Skeletal Stabilization Implant
A spinal implant is described in this disclosure. The implant includes first and second pieces separated by a controlled break location. Spinal implant kits having multiple spinal implant pieces derived from a common source also are disclosed.
Latest ZIMMER SPINE, INC. Patents:
This application claims priority to U.S. Provisional application 60/325,804, filed Sep. 28, 2001.
FIELD OF THE INVENTIONThe present invention relates generally to skeletal implants. More particularly, the present invention relates to implants for stabilizing intervertebral joints.
BACKGROUND OF THE INVENTIONChronic back problems cause pain and disability for a large segment of the population. In many cases, chronic back problems are caused by intervertebral disc disease. When an intervertebral disc is diseased, the vertebrae between which the disc is positioned may be inadequately supported, resulting in persistent pain. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain and debilitating effects associated with disc disease.
Spinal stabilization systems and procedures have been developed to stabilize diseased intervertebral joints and, in some cases, to fuse the vertebrae that are adjacent the diseased joint space. Most fusion techniques include removing some or all of the disc material from the affected joint, and stabilizing the joint by inserting an implant (e.g., a bone graft or other material to facilitate fusion of the vertebrae) in the cleaned intervertebral space.
Spinal implants can be inserted into the intervertebral space through an anterior approach, a posterior approach, or postero-lateral approach. The anterior approach involves a surgeon seeking access to the spine through the front (i.e., abdominal area) of the patient. The posterior approach involves a surgeon seeking access to the spine through the back of the patient. The postero-lateral approach is similar to the posterior approach with access coming more from either or both sides of the patient. A variety of different anterior, posterior and postero-lateral techniques are known.
It is often an advantage to use the posterior approach because such an approach typically involves a smaller and less intrusive opening than those required by anterior approach techniques. Because a posterior approach involves a smaller opening, two or more implants are often used in this approach as compared to using a single larger implant. For example, in one technique, adjacent vertebral bodies are stabilized by implanting separate implants between the vertebral bodies on opposite sides of a sagittal plane passing through the midline of the vertebral bodies. When using multiple implants to support adjacent vertebrae, it is desirable for the implants to have similar or identical mechanical properties so that uniform support is provided on both sides of the sagittal plane. In some instances, it also is desirable for the implants to have similar or identical biologic properties (e.g., to reduce the risk of tissue rejection and to enhance the uniformity of creeping substitution).
SUMMARY OF THE INVENTIONOne aspect of the present invention relates to skeletal implants and skeletal implant kits adapted to ensure that multiple implants used to support opposing vertebrae have been derived from the same source.
A variety of other aspects of the invention are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. The aspects of the invention relate to individual features, as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is directed to skeletal implants, skeletal implant kits and methods for placing implants between bones desired to be fused. It is preferred for the implants to be used for vertebral/spinal applications such as fusing cervical, thoracic and/or lumbar intervertebral joints. In the case of fusing an intervertebral joint, implants in accordance with the principles of the present invention can be implanted using an anterior, posterior or postero-lateral approach to the patient's vertebrae.
As used herein, an “implant” includes any implant suitable for facilitating fusion between adjacent bones and includes implants prepared from known implant materials including, non-bone material such as titanium, stainless steel, porous titanium, bio-glass, calcium phosphate, ceramic, carbon fiber-based polymers, biodegradable and polymers. However, it is preferred for implants in accordance with the principles of the present invention to be derived from natural bone tissue (e.g., allograft and xenograft bone). It is most preferred for implants in accordance with the principles of the present invention to be derived from natural bone such as from a cadaveric allograft bone source. For example, the implants can be derived by cross-sectioning cortical rings from cadaveric allograft bones such as femur, tibia or fibia bones. Alternatively, the implants can be formed/molded from ground, sintered or composite bone material. Bone tissue cut from a human femur bone is particularly suited for use in practicing the principles of the present invention. Xenograft bones (e.g., from a bovine source) also can be used.
The term “allograft” will be understood to mean a bone implant from a donor transplanted to a genetically dissimilar recipient of the same species. The term “xenograft” will be understood to mean a bone implant from a donor transplanted to a recipient of a different species.
