WO2013016523A1

WO2013016523A1 - Orthopedic implants

Info

Publication number: WO2013016523A1
Application number: PCT/US2012/048314
Authority: WO
Inventors: Cyril Voisard; Tom Overes
Original assignee: Synthes Usa, Llc; Synthes Gmbh
Priority date: 2011-07-28
Filing date: 2012-07-26
Publication date: 2013-01-31

Abstract

An orthopedic implant comprises an implant configured to support a first bone segment relative to a second bone segment. The implant is comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa. In embodiment, the implant is comprised of GUMMETAL®.

Description

TITLE OF THE INVENTION

[0001] Orthopedic Implants

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No.

61/512,665 filed July 28, 2011 entitled "Spinal Stabilization Member", incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0003] The present invention generally relates to orthopedic implants. In some embodiments, the present invention relates to orthopedic implants comprised of an elastic material.

BRIEF SUMMARY OF THE INVENTION

[0004] In one embodiment there is an orthopedic implant comprising an implant configured to support a first bone segment relative to a second bone segment, the implant being comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa.

[0005] In one embodiment, the material is metal. In one embodiment, the metal is a titanium alloy. In one embodiment, the titanium alloy is TiNbZrTa. In one embodiment, the titanium alloy is GUMMETAL®. In one embodiment, the implant is a spinal stabilization member. In one embodiment, the spinal stabilization member includes a cylindrical rod. In one embodiment, the cylindrical rod has a diameter of less than or equal to 8 mm. In a further embodiment, the implant comprises a first attachment member configured to couple to a first vertebra and having a first clamp member; and a second attachment member configured to couple to a second vertebra and having a second clamp member, wherein the spinal stabilization member is configured to couple to the first clamp member and the second clamp member.

[0006] In one embodiment, the implant is a total spinal disc replacement. In one embodiment, the implant is an intramedullary nail. In one embodiment, the implant is configured to allow the first bone segment to move relative to the second bone segment. In one embodiment, the implant is configured to move the first bone segment relative to the second bone segment.

[0007] In another embodiment, there is a spinal stabilization member for use in a spinal fixation system, the spinal stabilization member comprising an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa. [0008] In another embodiment, there is a method of implanting an orthopedic implant comprising: implanting an implant into a patient, the implant being configured to support a first bone segment relative to a second bone segment and being comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa; and cutting at least a portion of the implant off from an end of a remainder of the implant without further surface treatment to the end of the remainder of the implant. In one embodiment, the material is GUMMETAL®.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] The foregoing summary, as well as the following detailed description of embodiments of the orthopedic implants, will be better understood when read in conjunction with the appended drawings of an exemplary embodiment. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0010] In the drawings :

[0011] Fig. 1A is a top sectional view of a human vertebrae as is known in the art;

[0012] Fig. IB is a side view of the lumbar and sacral regions of a human spine as in known in the art; and

[0013] Fig. 2 is a partial side perspective view of an implanted internal fixation system having an orthopedic implant in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION [0014] Orthopedic implants are used to repair damage to the skeleton and related structures, and to restore mobility and function. Various devices, such as plates, nails, pins, rods, surgical mesh and screws, have been used to join fractured bones in the proper orientation for repair.

[0015] Orthopedic implants are most commonly fabricated from metal, such as titanium.

