US20100286777A1 - Stand alone anterior cage - Google Patents

Abstract

The present invention teaches an improved spinal fusion implant and method of implanting same. The implant includes a shell and an insert, the insert capable of situating first and second plates of the shell with respect to each other and of preventing unwanted loosening of fasteners placed through the shell and into the adjacent vertebral bodies. The method includes implanting a shell, selecting an insert from a plurality of inserts, and placing an insert between first and second plates of the shell.

Description

BACKGROUND OF THE INVENTION
• The present invention is directed to spinal implants, and more particularly, spinal fusion implants.
• The deterioration of vertebral bodies and/or vertebral discs is a major cause of back and neck pain in many patients. Through the years, many different techniques for restoring the natural anatomical spacing in the spine and thereby alleviating this pain have been developed and practiced by surgeons. For instance, implants and techniques for implanting such implants have been designed to preserve motion between adjacent vertebral bodies. These motion preserving implants are adapted to emulate a removed spinal disc. Examples of such implants (and the methods of implanting same) are disclosed in U.S. Pat. Nos. 6,989,032 (“the '032 patent”) and 7,169,182 (“the '182 patent”), the disclosures of which are hereby incorporated by reference herein. Nonetheless, even given the success of such motion preserving devices, it is still sometimes necessary to fuse adjacent vertebral bodies so that no movement is permitted therebetween.
• Spinal fusion surgery typically involves removing the disc material from between adjacent vertebral bodies, which thereby creates an empty intervertebral space. In this space is implanted an implant or cage that is then fixably mounted to the end plates of the adjacent vertebral bodies. Bone growth is often permitted through the implant, and is in fact sometimes provoked by the placement of bone growth inducing substances within the cage. However, even given this bone growth through the cage, it is sometimes necessary to at least initially mount the cage to the vertebral bodies through the use of fixation elements such as screws. Furthermore, it has also determined that providing an angled implant or cage can aid in returning the adjacent vertebral bodies to their natural “lordotic” angle.
• Even if a surgeon initially determines that he or she wishes to perform a motion preserving surgery on a patient, sometimes it becomes apparent during the procedure that a fusion procedure would benefit the patient. Likewise, surgeons often recognize the need to fuse vertebral bodies at levels adjacent to the initial one in question. Thus, it is desirable to have a fusion implant that can easily be implemented and implanted utilizing the tools and procedure used in a motion preserving surgery. Moreover, it is also desired to have such a fusion implant be easily implanted using those tools, easily affixed to the intervertebral bodies, and prevented from becoming dislodged even after just initially being implanted.
• Therefore, there exists a need for an improved spinal fusion device.
SUMMARY OF THE INVENTION
• A first aspect of the present invention is a spinal implant for fusing together first and second vertebral bodies. In accordance with one embodiment of this first aspect, the implant includes a first member having a first surface for engaging the first vertebral body, a second surface, and a first opening extending between the first and second surfaces. The implant also includes a second member having a third surface for engaging the second vertebral body, a fourth surface, and a second opening extending between the third and fourth surfaces. A living hinge connecting the first and second members is also included and preferably allows for movement of the first and second members with respect to one another. Finally, an insert is disposed between the first and second members, the insert covering the first and second openings about the second and fourth surfaces.
• In accordance with other embodiments of the first aspect, the second and fourth surfaces may include a projection for retaining the insert between the first and second members, and in other embodiments each of the second and fourth surfaces include these projections. The insert may be constructed of bone, polymer, metal, or the like. Furthermore, the implant may include a first screw disposed in a first opening and a second screw disposed in a second opening, and the insert may include a portion for preventing backout of the first and second screws. In still further embodiments, the first member may include a third opening extending between the first and second surfaces, and the second member may include a fourth opening extending between the third and fourth surfaces. In this embodiment, the insert may include a main body, a first portion for covering the first and second openings, and a second portion for covering the third and fourth openings. The insert may also include an aperture for engagement with a tool. In accordance with this further embodiment, a first screw may be disposed in the first opening, a second screw may be disposed in a second opening, a third screw may be disposed in the third opening, and a fourth screw may be disposed in the fourth opening. The insert includes a first portion for preventing backout of the first and second screws and a second portion for preventing backout of the third and fourth screws. Finally, in accordance with certain embodiments, the implant may include a bone growth aperture extending through the first member, the insert, and the second member, and the implant may be designed to provide a nonparallel relationship between the first and second surfaces, such that the vertebral bodies exhibit a similar relationship.
