GB2633837A

GB2633837A - Orthopaedic implant

Info

Publication number: GB2633837A
Application number: GB2314634.3A
Authority: GB
Inventors: Masure Frederik
Original assignee: Osstec Ltd
Current assignee: Osstec Ltd
Priority date: 2023-09-25
Filing date: 2023-09-25
Publication date: 2025-03-26
Also published as: GB202314634D0

Abstract

An implant component of an orthopaedic implant for arthroplasty. The implant component comprises a bone-interfacing side B having a central portion and a peripheral portion, the peripheral portion at least partially surrounding the central portion. The implant component comprises a second side A, opposite to the bone-interfacing side B, for interfacing with an articulating joint component AJC. The implant component 1 comprises a porous structure 111 providing the central portion of the bone-interfacing side B. The implant component comprises a substantially non-porous peripheral rim 112 extending around a perimeter of the porous structure and providing the peripheral portion of the bone-interfacing side B, the peripheral rim being connected to the porous structure. The peripheral portion of the bone-interfacing side B is divided into at least two portions, wherein a first portion P1 of the at least two portions is thicker, in a direction along the bone-interfacing side B, than a second portion P2 of the at least two portions.

Description

ORTHOPAEDIC IM PLANT

This invention relates generally, but not exclusively, to an implant component for an orthopaedic implant.

Components of conventional orthopaedic implants, such as components used in knee and shoulder implants, are often cast as a solid, single, metal component. In these implants, the elastic modulus of the implant is significantly greater than that of the bone, which can lead to stress shielding, which may cause bone loss and implant loosening. In other words, stress installed in the bone surrounding the implant is less than that which native bone would see, which leads to suboptimal behaviour of the bone.

This problem may be overcome by providing a porous structure for bone-interfacing surfaces. Because the elastic modulus of the porous surface is less than that of a solid is implant surface, more stress may be transferred to the bone adjacent the porous structure, and thereby reduce stress shielding effects. In other words more strain can be installed in the bone surrounding the implant, and it is broadly understood that: * strain rates of less than approximately 50 microstrain in bone material results in a reduction in bone mass; * strain between around 50 microstrain and 2000 microstrain results in bone remodelling; * strain between around 2000 microstrain and 3000 microstrain results in bone modelling; and * strain of around 4000 microstrain results in bone repair.

Under loading conditions of 0.5 to 2 times the bodyweight of the patient, loads representative of most activities of daily living, such as walking, standing, getting up and sitting down, a conventional, solid, implant will undergo negligible strain, which also results in negligible strain in the surrounding bone. This results in bone loss, or resorption, and implant loosening over time as the levels of strain installed into the bone are considerably below those required to achieve bone remodelling or modelling. This also leads to premature aging, for example cracking, of the bone material in the vicinity of the implant. Therefore, including porous bone-interfacing surfaces has advantages in that bone remodelling or bone modelling may be achieved, creating better fixation of the implant.

Furthermore, the porous structure may be designed with an elastic modulus which better matches that of surrounding bone material, and so may also allow for bone ingrowth into the implant, thereby improving implant fixation.

However, whilst such porous structures have advantages over solid implants, they are often provided with variation in the elastic modulus of the bone-interfacing surface. This can lead to uneven loading in the surrounding bone. In fact, in regions of higher elastic modulus, excessively high strains may be installed in the bone which, in some cases, might negate the benefit of the porous structure completely. For example, this can create strain distributions in the bone which do not produce the aforementioned advantages desired io when using porous implants. This may be especially pronounced in implants which have relatively large, planar, bone-interfacing surfaces, such as tibial trays, patellar implants and scapula or humeral implants.

It would therefore be advantageous to address at least some of these limitations.

According to an aspect of the invention there is provided an implant component for, e.g., use in, an orthopaedic implant for arthroplasty, e.g., joint replacement, the implant component comprising: a bone-interfacing side, e.g., configured to interface with bone material of a patient, the bone-interfacing side having a central portion and a peripheral portion, the peripheral portion at least partially surrounding the central portion; a porous structure providing the central portion of the bone-interfacing side; and a substantially non-porous peripheral rim extending around a perimeter of the porous structure and providing the peripheral portion of the bone-interfacing side, the peripheral rim being connected to the porous structure.

The implant component may comprise a second side, opposite to the bone-interfacing side, for interfacing with another component, for example an articulating joint component.

The peripheral portion of the bone-interfacing side may have a thickness, extending away from the central portion at any position around a perimeter of the central portion, which varies with position around the perimeter of the central portion.

The peripheral rim may have a thickness, extending away from the central portion at any position around a perimeter of the central portion, which varies with position around the perimeter of the central portion s The peripheral portion of the bone-interfacing side may be divided into at least two portions, wherein a first portion of the at least two portions is thicker than a second portion of the at least two portions. It will be appreciated that thickness is in a direction along, or parallel to, the bone-interfacing side.

The peripheral portion of the bone-interfacing side may be divided into at least two portions, wherein a first portion of the at least two portions has a greater thickness than a second portion of the at least two portions, the thickness extending away from the central portion at any position around a perimeter of the central portion.

is The peripheral rim may be divided into at least two portions, wherein a first portion of the at least two portions has a greater thickness than a second portion of the at least two portions, the thickness extending away from the central portion at any position around a perimeter of the central portion.

According to a further aspect of the invention there is provided an implant component for, e.g., for use in, an orthopaedic implant for arthroplasty, e.g., joint replacement, the implant component comprising: a bone-interfacing side, e.g., configured to interface with bone material of a patient, the bone-interfacing side having a central portion and a peripheral portion, the peripheral portion at least partially surrounding the central portion; a second side, opposite to the bone-interfacing side, for interfacing with an articulating joint component a porous structure providing the central portion of the bone-interfacing side; and a substantially non-porous peripheral rim extending around a perimeter of the porous structure and providing the peripheral portion of the bone-interfacing side, the peripheral rim being connected to the porous structure; wherein the peripheral portion of the bone-interfacing side is divided into at least two portions, wherein a first portion of the at least two portions is thicker, in a direction along the bone-interfacing side, than a second portion of the at least two portions.

It will be appreciated that thickness may be otherwise defined as being parallel to the bone-interfacing side. In other words, the peripheral portion of the bone-interfacing portion may be divided into at least two portions, wherein a first portion of the at least two portions has a greater thickness, in a direction extending away from the central portion at any position around a perimeter of the central portion, than a second portion of the at least two portions.

Because the peripheral rim is stiffer than the porous structure of the central portion, the majority of the force applied to the tibia through the tibial component is imparted by the peripheral rim because the porous structure is not sufficiently stiff to transmit as much force.

Therefore, increasing the thickness of the bone-interfacing side may reduce the stress installed in the bone by the peripheral rim, because the force is applied over a greater area. Accordingly, bone deformation in this region may be reduced, which may reduce subsidence of the implant component. By reducing the stress in the bone imparted by the first portion of the peripheral rim, and so reducing deformation of the bone in this region, is more stress may thus be transmitted through the porous structure to the bone material in contact with the porous structure, thereby producing strains in this bone material which better resemble strain observed in healthy, native bone material. This strain installed in the bone adjacent the porous structure may also better match strain in the porous structure, and so promote bone ingrowth into the porous structure, which may also increase the longevity of the implant. The implant component may also be advantageous in that the rim has increased strength at the first portion, for example to offer improved fatigue strength.

