hold the burr (830) to remove the anterior portion of the natural articular surface (422), thereby providing space for the shaft (710) of the burr (610) and the shaft (710) of the burr (800). Further, the talus burr holder (600) can be used to hold the burr (610) to remove the remainder of the natural articular surface (422) of the talus (420), thereby forming a convex anterior-posterior curvature of the prepared surface (620). Furthermore, the talus burr holder (600) can be used to form a slot, generally in the shape of a keel (212) of a talus prosthesis (102). Therefore, after using the talus bur holder (600) in combination with the bur (830), the bur (610), and the bur (800), the prepared surface (620) can be formed to receive the talus bone engagement surface (112) of the talus prosthesis (102). These processes can be rearranged and are described in detail later.

The base (630) of the talus burr holder (600) may include a foundation interface that may be used to attach the base (630) to the talus foundation (410). The foundation interface may include any structure suitable for securing the base (630) to the talus foundation (410). As illustrated in FIGS. 9A-9C , the foundation interface may include two holes (900) spaced apart in a manner similar to the threaded holes (550) of the movable member (502) of the talus foundation (410). The holes (900) may be smooth-bored. Accordingly, in order to secure the base (630) to the movable member (502), a fastener (902), which may be a screw, bolt, or the like, may be inserted through the hole (900) and rotated into engagement with the screw hole (550) of the movable member (502) of the talus foundation (410).

The base (630) may additionally include an arm coupling feature whereby the arm (640) is coupled to the base (630). The base (630) and the arm (640) may be movably coupled together via any combination of rotational and/or sliding joints. In one embodiment, the arm coupling feature provides a rotational coupling between the base (630) and the arm (640).

As illustrated in FIGS. 9A-9C, the arm engagement feature may include a pin (910) upon which the arm (640) is rotatably mounted. The pin (910) may include a head (912) having a male thread that can engage with a corresponding female thread within a hole (916) of the base (630) and a shank (914). The head (912) may have an interface that allows rotation of the head (912) with a tool, such as a screwdriver, to facilitate assembly of the talus burr holder (600). The head (912) may reside within a hole (918) of the base (630). A portion of the shank (914) adjacent the head (912) may be flattened to allow smooth engagement and rotation of the arm (640). The base (630) may further include two parallel plates (a front plate (920) and a rear plate (922)), between which the proximal portion of the arm (640) is captured. The front plate (920) may be formed with a hole (918) in which a head (912) is present, and the rear plate (922) may be formed with a hole (916) in which a shank (914) is fixed. Accordingly, the pin (910) may be inserted rearwardly through the hole (918) of the front plate (920) so as to be fixed in the hole (916) of the rear plate (922).

Additionally, the base (630) may include a base guide feature that assists in guiding the movement of the arm (640) relative to the base (630). The base guide feature may cooperate with a corresponding arm guide feature of the arm (640) to limit the range of movement of the arm (640), thereby limiting the range of movement of an attached cutting tool, such as a burr (610, 800, 830) relative to the talus (420). As illustrated in FIGS. 9A-9C , the base guide feature may include a rectangular window (930) having four guide surfaces (932). The guide surfaces (932) positioned so as to face the dorsal direction on the caudal side may limit the movement of the cutting tool in a dorsal direction toward the talus (420), as described below.

As illustrated in FIG. 9c, the arm (640) may be divided into a first arm member (950) and a second arm member (952). The second arm member (952) may be encased within the first arm member (950) such that the second arm member (952) slides within the first arm member (950) such that the arm (640) has an effectively adjustable reach relative to the pin (910). An elastic member may be used to bias the first arm member (950) away from the second arm member (952), thereby urging the arm (640) toward its maximum length. The elastic member may take the form of a linear spring (954) that is maintained in a compressed state. The linear spring (954) may be partially present within the cavity at the distal end of the second arm member (952).

The arm (640) can include a base engagement feature whereby the arm (640) is coupled to the base (630). The base engagement feature can be configured in a variety of ways and can be designed to cooperate with the arm engagement feature of the base (630). In FIGS. 9A-9C , the base engagement feature can include a slot (960) formed at a proximal end of the first arm member (950) and a cradle (962) formed at a proximal end of the second arm member (952). The slot (960) can extend in a head-to-tail direction and accommodate a pin (910) to allow the first arm member (950) to move up and down relative to the pin (910). The cradle (962) may be a concave semicircle so that the proximal end of the second arm member (952) can relatively smoothly contact and slide against the pin (910), and the proximal end of the second arm member (952) pushes upward against the pin (910) to force the first arm member (950) downward.

The arm (640) may further include a tool attachment interface to which a cutting tool may be attached. When the cutting tool is a burr, such as the burr (610), the burr (800), the burr (830), and/or the burr (860), the tool attachment interface may be referred to as a burr attachment interface. The burr attachment interface may be designed to maintain any one of the burrs (610), the burr (800), and the burr (830) in a fixed relationship with the first arm member (950). More precisely, the burr attachment interface may be designed to receive and secure an adapter (730) that is secured to any one of the burrs (610), the burr (800), and the burr (830).

As illustrated in FIGS. 9A-9C , the burr attachment interface may take the form of an attachment cannula (970) having a bore (972) formed to receive a cylindrical distal end (792) of the adapter (730). Additionally, the attachment cannula (970) may include one or more locking features that selectively lock the adapter (730) in position relative to the attachment cannula (970). The locking features may operate as bayonet fittings; thus, they may take the form of slots (974) that extend axially and circumferentially on the attachment cannula. Each of the slots (974) may be sized to receive one of the burr holder attachment protrusions (796) of the adapter (730).

Specifically, the adapter (730) can be inserted into the rear of the attachment cannula (970) such that the burr holder attachment protrusion (796) enters the axially extending portion of the slot (974) after being attached to a corresponding cutting tool. Once the burr holder attachment protrusion (796) reaches the end of the axially extending portion, the adapter (730) can be rotated about the axis of the attachment cannula (970), which can be co-linear with the cutting tool axis (740) of the cutting tool, such that the burr holder attachment protrusion (796) slides along the circumferentially extending portion of the slot (974). One or more snap features (not shown) can optionally cause the adapter (730) to snap into place in the attachment cannula (970). In any case, the combination of axial movement and rotation required to attach the adapter (730) to the attachment cannula (970) can ensure that the cutting tool remains rigidly held relative to the first arm member (950) until the insertion movement is reversed.

Additionally, the arm (640) may include an arm guide feature that cooperates with the base guide feature to limit movement of the arm (640) relative to the base (630). The arm guide feature may be any member that can interact with the base guide feature to limit relative movement between the base (630) and the arm (640). When the base guide feature includes a guide surface, the arm guide feature may preferably be a follower that can abut and/or be seated upon such guide surface.

Specifically, the base guide feature can be a post (980) protruding from the first arm member (950) between the pin (910) and the attachment cannula (970). The post (980) can protrude forwardly such that the post (980) resides in a rectangular window (930) of the base (630). The interaction of the guide surface (932) of the rectangular window (930) and the post (980) can restrict the movement of the attachment cannula (970) and the cutting tool to a generally rectangular area. In particular, the guide surface (932) at the bottom of the rectangular window (930) can control the cutting depth by restricting the movement of the cutting tool toward the talus (420).

More specifically, the guide surface (932) on the bottom of the rectangular window (930) can prevent the cutting tool axis (740) of the burr (610), the burr (800), or the burr (830) from moving closer to the talus (420) than the planar boundary. Similarly, the guide surface (932) on the side of the rectangular window (930) can prevent the cutting tool axis (740) of the burr (610), the burr (800), or the burr (830) from moving more centrally or laterally than the additional planar boundary. Accordingly, the post (980) of the arm (640) can cooperate with the rectangular window (930) of the base (630) such that the prepared surface (620) has a desired depth, width, and overall shape.

Additionally, the action of the linear spring (954) can help ensure that the prepared surface (620) has the desired shape. Specifically, the pressure applied by the linear spring (954) can ensure that the cut into the talus (420) extends to the desired full depth, thereby ensuring that the prepared surface (620) has the depth and consistency necessary to provide continuous extension of the bone to support the talus prosthesis (102). Nonetheless, the linear spring (954) can be adjusted to provide a force that can be easily resisted by the surgeon to remove bone with shallower cuts before extending the cutting tool to the maximum depth allowed by the interaction of the post (980) and the rectangular window (930). The manner in which a talus cutting guide including a talus foundation (410) and a talus bur holder (600) can be used to control resection of a talus (420) will be illustrated and described in more detail with respect to FIGS. 6A, 6B, and FIGS. 10A to 12.

Referring briefly to FIGS. 6A and 6B , in one embodiment, a talus foundation (410) and a talus burr holder (600) can be used to form a prepared surface (620) beginning with a posterior aspect of the prepared surface (620). Specifically, with the base (630) secured to the movable member (502) of the talus foundation (410) and the burr (830) secured to the arm (640), the movable member (502) can pivot toward its posterior position relative to the fixed member (500). This can position the cutting member (850) of the burr (830) over the posterior portion of the natural articular surface (422) of the talus (420). More specifically, until the surgeon is ready to resect the natural joint surface (422), the surgeon can secure the burr (830) over the natural joint surface (422) against the force of the linear spring (954), and the post (980) can be displaced from the guide surface (932) at the bottom of the rectangular window (930).

Thereafter, the surgeon lowers the burr (830) until the post (980) is seated on the guide surface (932) at the bottom of the rectangular window (930) so that the linear spring (954) presses the burr (830) into engagement with the natural joint surface (422). Thereafter, by moving the attachment cannula (970) in the medio-lateral direction, the burr (830) can be moved in the medio-lateral direction, which causes the post (980) to slide along the guide surface (932) in the medio-lateral direction at the bottom of the rectangular window (930). The post (980) can abut the guide surface (932) on the left and right sides of the rectangular window (930) to control the medio-lateral range of movement of the burr (830).

When the burr (830) extends beyond the medio-lateral extent of the natural joint surface (422), the movable member (502) can be rotated forward relative to the fixed member (500) to move the burr (830) toward the anterior portion of the natural joint surface (422). The medio-lateral movement of the burr (830) can be repeated as needed to remove material from the anterior portion of the natural joint surface (422). If desired, the medio-lateral movement of the burr (830) can also be performed during the anterior rotation of the movable member (502) to remove material from the overall anterior-posterior curvature of the natural joint surface (422).

As described above, the purpose of the burr (830) may be to remove sufficient material to allow the burr (610) and the burr (800) to engage the bone (420) without interference. In particular, in a later cutting step, the purpose may be to remove bone from the location where the shaft (710) of the burr (610) and the shaft (710) of the burr (800) will be positioned. Therefore, the burr (830) need not be used to resect the entire natural joint surface (422).