As shown in
Referring again to
Preferably, the controlled break location is configured to allow the first and second pieces 22, 24 of the implant member 20 to be manually broken or “snapped” apart without requiring the use of a tool. The controlled break structure ensures that the implant 20 will break at a predetermined location (e.g., at the axis of symmetry 38 for the embodiment of
Although the embodiment of
Referring again to
The grooves 44 of the implant 20 function to resist migration of the implant upon implantation between opposing bone surfaces. Other structures such as teeth, serrations, cross-cut serrations, notches, bumps, ridges, projections or other surface treatments could also be used.
While the implant 20 can have a constant thickness, it is preferred for the implant 20 to be slightly tapered. In one embodiment, the spinal implant 20 can be tapered about 3 degrees such that a front end 48 of the implant 20 has a thickness Tf that is greater than a thickness Tr located at a rear end 50 of the implant 20. The thicknesses Tf and Tr are labeled in
While other materials could be used, the spinal implant 20 is preferably derived from an allograft bone. In one embodiment, the implant 20 is a transverse cross-section from the femur of a cadaver, and includes a cortical ring. After the ring has been cross-sectioned, relatively soft bone tissue and marrow from the interior of the ring is preferably removed. Next, a portion of the outer cortical ring is removed (e.g., by a technique such as mechanically cutting with a blade or abrasion tool, laser cutting, etching, etc.) to provide the open end of the pocket 26 of the “C” shaped implant 20 (see
The configuration of the implant of
To implant the spinal implant 20, a diseased disc between two adjacent vertebrae 72, 74 is preferably removed using a conventional discectomy procedure (i.e., partial or complete discectomy). Opposing end plates 72′ and 74′ of the vertebrae 72, 74 are then preferably prepared to provide relatively flat contact surfaces. The end plates 72′, 74′ are then conditioned (e.g., with a rasp) to provide a more uniform and osteoconductive/osteoinductive site for the implant 20. After the implant site has been prepared, the sterile package of the kit 60 is opened, allowing the surgeon to access the implant 20. Preferably, the implant 20 is then manually “snapped” or broken into two pieces. One of the pieces 22 is then placed on the insertion tool 52. With the insertion tool, the surgeon inserts the first piece 22 into the cleared intervertebral space between the vertebrae 72, 74. Preferably, the first piece 22 is inserted using a posterior approach. As the first piece 22 is inserted, an insertion force is transferred through the insertion tool 52 to the insertion force surface 40 of the first implant piece 22. As shown in
It will be appreciated that the kit 60′ can be used in essentially the same manner as the kit 60, except the kit 60′ does not require the surgeon to manually break the spinal implant 20 into the separate first and second pieces 22, 24. In both embodiments, the surgeon can be assured that both the first and second pieces 22, 24 of the spinal implant 20 were derived from the same donor source.
With regard to the foregoing description, it is to be understood that changes may be made in detail without departing from the scope of the present invention. It is intended that the specification and depicted aspects of the invention may be considered exemplary, only, with a true scope and spirit of the invention being indicated by the broad meaning of the following claims.
Claims
1-25. (canceled)
26. A method of manufacturing a skeletal implant, the method comprising:
- isolating a segment of bone; and
- forming a controlled break location in the segment of bone.
27. The method of claim 26, wherein the bone is from an allograft bone source.
28. The method of claim 26, wherein the controlled break location is formed by forming a notch in the segment of bone.
29. A method of manufacturing a skeletal implant, the method comprising:
- isolating a segment of bone having first and second opposite pieces; and
- forming a controlled break location in the segment of bone positioned between the first and second pieces.
30. The method of claim 29 wherein isolating the segment of bone involves forming a convex outer boundary and a concave inner boundary, wherein forming the controlled break location involves forming a first notch at the outer boundary.
31. The method of claim 30, wherein forming the controlled break location further involves forming a second notch at the inner boundary.
32. A skeletal implant kit comprising:
- a first implant derived from a bone source;
- a second implant derived from the same bone source as the first implant; and
- a package containing the first and second implants.