The second side of the plate portion may comprise a central portion and a peripheral portion. The peripheral rim may provide the peripheral portion of the second side. The porous structure may provide the central portion of the second side. A solid layer may provide some or all of the central portion of the second side. The solid layer may be disposed on the porous structure.

The peripheral rim may be divided into at least two portions. A first portion of the peripheral rim may correspond to, or provide, the first portion of the peripheral portion of the bone-interfacing side. A second portion of the peripheral rim may correspond to, or provide, the second portion of the peripheral portion of the bone-interfacing side. The first portion of the peripheral rim may have a greater thickness than the second portion of the peripheral rim.

Any or each portion of the at least two portions of the peripheral portion of the bone-interfacing side, or of the at least two portions of the peripheral rim, may have a length, along the perimeter of the central portion, which is at least 5%, or at least 10%, 20%, 25%, 30%, 35%, 40% or 45% of a length of the perimeter of the central portion. That is, the first s portion of the peripheral portion of the bone-interfacing side, or of the peripheral rim, may have a length, along the perimeter of the central portion, which is at least 5%, or at least 10%, 20%, 25%, 30%, 35%, 40% or 45% of a length of the perimeter of the central portion. The second portion of the peripheral portion of the bone-interfacing side, or of the peripheral rim, may have a length, along the perimeter of the central portion, which is at least 5%, or at least 10, 20%, 25%, 30%, 35%, 40% or 45% of a length of the perimeter of the central portion. A third portion of the peripheral portion of the bone-interfacing side, or of the peripheral rim, may have a length, along the perimeter of the central portion, which is at least 5%, or at least 10%, 20%, 25%, 30%, 35%, 40% or 45% of a length of the perimeter of the central portion. The first portion may be located between the second and third is portions.

Any or each portion of the at least two portions of the peripheral portion of the bone-interfacing side, or of the at least two portions of the peripheral rim, may have a substantially constant, or uniform, thickness. The first portion of the peripheral portion of the bone-interfacing side, or of the peripheral rim, may be located between the second portion and a third portion of the at least two portions of the peripheral portion of the bone-interfacing side, or of the at least two portions of the peripheral rim. The first portion may have a greater thickness than the third portion. The thickness of the second portion and the third portion may be the same. An inner edge of each of the first, second and third portion, which is connected to the central portion, may be shaped to follow a corresponding outer shape of the peripheral portion.

The peripheral portion of the bone-interfacing side, or the peripheral rim, may comprise a first intermediate portion between, and adjacent, e.g., and connected to, both of, the first and second portions. The peripheral portion of the bone-interfacing side, or the peripheral rim, may comprise a second intermediate portion between, and adjacent, e.g., and connected to, both of, the second and third portions. The thickness of the first intermediate portion may vary with position between the first and second portions. The thickness of the second intermediate portion may vary with position between the second and third portions.

This may be advantageous in that the intermediate portions can provide gradual transitions and so reduce magnitudes of stress concentration installed in the bone beneath these intermediate portions.

At least a part of the thickness of the first intermediate portion may vary linearly with position s between the first and second portions. At least a part of the thickness of the second intermediate portion may vary linearly with position between the second and third portions. Intersections, or joining portions, between the first intermediate portion and each of the first and second portions may be rounded, for example filleted. Intersections, or joining portions, between the second intermediate portion and each of the second and third portions may be rounded, for example filleted. Advantageously, this may reduce the magnitudes of stress concentrations installed in the bone beneath these regions, as well as magnitudes of stress concentrations in the implant component.

The peripheral rim may extend around the entirety of the central portion. The peripheral rim is may have a height in a direction away from the bone-interfacing side, the height varying with position around the perimeter of the of the central portion. It will be appreciated that height is in a direction perpendicular to the bone-interfacing side.

The implant component may comprise a bone-insertion feature configured to be inserted into a corresponding slot or a cavity in a bone of a patient, for example for fixation, and/or alignment, of the implant component with the bone. The bone-insertion feature may extend from an insertion feature portion of the peripheral rim in a direction away from the bone-interfacing side. Advantageously, the implant component may be stronger because the bone insertion feature extends from the peripheral rim, instead of from the porous structure.

The thickness of the insertion feature portion of the peripheral rim may be greater than a thickness, in the same direction as the thickness of the insertion feature portion, of the bone-insertion feature. The thickness of the insertion feature portion of the peripheral rim may be greater than the thickness of the second and/or third portions of the peripheral rim. The thickness of the insertion feature portion of the peripheral rim may be less than the thickness of the first portion of the peripheral rim.

The peripheral rim may have a height in a direction away from the bone-interfacing side. The height may be greater at a location of an edge, or end, of the bone-insertion feature than away from the edge, or end, of the bone insertion feature. The height may be greater at respective locations of multiple edges, or ends, of the bone-insertion feature than away from the edges, or ends, of the bone-insertion feature. The height may be greater at a location corresponding to the first portion of the peripheral portion of the bone-interfacing side, or may be greater at the first portion of the peripheral rim, than at the second and/or third portions. Advantageously, the bending stiffness of the first portion may be increased s which may further protect the adjacent bone from high stresses. Advantageously, the increased height of the peripheral rim may better withstand stress concentrations caused by one or more edges of the bone-insertion feature.

The bone insertion feature may comprise an insertion feature central portion provided by a o porous structure, for example a lattice structure. The bone insertion feature may comprise a substantially non-porous insertion feature peripheral rim extending at least partially around a periphery of the insertion feature central portion. This may advantageously provide the ability for bone in-growth into the central portion while providing strength for the bone insertion feature to be inserted into bone, for example with a tight fit. The insertion is feature peripheral rim may also advantageously provide additional stiffness to the peripheral rim. The insertion feature peripheral rim may also advantageously provide a smoother outer surface to the bone insertion feature, to cause less abrasion to adjacent bone material.

In embodiments the implant component is a tibial component, which may otherwise be referred to as a tibial implant component, for an orthopaedic implant for knee arthroplasty, and a plate portion of the tibial component comprises the porous structure and the peripheral rim, an inferior side of the plate portion provides the bone-interfacing side which is configured to interface with a tibia of a patient and a superior side of the plate portion provides the second side, which is configured to interface with an articulating joint component of the knee implant. The plate portion may have a height of between 2 and 5 mm, for example between 2 and 4 mm, between 2 and 3 mm, between 3 and 5 mm or between 4 and 5 mm. In this example, the thickness is in a direction along the inferior side of the plate portion, or along or parallel to a plane of the plate portion. The height, in this example, is also perpendicular to the inferior side of the plate portion, or perpendicular to the plane of the plate portion.

The peripheral rim may comprise: a side portion, which is one of a medial portion or a lateral portion, in use, and which provides the first portion of the at least two portions; an anterior portion which provides the second portion of the at least two portions; and a posterior portion which provides a third portion of the at least two portions; wherein the side portion is located between the anterior portion and the posterior portion, s and wherein a thickness, in a direction parallel to the bone-interfacing side of the plate portion, of the side portion is greater than a thickness of one or each of the anterior portion and the posterior portion.

Advantageously, loads transmitted to the bone from tibial component on the lateral and/or io medial side of the plate portion may be distributed across more bone surface, due to the increased thickness of the side portion. This may reduce the deformation of bone adjacent the side portion, and so allow the tibial component to install more strain in bone material adjacent the porous structure. This may not only better resemble bone strain in healthy joints, but also promote bone in-growth into the porous structure. This, in turn, may reduce is or prevent subsidence of the tibial component. The side portion may also be strengthened by the increased thickness.