Once the burr (830) extends beyond the medio-lateral and anterior-posterior extent of the natural joint surface (422), the burr (830) can be removed from the attachment cannula (970) and instead the burr (610) can be secured to the attachment cannula (970). The burr (610) can be positioned over the posterior portion of the natural joint surface (422). The surgeon can hold the burr (610) over the partially resected natural joint surface (422) against the force of the linear spring (954). Again, the post (980) can be displaced from the guide surface (932) at the bottom of the rectangular window (930) until the surgeon is ready to incise the natural joint surface (422) with the burr (610).

Thereafter, the surgeon lowers the burr (610) until the post (980) rests against the guide surface (932) at the bottom of the rectangular window (930) so that the linear spring (954) presses the burr (610) into engagement with the natural joint surface (422). This is the position illustrated in FIGS. 6A and 6B . Then, by moving the attachment cannula (970) mediolaterally, the burr (610) can be moved mediolaterally (i.e., side to side), causing the post (980) to once again slide mediolaterally along the guide surface (932) at the bottom of the rectangular window (930). The post (980) can be adjacent the guide surface (932) at the left and right sides of the rectangular window (930) to control the range of mediolateral movement of the burr (610).

When the burr (610) extends beyond the central-lateral extent of the natural joint surface (422), the movable member (502) can be rotated forward relative to the fixed member (500) to move the burr (610) toward the anterior portion of the natural joint surface (422). This is the position illustrated in FIGS. 10a and 10b.

FIGS. 10A and 10B are anterior and posterior perspective views, respectively, of a talus burr holder (600) attached to a talus foundation (410) and the talus foundation attached to a talus (420), wherein the burr (610) is positioned to cut an anterior portion of a natural articular surface of the talus. The mediolateral movement of the burr (610) to remove material from the anterior portion of the natural articular surface (422) can be repeated as needed. If desired, the mediolateral movement of the burr (610) can also be performed during anterior rotation of the movable member (502) to remove material from the entire anterior-posterior curvature of the natural articular surface (422).

As illustrated in FIGS. 6b and 10b, the result may be the formation of a prepared surface (620). The prepared surface (620) will be further illustrated and described with respect to FIGS. 11a and 11b.

Figures 11a and 11b are a side cross-sectional view and an enlarged anterior perspective view, respectively, of a talus (420) with a talus foundation (410), a talus bur holder (600), and a talus (420) with a bur (610) positioned as in Figures 10a and 10b. The shape of the prepared surface (620) is illustrated in more detail, excluding the slot for the keel (212) of the talus prosthesis (102).

As illustrated in FIG. 11a, the prepared surface (620) can have a lateral cross-sectional shape that corresponds similarly to a side view of the talus prosthesis (102, see FIG. 2e) in a plane existing in the anterior-posterior direction (130) and the head-to-tail direction (134). The prepared surface (620) can include a convex anterior-posterior curvature (1100) having substantially the same radius as the anterior-posterior curvature (230) of the talus bone engaging surface (112) of the talus prosthesis (102). Anterior and posterior to the convex anterior-posterior curvature (1100), the prepared surface (620) can have two convex anterior-posterior curvatures (1110), which can have the same radii as portions of the talus bone engaging surface (112) that are anterior and posterior to the anterior-posterior curvature (230).

As illustrated in FIG. 11b, the prepared surface (620) may have a cross-sectional shape that corresponds similarly to the cross-sectional shape of the talus bone engagement surface (112) of the talus prosthesis (102, see FIG. 2e) in a plane existing in the medio-lateral direction (132) and the cephalo-caudal direction (134), except that the slot for the keel (212) of the talus prosthesis (102) is not yet formed. The prepared surface (620) may include a central extension (1120) having a generally linear shape and two concave medio-lateral curvatures (1130) on either side of the central extension (1120). The central extension (1120) can generally have a width substantially equal to the width of the central extension (222) of the talar bone engagement surface (112) of the talar prosthesis (102), and the concave central-lateral curvature (1130) can have a radius substantially equal to the radius of the central-lateral curvature (220) of the talar bone engagement surface (112) of the talar prosthesis (102).

The shape of the cutting member (720) of the burr (610) can determine various shape parameters of the prepared surface (620). Specifically, a radius (782) along the length of the cutting tool axis (740) of the cutting member (720) of the burr (610) can be substantially equal to a radius of the convex forward-backward curvature (1100). Similarly, a maximum radius (780) perpendicular to the cutting tool axis (740) of the cutting member (720) of the burr (610) can be substantially equal to a radius of the concave central-lateral curvature (1130).

As described above, it may be desirable to form a slot in the prepared surface (620) so that the surface (620) can securely receive the keel (212) of the ankle prosthesis (102). The formation of the slot is optional; in one embodiment, the ankle prosthesis may have no keel, or may include a keel having a built-in cutting member that forms the slot in response to pressure of the keel against bone. Additionally, in one embodiment, the slot may be formed prior to forming the remainder of the prepared surface (620). Thus, for example, the burr (800) may be used to form the slot prior to using the burr (610), as illustrated in FIGS. 11A and 11B , to form the prepared surface (620), and may also be used to form the slot prior to using the burr (830). Even assuming that the prepared surface (620) has already been formed as shown in FIGS. 11a and 11b, the formation of the slot will be illustrated in FIG. 12.

FIG. 12 is a perspective view illustrating the formation of a slot (1200) in a prepared surface (620) of a talus (420) using a burr (800). After completion of the previous bone removal step (or, optionally, prior to performing the steps described above), the burr (800) may be attached to an attachment cannula (970) of the talus burr holder (600) while the talus burr holder is secured to the movable member (502) of the talus foundation (410). The burr (800) may then be positioned over a central portion of the prepared surface (620). The surgeon may hold the burr (800) over the prepared surface (620) against the force of the linear spring (954). Again, until the surgeon is ready to form a slot in the prepared surface (620) with the bur (800), the post (980) can be displaced from the guide surface (932) at the bottom of the rectangular window (930).

The surgeon then holds the burr (800) in a mid-lateral position and lowers the burr (800) until the post (980) is positioned against the guide surface (932) of the bottom of the rectangular window (930), thereby causing the linear spring (954) to compress the burr (800) to engage the prepared surface (620). This is the position illustrated in FIG. 12. As the cutting member (820) of the burr (800) is lowered into the prepared surface (620), the cutting member (820) is able to form a slot (1200) substantially centered on the prepared surface (620). The diameter (822) of the cutting member (820) can be generally equal to the width of the keel (212) of the bone prosthesis (102). The slot (1200) may include a caudal end (not shown) having a generally hemispherical concave cross-sectional shape that accommodates a semicircular periphery (244) of the penetration portion (242) of the keel (212).

The keel (212) can interface with the slot (1200) in a manner that prevents the talus prosthesis (102) from moving mediolaterally with respect to the prepared surface (620) and facilitates secure attachment of the talus prosthesis (102) to the prepared surface (620). The remainder of the keel (212) and/or the talus bone engagement surface (112) of the talus prosthesis (102) can optionally include a porous surface and/or a coated surface designed to promote bone ingrowth and adhesion. Additionally or alternatively, the talus prosthesis (102) can be designed for use with bone cement to form a bond between the talus (420) and the talus prosthesis (102).

Once the prepared surface (620) including the slot (1200) is fully formed, the talus burr holder (600) can be removed from the talus foundation (410) along with any attached cutting tools. As in FIG. 5c, the talus foundation (410) can be held in position on the talus (420). Subsequently, as illustrated in FIGS. 13a through 13c, the talus foundation (410) can be used to facilitate attachment of the tibial cutting guide to the tibia.

FIGS. 13A to 13C are a front perspective view, a plan view, and a front head perspective view, respectively, of a tibial foundation (1300), and FIG. 13C illustrates an alignment block (1310) for fixing the tibial foundation (1300) to the tibia (1320). As illustrated, the tibial foundation (410) can remain fixed to the talus (420), and the alignment block (1310) can be attached to the tibial foundation (410) and the tibial foundation (1300) so that the tibial foundation (1300) is appropriately positioned relative to the joint.

As with the talus foundation (410), the tibial foundation (1300) may be part of a cutting guide that helps guide a cutting tool against the bone. A cutting tool holder, such as a tibial burr holder, may be attached to the tibial foundation (1300), as described below.

The tibial foundation (1300) may include a bone attachment interface that facilitates attachment of the tibial foundation (1300) to the tibia (1320). Any bone attachment feature known in the art may be used; in the embodiments of FIGS. 13A-13C, the bone attachment interface may take the form of a series of passageways (1330) through which pins (480) are inserted. As with the talus foundation (410), the passageways (1330) may be oriented obliquely with respect to one another such that the pins (480) are not parallel to one another. Thus, when the pins (480) are in place, the position and orientation of the tibial foundation (1300) may be substantially fixed with respect to the tibia (1320). There may be more passageways (1330) than are necessary for attachment of the tibial foundation (1300); Therefore, the surgeon can insert the pin (480) only through the passage (1330) positioned for optimal fixation of the pin (480) in the tibia (1320).

Additionally, the tibial foundation (1300) may include a tool holder attachment interface, or more specifically, a tibial burr holder interface that may be attached to a tibial burr holder that holds a cutting tool in the form of a burr. The tibial burr holder may include a base that may be attached to the tibial burr holder interface; thus, the tibial burr holder interface may also be referred to as a base attachment interface. The base attachment interface may be designed to secure the base relative to the tibial foundation (1300). Unlike the tibial foundation (410), the tibial foundation (1300) may not include a fixed member and a moveable member; rather, the entire tibial foundation may act as a fixed base for registration of the tibial burr holder. As illustrated in FIG. 13c, the base attachment interface may also be used to attach the tibial foundation (1300) to an alignment block (1310) to facilitate positioning of the tibial foundation (1300) relative to the tibia (1320).

In FIGS. 13A-13C, the base attachment interface may take the form of a button (1340) having a screw hole (1342) that may receive a screw tip of a fastener for attaching a tibial burr holder or alignment block to the button (1340). The button (1340) may also include an anterior rim (1344) and a posterior rim (1346) that cooperate to engage with the slot (1350). More precisely, the slot (1350) may include a ledge (1352) that defines a keyhole shape of the slot (1350). The ledge (1352) may be present between the anterior rim (1344) and the posterior rim (1346) to allow the button (1340) to slide up or down within the slot (1350). The slot (1350) may include a head end (1354) where no ledge (1352) is present. Thus, the head end (1354) may provide a circular opening into which a front rim (1344) and a rear rim (1346) may be inserted to allow assembly of a button into the plate (1360) in which the slot (1350) is formed.

As illustrated in FIG. 13c, the alignment block (1310) may include a body (1370) having a talus foundation interface attachable to a talus foundation (410) and a tibial foundation interface attachable to a tibial foundation (1300). Each foundation interface may provide a rigid fixation to its corresponding foundation such that the talus foundation (410) and the tibial foundation (1300) may be secured together in a predictable relative position.

