Hemi-artificial contoured spinal fusion implants made of a material other ...

HEMI-ARTIFICIAL CONTOURED SPINAL FUSION IMPLANTS MADE OF A MATERIAL OTHER THAN BONE

RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No. 10/112,747, filed Apr. 2, 2002; which claims the benefit of Provisional Application No. 60/281,187, filed Apr. 3, 2001, and Provisional Application No. 60/281,124, filed Apr. 2, 2001; all of which are incorporated by reference herein.

FIELD OF THE INVENTION

[0002] The present invention relates generally to interbody spinal implants preferably adapted for placement into an implantation space created across the height of a disc space between two adjacent vertebral bodies for the purpose of correcting spinal disease at that interspace. The spinal implants are made of an implant material that is other than bone and may or may not be resorbable. The implants are adapted such that fusion occurs at least in part through the implants.

DESCRIPTION OF THE RELATED ART

[0003] Implants for placement between adjacent vertebral bodies in the spine come in a variety of shapes and sizes and are made of a variety of materials. Such implants for use in human spinal surgery include implants made of selected inert materials, such as titanium, that have a structure designed to promote fusion of the adjacent vertebral bodies by allowing bone to grow through the implant to thereby fuse the adjacent vertebral bodies.

[0004] The spinal disc that resides between adjacent vertebral bodies maintains the spacing between those vertebral bodies and, in a healthy spine, allows for relative motion between the vertebrae. At the time of surgery, for example in the instance where fusion is intended to occur between adjacent vertebral bodies of a patient's spine, the surgeon typically prepares an opening at the site of the intended fusion by removing some or all of the disc material that exists between the adjacent vertebral bodies to be fused. Because the outermost layers of bone of the vertebral end plate are relatively inert to new bone growth, the surgeon must work on the end plate to remove at least the outermost cell layers of bone to gain access to the blood-rich, vascular bone tissue within the vertebral body. In this manner, the vertebrae are prepared in a way that encourages new bone to grow into or through an implant that is placed between the vertebral bodies.

[0005] Present methods of forming this space between adjacent vertebral bodies generally include the use of one or more of the following: hand held biting and grasping instruments known as rongeurs; drills and drill guides; rotating burrs driven by a motor; osteotomes and chisels, and a double wheel cutter or vertebral interspace preparation device. In particular, the double wheel cutter or vertebral interspace preparation device, as disclosed by Michelson in WO 99/63891, incorporated herein by reference, is adapted for linear insertion, i.e., insertion along a single axis, and without the need to substantially move the device from side to side within the disc space along a second axis. In such a preferred embodiment, the device has at its working end an

abrading element having a width generally corresponding to the width of the implant to be implanted.

[0006] There is a desire to improve congruity at the interfaces of the implant to the adj acent vertebral bodies, and to achieve stability of the implant. Therefore it is advantageous for the contour of the implants to closely match the implantation space formed between and at least in part into the adjacent vertebral bodies to allow a more uniform load transfer across the implant between the vertebral bodies.

[0007] As it is desirable to take advantage of all these benefits, there exists a need for an improved interbody spinal fusion implant made of a material other than bone having a configuration that provides for an improved congruity of the implant to the vertebral bodies and improved implant stability.

SUMMARY OF THE INVENTION

[0008] In accordance with the purposes of the present invention, as embodied and broadly described herein, an artificial interbody spinal fusion implant made of a material other than bone is provided for insertion at least in part into an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine. The implant includes a leading end for insertion first into the disc space and a trailing end opposite the leading end. The implant has a length from the leading end to the trailing end. The leading end is configured in the shape of approximately one half of a circle from side to side. The implant also includes opposed upper and lower portions between the leading and trailing ends that are adapted to be placed within the disc space to contact and support the adjacent vertebral bodies. The upper and lower portions are non-arcuate along at least a portion of the length of the implant. The upper and lower portions include at least one opening in communication with one another and adapted to hold bone growth promoting material for permitting for the growth of bone from vertebral body to vertebral body through the implant. The implant also includes opposite sides between the upper portion and lower portion, and between the leading and trailing ends. At least one of the opposite sides is at least in part straight along at least a portion of the length of the implant.