The thickness of either or both of the anterior portion and the posterior portion may be less than 11 times the thickness of the side portion, for example less than 10 times, 9 times, 8 times, 7 times, 6 times, 5 times or 4 times the thickness of the side portion. The side portion may have a thickness of between 2 and 15 mm, for example less than 14mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm or 8 mm, and for example more than 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm.

The peripheral rim may comprise a first intermediate portion between, and adjacent, e.g., and connected to, both of the anterior portion and the side portion. The peripheral rim may comprise a second intermediate portion between, and adjacent, e.g., and connected to, both of the posterior portion and the side portion. A thickness of the first intermediate portion may vary with position between the side portion and the anterior portion. A thickness of the second intermediate portion may vary with position between the side portion and the posterior portion. At least a part of the thickness of the first intermediate portion may vary linearly with position between the side portion and the anterior portion. At least a part of the thickness of the second intermediate portion may vary linearly with position between the posterior portion and side portion. Intersections, or joining portions, between the first intermediate portion and each of the anterior portion and the side portion may be rounded, for example filleted. Intersections, or joining portions, between the second intermediate portion and each of the posterior portion and the side portion may be rounded, for example filleted. Advantageously, this may reduce stress concentrations in these regions, both in the tibial component and in adjacent bone material.

The side portion may have a substantially constant, or uniform, thickness. The anterior portion may have a substantially constant, or uniform, thickness. The posterior portion may have a substantially constant thickness.

The peripheral rim may provide one or more securing element for attaching to an articulating joint component to the tibial component.

The tibial component may be for a partial knee implant. The tibial component may comprise a keel extending in an inferior direction, in use, from a keel portion of the peripheral rim.

is The keel portion may be located between the anterior portion and the posterior portion. The keel portion may be on an opposite side of the plate portion to the side portion. The keel may be elongate in shape. The keel may extend in a posterior to anterior direction of the tibial component, in use. Advantageously, the keel may provide greater surface area for contact with the bone, for a more robust orthopaedic implant, and may improve the bending strength of the tibial component. Further advantageously, the keel may provide increased bending strength and stiffness to the plate portion of the tibial component.

The keel portion of the peripheral rim may have a thickness which is greater than one or each of the thickness of the anterior portion and the posterior portion. The keel portion of the peripheral rim may have a thickness which is less than the thickness of the side portion.

The keel portion of the peripheral rim may have a length, along the perimeter of the central portion, which is at least 5%, or at least 10%, 20%, 25%, 30%, 35%, 40% or 45% of a length of the perimeter of the central portion. Advantageously, the keel portion of the peripheral rim may provide a solid base structure for the keel. The keel portion of the peripheral rim may have a thickness which is greater a thickness of the keel.

The keel may comprise a posterior end and an anterior end. The keel portion of the peripheral rim may have a height, in a direction extending away from the keel, which is greater in a location of the posterior end than away from the posterior end of the keel. The keel portion of the peripheral rim may have a height, in a direction extending away from the keel, which is greater in a location of the anterior end than away from the anterior end of the keel. Advantageously, the increased height may act to reduce or withstand stress concentrations caused by an intersection, or joining portion, of the keel and the peripheral rim at the respective end of the keel.

The keel may comprise a porous structure. Advantageously, the keel may allow or promote bone ingrowth into the porous structure. The keel may comprise a substantially non-porous keel peripheral rim extending around, for example around an entirety of, a periphery of the porous structure of the keel. Advantageously, the non-porous peripheral rim may provide o higher bending stiffness, and provide relatively smooth edges to the keel. The non-porous peripheral rim may enable the keel to better withstand impact forces used by the surgeon to insert the keel into the keel slot. The porous structure of the keel may be, or may comprise, a lattice structure. The lattice structure may comprise a plurality of struts connected together at nodes. Each strut may have a direction component in each of 3 is directions, e.g., in each of 3 Cartesian directions.

The keel may have a length with a posterior side at one end of the length. The keel may have a length with an anterior side at one end of the length, e.g., opposite to the posterior side. The keel may be configured to be inserted into a keel slot which extends in a posterior to anterior direction in a tibia of a patient.

The keel may have a trapezoidal shape. The keel may have a trapezoidal shape in that an anterior side of the keel extends away from the plate portion with a posterior direction component and a posterior side of the keel extends away from the plate portion with an anterior direction component. It will be understood that the posterior direction is a posterior direction when the keel is located in the keel slot and the anterior direction is an anterior direction when the keel is located in the keel slot.

Alternatively, the posterior side of the keel may comprise an overhanging portion to define an undercut between the overhanging portion and the plate portion. The undercut may be configured to engage with bone material when the keel is inserted into the keel slot. The overhanging portion of the posterior side of the keel may be substantially straight. The overhanging portion of the posterior side of the keel may extend away from the plate portion with a posterior direction component. It will be understood that the posterior direction is a posterior direction when the keel is located in the keel slot, in use. Advantageously, when a surgeon is performing knee arthroplasty from an anterior side, the overhanging portion of the posterior side of the keel can be located at a posterior end of the keel slot such that bone material is present in, or engages, the undercut between the overhanging portion and the plate portion. This may robustly secure the posterior side of the implant in place. This may enable better and more secure positioning of the tibial tray during total or partial knee arthroplasty. An angle between the bone-interfacing side of the plate portion and the overhanging portion, measured on a posterior of the posterior side, may be between 45 and 90 degrees, for example between 45 and 80 degrees, between 45 and 70 degrees, or between 45 and 60 degrees. The overhanging portion may comprise the furthest point of the posterior side of the keel from the plate portion. The posterior side of the keel may comprise a fillet or chamfer at an intersection, or joining portion, between the plate portion and the overhanging portion of the posterior side of the keel. The undercut may be defined between the furthest point of the posterior side of the keel from the plate portion and the fillet or chamfer. Advantageously, by providing a straight overhanging portion, pushing the is tibial component in the posterior direction, during surgery, may cause the tibial component to also move in an inferior direction to provide a more robust fit of the tibial component into the tibia.

The keel may comprise an or the anterior side at a second end of the keel, the second end being the opposite end to the posterior side in the length direction of the keel. The anterior side of the keel may extend away from the plate portion with a posterior direction component. It will be understood that the posterior direction is the posterior direction when the keel is located in the keel slot, in use. The posterior side of the keel may comprise a contact portion configured to contact bone material when in the keel slot, the contact portion extending in a direction away from the plate portion with a posterior direction component.

In other words, the contact portion of the anterior side of the keel may extend in the posterior direction away from the plate portion. The anterior side of the keel may comprise a fillet or chamfer at an intersection, or joining portion, between the plate portion and the contact portion of the anterior side of the keel. Advantageously, when the surgeon is performing knee arthroplasty from an anterior side, the anterior side, or the contact portion, of the keel can be slid along an anterior bone surface of the keel slot, which may cause the keel to move in a posterior direction to provide more secure engagement between the posterior side of the keel and the posterior side of the keel slot.

The anterior side of the keel, or the contact portion of the anterior side of the keel, may be substantially straight. The anterior side of the keel, or the contact portion of the anterior side of the keel, may extend from the plate portion at an angle, measured on an anterior of the anterior side, of between 90 and 160 degrees on the anterior side of the keel, for example between 100 and 160 degrees, between 110 and 160 degrees, between 120 and 160 degrees or between 130 and 160 degrees. Advantageously, this may allow a greater number of tibial components to be additively manufactured on a platen, as the tibial components can be manufactured with the plate portion substantially vertical and the anterior side of the keel facing downwards, without a requirement that support elements io are used to support the keel. This is advantageous because support elements require removal in a later manufacturing step, and so this may make manufacturing more efficient.