As illustrated in FIG. 13c, the talus foundation interface may include two holes (1380) configured similarly to the two holes (900) of the talus burr holder (600). The holes (1380) may be spaced apart in a manner similar to the screw holes (550) of the movable member (502) of the talus foundation (410) and may be smooth-bored. Accordingly, a fastener, such as a screw, bolt, or the like, such as a fastener (902) of the talus burr holder (600), may be inserted through the holes (1380) to secure the alignment block (1310) to the movable member (502) and may be rotated to engage the screw holes (550) of the movable member (502) of the talus foundation (410).

The tibial foundation interface may include a hole (1390), which may be perforated smoothly, such as the hole (1380). A fastener, such as a fastener (902) of a talus burr holder (600), such as a screw, bolt, or the like, may be inserted through the hole (1390) to secure the tibial foundation (1300) to the alignment block (1310) and may be rotated to engage the hole (1342) of the tibial foundation (1300).

The alignment block (1310) may be secured to the talus foundation (410) by, for example, securing the hole (1380) to the screw hole (550) of the movable member (502) using the fastener (902). The movable member (502) may be positioned at a predictable location, such as at the forward end of the range of motion relative to the fixed member (500), when the alignment block (1310) is attached. If desired, the movable member (502) may be secured in place relative to the fixed member (500), for example, using a guide knob (540).

Next, the tibial foundation (1300) may be secured to the alignment block (1310) by, for example, securing the hole (1390) to the hole (1342) of the tibial foundation (1300) using a fastener, such as a screw or bolt. In an alternative embodiment, the alignment block (1310) may be first secured to the tibial foundation (1300) and then secured to the talus foundation (410).

In either case, after attaching the alignment block (1310) to the talus foundation (410) and the tibial foundation (1300), the tibial foundation (1300) can be in a predictable position relative to the talus foundation (410) and the ankle joint. Thus, the tibial foundation (1300) can be used to guide the resection of the tibia (1320). Thus, as illustrated, the tibial foundation (1300) can be secured to the tibia (1320) by inserting the pin (480) through the passage (1330) of the tibial foundation (1300) and securing the distal end of the pin (480) to the bone of the tibia (1320). Once the tibial foundation (1300) is secured to the tibia (1320), the alignment block (1310) can be separated from the tibial foundation (410) and the tibial foundation (1300). Additionally, the tibial foundation (410) can be separated from the tibial foundation (420) by removing the pin (480) from the tibial foundation (420).

Next, the tibial foundation (1300) can be used in conjunction with the tibial burr holder to form a tibial guide assembly that guides the burr to the tibia. This will be described in more detail with respect to FIGS. 14A to 14C.

FIGS. 14A, 14B, and 14C are a frontal perspective view, a side view, and a frontal perspective view, respectively, of a tibial burr holder (1400), wherein FIG. 14C illustrates a state in which the tibial burr holder (1400) is secured to a tibial foundation (1300) and a tibia (1320). The tibial foundation (1300) and the tibial burr holder (1400) can be joined to form a tibial guide assembly that guides movement of the burr (860) relative to the tibia (1320) to form a prepared surface on the tibia (1320) formed to receive a prosthesis, such as the tibial prosthesis (104) of FIGS. 1A to 1C and 3A to 3E. Meanwhile, Fig. 15 is a cross-sectional view of a tibial burr holder (1400) fixed to a tibia (1320) and a tibial foundation (1300). The configuration and operation of the tibial burr holder will be described with reference to Figs. 14a to 15.

Specifically, a tibial burr holder (1400) can be secured to a hole (1390) in a tibial foundation (1300). The tibial burr holder (1400) allows movement of the burr (860) (e.g., in a medio-lateral direction and a cephalad-caudal direction) to create a desired contour of a prepared surface (1420, see FIG. 15) of the tibia (1320). The use of the burr (860) is merely exemplary; those skilled in the art will recognize that a variety of cutting tools may be used to form the prepared surface (1420). Such cutting tools may include rotating and/or translating tools, such as burrs, reamers, reciprocating saws, and the like.

As illustrated, the tibial bur holder (1400) may include a base (1430) secured to a tibial foundation (1300) and an arm (1440) that moves relative to the base (1430). Movement of the arm (1440) relative to the base (1430) may cause the bur (860) to move in a medio-lateral direction on the tibia (1320). The base (1430) and arm (1440) may cooperate to provide limited movement of the cutting tool relative to the tibia (1320), in a manner similar to that of the tibial bur holder (600), as described below.

The base (1430) of the tibial bur holder (1400) can include a foundation interface that can be used to attach the base (1430) to the tibial foundation (1300). The foundation interface can include any structure suitable for securing the base (1430) to the tibial foundation (1300). As illustrated in FIGS. 14A-15 , the foundation interface can include a hole (1450) that can be aligned with the hole (1342) of the button (1340) of the tibial foundation (1300) such that a fastener (1452), such as a screw or bolt, can be inserted through the hole (1450) and rotated to engage with the hole (1342) of the button (1340) of the tibial foundation (1300) to secure the base (1430) to the tibial foundation (1300).

The base (1430) may further include an arm coupling feature whereby an arm (1440) is coupled to the base (1430). The base (1430) and the arm (1440) may be movably coupled together via any combination of rotational and/or sliding joints. In one embodiment, the arm coupling feature provides a rotatable coupling between the base (1430) and the arm (1440).

As illustrated in FIGS. 14A-15, the arm engagement feature may include a pin (1460) upon which the arm (1440) is rotatably mounted. The pin (1460) may include a head (1462) and a shank (1464) having male threads that may engage with corresponding female threads in a hole (1466) of the base (1430). The head (1462) may include an interface that allows the head (1462) to be rotated with a tool, such as a screwdriver, to facilitate assembly of the tibial bur holder (1400). The head (1462) may reside within the hole (1468) of the base (1430). A portion of the shank (1464) adjacent the head (1462) may be smooth to allow the arm (1440) to rotate smoothly thereon. The base (1430) may further include two front plates (1470) and one rear plate (1462), between which the arm (1440) is typically captured. A hole (1468) in which a head (1462) is present may be formed at the top of the front plate (1470), and a hole (1466) in which a shank (1464) is fixed may be formed in the rear plate (1472).

Thus, the pin (1460) can be inserted rearwardly through the hole (1468) in the top of the front plate (1470) to be secured into the hole (1466) of the rear plate (1462).

Additionally, the base (1430) may include a base guide feature that assists in guiding movement of the arm (1440) relative to the base (1430). The base guide feature may cooperate with a corresponding arm guide feature of the arm (1440) to limit the range of movement of the arm (1440), thereby limiting the range of movement of an attached cutting tool (such as the burr (860), the burr (800), or the burr (830)) relative to the tibia (1320). As illustrated in FIGS. 14A-15 , the base guide feature may include a notch (1480) having a plurality of guide surfaces (1482). Any one of the guide surfaces (1482) may be oriented caudally to limit movement of the cutting tool in a cephalad direction relative to the tibia (320), as described below. The remaining guide surfaces (1482) can be oriented in a central-lateral direction to limit movement of the cutting tool in the central and lateral directions.

As illustrated in FIG. 15, the arm (1440) may be divided into a first arm member (1500) and a second arm member (1502). The second arm member (1502) may be nested within the first arm member (1500) such that the second arm member (1502) is slidable within the first arm member (1500) so that the arm (1440) has an effective adjustable reach relative to the pin (1460). An elastic member may be used to space the first arm member (1500) from the second arm member (1502), thereby urging the arm (1440) toward its maximum length. The elastic member may take the form of a linear spring (1504) that is typically maintained in a compressed state. The linear spring (1504) may be partially present in the cavity of the distal end of the second arm member (1502). The first arm member (1500) may include an opening (1506) through which the fastener (1452) is accessible from the front of the tibial burr holder (1400).

The arm (1440) can include a base coupling feature through which the arm (1440) is coupled to the base (1430). The base coupling feature can be configured in a variety of ways and can be designed to cooperate with the arm coupling feature of the base (1430). In FIG. 15, the base coupling feature can include a slot (1510) formed in the first arm member (1500) and a cradle (1512) formed on an upper end of the second arm member (1502). The slot (1510) can extend in a head-to-tail direction and can receive a pin (1460) that allows the first arm member (1500) to move up and down relative to the pin (1460). The cradle (1512) may be a concave semicircle so that the upper portion of the second arm member (1502) can relatively smoothly contact and slide against the pin (1460) while the first arm member (1500) is pushed upward while allowing the end of the second arm member (1502) to push downward against the pin (1460).

The arm (1440) may further include a tool attachment interface to which a cutting tool may be attached. Where the cutting tool is a burr, such as the burr (610), the burr (800), the burr (830), and/or the burr (860), the tool attachment interface may be referred to as a burr attachment interface. The burr attachment interface may be designed to maintain any one of the burr (860), the burr (800), and the burr (830) in a fixed relationship with the first arm member (1500). More precisely, the burr attachment interface may be designed to receive and secure an adapter (730) secured to any one of the burr (860), the burr (800), and the burr (830).

As illustrated in FIGS. 14A-15, the burr attachment interface can take the form of an attachment cannula (970) substantially identical to the attachment cannula (970) of the tibial burr holder (600). Thus, the attachment cannula (970) of the tibial burr holder (1400) can include a bore (972) sized to receive the cylindrical distal end (792) of the adapter (730). Additionally, the attachment cannula (970) can include at least one locking feature selectively locking the adapter (730) in position relative to the attachment cannula (970). The locking features can act as bayonet fittings; thus, they can take the form of slots (974) that extend axially and circumferentially on the attachment cannula. Each slot (974) can be sized to receive one of the burr holder attachment protrusions (796) of the adapter (730). The adapter can be received within and interlocked with the attachment cannula (970) as described with respect to the talus burr holder (600).

Additionally, the arm (1440) may include an arm guide feature that cooperates with the base guide feature to limit movement of the arm (1440) relative to the base (1430). The arm guide feature may be any member that can interact with the base guide feature to help limit relative motion between the base (1430) and the arm (1440). If the base guide feature includes a guide surface, the arm guide feature may preferably be a follower that can abut and/or be seated upon such guide surface.

Specifically, the base guide feature can be a post (1490) protruding from the first arm member (1500) between the pin (1460) and the attachment cannula (970). The post (1490) can protrude forwardly such that the post (1490) resides within the notch (1480). The interaction of the post (1490) and the guide surface (1482) of the notch (1480) can restrict the movement of the attachment cannula (970) and the cutting tool to a generally rectangular area. In particular, the guide surface (1482) above the notch (1480) can restrict the movement of the cutting tool toward the tibia (1320), thereby controlling the depth of resection.

More specifically, the guide surface (1482) on the top of the notch (1480) can prevent the cutting tool axis (740) of the burr (860), the burr (800), or the burr (830) from moving closer to the tibia (1320) than the planar boundary. Similarly, the guide surface (1482) on the side of the notch (1480) can prevent the cutting tool axis (740) of the burr (860), the burr (800), or the burr (830) from moving further in a central or lateral direction than the additional planar boundary. Accordingly, the post (1490) of the arm (1440) can cooperate with the notch (1480) of the base (1430) such that the prepared surface (1420) has a desired depth, width, and overall shape.