• The second aspect of the present invention is also directed to a spinal implant for implantation between first and second vertebral bodies. In accordance with one embodiment of this second aspect, the implant includes a shell and an insert. The shell preferably includes a first plate for engaging the first vertebral body, the first plate including a first hole formed therethrough, a second plate for engaging the second vertebral body, the second plate including a second hole formed therethrough, and a resilient member connecting the first and second plates. The insert on the other hand may include a main body and a portion capable of covering at least one of the first or second holes when the insert is disposed between the first and second plates.
• In accordance with other embodiments of the second aspect, the implant may include a first screw disposed in the first hole, and a second screw disposed in the second hole. A portion of the insert is preferably capable of preventing backout of both of the first and second screws when the insert is disposed between the first and second plates. The insert may be constructed at least partially from materials selected from the group consisting of bone, polymer, and metal. At least one of the first and second plates may include a projection for retaining the insert between the first and second plates, but in certain embodiments both the first and second plates may include such projections. The implant may also include a third hole formed through the first plate and a fourth formed through the second plate, and a first screw disposed in the first hole, a second screw disposed in the second hole, a third screw disposed in the third hole, and a fourth screw disposed in the fourth hole. The insert may include a first portion for preventing backout of the first and second screws and a second portion for preventing backout of the third and fourth screws. A bone growth aperture may extend through the first member, the insert, and the second member. The insert may include an aperture for engagement with the tool. Preferably, the first and second plates are located in nonparallel planes, and such may be caused by the insert being placed therebetween.
• The third aspect of the present invention is a method of fusing together first and second vertebral bodies. In accordance with one embodiment of the present invention, the method includes the steps of preparing a space between the first and second vertebral bodies to a spinal implant, implanting a shell, the shell including a first plate, a second plate, and a living hinge connecting the first and second plates, placing a first screw through the first plate and into the first vertebral body, placing a second screw through the second plate and into the second vertebral body, and inserting an insert between the first and second plates, wherein the insert prevents backout of the first and second screws.
• In accordance with other embodiments of this third aspect, the inserting step may cause the first and second plates to move with respect to each other and such movement between the first and second plates is preferably translated to the first and second vertebral bodies. The method may also include the step of choosing an insert from a plurality of inserts. Moreover, the method may include the step of placing a third screw through the first plate and into the first vertebral body, and the step of placing a fourth screw through the second plate in the intervertebral body. Preferably, the insert prevents backout of the first, second, third, and fourth screws. The method may also include the step of retaining the insert between the first and second plates, where this retaining step may include engaging the insert with projections formed on the first and second plates. Finally, the method may also include the step of allowing bone growth through an aperture formed through the first plate, the insert, and the second plate.
BRIEF DESCRIPTION OF THE DRAWINGS
• A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description with reference to the accompanying drawings in which:
• FIG. 1 is a perspective view of an intervertebral fusion implant according to one embodiment of the present invention.
• FIG. 2 is a front view of the implant shown inFIG. 1.
• FIG. 3 is a rear view of the implant shown inFIG. 1.
• FIG. 4 is a right side view of the implant shown inFIG. 1.
• FIG. 5 is a top view of the implant shown inFIG. 1.
• FIG. 6 is a cross-sectional view of the implant shown inFIG. 1 taken along line A-A ofFIG. 5.
• FIG. 7 is a perspective view of a shell from the implant ofFIG. 1.
• FIG. 8 is a front view of the shell shown inFIG. 7.
• FIG. 9 is a right side view of the shell shown inFIG. 7.
• FIG. 10 is a perspective view of an insert from the implant shown inFIG. 1.
• FIG. 11 is a front view of the insert shown inFIG. 10.
• FIG. 12 is a rear view of the insert shown inFIG. 10.
• FIG. 13 is a right side view of the insert shown inFIG. 10.
• FIG. 14 is a top view of the insert shown inFIG. 10.
• FIG. 15 is a prospective view of adjacent vertebral bodies having been prepared to receive a fusion implant.
• FIG. 16 is a prospective view of the vertebral bodies ofFIG. 15 having the shell shown inFIG. 7 implanted therebetween.
• FIG. 17 is a prospective view similar to the one shown inFIG. 16 with screws implanted through the shell and into the adjacent vertebral bodies.
• FIG. 18 is a view similar to that ofFIG. 17 with the insert ofFIG. 10 partially implanted.
• FIG. 19 is a view similar toFIG. 18 with the insert completely implanted.
DETAILED DESCRIPTION