The angle between the overhanging portion of the posterior side of the keel and the bone-interfacing side of the plate portion, measured on a posterior of the posterior side of the is keel, may be greater than the angle between the contact portion of the anterior side of the keel and the bone-interfacing side of the plate portion, measured on a posterior of the anterior side of the keel.

The keel may comprise an inferior side extending between the posterior side and the or an anterior side of the keel. The inferior side may be substantially parallel to the plate portion.

The inferior side may be substantially straight.

In embodiments the keel may comprise one or more reinforcing region. Each of the one or more reinforcing region may divide regions of the porous structure of the keel. That is, the porous structure of the keel may be divided by the reinforcing regions. Each reinforcing region may be substantially non-porous. Each of the one or more reinforcing region may have an elastic modulus which is greater than that of the porous structure. Each of the one or more reinforcing region may be substantially non-porous, or solid. Each of the one or more reinforcing region may extend in any one of the following directions: between the or an inferior side of the keel and the plate portion or a part of the keel peripheral rim which is connected to the plate portion; between the inferior side of the keel and the posterior side of the keel; between the inferior side of the keel and the or an anterior side of the keel; between the posterior side of the keel and the plate portion or a part of the keel peripheral rim which is connected to the plate portion; between the anterior side of the keel and the plate portion or a part of the keel peripheral rim which is connected to the plate portion; between the posterior side of the keel and the anterior side of the keel.

s Advantageously, the one or more reinforcing region may be used to provide additional strength or stiffness to the keel. The size and/or position of each of the reinforcing region may be optimised to provide the required strength or stiffness whilst maintaining a maximum amount of porous structure.

o The keel may have a thickness, or a maximum thickness, in the medial to lateral direction, of between 1 and 5 mm. The keel may become narrower with distance from the plate portion. It will be understood that narrower here means in a medial to lateral direction, in use. Advantageously, this may aid with insertion of the keel into the keel slot.

is The tibial component may comprise one or more peg, or bone-insertion peg, extending from the bone-interfacing side of the plate portion. The tibial component may comprise two pegs extending from the bone-interfacing side of the plate portion. The or each peg may be configured to be received in a respective hole, for example a reamed hole, in the tibia of the patient. The or each peg may extend from the porous structure of the plate portion of the tibial component. The or each peg may extend away from the plate portion in a posterior direction, in use. The or each peg may extend away from the bone-interfacing side of the plate portion with a posterior direction component. The or each peg may comprise a porous, or lattice, structure. The or each peg may comprise a porous, or lattice, structure through an entire thickness, or width, of the peg. The or each peg may comprise a solid peripheral portion extending around the porous, or lattice structure, at a tip of the peg.

The porous structure may be or comprise a lattice structure. The lattice structure may comprise a plurality of struts connected together at nodes. The porous structure of the keel and/or the plate portion may have an elastic modulus, e.g., a bulk elastic modulus, of between 0.1 and 5 GPa. The porous structure of the keel and/or the plate portion may have a porosity of between 5 and 30 %. The lattice structure of the keel and/or the plate portion may have a strut density of between 2 and 7 struts per mm3. Each strut may have a thickness, or diameter, of between 100 and 400 microns.

The component may be a unitary structure. The implant component may be metallic. The implant component may be made from titanium alloy, for example Ti64. The implant component may be manufactured using additive manufacturing, for example laser sintering. The implant component may comprise metal particles which are fused together.

According to a further aspect of the invention, there is provided a method of performing surgical arthroplasty, or a method of performing arthroplasty on a cadaveric specimen, the method comprising: o preparing a bone of a joint for receiving the aforementioned component; and attaching the implant component to the prepared bone such that the bone-interfacing side of the implant component interfaces with bone material.

According to a further aspect of the invention there is provided a method of manufacturing is any one of the aforementioned implant components, the method comprising: providing metal powder; and selectively heating areas of the metal powder to fuse the metal powder together into a unitary metal component which is the implant component.

According to a further aspect of the invention there is provided computer readable instructions which, when executed by an additive manufacturing machine, are configured to implement the aforementioned method of manufacturing an implant component.

Advantageously, the additive manufacturing method may also be more efficient due to the ability to selectively heat specific, small areas of metal powder.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. It will be appreciated that anatomical directions used throughout, refer to anatomical directions when the implant component is in-situ in the intended position and orientation in a patient. That is, posterior, anterior, superior, inferior, lateral and medial have their usual meanings, and refer to when the implant component is in-situ in the intended position and orientation in a patient. It will be understood that the implant component may be configured to provide a part of the orthopaedic implant for arthroplasty, and the tibial component may be configured to provide a part of the orthopaedic implant for knee arthroplasty.

Another aspect of the invention provides a computer program element comprising and/or describing and/or defining a three-dimensional design, e.g. of the implant component described above or an embodiment thereof. The three-dimensional design may be for use with a simulation means or an additive or subtractive manufacturing means, system or device.

The computer program element may be for causing, or operable or configured to cause, an io additive or subtractive manufacturing means, system or device to manufacture the implant component described above or an embodiment thereof. The computer program element may comprise computer readable program code means for causing an additive or subtractive manufacturing means, system or device to execute a procedure to manufacture the implant component described above or an embodiment thereof.

A further aspect of the invention provides a computer program element comprising computer readable program code means for causing a processor to execute a procedure to implement one or more steps of the aforementioned method.

A yet further aspect of the invention provides the computer program element embodied on a computer readable medium.

A yet further aspect of the invention provides a computer readable medium having a program stored thereon, where the program is arranged to make a computer execute a procedure to implement one or more steps of the aforementioned method.

A yet further aspect of the invention provides a control means or control system or controller comprising the aforementioned computer program element or computer readable medium.

For purposes of this disclosure, and notwithstanding the above, it is to be understood that any controller(s), control units and/or control modules described herein may each comprise a control unit or computational device having one or more electronic processors. The controller may comprise a single control unit or electronic controller or alternatively different functions of the control of the system or apparatus may be embodied in, or hosted in, different control units or controllers or control modules. As used herein, the terms "control unit" and "controller" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) or control module(s) to implement the control techniques s described herein (including the method(s) described herein). The set of instructions may be embedded in one or more electronic processors, or alternatively, may be provided as software to be executed by one or more electronic processor(s).

For example, a first controller may be implemented in software run on one or more o electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present invention is not intended to be limited to any particular arrangement. In any event, the set of instructions described herein may be embedded in a is computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms "may", "and/or", "e.g.", "for example" and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an isometric view of an inferior side of a tibial component of an orthopaedic implant for partial knee arthroplasty; Figure 2 is an isometric view of a superior side of the tibial component shown in Figure 1; Figure 3 is a plan view of the superior side of the tibial component shown in Figure 1; Figure 4 is an image of a tibial component for partial knee arthroplasty; Figure 5 is another image of the tibial component shown in Figure 4; Figure 6 is an isometric view of an inferior side of a tibial component according to a second embodiment; is Figure 7 is an isometric view of an inferior side of a tibial component according to a third embodiment; Figure 8 is an isometric view of an inferior side of a tibial component according to a fourth embodiment; Figure 9 is an image of a lattice structure in a tibial component; Figure 10 is a schematic of a resected tibia prepared to receive the tibial component of Figure 1; Figure 11 shows results of a finite element analysis study comparing the strain installed in bone by tibial components as shown in Figures 4 and 5.