Additionally, the action of the linear spring (1504) can assist in ensuring that the prepared surface (1420) assumes the desired shape. Specifically, the pressure exerted by the linear spring (1504) ensures that the cut into the tibia (1320) extends to the desired full depth, thereby ensuring that the prepared surface (1420) has the depth and consistency necessary to provide continuous extension of the bone to support the tibial prosthesis (104). Nevertheless, the linear spring (1504) can be adjusted to provide a force that can be easily resisted by the surgeon to remove bone with shallower cuts before extending the cutting tool to the maximum depth allowed by the interaction of the post (1490) and the notch (1480).

To form a prepared surface (1420) on the distal end of the tibia (1320), the tibial bur holder (1400) can be used in a similar manner to the talus bur holder (600), except that the tibial bur holder (1400) does not have a movable member. Thus, there is no need to move the cutting tool in an anterior-posterior direction. Rather, all cutting can be done along the same anterior-posterior reference. The cutting can optionally begin with the bur (830) to remove sufficient bone to create space for the shaft (710) of the bur (860), and then the cutting can continue with the bur (860) to outline the prepared surface (1420), except for a slot in the keel (312) of the tibial prosthesis (104). The bur (800) can be used to form such a slot.

As with the talus bur holder (600), the linear spring (1504) may be used to obtain an appropriate cutting depth. Specifically, the surgeon may position the cutting member (850) of the bur (830) beneath the natural joint surface of the tibia (1320). The surgeon may then hold the bur (830) beneath the natural joint surface against the force of the linear spring (1504), and the post (1490) may be displaced beneath the guide surface (1482) above the notch (1480), and he or she is ready to resect the natural joint surface.

The surgeon raises the burr (830) until the post (1490) is positioned against the guide surface (1482) at the top of the notch (1480) such that the linear spring (1504) presses the burr (830) into engagement with the natural joint surface. The burr (830) then moves the attachment cannula (970) mediolaterally (i.e., side to side) such that the post (1490) slides mediolaterally along the guide surface (1482) at the top of the notch (1480). The post (1490) can be adjacent the guide surface (1482) on the left and right sides of the notch (1480) to control the mediolateral range of movement of the burr (830).

Once the burr (830) extends beyond the mediolateral extent of the natural joint surface (422), the burr (830) can be removed from the attachment cannula (970) and instead the burr (860) can be secured to the attachment cannula (970). The burr (860) can then be positioned beneath the natural joint surface of the tibia (1320). The surgeon can then hold the burr (860) beneath the partially resected natural joint surface against the force of the linear joint spring (1504). Again, the post (1490) can be displaced from the guide surface (1482) at the top of the notch (1480) until the surgeon is ready to resect the natural joint surface with the burr (860).

Thereafter, the surgeon can elevate the burr (860) until the post (1490) is seated against the guide surface (1482) at the top of the notch (1480) so that the linear spring (1504) presses the burr (860) into engagement with the natural joint surface. The burr (860) can then be moved in the medio-lateral direction (i.e., side to side) by moving the attachment cannula (970) in the medio-lateral direction, causing the post (1490) to slide once again in the medio-lateral direction along the guide surface (1482) at the top of the notch (1480). To control the range of medio-lateral movement of the burr (860), the post (1490) can be adjacent the guide surface (1482) on the left and right sides of the notch (1480).

Hereinafter, the prepared surface (1420) may include a shape similar to the prepared surface (620) of the talus (420), but having a concave anterior-posterior curve (1592) instead of a convex anterior-posterior curve (1100). A portion of the concave anterior-posterior curve (1592) is illustrated in FIG. Referring again briefly to FIG. 11B , the prepared surface (1420) may include, in addition to the concave anterior-posterior curve (1592), two convex anterior-posterior curves (1110) positioned anterior and posterior to the concave anterior-posterior curve (1592) in a plane parallel to the anterior-posterior direction (130) and the cephalad-caudal direction (134). Additionally, in a plane parallel to the medio-lateral direction (132) and the cephalo-caudal direction (134), the prepared surface (1420) can include a central extension (1120) and two concave medio-lateral curvatures (1130) located on either side of the central extension (1120). Thus, when a slot for the keel (312) is formed as illustrated in FIGS. 3A to 3E , the prepared surface (1420) can include a shape that generally complements the shape of the tibial bone engagement surface (122) of the tibial prosthesis (104).

Once the burr (860) has passed the mid-lateral extent of the natural articular surface, the burr (860) can be removed from the attachment cannula (970) and the burr (800) can be secured thereto instead. The burr (800) can then be positioned beneath the central portion of the prepared surface (1420). The surgeon can then hold the burr (800) beneath the prepared surface (1420) against the force of the linear spring (1504). Again, the post (1490) can be displaced from the guide surface (1482) above the notch (1480) until the surgeon is ready to form a slot in the prepared surface (1420) with the burr (800).

Thereafter, the surgeon positions the burr (800) in a mediolateral center and raises the burr (800) until the post (1490) is positioned against the guide surface (1482) at the top of the notch (1480), causing the linear spring (1504) to press the burr (800) to engage the prepared surface (1420). As the cutting member (820) of the burr (800) is raised into the prepared surface (1420), the cutting member (820) can form a slot (1598) substantially centered on the prepared surface (1420). The diameter (822) of the cutting member (820) can be generally equal to the width of the keel (312) of the tibial prosthesis (104). The slot (1598) may have a head end having a generally hemispherical concave cross-sectional shape that accommodates the semicircular periphery (344) of the penetration portion (342) of the keel (312).

The keel (312) can interface with the slot (1598) in a manner that prevents the tibial prosthesis (104) from moving mediolaterally with respect to the prepared surface (1420) and further facilitates fixed adhesion of the tibial prosthesis (104) to the prepared surface (1420). The keel (312) and/or the remainder of the tibial bone engagement surface (122) of the tibial prosthesis (104) may optionally have a porous surface and/or a coated surface designed to promote bone ingrowth and adhesion. Additionally or alternatively, the tibial prosthesis (104) may be designed for use with a bone cement that forms an adhesion between the tibia (1320) and the tibial prosthesis (104).

Once the prepared surface (1420) including the slot (1598) is fully formed, the tibial foundation (1300) can be removed from the tibial foundation (1300) along with any attached cutting tools. Additionally, the tibial foundation (1300) can be removed from the tibia (1320) to remove any obstructions from the joint space. Thereafter, the talar prosthesis (102) and the tibial prosthesis (104) can be positioned on the prepared surface (620) of the talus (420) and the prepared surface (1420) of the tibia (1320), respectively. The resulting configuration is illustrated and described in connection with FIG. 16 .

FIG. 16 is a cross-sectional view illustrating a talus (420) and a tibia (1320), wherein a talus prosthesis (102) is secured to a prepared surface (620) of the talus (420) and a tibial prosthesis (104) is attached to a prepared surface (1420) of the tibia (1320). The talus articular surface (110) can be articulated with the tibial articular surface (120) in a manner that generally mimics the articulation of a natural ankle joint. The varying curvatures of the prepared surface (620) and the prepared surface (1420), along with the matching curvatures of the talus bone engagement surface (112) and the tibial bone engagement surface (122), can help maintain the talus prosthesis (102) and the tibial prosthesis (104) in place while preserving sufficiently healthy bone to withstand stresses encountered during joint use.

In one embodiment (not shown), a surgical navigation and/or surgical robotic system may be used to facilitate preparation of the talus (420) and/or the tibia (1320). Some of the steps presented above may be automated. A surgical navigation system, a surface mapping system, and the like may be used to determine the location and dimensions of the cut to be performed. The path of travel for cutting the talus (420) and the tibia (1320) may be mechanized, for example, using a motorized system in addition to or instead of elements of the talus guide assembly and/or the tibial guide assembly. Such a motorized system may optionally mimic the travel constraints of the talus guide assembly and/or the tibial guide assembly, thereby allowing access to and preparation of the articular surfaces from an anterior approach as disclosed herein.

In alternative embodiments, the ankle arthroplasty system may include many different features. In exemplary embodiments, one or more of the following features may be included: (1) the ability to slide the tibial foundation to allow for a closer (i.e., deeper) cut into the tibia; (2) the tibial foundation to swing along an arc to enhance anterior/posterior dissection of the tibia; (3) the ability of the tibial cutting guide to adjust the varus/valgus and/or medial/lateral position in which it cuts the tibia; (4) the use of a screw set to facilitate attachment of the tibial cutting guide to the tibia; (5) the use of a talus specimen to facilitate proper positioning of the tibial resection; and (6) the use of a patient-specific bone attachment interface to the talus and/or tibia. These features will be illustrated and described with respect to FIGS. 17A-26B .

FIG. 17a is a perspective view of a talus (420), showing a portion of the specimen (400) illustrated in FIGS. 4a-4c with a talus foundation (1710) according to an alternative embodiment positioned on a concave curvature (458) of the talus (420). The specimen (400) can be used to position the talus foundation (1710) relative to the talus (420) in much the same manner as described with respect to FIGS. 4a-4c.

FIG. 17b is a perspective view of the talus foundation (1710) illustrated in FIG. 17a, showing the talus foundation (1710) fixed to the talus (420). The talus foundation (1710) may include a similar configuration to the talus foundation (410). However, the talus foundation (1710) may include a fixed member (1700) and a movable member (1702) that are configured somewhat differently from the corresponding configurations of the talus foundation (410).

Specifically, the anchoring member (1700) can be secured to the talus (420) using a pin (480) passing through a passage (510) of the anchoring member (1700). Additionally, the anchoring member (1700) can include an arcuate slot (1712) centered about the axis (514). However, the arcuate slot (1712) may not include the arcuate groove (516) of the arcuate slot (512) of FIG. 5C. Additionally, the latch (518) may be absent from the anchoring member (1700). Instead, the anchoring member (1700) can include a clasp (1718) in the form of a circular groove positioned centered in each of the arcuate slots (1712). The latch (1718) can be used for securing. For example, when the tibial foundation is positioned relative to the talus foundation (1710), the clasp (1718) can be used to secure the position of the movable member (1702) relative to the fixed member (1700) at the center point of the arched slot (1712). A circular fastener (not shown) can be coupled to the movable member (1702) and positioned within the clasp (1718) to secure the movable member (1702) in place relative to the fixed member (1700).

The movable member (1702) may include a roller (530) that rolls within an arcuate slot (1712) to allow the movable member (1702) to pivot about an axis (514). Instead of the threaded holes (550) of the movable member (502), the movable member (502) may include two receiving slots (1750) extending and opening at their proximal ends to receive corresponding features of a talus burr holder, as will be illustrated and described with respect to FIGS. 18A and 18B. The movable member (1702) may further include a threaded hole (1760) to receive a fastener of the talus burr holder.