33. The implant kit of claim 32, wherein the bone source is a cadaveric femur bone.
34. The implant kit of claim 32, wherein the first and second implants are substantially the same size and shape.
35. A skeletal implant kit comprising:
- a unitary implant breakable into a plurality of pieces, the implant being derived from a bone source;
- a package containing the unitary implant.
36. The skeletal implant kit of claim 35, wherein the unitary implant is manually breakable.
37. The skeletal implant kit of claim 35, wherein the unitary implant is breakable into first and second pieces.
38. The skeletal implant kit of claim 35, wherein the pieces are substantially the same size and shape.
39. The skeletal implant kit of claim 35, wherein the bone source is a cadaveric femur bone.
40. A method for stabilizing bone surfaces, the method comprising:
- inserting a first implant between the bone surfaces, the first implant comprising a first portion of a bone source; and
- inserting a second implant between the bone surfaces, the second implant comprising a second portion from the bone source.
41. The method of claim 40, wherein the bone source is from a human donor.
42. The method of claim 40, wherein the bone source is a femur bone.
43. The method of claim 40, wherein the bone source includes an allograft bone source.
44. The method of claim 40, wherein the first and second implants are inserted from a posterior approach.
45. The method of claim 40, wherein the first and second implants are derived from a unitary implant.
46. A method for stabilizing two vertebrae, the method comprising:
- separating a one-piece implant into at least two implant pieces;
- inserting a first one of the implant pieces between the two vertebrae; and
- inserting a second one of the implant pieces between the two vertebrae.
47. The method of claim 46, wherein the first and second implant pieces are inserted from a posterior approach.
48. The method of claim 46, further comprising obtaining the one-piece implant from a sterile package before separating the one-piece implant into the first and second implant pieces.
49. The method of claim 46, wherein the one-piece implant is separated into the first and second pieces by manually breaking the one-piece implant.
50. The method of claim 49, wherein the one-piece implant is broken at a predefined break location.
51. The method of claim 46, wherein the one-piece implant is separated into the first and second pieces by cutting the one-piece implant with a tool.
52. The method of claim 46, wherein the one-piece implant is from an allograft bone source.
53. A skeletal implant comprising:
- a first implant portion;
- a second implant portion; and
- a third portion joining, and integral with, the first and second implant portions and having a breakable location,
- the first and second implant portions being adapted to be independently implantable into a patient after the third portion is broken at the breakable location, each of the first and second implant portions comprising a mounting structure adapted to engage an insertion tool for implanting the portion, wherein the mounting structure comprises a force-application surface and an opening defined through the surface, the opening adapted to receive a protrusion on the insertion tool.
54. The implant of claim 53, wherein each of the first and second implant portions has an upper surface adapted to engage a first vertebra in the patient and a lower surface adapted to engage a second vertebra in the patient.
55. The implant of claim 54, wherein the opening is an elongated channel along a longitudinal axis, and the force-application surface is substantially perpendicular to the longitudinal axis.
56. A skeletal implant comprising:
- first and second implant members, each comprising: a top surface adapted to engage and support an upper vertebra, and a bottom surface adapted to engage and support a lower vertebra; and
- a single controlled break location positioned between the first and second implant members, the controlled break location including a region of reduced cross-sectional area, the region of reduced cross-sectional area being smaller than nominal cross-sectional areas of each of the first and second implant members, wherein the first and second implant members are symmetrically disposed with respect an axis of symmetry passing through the controlled break location.
57. A skeletal implant comprising:
- first and second implant members, each comprising: a top surface adapted to engage and support an upper vertebra, and a bottom surface adapted to engage and support a lower vertebra; and
- a single controlled break location positioned between the first and second implant members, the controlled break location including a region of reduced cross-sectional area, the region of reduced cross-sectional area being smaller than nominal cross-sectional areas of each of the first and second implant members, wherein the skeletal implant member is C-shaped.
Type: Application
Filed: Sep 11, 2006
Publication Date: Jan 11, 2007
Applicant: ZIMMER SPINE, INC. (Minneapolis, MN)
Inventors: Chistopher Banick (Orono, MN), Jack Dant (St. Paul, MN), David Hanson (St. Louis Park, MN), Rodney Houfburg (Prior Lake, MN)
Application Number: 11/530,681
International Classification: A61F 2/44 (20060101);