Referring to Figures 1 to 5, there is shown an implant component for an orthopaedic implant, which in this example is a tibial component 1 for an orthopaedic implant for partial knee arthroplasty. That is, the tibial component 1 is configured to provide a part of the orthopaedic implant. The tibial component 1 may also be referred to as a tibial implant component. It will be appreciated that anatomical directions used to describe the tibial component 1, and used to describe subsequent embodiments of the invention, relate to anatomical directions when the tibial component is correctly installed in a patient. More specifically, lateral, medial, posterior, anterior, superior and inferior all have their usual anatomical meanings, and relate to the respective direction when the tibial component is located in the patient.

The tibial component 1 has a plate portion 11 which has a bone-interfacing side B on the inferior side thereof, the bone-interfacing side being configured to interface with tibial bone material of a patient, in use. The bone-interfacing side B of the plate portion 11 has a central portion and a peripheral portion, the peripheral portion at least partially surrounding the s central portion. The plate portion has a porous structure 111, which in this example is a lattice structure 11, as shown in Figure 4. However, it will be appreciated that other porous structures may be used. The lattice structure 111 provides the central portion of the bone-interfacing side B. The plate portion 11 has a substantially non-porous peripheral rim 112 extending around a perimeter of, and connected to, the lattice structure 111. The peripheral rim 112 provides the peripheral portion of the bone-interfacing side B. The peripheral rim 112 extends around the entirety of the porous structure 111. The plate portion 11 has a height HD of between 2 and 5 mm. A superior side of the plate portion 11 provides an second side A for interfacing with an articulating joint component AJC, shown in Figure 5. The second side A is on the opposite side of the plate portion 11 to the bone-interfacing is side B. The peripheral rim provides a peripheral portion of the second side. The lattice structure provides a central portion of the second side. Where the central portion of the second side if provided by a solid layer, this solid layer is disposed on the lattice structure. The articulating joint component AJC may be attached to the second side A via attachment to the peripheral rim 112 or via attachment to the porous structure 111. The articulating joint component AJC, in this example, is configured for articulation with an articulation surface of a femoral component (not shown) or of a femur (not shown).

The peripheral portion of the bone-interfacing side B is divided into at least two portions, which, in this example, correspond to the peripheral rim 112 being divided into at least two portions. This is because, in this example, a thickness TD of the peripheral rim 112, is substantially constant across a height HD at any position around the peripheral rim 112. A first portion of the at least two portions is a side portion P1, which is either a medial or lateral side of the tibial component, in use. In this example the side portion P1 is located between a second portion, which is an anterior portion P2, in use, and a third portion, which is a posterior portion P3, in use, of the peripheral rim 112. The side portion P1 has a greater thickness TD than the anterior portion P2 and a greater thickness TD than the posterior portion P3. The thickness TD of each of the anterior and posterior portions P2, P3 is less than 11 times the thickness TD of the side portion P1. In this example, each of the side, anterior and posterior portions P1, P2, P3 has substantially uniform, or constant, thickness TD. In this example the peripheral rim 112 of the tibial component 1 has a first intermediate portion 11 located between, adjacent and connected to both of, the anterior portion P2 and the side portion P1. The peripheral rim 112 of the tibial component 1 has a second intermediate portion 12 located between, adjacent and connected to both of, the posterior portion P3 and the side portion P1. The thickness TD of the first intermediate portion 11 s varies with position between the side portion P1 and the anterior portion P2, and the thickness TD of the second intermediate portion 12 varies with position between the side portion P1 and the posterior portion P3. A thickness TD of at least a part of the first intermediate portion 11 varies linearly with position between the side and anterior portions P1, P2. A thickness TD of at least a part of the second intermediate portion 12 varies linearly o with position between the side and posterior portions P1, P3. Intersections, or joining portions, between the first intermediate portion 11 and each of the side and anterior portions P2, P3 are rounded. Intersections, or joining portions, between the second intermediate portion 12 and each of the side and posterior portions P1, P3 are rounded. This design of peripheral rim 112 may reduce stress concentrations where the intermediate portions 11, 12 is meet the side, anterior and posterior portions P1, P2, P3 of the peripheral rim 112. As shown by the dashed arrowhead lines in Figure 3, the thickness TD is defined along or parallel to the bone-interfacing side. This may also be referred to as along or parallel to a plane of the plate portion 11, in this example. The thickness TD may also be defined as extending away from the central portion at any position around a perimeter of the central portion. That is, the thickness TD is in a direction which is normal to the perimeter of the central portion at each location on the perimeter. It will be appreciated that, using this definition, the direction normal to the perimeter refers to the direction normal to the perimeter on a macro scale, and does not account for surface details of the porous structure.

In this example, the side portion P1 of the peripheral rim has a length which is around 20% of a length of the perimeter of the central portion. The side portion P1 has a thickness TD which is between 2 and 15 mm. The anterior and posterior portions P2, P3 have lengths which are around 10% of the length of the perimeter of the central portion. The side, anterior and posterior portions P1, P2, P3 are shaped to follow a corresponding outer shape of the peripheral portion. That is, the thickness of each of the side, anterior and posterior portion P1, P2, P3 is uniform along the respective length. The first and second intermediate portions 11, 12 have lengths which are around 5% of the length of the perimeter of the central portion. It will be appreciated that the lengths of any of these portions may be different, and can be tailored to the specific requirements of the implant components, to achieve optimum strain distribution in the bone.

The tibial component 1 shown in Figures 1 to 5 is for a partial knee implant. The tibial component 1 has a bone-insertion feature in the form of a keel 12. The keel 12 extends in an inferior direction, in use, from an insertion feature portion, which in this example is a keel portion P4, of the peripheral rim 112. The keel 12 is orientated in an anterior to posterior direction and is configured to be inserted into a keel slot in a tibia of a patient, in use. The keel 12 has a posterior end 121 and an anterior end 122. In this example, the keel portion P4 of the peripheral rim 112 has a thickness TD which is greater than the thickness TD of the anterior and posterior portions P2, P3. However, it will be appreciated that, in other examples, the anterior, posterior and keel portions P2, P3, P4 all have the same thickness dimension TD, effectively providing one portion with a thickness dimension TD which is less than that of the side portion P1. The keel portion P4 of the peripheral rim 112 has a is thickness TD which is less than the thickness TD of the side portion P1. The thickness of the keel portion P4 is greater than a thickness of the keel 12. The keel portion P4 thereby provides a robust base for the keel 12 of the tibial component 1.

In this example, the keel portion P4 of the peripheral rim 112 has a height HD, in a direction extending away from the keel 12, which is greater in a location of the posterior end 121 of the keel 12 than away from the posterior end 121 of the keel 12. This may reduce the effects of stress concentrations at the posterior end 121 of the keel 12. In other examples, the keel portion P4 of the peripheral rim 112 also has a height HD, in the direction extending away from the keel 12, which is greater in a location of the anterior end 122 of the keel 12 than away from the anterior end 122 of the keel 12, again, to reduce the effects of stress concentrations caused by the end of the keel 12. It will be appreciated that height HD is define in a direction perpendicular to the bone-interfacing side, or may also be referred to as perpendicular to the plane of the plate portion 11.