Referring to FIGS. 18a, 18b and 19, the talus foundation (1710) of FIGS. 17a and 17b is illustrated in perspective, side and cross-sectional views, wherein a talus burr holder (1800) is illustrated fixed to a movable member (1702) of the talus foundation 1710. The talus burr holder (1800) may include a similar configuration to the talus burr holder (600) of FIGS. 6a and 6b, but differs in that the talus burr holder (1800) may be configured to be attached to the movable member (1702) rather than the movable member (502) of FIGS. 5a to 5c.

Specifically, the talus burr holder (1800) can include a base (1830) secured to the movable member (1702). The base (1830) can include a pair of flanges (1840) at the central and lateral edges that slide into receiving slots (1750) of the movable member (1702). The base (1830) can include a hole (1850) that aligns with a threaded hole (1760) of the movable member (1702). To secure the base (1830) to the movable member (1702), the hole (1850) can receive a bolt (1860) having a threaded end that engages a thread of the threaded hole (1760). The hole (1850) may be extended vertically to allow proximal/distal adjustment of the position of the base (1830) relative to the moving member (1702), thereby allowing the surgeon to adjust the depth of cut of the talus (420).

The talus foundation (1710) and the talus burr holder (1800) can cooperate to function in a similar manner to the talus foundation (410) and the talus burr holder (600) described above. The talus burr holder (1800) can include an arm (640) that moves relative to the base (1830) with a constraint provided by the connection between the arm (640) and the base (1830). The arm (640) can be coupled to the burr (610) (or any other type of burr described above) to guide movement of the burr (610) to cut the talus (420) by forming a prepared surface (620).

With the talus foundation (1710) in place, the tibial cutting guide can be referenced to the talus foundation (1710) and then secured to the tibia. An alignment block may be used for this purpose, as illustrated and described with respect to FIGS. 20A through 22C.

Referring to FIGS. 20A through 20E, an alignment block (2010) according to an alternative embodiment is illustrated. The alignment block (2010) may be functionally similar to the alignment block (1310), and may include some modifications for additional functionality.

As illustrated, the alignment block (2010) may include a fixation piece (2020), an adjustment arm (2022), and an alignment rod (2024). The fixation piece (2020) may be fixed to the movable member (1702) of the talus foundation (1710) in a manner that allows for central/lateral adjustment of the alignment block's (2010) position relative to the movable member (1702). The adjustment arm (2062) may be coupled to the fixation piece (2020) in a manner that allows for varus/valgus adjustment of the orientation of the adjustment arm (2022) relative to the fixation piece (2020). Additionally, the adjustment arm (2062) may be coupled to the tibial cutting guide in a manner that allows for distal/proximal adjustment of the position of the tibial cutting guide (illustrated in subsequent drawings) relative to the adjustment arm (2022).

More specifically, the fixed piece (2020) may include two attachment slots (2030) that receive fixed screws (2032). The fixed screws (2032) may include threaded ends that engage threads within the threaded holes (1760) of the movable member (1702). The attachment slots (2030) may be sufficiently long to allow for horizontal adjustment of the position of the fixed piece (2020) relative to the movable member (1702). If desired, the fixed piece (2020) may be secured in position relative to the movable member (1702) by tightening the screws (2032), and then adjusted by loosening the screws (2032), moving the fixed piece (2020), and then tightening the fixed screws (2032) onto the fixed piece (2020) in the new position.

Additionally, the fixed piece (2020) may include a protrusion (2034) protruding from the body of the fixed piece (2020) toward the adjusting arm (2022). The protrusion (2034) may include a screw hole (2036). Additionally, the fixed piece (2020) may include a screw hole (2038) positioned above the protrusion (2034) along with the screw hole (2036). Additionally, the fixed piece (2020) may include a mantle (2040) positioned above the attachment slot (2030).

The adjustment arm (2022) may include a hole (2050) in its lower portion through which the bolt (2052) may be inserted and tightened to engage the threaded hole (2036) in the projection (2034) of the fixed piece (2020). The bolt (2052) may be rotatably positioned in the hole such that the adjustment arm (2022) may pivot about the axis of the bolt (2052) until the adjustment arm (2022) is secured in place relative to the fixed piece (2020). The bolt (2052) may be selectively tightened to pressurize the adjustment arm (2022) against the fixed piece (2020), thereby locking further rotation of the adjustment arm (2022) relative to the fixed piece (2020).

Additionally, the adjustment arm (2022) may include an adjustment slot (2054) positioned over the hole (2050) having an elongated arched shape centered about the center of the hole (2050). The adjustment slot (2054) may receive a bolt (2056) threaded to engage the hole (2038) of the fixed piece (2020). The bolt (2056) may be relatively loose within the adjustment slot (2054) such that the engagement of the adjustment slot (2054) and the bolt (2056) allows the adjustment arm (2022) to rotate relative to the fixed piece (2020), but the proximity of the ends of the bolt (2056) and the adjustment slot (2054) limits the range of rotation of the adjustment arm (2022) relative to the fixed piece (2020). This relative rotation between the adjusting arm (2022) and the fixation piece (2020) may allow for adjustment of the mediolateral position of the incision surface of the tibia upon which the tibial prosthesis (104) is to be placed. The bolt (2056) may be selectively tightened to press against the adjusting arm (2022), thereby locking further rotation of the adjusting arm (2062) relative to the fixation piece (2020).

Additionally, the adjustment arm (2022) may include a tibial foundation attachment hole (2058) into which a tibial foundation attachment bolt (2060) may be inserted, such that a threaded end of the tibial foundation attachment bolt (2060) engages a corresponding threaded hole on the tibial foundation (as illustrated later). As with the tibial foundation (1300) of FIGS. 13A and 13B , the threaded hole may optionally be on a vertically movable member, wherein the hole (1342) is formed in the button (1340) and slides vertically within the slot (1350). Thus, the tibial foundation attachment hole (2058) and the tibial foundation attachment bolt (2060) allow for coupling the adjustment arm (2022) to the tibial foundation in a manner that allows for adjustment of the vertical position (i.e., proximal/distal position) of the tibial foundation on the tibia, thereby allowing for adjustment of the proximal/distal depth at which the tibia is cut.

The tibial foundation attachment bolt (2060) can be selectively tightened to press against the adjustment arm (2022) to lock further rotation of the adjustment arm (2222) relative to the fixation piece (2020) and/or lock proximal/distal movement of the tibial cutting guide relative to the adjustment arm (2222). In one embodiment, tightening the tibial foundation attachment bolt (2060) can lock further rotation of the adjustment arm (2022) relative to the fixation piece (2020) and further proximal/distal sliding movement of the tibial foundation relative to the adjustment arm (2022). Thus, the tibial foundation attachment bolt (2060) can be selectively tightened to secure the position of the tibial foundation relative to the fixation piece (2020). As described above, the central/lateral position for the movable member (1702) can be fixed via the fixing screw (2032).

The adjustment arm (2022) may further include a rod opening (2062) for receiving an alignment rod (2024). More specifically, the alignment rod (2024) may include a proximal end (2070) and a distal end (2072). The distal end (2072) may be received within the rod opening (2062) to secure the alignment rod (2024) in place relative to the adjustment arm (2022). The alignment rod (2024) may then be used to assist in adjusting the position and/or orientation of the adjustment arm (2022) relative to the moveable member (1702). In one embodiment, the distal end (2072) of the alignment rod (2024) can be aligned with the knee, tibial tuberosity or other anatomical feature to ensure that the adjustment arm (2022) is properly positioned in the mediolateral/lateral direction and properly oriented for varus/valgus adjustment. Optionally, the alignment rod (2024) can be used to facilitate proper anterior/posterior positioning of the tibial foundation relative to the talar foundation (1710), as described below.

FIGS. 21A, 21B, 22A, 22B and 22C are perspective, side, front, perspective and cross-sectional views, respectively, of a tibial foundation (1710) attached to a tibia (420), wherein the tibial foundation (2110) is positioned relative to the tibia (1320) using an alignment block (2010) and a tibial specimen (2120). FIG. 21A illustrates the tibial foundation (2110) secured to the tibia (1320), and FIG. 22B illustrates the isolated tibial specimen (2120). As in the previous embodiments, a “tibial cutting guide” attachable to the tibia (1320) may include a tibial foundation (2110) and a tibial burr holder (illustrated below) attachable to the tibial foundation (2110).

The tibial foundation (2110) may include a structure similar to the talus foundation (1710). Accordingly, the tibial foundation (2110) may include a fixed member (2100) and a movable member (2102). The fixed member (2100) may include two arched slots (1712) similar to the arched slots (1712) of the fixed member (1700) of the talus foundation (1710). The movable member (2102) may include two side walls (2150), and the rollers (530) extend in a mediolateral direction from the side walls (2150) so as to be positioned within the arched slots (1712) of the fixed member (2100). Accordingly, the movable member (2102) may rotate about an axis (2114) relative to the fixed member (2100).

Additionally, the moving member (2102) of the tibial foundation (2110) may include a button (1340) and a slot (1350), which may be similar in configuration to the tibial foundation (1300) of FIGS. 13A and 13B. Thus, the button (1340) and the slot (1350) may provide proximal/distal adjustment of the position of the tibial foundation (2110) relative to the adjustment arm (2022) of the alignment block (2010). As most clearly illustrated in FIG. 22C, the button (1340) may receive a threaded end of a tibial foundation attachment bolt (2060) that secures the adjustment arm (2022) to the moving member (2102) of the tibial foundation (2110).

First, the alignment block (2010) can be secured to the movable member (1702) of the talus foundation (1710) by inserting the threaded end of the set screw (2032) into the screw hole (1760) of the movable member (1702) of the talus foundation (1710) with the shanks of the set screw (2032) within the attachment slots (2030) of the fixed piece (2020), and then tightening the set screw (2032) into the fixed piece (2020) in a desired central-lateral direction relative to the movable member (1702). If desired, the set screw (2032) can be loosened and the central-lateral position of the fixed piece (2020) can be adjusted relative to the movable member (1702). Thereafter, the set screw (3232) can be retightened to secure the set piece (2020) to the movable member (1702). If desired, the alignment rod (2024) of the alignment block (2010) can be aligned with an anatomical feature, such as the tibial tuberosity, to facilitate central-lateral positioning.

Next, the adjustment arm (2022) can be pivotally coupled to the fixation piece (2020). This can be accomplished by inserting a threaded end of a bolt (2052) through a hole (2050) in the adjustment arm (2022) and tightening the threaded end into a hole (2036) in a projection (2034) of the fixation piece (2020). As described above, a slight gap can be left between the shank of the bolt (2052) and the hole (2050) to allow the adjustment arm (2022) to rotate relative to the fixation piece (2020) to allow for varus/valgus adjustment of the orientation of the tibial prepared surface relative to the talar prepared surface.