[0009] In accordance with the purposes of the present invention, as embodied and broadly described herein, an interbody spinal fusion implant made of a material other than bone is provided for insertion at least in part into an implantation space formed across the height of a disc space between adjacent vertebral bodies of a human spine. The implant includes a leading end for insertion first into the disc space and a trailing end opposite the leading end. The implant has a length from the leading end to the trailing end. The leading end is configured from side to side in the shape of approximately one half of a first circle. The trailing end has a radius of curvature of a second circle from side to side. The second circle has a radius greater than the radius of the first circle. The implant also includes opposed upper and lower portions between the leading and trailing ends that are adapted to be placed within the disc space to contact and support the adjacent vertebral bodies. The upper and lower portions include at least one opening in communication with one another and adapted to hold bone growth promoting material for permitting for the growth of bone from vertebral body to vertebral body through the implant. The implant has a maximum width that is greater than one-half of the width of the adjacent vertebral bodies into which the implant is adapted to be inserted.

[0010] Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a top plan view of a vertebral body in the lumbar spine with an implantation space formed to receive a spinal implant having a radius of curvature at the leading end that is less than the radius of curvature of the trailing end of the anterior aspect of the vertebral body between the sides of the implantation space.

[0012] FIG. 2 is a side elevation view of two adjacent vertebral bodies in the lumbar spine with the implantation space of FIG. 1 formed across the height of the spinal disc and into the adjacent vertebral bodies.

[0013] FIG. 3 is a side perspective view of the implantation space of FIG. 1.

[0014] FIG. 4 is a top plan view of a vertebral body in the cervical spine with an implantation space formed to receive a spinal implant having a radius of curvature at the leading end that is less than the radius of curvature of the trailing end of the anterior aspect of the vertebral body.

[0015] FIG. 5 is a side elevation view of two adjacent vertebral bodies in the cervical spine with the implantation space of FIG. 4 formed across the height of the spinal disc and into the adjacent vertebral bodies.

[0016] FIG. 6 is a side perspective view of the implantation space of FIG. 4.

[0017] FIG. 7 is a top plan view of a vertebral body in the lumbar spine and a preferred embodiment of an implant in accordance with the present invention installed into the implantation space of FIG. 1.

[0018] FIG. 8 is a side elevation view of two adjacent vertebral bodies with the implant of FIG. 7 installed into the implantation space of FIG. 1 formed across the height of the spinal disc and into the adjacent vertebral bodies.

[0019] FIG. 9 is a top plan view of the implant of FIG. 7.

[0020] FIG. 10 is a side elevation view of the implant of FIG. 7.

[0021] FIG. 11 is a leading end view of the implant of FIG. 7.

[0022] FIG. 12 is a trailing end view of the implant of FIG. 7.

[0023] FIG. 13 is a top plan view of another preferred embodiment of an implant in accordance with the present invention for use in the implantation space of FIG. 4.

[0024] FIG. 14 is a rear perspective view of another preferred embodiment of an implant in accordance with

another preferred embodiment of the present invention having two members that are preferably mirror images of one another.

[0025] FIG. 15 is a top plan view of one of the members of the implant of FIG. 14.

[0026] FIG. 16 is an interior side elevation view of one of the members of the implant of FIG. 14.

[0027] FIG. 17 is an exterior side elevation view of one of the members of the implant of FIG. 14.

[0028] FIG. 18 is a leading end view of one of the members of the implant of FIG. 14.

[0029] FIG. 19 is a trailing end view of one of the members of the implant of FIG. 14.

[0030] FIG. 20 is a top plan view of another preferred embodiment of an implant in accordance with the present invention with bone engaging screws.

[0031] FIG. 21 is a side elevation view of the implant of FIG. 20.

[0032] FIG. 22 is a leading end view of the implant of FIG. 20.

[0033] FIG. 23 is a trailing end view of the implant of FIG. 20 with the bone engaging screws and lock installed.

[0034] FIG. 24 is a trailing end view of the implant of FIG. 23 without the bone engaging screws and lock installed.

[0035] FIG. 25 is a partial cross sectional side view of a preferred embodiment of a bone screw lock in accordance with the present invention for use with the implant of FIG. 20.

[0036] FIG. 26 is a cross sectional side view of another preferred embodiment of a bone screw lock in accordance with the present invention.

DETAILED DESCRIPTION OF THE
INVENTION

[0037] The following description is intended to be representative only and not limiting and many variations can be anticipated according to these teachings, which are included within the scope of this inventive teaching. Reference will now be made in detail to the preferred embodiments of this invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0038] FIGS. 1-3 show an implantation space 50 formed across the height of the space occupied by a spinal disc D and into vertebral bodies V in the lumbar spine. Implantation space 50 is preferably formed with the apparatus and method disclosed by Michelson in U.S. Pat. No. 6,083,228, and WO 99/63891, the disclosures of which are both incorporated herein by reference. The instruments and method are not the subject matter of this application. It is understood that the preparation of the implantation space shown therein are a preferred instrument and method of preparing the implantation spaces and that any method and instrumentation