Titanium has a high tensile strength and has proven to be biocompatible. Bone tissue also grows and attaches to the surface of titanium more readily than other materials. In some applications however, titanium and titanium alloys typically used in orthopedic applications do not have desirable elastic properties. Certain composite or polymeric materials have been used to provide elastic properties but such materials do not have desirable strength properties, may not be biocompatible, and are susceptible to breakage, creep, or deformation. [0016] In one embodiment, the present invention is an orthopedic implant comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa. In one embodiment, the implant is comprised of GUMMETAL®, manufactured by Toyota Material Incorporated of Japan. [0017] Though GUMMETAL® has been discovered to be useful for the present invention, the implant may be comprised of alternative materials to achieve various desired characteristics such as strength, rigidity, elasticity, compliance, biomechanical performance, durability and radiolucency or imaging preference. In one embodiment, the implant is comprised of metal. In one embodiment, the implant is comprised of an elastic metal. In one embodiment, the implant is comprised of a superelastic metal. In one embodiment, the implant is comprised of a metal that has a low Young's modulus (e.g., as low as approximately 40 Gpa), high tensile strength (e,g., as high as approximately 2000 Mpa), high elasticity (e.g., over 2.5% elastic deformability), high plasticity (e.g., over 99.9% cold workability) and is non-toxic (e.g., nickel free). In one embodiment, the implant is comprised of a titanium (Ti) alloy. In one embodiment, the implant is comprised of TiNbZrTa. In one embodiment, the implant is comprised of a soft titanium alloy. In one embodiment, the implant is comprised of a GUMMETAL® that is a Ti-based multinary alloy TiNbTaZrO. In one embodiment, the implant is comprised of a GUMMETAL® that belongs to a class β-type titanium alloy. In one embodiment, the implant is comprised of a GUMMETAL® that has the concentration Ti-36Nb-2Ta- 3Zr-0.3O in mass %. [0018] In other embodiments, the implant includes one or more thermoplastics such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone PEKK) and polyetherketone (PEK), carbon fiber reinforced PEEK composites, PEEK-BaS04 composites, ceramics and composites thereof such as calcium phosphate (e.g. SKELITETM), polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, polyurethanes of any durometer, epoxy and/or silicone.

[0019] In one embodiment, the implant is comprised of a homogenous material. In one embodiment, the implant is comprised of a heterogeneous material such as a combination of two or more of the above-described materials.

[0020] In one embodiment, the implant, having elastic properties, more easily conforms to the shape of the bone. In one embodiment, conformity of the implant is especially useful when used in intramedullary nailing. In one embodiment, the implant responds better to high peak loads, that is the peak loads are more easily dispersed since the implant will easily deform upon application but return to its original position after the peak load is removed.

[0021] In one embodiment, the implant is configured to support a first bone segment relative to a second bone segment. In one embodiment, the implant is configured to allow the first bone segment to move relative to the second bone segment. In one embodiment, the implant moves the first bone segment relative to the second bone segment. In one embodiment, the implant acts similarly to a superelastic material like nitinol in as much as the implants tend to spring back or return to an unstressed state. In one embodiment, the implant is used in deformity corrections to gradually move bones or bone segments relative to one another over time. For example, the implant may be used to treat scoliosis as described in the exemplary embodiment below. In some embodiments, the implant, due to the relatively low stiffness, and high elasticitiy - when compared with implants of similar dimensions made of stainless steel or stiff Titanium and its alloys - will allow mircomotion between first and second bone segments. In some embodiments, a fractured bone surface will be more stimulated through micromotions and develop more quantity and uniform callus, thus improving osteointegration of the implant.

[0022] In some embodiments, the implant, when cut, produces a smoother surface where it was cut than a surface of traditional metals that may leave sharp and dangerous protrusions when cut. In one embodiment, the implant is configured to provide a smooth end surface once cut. In one embodiment, after cutting at least a portion of the implant off from an end of a remainder of the implant no further surface treatment to the end of the remainder of the implant is required. In one embodiment, providing a smooth surface after cutting the implant, which is useful when the implant's, such as a rod, length are to be adapted by cutting to match a specific patient's anatomy, there is a reduced need to additionally smooth or round the cut surface in order to reduce soft tissue irritation.

[0023] In one embodiment, the implant is a spinal stabilization member, an example of which is described below. In one embodiment, the implant is a total spinal disc replacement. In one embodiment, the implant is an intramedullary nail. In one embodiment, an intramedullary nail is approximately 17mm in diameter. In one embodiment, the implant is a clavicle nail. In one embodiment, the implant is a femoral nail. In one embodiment, the implant is a humeral nail. In one embodiment, the implant is a tibia nail. In one embodiment, the implant is a bone plate. In one embodiment, the implant is a non-load bearing plate. In one embodiment, the implant is a hand plate. In one embodiment, the implant is a femoral fixation screw. In one embodiment, the implant is a total disc replacement (TDR). In one embodiment, the TDR implant is configured to provide certain clinical range of motion between two vertebrae. In one embodiment, the implant is a standalone fusion device. In one embodiment, the implant is a spinal cage. In one embodiment, the implant is a cervical and lumbar spine. In one embodiment, the implant is a vertebral body stent. In one embodiment, the implant is an intramedullary rib splint. In one embodiment, the implant is a contourable mesh. In one embodiment, the implant is a cranial bone flap such as a FlapFix. In one embodiment, the implant is an orbital floor. In one embodiment, the implant is a reconstruction plate. In one embodiment, the implant is a prosthesis shaft. In one embodiment, the implant is a cable. In one embodiment, the implant is a surgical staple. In one embodiment, the implant is a surgical clip. In one embodiment, the implant is a stent. In one embodiment, the implant is an expandable stent.