• Referring to the drawings, wherein like reference numerals refer to like elements,FIGS. 1-6 depict a first embodiment intervertebral fusion device or spinal implant for fusing together first and second vertebral bodies, designated generally byreference numeral10. As is shown in the drawings,implant10 includes ashell12 and aninsert14. Moreover,implant10 is also provided with a plurality of fasteners (shown in the drawings as screws16a-d) for placement through portions of the shell and into adjacent vertebral bodies. However, one of ordinary skill in the art would readily recognize that other types of fasteners could be utilized, e.g., pins or the like. The specifics of each of the components ofimplant10, as well as their operation and use will be discussed more fully below.
• As is shown inFIGS. 1-6 and even more specifically shown inFIGS. 7-9,shell12 includes a first plate ormember18, a second plate ormember20, and a pair of resilient or livinghinge members22aand22b.First member18 includes afirst surface24 for engaging an upper vertebral body, asecond surface26 for engagement withinsert14, a plurality of bone growth apertures collectively referred to byreference numeral28, and twofastener holes30 and32.First surface18 is formed with a plurality of vertebral body engaging members, includingteeth34 and surfaces36.Second surface26 is formed with countersunksurfaces38 and40 in the vicinity of fastener holes30 and32, respectively, and aprojection42 extending towardsecond member20. Similarly,second member20 includes athird surface44 for engagement with the lower vertebral body, afourth surface46 for engagement withinsert14, a plurality of bone growth apertures collectively referred to withreference numeral48, and twofastener holes50 and52. Also in a similar fashion tofirst member18,third surface44 is formed with vertebral engagingelements including teeth54 and surfaces56, whilesecond surface46 includescountersinks58 and60 in the vicinity of fastener holes50 and52, respectively, andprojection62 extending toward first18. Moreover, as is best shown inFIG. 8, extending fromsecond surface26 offirst member18 are extensions64 and66, and extending fromfourth surface46 ofsecond member20 are extensions68 and70. These extensions create a substantiallyrectangular space72 for reception ofinsert14, as will be discussed more fully below.First plate18 may also includeapertures74 andsecond plate20 may includeapertures76, which are utilized in engaging an insertion tool.
• Resilient members22aand22bare shown as living hinges. Essentially, these elements are curved elements being made of a material capable of bending upon an application of force to one of or both of first andsecond members18 and20. For example, upon placement of differentlysized inserts14 between the first and second members, hinges22aand22bare capable of allowing for the expansion or the contraction of the device. While shown in the drawings as being composed of the same material as first andsecond members18 and20, it is noted thatmembers22aand22bcan be constructed of different materials. Likewise, the overall shape ofmembers22aand22bcan vary from the rounded structures shown in the drawings.
• In the embodiment shown in the drawings,shell12 is formed of titanium, but it is noted that other materials such as stainless steel, polymer, or the like can be utilized. It is also noted that the specific configuration ofshell12 may widely vary in different embodiments of the present invention. For example, the overall shape of the shell which is shown as being similar in nature to the implants shown and described in the '032 and '182 patents, but may vary depending upon the different portion of the spine in which it is to be implanted or the design of an implant of which it is to emulate. The vertebral engaging surfaces may also vary, including the specific vertebral engaging members disposed thereon. Furthermore, the apertures extending through the first and second members may vary, including the overall amount of bone growth apertures and screw holes. While fastener holes30,32,50, and52 are shown as being angled, other angles and/or perpendicular configurations are contemplated. Likewise, the configuration ofprojections42 and62 may also vary as can thespace72 for acceptinginsert14.
• Turning now to the configuration ofinsert14, it is noted that such is preferably of a unitary construction. However, in other embodiments, different configurations are contemplated. With specific reference toFIGS. 10-14, insert14 includes amain body80 having afront face82, arear face84, atop surface86, abottom surface88, aleft side surface90, and aright side surface92. Extending from the left and right areflanges94 and96, such that they form a continuous surface withfront face82,flange94 includes arear face95, andflange96 includes arear face97. In addition, as is shown in the drawings, formed through top surface and bottom surface is anaperture98, which generally cooperates withapertures28 and48 of first andsecond members18 and20, respectively, in order to provide for a bone growth channel between adjacent vertebral bodies. Finally, front face includes anaperture100, which is shown as being threaded for engagement with an insertion tool (not shown).
• It is to be understood thatinsert14 may widely vary from that which is shown in the drawings. For one, insert14 may vary to properly cooperate with variations ofshell12. Certain portions ofinsert14 may also vary and still be capable of cooperating withshell12 as shown. For instance,flanges94 and96 may simply be extensions of front face82 (i.e., rectangular) rather than the rounded structures that are illustrated in the drawings. Moreover,aperture100 may be configured differently to engage an insertion tool (not shown). For instance, insert14 may include anaperture100 which is meant to cooperate with a spring detent or the like. Additionally, insert14 may include a differently configured aperture98 (or multiple apertures) for cooperation with like apertures formed in first andsecond members18 and20 ofshell12. Finally, insert14 may be constructed of many different types of materials. For example, it is contemplated to forminsert14 of PEEK™ or of a biological material such as bone. In the case of the latter, the patient's own bone may be utilized to forminsert14 by any one of many known processes.