In this example the posterior side 121 of the keel 12 has an overhanging portion to define an undercut between the overhanging portion and the plate portion 11. The undercut is configured to engage with bone material when the keel 12 is inserted into the keel slot in the tibia of the patient. The overhanging portion of the posterior side 121 of the keel 12 is substantially straight and extends away from the plate portion 11 with a posterior direction component. An angle between the bone-interfacing side of the plate portion 11 and the overhanging portion of the posterior side 121 of the keel 12, is around 70°, measured on a posterior side of the posterior side 121 of the keel 12. The overhanging portion has the furthest point of the posterior side 121 of the keel 12 from the plate portion 11. The posterior side 121 of the keel 12 has a fillet at an intersection, or joining portion, between the plate s portion 11 and the overhanging portion of the posterior side 121 of the keel 12. The undercut is defined between the furthest point of the posterior side 121 of the keel 12 from the plate portion 11 and the fillet. The anterior side 122 of the keel 12 extends away from the plate portion 11 with a posterior direction component. The anterior side 122 of the keel 12 has a contact portion configured to contact bone material when in the keel slot. The contact lo portion extends in a direction away from the plate portion 11 with a posterior direction component. The contact portion of the anterior side 122 of the keel 12 is substantially straight and extends from the plate portion 11 at an angle of around 140°, measured on an anterior of the anterior side 122 of the keel 12. The anterior side 122 of the keel 12 has a fillet at an intersection, or joining portion, between the plate portion 11 and the contact is portion of the anterior side 122 of the keel 12. The keel 12 has an inferior side extending between the posterior side 121 and the anterior side 122. The inferior side is substantially parallel to the plate portion 11 and is substantially straight.

In this example, the keel 12 has a porous structure, which is a lattice structure 124, and a substantially non-porous keel peripheral rim 123 extending around, and connected to, a periphery of the lattice structure 124. That is, a part of the keel peripheral rim 123 provides the posterior side 121 of the keel 12, another part of the keel peripheral rim 123 provides the anterior side 122 of the keel 12 and another part of the keel peripheral rim 123 provides the inferior side of the keel 12. Another part of the keel peripheral rim 123, which extends between the posterior and anterior sides 121, 122 of the keel 12, is connected to the plate portion 11. The keel 12 has a first reinforcing region 125a extending between the inferior side of the keel 12 and the posterior side 121 of the keel 12. The keel 12 has a second reinforcing region 125b and a third reinforcing region 125c, each of the second and third reinforcing regions 125b, 125c being spaced apart and extending between the inferior side of the keel 12 and the part of the keel peripheral rim 123 which is connected to the plate portion 11. The first, second and third reinforcing regions 125a-c are substantially solid and divide the lattice structure of the keel 12. However, it will be appreciated that each reinforcing region 125a, 125b, 125c may, instead, be provided by porous or lattice structure having a greater elastic modulus than the lattice structure of the central portion 124 of the keel 12. In this way, the reinforcing regions 125a-c provide stiffeners, or strengtheners, for the keel 12. It will be appreciated that different numbers and configurations of reinforcing regions may be provided. For example, in other embodiments reinforcing regions may extends between the inferior side of the keel 12 and the anterior side 122 of the keel 12; the posterior side 121 of the keel 12 and the part of the keel peripheral rim 123 which is connected to the plate portion; the anterior side 122 of the keel 12 and the part of the keel peripheral rim 123 which is connected to the plate portion; or the posterior side 121 of the keel 12 and the anterior side 122 of the keel 12.

In this example, the tibial component 1 has two bone-insertion pegs 13 extending from the bone-interfacing side B of the plate portion 11. The bone insertion pegs 13 are configured to be receiving in reamed holes in the tibia of the patient. Each peg 13 extends away from the bone-interfacing side B with a posterior direction component. Some or all of each peg 13 is provided with a porous structure, which in this case is a lattice structure, to allow or promote bone ingrowth into the respective peg. Tips 131 of each peg 13 are provided with is a solid peripheral rim extending around the porous structure, as shown in Figure 4.

Referring now to Figure 6, there is shown another embodiment of a tibial component 1' for partial knee arthroplasty. Similar features of this tibial component 1' are denoted with the same reference numerals as the tibial component 1 of the previous embodiment, with a succeeding prime (I The tibial component 1' of this embodiment differs from the tibial component 1 of the previous embodiment in that the keel 12' has a trapezoidal shape. That is, the keel 12' does not have an overhanging portion on the posterior side 121', but, instead, the posterior side 121' extends away from the bone-interfacing side B' with an anterior direction component. The keel 12' of this embodiment also does not have a lattice structure but is completely solid. The tibial component 1' of this embodiment also differs from the tibial component 1 of the previous embodiment in that the side portion P1' of the peripheral rim 112' has a smaller thickness TD', and is located closer to the anterior side of the plate portion 11', than the side portion P1 of the tibial component 1 of the previous embodiment. The tibial component 1' of this embodiment also differs from the tibial component 1 of the previous embodiment in that there are no bone-insertion pegs.

Referring now to Figure 7, there is shown another embodiment of a tibial component 1" for partial knee arthroplasty. Similar features of this tibial component 1" are denoted with the same reference numerals as the tibial component 1 of the first embodiment, with a succeeding double-prime ("). The tibial component 1" of this embodiment differs from the tibial component 1 of the first embodiment in that the keel 12" has a trapezoidal shape. That is, the keel 12" does not have an overhanging portion on the posterior side 121", but, instead, the posterior side 121" extends away from the bone-interfacing side B" with an anterior direction component. The keel 12" of this embodiment also does not have a lattice structure but is completely solid. The tibial component 1" of this embodiment also differs from the tibial component 1 of the first embodiment in that the side portion P1" of the peripheral rim 112" has a larger thickness TD", and is located closer to the anterior side of the plate portion 11", than the side portion P1 of the tibial component 1 of the first embodiment. The tibial component 1" of this embodiment also differs from the tibial io component 1 of the previous embodiment in that there are no bone-insertion pegs.

Referring now to Figure 8, there is shown another embodiment of a tibial component 1-for partial knee arthroplasty. Similar features of this tibial component 1" are denoted with the same reference numerals as the tibial component 1 of the first embodiment, with a is succeeding triple-prime (-). The tibial component 1-of this embodiment differs from the tibial component 1 of the first embodiment in that the keel 12-has a trapezoidal shape. That is, the keel 12" does not have an overhanging portion on the posterior side 121-, but, instead, the posterior side 121"' extends away from the bone-interfacing side B" with an anterior direction component. The keel 12'" of this embodiment also only has two reinforcing regions 125a-, 125b-. The reinforcing regions 125a"', 125-are spaced apart from one another and extend between the inferior side of the keel 12-and the part of the keel peripheral rim 123-which is connected to the plate portion 11-.

It will be appreciated that features from all four embodiments described with reference to Figures 1-8 are combinable. For example, the peripheral rim shape of any embodiment may be used with the keel of any other embodiment. Furthermore, in other embodiments no keel is present at all, and the entirety of the peripheral rim provides a bone-interfacing side. In other embodiments there are no pegs present. In other embodiments there are no pegs nor keel present, and merely fixing means, for example screws or other fasteners, or adhesive, used to attach the tibial component to the tibia. In other embodiments, there may be other areas of the peripheral rim with an increased height, such as at the side portion. The increased height may be used to mitigate effects of stress concentrations, as described previously, to increase bending stiffness and strength, or to provide fixation means for the articulating joint component AJC. Similarly, the height may be uniform around the entirety of the peripheral rim. Another possible variation in all embodiments is that, instead of the lattice structure providing the central portion of the second side, a solid layer may provide some or all of the central portion of the second side, the solid layer being disposed on the lattice structure.