[0024] In one embodiment, one or more surgical instruments are comprised of material similar to the implants described herein. In one embodiment, the surgical instrument is a reamer.

[0025] Referring to prior art Figs. 1A and IB, the spine 120, also known as the vertebral column or the spinal column, is a flexible column of vertebral bones or vertebrae 100 held together by muscles, ligaments and tendons. The spine 120 extends from the cranium (not shown) to the coccyx 126, encasing a spinal cord 128 and forming the supporting axis of the body (not shown). The spinal cord 128 is a thick bundle of nerve tissue or nerves that branch off to various areas of the body for the purposes of motor control, sensation, and the like. The spine 120 includes seven cervical vertebrae (not shown), twelve thoracic vertebrae (not shown), five lumbar vertebrae, Li-L_v, five sacral vertebrae, Si-Sy, and three coccyx vertebrae. The sacral and coccyx vertebrae are each fused to one another, thereby functioning as a single unit. Fig. IB shows the lumbar region 122, the sacral region 124 and the coccyx 126 of the spine 120 and that the vertebrae 100 are stacked one upon another. The top portion 100a and bottom portion 100b of each vertebra 100 is slightly concave. The opposing concave vertebral surfaces form the intervertebral space 121 in which an

intervertebral disk 214 (see Fig. 2) resides. Each of the intervertebral disks 214 has a soft core referred to as a nucleus pulposus or nucleus (not shown).

[0026] In Fig. 1A, directional arrow 101a is pointing in the posterior direction and directional arrow 101b is pointing in the anterior direction. Fig. 1 A shows that each vertebra 100 includes a body 106 in the innermost portion, a spinal canal 108 and a spinous process 102 at the posterior- most end of the vertebra 100. The vertebrae 100 are substantially similar in composition, but vary in size from the larger lumbar to the smallest coccyx vertebrae 126. Each vertebra 100 further includes two transverse processes 104 located on either side and a protective plate-like structure referred to as a lamina 110. Nerves from the spinal cord 128 pass through the spinal canal 108 and foramina 112 to reach their respective destinations within the body.

[0027] Referring to Fig. 2, after spine surgery, adjacent vertebrae 100 may require a fixation system to be secured to the side of the spine 120 where the surgeon accessed the vertebrae 100 to keep the vertebrae 100 from substantially moving relative to one another. In some instances, the fixation system is removed after a period of time such as after two or more vertebrae 100 have been fused together. Fixation system 234 may include two or more attachment members 236 for securing fixation system 234 to the spine 120.

[0028] Attachment member 236 may include a clamp assembly or clamp member 236a configured to secure stabilization member 238, or the implant as discussed above, to spine 120. In one embodiment, each attachment member 236 receives a portion of stabilization member 238. In one embodiment, each attachment member 236 is adjustable to clamp onto or securely attach to stabilization member 238. In one embodiment, each attachment member 236 includes clamp member 236a, such as a screw head, that is configured to couple with an adjustment tool, such as an Allen wrench, to tighten attachment member 236 onto stabilization member 238. In one

embodiment, clamp member 236a includes a tool socket 236b such as a hexagonal, slot or Phillips and/or square or hex head configured to couple with the adjustment tool. In one embodiment, clamp member 236a surrounds a portion of stabilization member 238. In other embodiments, clamp member 236a partially surrounds a portion of stabilization member 238. In one embodiment, clamp member 236a is configured to substantially match the outer contour of stabilization member 238. Clamp members 236a may be releaseably or permanently secured to stabilization member 238, as described further below, using any attachment device and/or attachment material.

[0029] Clamp members 236a are securable to vertebrae 100 using a fastener 236c. Clamp members 236a may be secured to vertebrae 100 by any attachment device such as nails, screws and/or attachment materials such as cement. In one embodiment, fastener 236c includes a screw such as a pedicle screw. Each attachment member 236 may each be attached to vertebra 100 such as to the transverse processes 104 of vertebrae 100.