Next, the threaded end of the bolt (2056) can be inserted into the hole (2038) of the fixed piece (2020) through the adjustment slot (2054) and tightened in the hole (2038). Also, as described above, sufficient clearance is maintained between the shank of the bolt (2056) and the wall of the adjustment slot (2054) to allow the shank of the bolt (2056) to slide along the arched passage between the ends of the adjustment slot (2054). This interaction can limit the pivotal range of movement of the adjustment arm (2022) relative to the fixed piece (2020), which limits the varus/valgus adjustment between the fixed piece (2020) and the adjustment arm (2022) to an allowable predetermined range. To facilitate such varus/valgus positioning, if desired, the alignment rod (2024) of the alignment block (2010) may be aligned with an anatomical feature such as the tibial tuberosity.

Next, the tibial foundation (2110) may be secured to the adjusting arm (2022). As described above, this may be accomplished by inserting a threaded end of a tibial foundation attachment bolt (2060) through a hole (2050) of the adjusting arm (2022), and then tightening the threaded end of the tibial foundation attachment bolt (2060) to engage the hole (1342) of the tibial foundation (2110) moving member (2102) button (1340). Until the head of the tibial foundation attachment bolt (2060) is tightened against the adjustment arm (2022), the button (1340) can slide proximally/distally within the slot (1350), thereby allowing proximal/distal adjustment of the tibial foundation (2110) position relative to the alignment block (2010) and the talus foundation (1710). This proximal/distal adjustment allows the surgeon to adjust the depth of cut of the tibia (1320). The tibial foundation attachment bolt (2060) can be tightened such that the head of the tibial foundation attachment bolt (2060) is tightly adjacent the adjustment arm (2242) to lock further movement of the button (1340) within the slot (1350), thereby preventing further proximal/distal adjustment.

Through the use of a tibial specimen (2120), additional adjustment of the anterior/posterior position of the tibial foundation (2110) relative to the talus foundation (1710) may be facilitated. As most clearly illustrated in FIGS. 22B and 22C, the tibial specimen (2120) may include a simulated talus bearing member (2200) and a tibial adjustment member (2202).

As described above, prior to attaching the alignment block (2010) and the tibial foundation (2110) to the talus foundation (1710), the simulated talus bearing member (2200) can be formed to rest on the prepared surface (620) of the talus (420). Thus, the simulated talus bearing member (2200) can include a bone attachment surface (2210) having the same shape as the talus bone engagement surface (112) of the talus prosthesis (102). Additionally, the simulated talus bearing member (2200) can include anterior/posterior grooves (2220) that generally follow the shape of the talus articular surface (110) of the talus prosthesis (102).

The tibial adjustment member (2202) can include a curved bearing portion (2230) and a front tongue (2240). The curved bearing portion (2230) can include an arcuate shape having a radius of curvature that matches the radius of curvature of the front/back groove (2220) of the simulated tibial bearing member (2200). Accordingly, the curved bearing portion (2230) can be slidable in the front and back directions within the front/back groove (2220). As most clearly illustrated in FIG. 22C , the front tongue (2240) can protrude forwardly to engage the alignment block (2010). More specifically, the front tongue (2240) can include a rear protrusion (2250) and a front protrusion (2260). As shown in FIG. 22c, the rear protrusion (2250) and the front protrusion (2260) can be spaced apart such that the bottom of the fixing piece (2020) of the alignment block (2010) is positioned between them.

Additionally, the tibial adjustment member (2202) may include a pair of markers (2270) that may be positioned at predetermined anterior and posterior locations on the curved bearing portion (2230). The markers (2270) may be used by the surgeon to visualize the anterior/posterior location of the curved bearing portion (2230) relative to the tibial bearing member (2200). If desired, the markers (2270) may be radio-opaque so as to be readily detected and viewed using surgical imaging, such as fluoroscopy.

As most clearly illustrated in FIG. 22c, in operation, the tibial specimen (2120) can be positioned such that the anterior tongue (2240) engages the fixation piece (2020) between the posterior projection (2250) and the anterior projection (2260). As most clearly illustrated in FIG. 21b, the tibial foundation (2110) can be secured such that the moveable member (2102) can be secured in a neutral position relative to the fixation member (2100). This can be accomplished by moving the moveable member (2102) to the neutral position relative to the fixation member (2100) and then locking the roller (530) of the moveable member (2102) within the center of the arcuate slot (512), for example, through the use of a fastener (not shown) that engages the roller (530) to the latch (1718) of the arcuate slot (512).

Initially, the talus foundation (1710) may be in an anterior position with the roller (530) of the movable member (1702) proximate the bottom of the arcuate slot (512) of the fixed member (1700). This is also most clearly seen in FIG. 21B . From this position, the movable member (1702) is moved anteriorly, causing the alignment block (2010), the tibial adjustment member (2202) of the tibial specimen (2120) (which is coupled to the fixed piece (2020) of the alignment block (2010) as described above), and the tibial foundation (2110) (which is not yet coupled to the tibia (1320)) to rotate anteriorly. If the marker (2270) indicates that the curved bearing portion (2230) is in a generally neutral position (i.e., centered in the anterior/posterior direction within the anterior/posterior groove (2220)) with respect to the anterior/posterior groove (2220) of the tibial bearing member (2200), then the tibial foundation (2110) can be considered to be in an appropriate anterior/posterior position with respect to the tibial foundation (1710).

As described above, when the tibial foundation (2110) is properly positioned in the medio-lateral, proximal/distal, and anterior/posterior directions within the varus/valgus foot, the tibial foundation (2110) can be secured to the tibia (1320). The securing member (2100) can include a passageway (510) that receives a pin (480), such as a pin (480) that attaches the talus foundation (1710) to the talus (420).

To ensure that the process of securing the tibial foundation (2110) to the tibia (1320) with the pin (480) does not cause movement of the position of the tibial foundation (2110), a standoff screw (2180) may be used. The standoff screw (2180) may include a threaded shank inserted through a threaded hole in the fixation member (2100) of the tibial foundation (2110) and a blunt end (not shown) adjacent the tibia (1320). Prior to securing the tibial foundation (2110) to the tibia (1320) with the pin (480), the standoff screw (2180) may be inserted through a corresponding hole in the fixation member (2100) and advanced until the blunt end engages the tibia (1320) without significantly penetrating the tibia (1320). Thus, the standoff screw (2180) can prevent the fixation member (2100) from moving closer to the tibia (1320) when the pin (480) is driven into the bone. In connection with at least one talus member, such as the talus foundation (1710), a similar standoff screw (not shown) can optionally be used.

Once the tibial foundation (2110) is secured to the tibia (1320), the alignment block (2010) and the talus foundation (1710) can be removed separately from each other, from the tibial foundation (2110), and from the talus (420) to create space for a tibial incision. This can be accomplished by using a tibial burr holder (2300) which may be similar in function and configuration to the talus burr holder (600) of FIGS. 6A and 6B. The tibial burr holder (2300) is illustrated in more detail in FIG. 23.

FIG. 23 is a perspective view illustrating a tibial burr holder (2300) secured to a tibial foundation (2110) for retaining a burr (860) relative to the tibia (1320). The tibial foundation (2110) and the tibial burr holder (2300) may be joined to form a tibial guide assembly that guides movement of the burr (860) relative to the tibia (1320) to form a prepared surface on the tibia (1320) configured to receive a prosthesis, such as the tibial prosthesis (104) of FIGS. 1A-2E.

Specifically, the tibial burr holder (2300) may be secured to the movable member (2102) of the tibial burr (2110) such that the tibial burr holder (2300) is pivotable relative to the fixed member (2100) and the tibia (1320) along with the movable member (2102). Additionally, the tibial burr holder (2300) may allow for additional movement of the burr (860) (e.g., in a medio-lateral and cephalad-caudal direction) to create a desired contour of the prepared surface of the tibia (1320). The use of the burr (860) is merely exemplary; those skilled in the art will recognize that a variety of cutting tools may be used to form the prepared surface on the tibia (1320). Such cutting tools may include rotating and/or translating tools, such as burrs, reamers, reciprocating saws, and the like.

As illustrated, the tibial burr holder (2300) may include a base (2330) secured to a movable member (2102) of a tibial foundation (2110) and an arm (2340) that moves relative to the base (2330). Movement of the arm (2340) relative to the base (2330) may allow the burr (860) to move in a mediolateral-to-medial direction on the tibia (1320), in addition to the anterior-posterior rotation provided by movement of the movable member (2102) relative to the tibia (1320).

The base (2330) may further include an arm coupling feature whereby an arm (2340) is coupled to the base (2330). The base (2330) and the arm (2340) may be movably coupled together via any combination of rotational and/or sliding joints. In one embodiment, the arm coupling feature provides a rotatable coupling between the base (2330) and the arm (2340).

As illustrated in FIG. 23, the arm engagement feature may include a pin (2310) upon which the arm (640) is rotatably mounted. The pin (2310) may include a head and a shank (not shown) having male threads that may engage with corresponding female threads in holes (not shown) in the base (2330). The head may include an interface that allows rotation of the head with a tool, such as a screwdriver, to facilitate assembly of the tibial bur holder (2300). The head may reside within the hole (2318) in the base (2330). A portion of the shank adjacent the head may be flattened to allow the arm (2340) to engage and rotate smoothly. The base (2330) may further include two parallel plates, an anterior plate (2320) and a posterior plate (2322), between which a proximal portion of the arm (2340) may be captured. A hole (2318) in which a head is present may be formed in the front plate (2320), and a hole in which a shank is fixed may be formed in the rear plate (2322). Accordingly, the pin (2310) may be inserted rearwardly through the hole (2318) of the front plate (2320) to be fixed to the hole of the rear plate (2322).

Additionally, the base (2330) may include a base guide feature that assists in guiding the movement of the arm (2340) relative to the base (2330). The base guide feature may cooperate with a corresponding arm guide feature of the arm (2340) to limit the range of movement of the arm (2340), thereby limiting the range of movement of an attached cutting tool, such as a burr (860), a burr (800), or a burr (830), relative to the tibia (1320).

As illustrated in FIG. 23, the base guide feature may include a rectangular recess (2328) having three guide surfaces (2332). The guide surfaces (2332) positioned at the head (and oriented toward the head, or facing downward when viewed in FIG. 23) may serve to limit movement of the cutting tool in the head direction toward the tibia (1320). The guide surfaces (2332) oriented centrally and laterally may limit movement of the cutting tool in the central/lateral directions, as described below.

As with the arm (640) of the talus burr holder (600), the arm (2340) may be divided into a first arm member (2350) and a second arm member (not shown). The second arm member may be encased within the first arm member (2350) such that the second arm member slides within the first arm member (2350) such that the arm (2340) has an effectively adjustable reach relative to the pin (2310). The first arm member (2350) is biased away from the second arm member to urge the arm (2340) toward its maximum length. The resilient member may take the form of a linear spring (not shown) that is generally maintained in a compressed state. The resilient member (not shown) may be used to bias the first arm member (2350) away from the second arm member, thereby urging the arm (2340) toward its maximum length. The elastic member may take the form of a linear spring (not shown) that is maintained in a compressed state.