Referring now to Figure 9, there is shown an illustration of the lattice structure used in the various features in the various embodiments. More specifically, the lattice structure shown in Figure 9 is representative of the lattice structure of the central portions of the plate portions 11, 11, 11", 11-as well as the central portion of the keel 12, 12''. The lattice structure is formed of a plurality of struts S connected together at nodes N. Most or each io strut has direction components in all three Cartesian coordinates. In other words, most of the struts S do not extend within just one plane. The lattice structure has an elastic modulus of between 0.1 and 5 GPa. It will be appreciated that the elastic modulus refers to the bulk elastic modulus of the lattice structure, and not the elastic modulus of just each strut S. The lattice structure has a porosity of between 5 and 30 %. The lattice structure has a strut is density of between 2 and 7 struts per mm3. Each strut has a thickness, or diameter, of between 100 and 400 microns.

In all embodiments the tibial component is unitary and metallic. The tibial component is produced via additive manufacturing, by providing metal powder and selectively heating areas of the metal powder to fuse the metal powder together into the unitary metal component which is the tibial component. This additive manufacturing may use a technique referred to as laser sintering. The additive manufacturing process is controlled by computer readable instructions which, when executed by an additive manufacturing machine, are configured to implement the manufacturing method to produce the tibial component. The tibial component, in this example, is produced using a titanium alloy, for example Ti64.

The use of any of the first embodiment of the tibial component 1 in partial knee arthroplasty will now be described with reference to Figure 10 which shows schematics of a resected tibia. Figure 10A shows a view of the resected tibia looking in an inferior direction, and Figure 10B shows a section view through the tibia in a plane along which the keel 12 lies.

As the tibia is prepared for partial knee arthroplasty in this example, there is a resected side TR and a non-resected side TN. The resected side TR has a keel slot 21 with a shape corresponding to the keel 12 of the tibial component 1. The keel slot 21 has a posterior end 23 which is shaped to engage with the undercut, formed by the overhanging portion of the posterior side 121 of the keel 12. The keel slot 21 has an anterior end 24 which is shaped correspondingly to the anterior side 122 of the keel 12. The resected side TR of the tibia also has two holes 25, which have sizes, positions and inclinations corresponding to the pegs 13 on the tibial component 1.

s When a surgeon, after preparing the tibia for receiving the tibial component 1 and operating from the anterior side of the knee, inserts the keel into the keel slot, the undercut engages with the posterior end 23 of the keel slot to prevent the posterior side of the tibial component 1 from lifting as the anterior side of the keel 12 is pushed into the keel slot 21. The shape of the anterior side 122 of the keel 12 and the anterior end 24 of the keel slot 21 further o enforce the engagement at the posterior end of the keel 12 as the anterior end 122 of the keel 12 is pushed in an inferior direction, as the corresponding shapes also push the keel 12 in a posterior direction. Also, during this motion, the pegs 13 are received in the respective holes 25 in the tibia. When the tibial component 1 is in place on the tibia, the bone-interfacing side B of the plate portion 11 is in contact with an interfacing surface 22 of is the resected side TR of the tibia.

After surgery, when the patient uses the knee with the tibial component 1 implanted therein, loading, for example bodyweight loading, will pass through the articulating joint component to the second side of the plate portion 11. Part of the load will be transmitted to the tibia through the peripheral rim 112, and part will be transmitted through the porous structure 111. It has surprisingly been found that, by increasing the thickness of the side portion P1, less strain is imparted into the bone beneath the side portion P1 of the peripheral rim 112 which leads to greater strain being imparted into the bone beneath the porous structure 111, thereby better resembling strain in the same location in a healthy knee without arthroplasty. This effect is illustrated subsequently in Example 1.

It will be appreciated that the tibial component 1-of Figure 8 operates in the same way, with the same effect of producing strain in the bone beneath the porous structure 111-that better resembles that in a healthy joint. In this case, however, the keel slot in the resected tibia is shaped to conform with the trapezoidal keel 12'.

In both the tibial component 1 of Figures 1to 5 and the tibial component 1-of Figure 8, this better matching of strain to that expected in healthy bone also means that the strain installed in the interfacing surface 22 of the tibia better matches the strain in the porous structure, and so bone growth is encouraged in the porous structure. Furthermore, due to the porous structure present in the keel, bone in-growth is encouraged through the keel as well.

It will also be appreciated that the tibial components 1', 1" of Figures 6 and 7 have the same s advantage in that the increased thickness TD', TD" of the side portion P1', P1" leads to strains being installed in the bone beneath the porous structure which better matches the strain in healthy bone, albeit by different amounts. However, in these implants there is no bone-ingrowth through the keel as the keels are solid.

o Example 1

Referring now to Figure 11, results of a finite element analysis are presented, which illustrate the magnitudes and distributions of strains installed in the tibia beneath the plate portion of various designs of tibial component.

is In Figure 11, the strain contour maps showing finite element analysis (FEA) results, are arranged in columns A-D which show simulated strains at various depths below a surface of the tibia which interfaces with the respective tibial component, with the top row of results being at the interface between the bone and the tibial component. Column E is a key to the strain distribution in the strain contour maps. Beneath each strain contour map of strain is a schematic of the tibial component which was used in the simulation.

Results A show the strain distribution at this location in native, healthy bone with no implant present, and so represent the ideal strain distribution. The peak stress is at the centre of the tibia, and is around 1000 microstrain.

Results B show the strain distribution beneath the tibial component 1' shown in Figure 6. The strain in the bone adjacent the side portion P1' in this case is simulated to be around 1000 microstrain, and the strain in the bone adjacent the lattice central portion 111' is around 670 microstrain.

Results C show the strain distribution beneath the tibial component 1" shown in Figure 7. The strain in the bone adjacent the side portion P1" in this case is around 340 microstrain, and the strain in the bone adjacent the lattice central portion 111" is around 1000 microstrain.

Results D shown the strain distribution beneath a completely solid tibial component, as indicated in the schematic of the tibial component below the colour maps. The strain in the bone adjacent the area of the side portion in this case is simulated to be around 780 microstrain, and in the bone adjacent the area of the central portion (at the location where the lattice structure is in B and C) is around 450 microstrain.

These results show that, by increasing the thickness of the side portion of the peripheral rim, strain installed in the bone beneath the lattice structure better matches that seen in healthy bone with no implant. Furthermore, strain is greatly reduced in the bone material o beneath the side portion, which helps to reduce subsidence of the tibial component, over time. Not shown in this study is the effect of a peripheral rim with no increased thickness at the side portion, but it will be appreciated that the strain underneath this peripheral rim would be even greater than that below the side portion P1' in results B, due to a higher concentration of forcing acting on the bone through the peripheral rim.

It will be appreciated by those skilled in the art that, whilst the embodiment of this invention are presented with reference to a tibial component for partial knee arthroplasty, another example provides an implant component which is a tibial component for an orthopaedic implant for total knee arthroplasty. In such an embodiment, the tibial component has a plate portion which is configured to interface with an entire resected tibia. The tibial component has a solid peripheral rim extending around the entirety of a porous, or lattice, structure, an inferior side of each of the porous structure and the peripheral rim providing a bone-interfacing side configured to interface with the resected tibia. Lateral and medial portions, which may also be referred to as side portions, of the peripheral rim have thicknesses which are greater than a thickness of each of anterior and posterior portions of the peripheral rim.

It will be appreciated that, in this embodiment, strain would also be reduced in bone material beneath the side portions of the peripheral rim due to the side portion having an increased thickness, thereby allowing the porous structure to install more strain into the bone adjacent the porous structure.