[0030] Stabilization members may be purposefully highly rigid or unbendable along an axial length so as to allow two or more vertebrae 100 to be substantially fixed relative to one another. Such high strength stabilization members may be useful in deformity corrections of the spine 120. Stabilization members may be made of titanium alloys such as Ti6A17Nb or TiA14V or cobalt chromium alloy such as CoCr. [0031] In one embodiment, fixation system 234 supports two or more vertebrae 100 relative to each other while allowing for some movement of the attached vertebrae 100 relative to one another. Allowing for some degree of movement between attached vertebrae 100 may be desirable in some instances, such as to increase the stimulation of bone growth from vertebral body end plates. In other embodiments, gradual movement between vertebrae 100 may be desirable to correct a deformity such as scoliosis. Polymer-based rods are used in fixation systems that allow for some movement of attached vertebrae 100 relative to one another. Such rods may offer limited static and dynamic strength and therefore require relatively large diameter rods to be effective in stabilizing the spine.

[0032] In one embodiment, stabilization member 238 is comprised of a high tensile strength member with a lower or ultra-low elastic modulus. In one embodiment, stabilization member 238 is comprised of a high tensile strength member with a lower elastic modulus and a smaller cross sectional diameter. In one embodiment, where adjacent attachment members 236 are spaced apart approximately 4 cm to approximately 6 cm, stabilization member 238 having a diameter d of approximately 6 mm allows for approximately 2 mm of movement in a radial direction between adjacent attachment members 236.

[0033] In one embodiment, stabilization member 238 is a cylindrical rod having a diameter d. In other embodiments, stabilization member 238 has any cross sectional shape such as oval, square or triangle.

[0034] In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of approximately 30 GPa to approximately 60 GPa. In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of approximately 40 GPa. In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of 40 GPa. In one embodiment, stabilization member 238 has a tensile strength of approximately 800 MPa to approximately 1200 GPa. In one embodiment, stabilization member 238 has a tensile strength of approximately 1000 MPa. In one embodiment, stabilization member 238 has a tensile strength of at least 1000 MPa. In one embodiment, stabilization member 238 has a tensile strength of 1000 MPa. In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of approximately 40 GPa and a tensile strength of approximately 1000 MPa. In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of 40 GPa and a tensile strength of at least 1000 MPa. In one embodiment, stabilization member 238 has an elastic modulus in the cold worked state of 40 GPa and a tensile strength of 1000 MPa. In one embodiment, stabilization member 238 has a radial shear load of approximately 500 N. [0035] In one embodiment, stabilization member 238 is comprised of metal. In one embodiment, stabilization member 238 is comprised of a metal that has a low Young's modulus (e.g., as low as approximately 40 Gpa), high tensile strength (e,g., as high as approximately 2000 Mpa), high elasticity (e.g., over 2.5% elastic deformability), high plasticity (e.g., over 99.9% cold workability) and is non-toxic (e.g., nickel free). In one embodiment, stabilization member 238 is comprised of a titanium (Ti) alloy. In one embodiment, stabilization member 238 is comprised of a soft titanium alloy. In one embodiment, stabilization member 238 is comprised of GUMMETAL®. In one embodiment, stabilization member 238 is comprised of a GUMMETAL® that is a Ti-based multinary alloy TiNbTaZrO. In one embodiment, stabilization member 238 is comprised of a GUMMETAL® that belongs to a class β-type titanium alloy. In one embodiment, stabilization member 238 is comprised of a GUMMETAL® that has the concentration Ti-36Nb-2Ta-3Zr-0.3O in mass %. In one embodiment, stabilization member 238 is comprised of TiNbZrTa.

[0036] In some embodiments, stabilization member 238 is comprised of a single material. In other embodiments, stabilization member 238 is comprised of more than one material. In one embodiment, stabilization member 238 has an inner core comprised of a first material and an outer core comprised of a second material. In one embodiment, stabilization member 238 has a coating. In one embodiment, stabilization member 238 is substantially solid. In other embodiments, stabilization member 238 is at least partially hollow. In some embodiments, stabilization member 238 has a lower degree of flexibility in one radial direction than another radial direction (e.g., greater flexibility along the sagittal plane than the coronal plane) such as by having a rectangular cross section.