The arm (2340) can include a base coupling feature through which the arm (2340) is coupled to the base (2330). The base coupling feature can be configured in a variety of ways and can be designed to cooperate with the arm coupling feature of the base (2330). The base coupling feature can optionally include a slot and a cradle, such as the slot (960) and cradle (962) illustrated in FIGS. 9A-9C.

The arm (2340) may further include a tool attachment interface to which a cutting tool may be attached. When the cutting tool is a burr, such as the burr (860), the burr (800), the burr (830), and/or the burr (610), the tool attachment interface may be referred to as a burr attachment interface. The burr attachment interface may be designed to maintain any one of the burr (860), the burr (800), or the burr (830) in a fixed relationship with the first arm member (2350). More precisely, the burr attachment interface may be designed to receive and secure an adapter (730) that is secured to any one of the burr (860), the burr (800), or the burr (830).

As shown in FIGS. 9A-9C, the attachment interface of FIG. 23 may take the form of an attachment cannula (970) having a bore formed to receive a cylindrical distal end of the adapter (730). Additionally, the attachment cannula (970) may include one or more locking features that are capable of selectively locking the adapter (730) in position relative to the attachment cannula (970).

Additionally, the arm (2340) may include an arm guide feature that cooperates with the base guide feature to limit movement of the arm (2340) with respect to the base (2330). The arm guide feature may be any member that can interact with the base guide feature to limit relative movement between the base (2330) and the arm (2340). If the base guide feature includes a guide surface, the arm guide feature may preferably be a follower that can abut and/or be seated upon such guide surface.

Specifically, the base guide feature can be a post (2380) protruding from the first arm member (2350) between the pin (2310) and the attachment cannula (970). The post (2380) can protrude forwardly such that the post (2380) resides in a rectangular recess (2328) of the base (2330). The interaction of the guide surface (2332) of the rectangular recess (2328) and the post (2380) can restrict the movement of the attachment cannula (970) and the cutting tool to a generally rectangular cephalad boundary. In particular, the guide surface (2332) above the rectangular recess (2328) can control the cutting depth by restricting the movement of the cutting tool toward the tibia (1320).

More specifically, the guide surface (2332) on the upper portion of the rectangular recess (2328) can prevent the cutting tool axis (740) of the burr (860), the burr (800), or the burr (830) from moving closer to the tibia (1320) than the planar boundary. Similarly, the guide surface (2332) on the side surface of the rectangular recess (2328) can prevent the cutting tool axis (740) of the burr (860), the burr (800), or the burr (830) from moving more centrally or laterally than the additional planar boundary. Accordingly, the post (2380) of the arm (2340) can cooperate with the rectangular recess (2328) of the base (2330) such that the prepared surface (2320) has a desired depth, width, and overall shape.

Additionally, the action of the linear spring within the arm (2340) can help ensure that the prepared surface of the tibia (1320) has the desired shape. Specifically, the pressure applied by the linear spring can ensure that the cut into the tibia (1320) extends to the desired full depth, thereby ensuring that the prepared surface has the depth and consistency necessary to provide continuous extension of the bone to support the tibial prosthesis (104). Nevertheless, the linear spring can be adjusted to provide a force that can be easily resisted by the surgeon to remove bone with shallower cuts before extending the cutting tool to the maximum depth allowed by the interaction of the post (2380) and the rectangular recess (2328). Thus, a tibial cutting guide including a tibial foundation (2110) and a tibial bur holder (2300) can be used to control the resection of the tibia (1320).

With the tibial bur holder (2300) secured to the tibial foundation (2110), the tibial foundation (2110) can be used to guide the movement of the tibial bur holder (2300) cutting the tibia (1320) to form a prepared surface on the tibia (1320) to receive the tibial prosthesis (104). The movable member (2102) of the tibial foundation (2110) is unlocked from the neutral position as shown in FIG. 21B to allow the movable member (2102), the tibial bur holder (2300), and the bur (860) to pivot anteriorly/posteriorly relative to the fixed member (2100) as the tibia (1320) reams. This anterior/posterior movement may cause the tibial prepared surface to have an anterior/posterior curvature that is longer than the length of the cutting member (880) of the burr (860).

In much the same manner that the talus foundation (1710) or the talus foundation (410) guides the movement of the burr (610), the burr (830), and/or the burr (800), the tibial foundation (2110) can be used to guide the movement of the burr (830), the burr (860), and/or the burr (800). The prepared surface on the tibia (1320) can be formed starting on the posterior aspect or the anterior aspect of the prepared surface. In one embodiment, the burr (830) can first be applied to create a relatively shallow cut in the tibia (1320) that clears a path for the burr (860) and/or the burr (800) to enter the joint space and create a deeper cut that accommodates the shape of the tibial bone engagement surface (122) of the tibial prosthesis (104).

More specifically, as in the talus foundation (1710) and the talus foundation (410), the surgeon can secure the burr (830) beneath the natural joint surface of the tibia (1320) against the force of the linear spring within the arm (2340) until the surgeon is ready to resect the natural joint surface (422), and the post (2380) can be displaced from the guide surface (2332) above the rectangular recess (2328).

Thereafter, the surgeon elevates the burr (830) until the post (2380) seats against the guide surface (2332) on top of the rectangular recess (2328) such that the linear spring compresses the burr (830) to engage the natural articular surface of the tibia (1320). Thereafter, by moving the attachment cannula (970) in the medio-lateral direction, the burr (830) can be moved in the medio-lateral direction (i.e., side to side), which causes the post (2380) to slide along the guide surface (2332) in the medio-lateral direction over the rectangular recess (2328). The post (2380) can abut the guide surface (2332) on the left and right sides of the rectangular recess (2328) to control the medio-lateral range of movement of the burr (830).

When the burr (830) extends beyond the medio-lateral extent of the natural articular surface of the tibia (1320), the movable member (2102) can be rotated anteriorly or posteriorly relative to the fixed member (2100) to translate the burr (830) toward the opposite side of the natural articular surface of the tibia (1320) (i.e., posteriorly or anteriorly). The medio-lateral movement of the burr (830) can be repeated as needed to remove material from the opposite side of the natural articular surface of the tibia (1320). If desired, the medio-lateral movement of the burr (830) can also be performed during the anterior or posterior rotation of the movable member (2102) to remove material from the overall anterior-posterior curvature of the natural articular surface of the tibia (1320).

As described above, the purpose of the burr (830) may be to remove sufficient material to allow the burr (860) and/or the burr (800) to engage the tibia (1320) without obstruction. In particular, in a later cutting step, the burr (860) may be to remove bone from the location where the shaft (710) of the burr (800) is to be positioned. Thus, the burr (830) need not be used to resect the entire natural articular surface of the tibia (1320).

Once the burr (830) extends beyond the medio-lateral extent and anterior-posterior extent of the natural articular surface of the tibia (1320), the burr (830) may be removed from the attachment cannula (970) and instead a burr (860) may be secured to the attachment cannula (970). The burr (860) may be positioned over the anterior or posterior portion of the natural articular surface of the tibia (1320). The surgeon may hold the burr (860) beneath the partially resected natural articular surface of the tibia (1320) against the force of the linear spring within the arm (2340). Again, the post (2380) may be displaced from the guide surface (2332) over the rectangular recess (2328) until the surgeon is ready to incise the natural articular surface of the tibia (1320) with the burr (860).

Thereafter, the surgeon elevates the burr (860) until the post (2380) is positioned against the guide surface (2332) above the rectangular recess (2328), such that the linear spring within the arm (2340) compresses the burr (860) to engage the natural articular surface of the tibia (1320). Then, by moving the attachment cannula (970) mediolaterally, the burr (860) can be moved mediolaterally (i.e., side to side), causing the post (2380) to once again slide mediolaterally along the guide surface (2332) above the rectangular recess (2328). The post (2380) can be adjacent the guide surface (2332) on the left and right sides of the rectangular recess (2328) to control the range of mediolateral movement of the burr (860).

When the burr (860) extends beyond the mediolateral extent of the natural articular surface of the tibia (1320), the moving member (2102) can be rotated anteriorly or posteriorly relative to the fixed member (2100) to move the burr (860) toward the anterior or posterior portion of the natural articular surface of the tibia (1320). The burr (860) can be translated mediolaterally/laterally during this anterior-posterior movement to ensure that the prepared surface of the tibia (1320) is fully formed.

As with the prepared surface (620) of the talus (420), it may be desirable to form a slot in the prepared surface of the tibia (1320) so that the prepared surface can securely receive the keel (312) of the tibial prosthesis (104). The formation of the slot is optional; in one embodiment, the ankle prosthesis may have no keel, or may include a keel having a built-in cutting member that forms the slot in response to pressure of the keel against the bone. Additionally, in one embodiment, the slot may be formed prior to forming the remainder of the prepared surface of the tibia (1320). Thus, for example, the burr (800) may be used to form the slot prior to using the burr (860), and may also be used to form the slot prior to using the burr (830) to form the prepared surface of the tibia (1320).

After completion of the previous bone removal step (or, optionally, prior to performing the steps as described above), with the tibial bur holder (2300) secured to the movable member (2102) of the tibial foundation (2110), the bur (800) can be attached to the attachment cannula (2370) of the tibial bur holder (2300). The bur (800) can then be positioned beneath the central portion of the prepared surface of the tibia (1320). The surgeon can then hold the bur (800) beneath the prepared surface of the tibia (1320) against the force of a linear spring within the arm (2340). Again, the post (2380) can be displaced from the guide surface (2332) of the bottom of the rectangular recess (2328) until the surgeon is ready to form a slot in the prepared surface of the tibia (1320) with the bur (800).

Thereafter, the surgeon raises the burr (800) while maintaining the burr (800) in a medio-lateral center position until the post (2380) is positioned against the guide surface (2332) above the rectangular recess (2328), such that the linear spring within the arm (2340) urges the burr (800) into engagement with the prepared surface of the tibia (1320). As the cutting member (820) of the burr (800) is lowered into the prepared surface of the tibia (1320), the cutting member (820) can substantially form a slot corresponding to the slot (1200) of FIG. 12 in the center of the prepared surface of the tibia (1320). The diameter (822) of the cutting member (820) can be substantially equal to the width of the keel (312) of the tibial prosthesis (104). The slot may include a cephalad end having a generally hemispherical concave cross-sectional shape that accommodates a semicircular periphery (344) of the penetration portion (342) of the keel (312).

Accordingly, the prepared surface of the tibia (1320) can be formed into a shape suitable for the shape of the tibial bone engagement surface (122) of the tibial prosthesis (104). Once the prepared surface of the tibia (1320) is completely formed, the tibial bur holder (2300) can be separated and removed from the tibial foundation (2110), and the tibial foundation (2110) can be separated and removed from the tibia (1320). The joint space can then be prepared to receive the talus prosthesis (102) and the tibial prosthesis (104).