The implant component may also be for other orthopaedic components. One example is a patellar component, with a bone-interfacing side configured to interface with a patellar, and a second side configured to interface with an articulating joint component. Such a patellar component may have a peripheral rim surrounding a porous, or lattice structure, a side of the peripheral rim and porous structure providing the bone-interfacing side. A first portion of the peripheral rim has a greater thickness than a second portion, thereby reducing strain in the patellar beneath the first portion and so allowing the porous structure to install more strain into the bone adjacent the porous structure. The patellar component may have intermediate portions between side and second and/or third portions, as described with s reference to the tibial component.

Another example is a scapula or humeral component for a shoulder implant, with a bone-interfacing side configured to interface with a scapula or humerus, and a second side configured to interface with an articulating joint component. Such a scapula or humerus o component has a peripheral rim surrounding a porous, or lattice structure, a side of the peripheral rim and porous structure providing the bone-interfacing side. A first portion of the peripheral rim has a greater thickness than a second portion, thereby reducing strain in the scapula or humerus beneath the first portion and so allowing the porous structure to install more strain into the bone adjacent the porous structure. The scapula or humerus is component may have intermediate portions between side and second and/or third portions, as described with reference to the tibial component.

These other examples of implant component may have bone-insertion features as described with reference to the tibial components, e.g., a keel and/or bone-insertion pegs.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMS1. An implant component of an orthopaedic implant for arthroplasty, the implant component comprising: a bone-interfacing side having a central portion and a peripheral portion, the peripheral portion at least partially surrounding the central portion; a second side, opposite to the bone-interfacing side, for interfacing with an articulating joint component; a porous structure providing the central portion of the bone-interfacing side; o and a substantially non-porous peripheral rim extending around a perimeter of the porous structure and providing the peripheral portion of the bone-interfacing side, the peripheral rim being connected to the porous structure; wherein the peripheral portion of the bone-interfacing side is divided into at least is two portions, wherein a first portion of the at least two portions is thicker, in a direction along the bone-interfacing side, than a second portion of the at least two portions.
2. An implant component according to claim 1, wherein each portion of the at least two portions has a length, along the perimeter of the central portion, which is at least 10% of a length of the perimeter of the central portion.
3. An implant component according to claim 1 or claim 2, wherein each portion of the at least two portions of the peripheral portion of the bone-interfacing side, has a substantially uniform thickness.
4. An implant component according to any preceding claim, wherein the second portion is located between the first portion and a third portion of the at least two portions, the second portion having a greater thickness than the third portion.
5. An implant component according to claim 4, wherein the peripheral portion of the bone-interfacing side comprises a first intermediate portion between, and adjacent both of, the first and second portions, and a second intermediate portion between, and adjacent both of, the second and third portions, the thickness of the first intermediate portion varying with position between the first and second portions, and the thickness of the second intermediate portion varying with position between the second and third portions.
6. An implant component according to any preceding claim, wherein the peripheral rim has a height in a direction away from the bone-interfacing side, the height varying with position around the perimeter of the of the central portion.
7. An implant component according to any preceding claim, the implant component comprising a bone-insertion feature configured to be inserted into a corresponding io slot or a cavity in a bone of a patient, the bone-insertion feature extending from an insertion feature portion of the peripheral rim in a direction away from the bone-interfacing side.
8. An implant component according to claim 7, wherein the thickness of the insertion is feature portion of the peripheral rim is greater than a thickness, in the same direction as the thickness of the insertion feature portion, of the bone-insertion feature.
9. An implant component according to claim 7 or claims 8, wherein the peripheral rim has a or the height in a direction away from the bone-interfacing side, the height being greater at a location of an edge of the bone-insertion feature than away from the edge of the bone insertion feature.
10. An implant component according to any preceding claim, wherein the implant component is a tibial component for an orthopaedic implant for knee arthroplasty, and wherein a plate portion of the tibial component comprises the porous structure and the peripheral rim, an inferior side of the plate portion provides the bone-interfacing side which is configured to interface with a tibia of a patient, and a superior side of the plate portion provides the second side, which is configured to interface with an articulating joint component of the knee implant..
11. An implant component according to claim 10, wherein the peripheral rim comprises: a side portion, which is one of a medial portion or a lateral portion, in use, and which provides the first portion of the at least two portions; an anterior portion which provides the second portion of the at least two portions; and a posterior portion which provides a third portion of the at least two portions; wherein the side portion is located between the anterior portion and the posterior portion, and wherein a thickness, in a direction parallel to the bone-interfacing side of the plate portion, of the side portion is greater than a thickness of one or each of the anterior portion and the posterior portion.
12. An implant component according to claim 11, wherein the thickness of one or each of the anterior portion and the posterior portion is less than 11 times the thickness of the side portion.
13. An implant component according to either of claims 11 or 12, wherein the peripheral rim comprises a first intermediate portion between, and adjacent both of, the anterior portion and the side portion, and a second intermediate portion between, and adjacent both of, the posterior portion and the side portion, a thickness of the first is intermediate portion varying with position between the side portion and the anterior portion, and a thickness of the second intermediate portion varying with position between the side portion and the posterior portion.
14. An implant component according to claim 13, wherein the side portion has a substantially constant thickness, the anterior portion has a substantially constant thickness and the posterior portion has a substantially constant thickness.
15. An implant component according to any of claims 10 to 14, wherein the tibial component is for a partial knee implant and comprises a keel extending in an inferior direction, in use, from a keel portion of the peripheral rim.
16. An implant component according to claim 15, wherein the keel portion of the peripheral rim has a thickness which is greater than one or each of the thickness of the anterior portion and the posterior portion.
17. An implant component according to claim 16, wherein the keel comprises a posterior end and an anterior end, and wherein the keel portion of the peripheral rim has a height, in a direction extending away from the keel, which is greater in a location of the posterior end and/or a location of the anterior end of the keel than away from the posterior and/or anterior end of the keel.
18. An implant component according to any of claim 15 to 17, wherein the keel portion of the peripheral rim is located between the anterior portion and the posterior portion of the peripheral rim, and opposite to the side portion.
19. An implant component according to any of claims 15 to 18, wherein the keel comprises a porous structure and a substantially non-porous keel peripheral rim extending around a periphery of the porous structure of the keel.
20 An implant component according to claim 19, wherein the keel comprises one or more reinforcing region, each of the one or more reinforcing region dividing regions of the porous structure of the keel, having a greater elastic modulus than the porous structure, and extending in any one of the following directions: between the or an inferior side of the keel and the plate portion or a part of is the keel peripheral rim which is connected to the plate portion; between the inferior side of the keel and the posterior side of the keel; between the inferior side of the keel and the or an anterior side of the keel; between the posterior side of the keel and the plate portion or a part of the keel peripheral rim which is connected to the plate portion; between the anterior side of the keel and the plate portion or a part of the keel peripheral rim which is connected to the plate portion; between the posterior side of the keel and the anterior side of the keel.
21. An implant component according to any of claim 10 to 20, comprising one or more bone-insertion peg, extending from the porous structure of the bone-interfacing side of the plate portion.
22. An implant component according to any preceding claim, wherein the or any porous structure is a lattice structure, the lattice structure comprising a plurality of struts connected together at nodes.
23. An implant component according to any preceding claim, wherein the implant component is unitary and metallic.
24. A method of manufacturing an implant component according to any preceding claim, the method comprising: providing metal powder; and selectively heating areas of the metal powder to fuse the metal powder together into a unitary metallic component which is the implant component.
25. Computer readable instructions which, when executed by an additive manufacturing machine, are configured to implement the method according to claim 24.