[0037] In one embodiment, stabilization member 238 is a solid cylindrical rod comprised of metal and has a diameter d of less than or equal to approximately 8 mm. In one embodiment, the cylindrical rod has a diameter of between approximately 4 mm and approximately 8 mm. In one embodiment, the cylindrical rod has a diameter of between 4 mm and 8 mm. In one embodiment, the cylindrical rod has a diameter of one of approximately 4 mm, approximately 5 mm,

approximately 6 mm, approximately 7 mm or approximately 8 mm. In one embodiment, the cylindrical rod has a diameter of one of 4 mm, 5 mm, 6 mm, 7 mm or 8 mm. In one embodiment, stabilization member 238 is a solid cylindrical rod comprised of TiNbZrTa and has a diameter d of less than or equal to approximately 8 mm. In one embodiment, stabilization member 238 is a solid cylindrical rod comprised of GUMMETAL® and has a diameter d of less than or equal to approximately 8 mm. In one embodiment, stabilization member 238 is a solid cylindrical rod comprised of TiNbZrTa and has a diameter d of 8 mm. In one embodiment, stabilization member 238 is a solid cylindrical rod comprised of GUMMETAL® and has a diameter d of 8 mm.

[0038] In one embodiment, the fixation system 234 may be attached to two or more vertebrae 100 using the attachment members 236 to secure a stabilization member 238 to the spine 120. The stabilization member 238 may be moveable, axially and/or radially, relative to the attachment members 236 after the attachment members 236 are secured to the spine in order to position the vertebrae 100 relative to one another. Once the stabilization member 238 and spine 120 are in the desired position, the stabilization member 238 may be secured in place using clamp members 236a to at least temporarily fix the stabilization member 238 with respect to each attachment member 236. In other embodiments, the stabilization member 238 is fixed with respect to one or more attachment members 236 and/or is integral with respect to one or more of the attachment members 236 prior to inserting the fixation system 234 into the body.

[0039] It will be appreciated by those skilled in the art that changes could be made to the exemplary embodiments shown and described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the exemplary embodiments shown and described, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the claims. For example, specific features of the exemplary embodiments may or may not be part of the claimed invention and features of the disclosed embodiments may be combined. Unless specifically set forth herein, the terms "a", "an" and "the" are not limited to one element but instead should be read as meaning "at least one".

[0040] It is to be understood that at least some of the figures and descriptions of the invention have been simplified to focus on elements that are relevant for a clear understanding of the invention, while eliminating, for purposes of clarity, other elements that those of ordinary skill in the art will appreciate may also comprise a portion of the invention. However, because such elements are well known in the art, and because they do not necessarily facilitate a better understanding of the invention, a description of such elements is not provided herein.

Claims

CLAIMS I/we claim:

1. An orthopedic implant comprising: an implant configured to support a first bone segment relative to a second bone segment, the implant being comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa.

2. The orthopedic implant of claim 1, wherein the material is metal.

3. The orthopedic implant of claim 2, wherein the metal is a titanium alloy.

4. The orthopedic implant of claim 3, wherein the titanium alloy is TiNbZrTa.

5. The orthopedic implant of claim 3, wherein the titanium alloy is GUMMETAL®.

6. The orthopedic implant of claim 1, wherein the implant is a spinal stabilization member.

7. The orthopedic implant of claim 6, wherein the spinal stabilization member includes a cylindrical rod.

8. The orthopedic implant of claim 7, wherein the cylindrical rod has a diameter of less than or equal to 8 mm.

9. The orthopedic implant of claim 6 further comprising: a first attachment member configured to couple to a first vertebra and having a first clamp member; and a second attachment member configured to couple to a second vertebra and having a second clamp member, wherein the spinal stabilization member is configured to couple to the first clamp member and the second clamp member.

10. The orthopedic implant of claim 1, wherein the implant is a total spinal disc replacement.

11. The orthopedic implant of claim 1 , wherein the implant is an intramedullary nail.

12. The orthopedic implant of claim 1, wherein the implant is configured to allow the first bone segment to move relative to the second bone segment.

13. The orthopedic implant of claim 1, wherein the implant is configured to move the first bone segment relative to the second bone segment.

14. A method of implanting an orthopedic implant comprising: implanting an implant into a patient, the implant being configured to support a first bone segment relative to a second bone segment and being comprised of a material having an elastic modulus of approximately 40 GPa and a tensile strength of at least approximately 1000 MPa; and cutting at least a portion of the implant off from an end of a remainder of the implant without further surface treatment to the end of the remainder of the implant.

15. The method of claim 14, wherein the material is GUMMETAL®.