In one embodiment, the talar prosthesis (102) and the tibial prosthesis (104) may be inserted generally posteriorly such that the keel (212) of the talar prosthesis (102) slides posteriorly into the slot (1200) of the surface (620) of the talus (420) and the keel (312) of the tibial prosthesis (104) slides posteriorly into the corresponding slot of the prepared surface of the tibia (1320). In particular, incidental head/tail translation and/or rotation of the talar prosthesis (102) and/or tibial prosthesis (104) may be applied to fully seat the talar prosthesis (102) and the tibial prosthesis (104) on their respective prepared surfaces. However, it is advantageous to minimize the amount of distraction required in the joint space. Therefore, it is preferable that the insertion vectors of the talus prosthesis (102) and the tibial prosthesis (104) be in the posterior direction.

Additionally, advantageously, there may be no protruding features into the talus (420) or tibia (1320) having surfaces facing anteriorly or posteriorly, which would otherwise require such features to insert into the bone in a cephalad or caudal direction (i.e., proximal or distal). Such insertion vectors require excessive distraction of the joint space and thus may be expanded to accommodate the cephalad or caudal movement required to seat the talar prosthesis (102) or tibial prosthesis (104), which may result in damage to surrounding tissues.

In one embodiment, the guide mechanism may include patient-specific elements that are custom-made to conform to a portion of the patient's anatomy. Such a guide mechanism may be manufactured for the talus and/or tibia. An example of such a guide mechanism will be illustrated and described with respect to FIGS. 24A through 26B.

Figures 24a, 24b, and 24c are plan, bottom, and side views, respectively, of a patient-specific mounting plate (2400) that may be used as part of a patient-specific guide mechanism for a talus according to one embodiment. As illustrated, the patient-specific mounting plate (2400) may include an outer side (2410) facing away from the bone and a bone-facing side (2420).

The patient-specific mounting plate (2400) can include a bone attachment interface in the form of a bone attachment hole (2430) that can be positioned on either side of the patient-specific mounting plate (2400) between the outer side (2410) and the bone-facing side (2420). The bone attachment hole (2430) can receive a screw (illustrated below) that secures the patient-specific mounting plate (2400) to the talus (420). As illustrated, the bone attachment hole (2430) can include a countersink (2460) that receives the head of a bone screw.

Additionally, the patient-specific mounting plate (2400) may include an interface through which the remainder of the fixation member of the talus foundation may be secured to the patient-specific mounting plate (2400). In FIGS. 24A and 24B , this interface comprises a pair of component attachment holes (2440) extending from the exterior side (2410) to the bone-facing side (2420). As described below, the component attachment holes (2440) may accommodate a fastener for attaching the patient-specific mounting plate (2400) to another component. The component attachment holes (2440) may optionally be threaded to accommodate a threaded end of a fastener used to secure another component to the patient-specific mounting plate (2400).

As illustrated in FIG. 24b, the bone-facing side (2420) may include a contoured surface (2470) formed to conform to the contour of a portion of the talus (420) to which the patient-specific mounting plate (2400) is to be attached, which may be a portion of the talus (420) anterior to and/or periphery of the natural joint surface (422). The contoured surface (2470) may be manufactured using any process known in the art. In one embodiment, the contoured surface (2470) may be manufactured by exposing an adjacent portion of the talus (420), taking a mold of the talus, and then creating a model that resembles the adjacent portion of the talus (420). The model may be imprinted into a malleable block that forms the contoured surface.

In an alternative embodiment, CT scan data or other images of the talus (420) can be used to custom-manufacture a patient-specific mounting plate (2400) having a contoured surface (2470). For example, the CT scan data can be used in a milling machine to form the contoured surface (2470) into a block of metal, plastic or other material. Alternatively, the CT scan data can be used in an additional manufacturing process to custom-manufacture a patient-specific mounting plate (2400) having a contoured surface (2470) that precisely matches the shape of a surface adjacent the talus (420).

In either case, the contour surface (2470) is formed to conform to an adjacent portion of the talus (420). Thus, the patient-specific mounting plate (2400) can be securely secured to the talus (420) without ambiguity as to where the patient-specific mounting plate (2400) is to be attached. The process of aligning the patient-specific mounting plate (2400) with the talus (420) can be performed when the contour surface (2470) is planned. If desired, measurements can be made prior to the fabrication of the contour surface (2470) to determine the shape of the contour surface (2470), as well as the precise location and orientation of the contour surface (2470) within the patient-specific mounting plate (2400), which results in the formation of the prepared surface at the appropriate location and orientation on the talus (420).

FIG. 25A is a perspective view of a patient-specific mounting plate (2400) positioned on a talus (420). As shown, the outer side (2410) faces upward and the bone-facing side (2420) faces the talus (420), with a contoured surface (2470) positioned opposite the region of the talus (420) adjacent the natural joint surface (422). The shape of the contoured surface (2470) can be precisely matched to the shape of the talus (420) upon which it is placed, such that the patient-specific mounting plate (2400) can be secured to the talus (420) in only one location and orientation. The patient-specific mounting plate (2400) can be secured to the talus (420) using bone screws (2590).

FIG. 25b is a perspective view of the patient-specific mounting plate (2400) and the talus (420) of FIG. 24a, showing a stationary component (2500) secured to the patient-specific mounting plate (2400) and the stationary member of FIGS. 17a and 17b to form a stationary member having a similar function to the stationary member (500) of FIGS. 5a and 5b. The stationary component (2500) can be secured to the patient-specific mounting plate (2400) using screws (shown later).

The patient-specific mounting plate (2400) and the fixation element (2500) can cooperate with the moveable member to form the talus foundation (2510). As illustrated, the moveable member can be similar or identical to the moveable member (1702) of the talus foundation (1710) of FIGS. 17A and 17B. Once assembled, the talus foundation (2510) of FIG. 25B can be similar in motion to the talus foundation (1710) of FIGS. 17A and 17B and can guide rotation of the burr about the axis (2114).

FIGS. 26A and 26B are plan and side views, respectively, of the talus foundation (2510) illustrated in FIGS. 25A and 25B, wherein the talus bur holder (1800) is secured to a movable member formed by a patient-specific mounting plate (2400) and a fixation element (2500). As illustrated, the patient-specific mounting plate (2400) is secured to the fixation element (2500) using screws (2600). In a manner similar to the talus foundation (1710) to guide the movement of the talus bur holder (1800) such that the bur (610), bur (800), and/or bur (830) incise the natural joint surface (422) to form a prepared surface (620) on the talus (420).

Figures 24a-26b illustrate the use of patient-specific tibial components. Those skilled in the art will recognize how patient-specific tibial components can be formed using the same principles. Such components can be incorporated into a tibial foundation that is functionally similar to the tibial foundation (1300) of Figures 13a-15, or that is functionally similar to the tibial foundation (2110) of Figures 21a-21b.

Those skilled in the art will recognize that the systems and methods described above represent only some of the systems and methods by which ankle arthroplasty may be performed. Alternative methods, cutting tools, guide assemblies, and implants may be used within the scope of the present invention.

Any method disclosed herein comprises at least one step or action for performing the described method. The method steps and/or actions may be interchanged. In other words, unless a particular order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified.

Throughout this specification, references to “an embodiment” or “the embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the phrases or variations thereof recited throughout this specification are not necessarily all referring to the same embodiment.

Similarly, in the description of the embodiments above, it should be understood that, for the purpose of streamlining the invention, various features have sometimes been grouped together in a single embodiment, drawing, or description thereof. However, this disclosure should not be interpreted as reflecting an intention that any claim requires more features than are expressly recited in that claim. Rather, as the following claims reflect, aspects of the invention exist in combinations of fewer than all of the features of any single disclosed embodiment. Accordingly, the claims following this Detailed Description are expressly incorporated into this specification, with each claim standing on its own as a separate embodiment. The invention encompasses all permutations of the independent claims, along with their dependent claims.

The recitation of the term "first" in the claims with respect to a feature or element does not necessarily imply the presence of a second or additional feature or element. It will be apparent to those skilled in the art that changes may be made in the details of the embodiments described herein without departing from the basic principles described herein.

While specific embodiments and applications of the present invention have been illustrated and described, it is to be understood that the scope of the appended claims is not limited to the precise construction and elements disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and system disclosed herein.

Claims (80)

A talar articular surface formed to replace a natural talar articular surface; and
A talar joint prosthesis comprising a talar bone engagement surface formed to mate with a prepared talar surface of the talus;
A tibial articular surface formed to replace the natural tibial articular surface and to articulate with the talar articular surface; and
A tibial joint prosthesis comprising a tibial bone engagement surface formed to mate with a tibial prepared surface of the tibia;
Each of the above talus bone joint surface and the above tibial bone joint surface;
A first anterior-posterior flexion extending in the anterior-posterior direction; and,
comprising a first central-lateral curvature having a convex shape and extending in the central-lateral direction;
The first anterior-posterior curvature of the talar bone articulation surface comprises a concave curvature, the talar bone articulation surface comprises a second mediolateral curvature having a convex shape and extending in a mediolateral direction, and a central extension extending in a straight line along the mediolateral direction between the first mediolateral curvature of the talar bone articulation surface and the second mediolateral curvature of the talar bone articulation surface.
The first anterior-posterior curvature of the tibial bone joining surface comprises a convex curvature, the tibial bone joining surface comprises a second mediolateral curvature having a convex shape and extending in a mediolateral direction, and a central extension extending in a straight line along the mediolateral direction between the first mediolateral curvature of the tibial bone joining surface and the second mediolateral curvature of the tibial bone joining surface.
Arthroplasty system. In claim 1,
An arthroplasty system wherein the first anterior-posterior curvature of the talar bone joining surface and the tibial bone joining surface extends along the entire anterior-posterior length of the talar bone joining surface and the tibial bone joining surface. In claim 1,
At least one of the above talus bone connecting surface and the above tibial bone connecting surface further comprises a keel protruding from the first anterior-posterior curvature and extending along the anterior-posterior direction, the keel comprising:
The base part,
A penetration portion extending from the base portion to penetrate the prepared surface of the talus or the prepared surface of the tibia, and having a semicircular circumference
An arthroplasty system comprising: In claim 1,
The above talar articular surface comprises two convex talar curvatures extending in the mediolateral direction and a concave talar curvature extending in the mediolateral direction between the two convex talar curvatures,
The above tibial articular surface comprises two concave tibial curvatures extending in the mediolateral direction and a convex tibial curvature extending in the mediolateral direction between the two concave tibial curvatures,
An arthroplasty system wherein the talar joint surface and the tibial joint surface are formed such that the two concave tibial curvatures are in the same plane as the two convex talar curvatures when the tibial joint prosthesis is positioned at the center of the talar joint prosthesis. delete delete In claim 1, the talus bone joint surface is:
An arthroplasty system further comprising a keel protruding from the first anterior-posterior curvature of the talus bone joint surface and extending in the anterior-posterior direction. delete delete In claim 1, the tibial bone joint surface is:
An arthroplasty system further comprising a keel protruding from the first anterior-posterior curvature of the tibial bone joint surface and extending in the anterior-posterior direction. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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