• During a surgical procedure in which the above-discussedimplant10 is implanted, the surgeon first sees to the preparation of the intervertebral space between the adjacent vertebral bodies in order to be capable of receivingshell12. This is shown inFIG. 15 and may include the removal of disc material and/or the preparation of the end plates of the vertebral bodies.Shell12 is then inserted in the prepared space (seeFIG. 16). In this regard, an insertion tool (not shown) may be engaged withapertures74 and/or76 of the first or second plates, orshell12 may simply be placed by hand into the space. The above-discussed features ofsurfaces24 and44 (i.e., spikes34 and surfaces36) may aid in the retainment ofshell12 between the adjacent vertebral bodies. Once in place, fasteners (such as screws16a-16dshown inFIGS. 1-6) may be placed through fastener holes30,32,50, and52 and into the adjacent vertebral bodies (seeFIG. 17). Once again, it is noted that fastener holes30,32,50, and52 may be angled in any fashion to allow for specific placement of the fasteners throughshell12 and into the intervertebral bodies. It is noted that although the fasteners are shown inFIGS. 1-6 as screws having specific configurations, many different fastener configurations may be employed in fixingshell12 to adjacent vertebral bodies, including differently configured screws.
• Withshell12 in place, insert14 may then be placed between first andsecond plates18 and20, preferably into above-discussedspace72.Insert14 partially inserted intoshell12 is shown inFIG. 18. In placinginsert14, a tool (not shown) may be engaged with the threading ofaperture100, or, in the case of a differently configured aperture, another type of connection. Prior to engaging the insert with the tool, a surgeon may select oneinsert14 from a plurality of differently sized and/or shaped inserts. These different inserts ultimately affects the disposition ofplates18 and20 ofshell12. For example, a larger sized insert would increase the distance betweenplates18 and20, while differently shaped inserts may affect the amount of angle between the plates. Thus, depending upon the spacing or lordotic angle desired between adjacent vertebral bodies, different inserts having different sizes and/or differently angled upper and lower surfaces may be selected.
• Once the surgeon makes the proper determination of the insert to utilize, it is coupled with a tool (not shown) or placed by hand betweenplates18 and20 (seeFIG. 18). This placement of the insert preferably movesplates18 and20, and thusly the adjacent vertebral bodies to the position desired. Living hinges22aand22ballow for this movement while at the sametime forcing plates18 and20 towardinsert14. At a certain point, front face ofinsert14 is pushedpast projections42 and62 so that the insert is forcibly maintained withinspace72 of shell12 (seeFIG. 19). In this regard, it is noted thatprojections42 and62 are designed as ramps, which preferably allow for the easy insertion ofinsert14 withinspace72. However, once front face ofinsert14passes projections42 and62, the insert is thereby retained within the space. It is noted that other configurations forprojections42 and62 may be employed. Once in this position, flanges94 and96 ofinsert14 are disposed at least partially over a portion of the fasteners placed within fastener holes30,32,50, and52. In the preferred embodiment shown in the drawings,flanges94 and96 are placed over the heads of screws16a-16d(best shown inFIG. 2). This final position forinsert14 and its projections preferably prevents the loosening or backout of the screws that may occur. In other words,flanges94 and96 prevent the screws from coming out of the vertebral bodies.
• As is mentioned above, insert14 may be made of various materials. For example, the insert may be constructed at least partially of metal, polymer, and/or bone material. In the latter case, insert14 may encourage growth of bone throughaperture28,aperture98, andaperture48 to thereby fuse the adjacent vertebral bodies. Furthermore, it is contemplated that bone growth including substances may be placed within these apertures (or one of the apertures) in order to even further facilitate or, in the case of inserts constructed of nonbone material, promote such growth. It is contemplated that other embodiments ofshell12 and insert14 may include additional apertures which promote further grown from adjacent vertebral bodies therethrough.
• Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (37)

1. A spinal implant for fusing together first and second vertebral bodies, the implant comprising:

a first member having a first surface for engaging the first vertebral body, a second surface, and a first opening extending between the first and second surfaces;

a second member having a third surface for engaging the second vertebral body, a fourth surface, and a second opening extending between the third and fourth surfaces;

a living hinge connecting the first and second members and allowing for movement of the first and second members with respect to one another; and

an insert disposed between the first and second members, the insert covering the first and second openings about the second and fourth surfaces.

2. The spinal implant ofclaim 1, wherein one of the second or fourth surfaces includes a projection for retaining the insert between the first and second members.

3. The spinal implant ofclaim 2, wherein each of the second and fourth surfaces include projections.

4. The spinal implant ofclaim 1, wherein the insert is constructed of bone.

5. The spinal implant ofclaim 1, wherein the insert is constructed of a polymer.

6. The spinal implant ofclaim 1, wherein the insert is constructed of a metal.

7. The spinal implant ofclaim 1, further comprising a first screw disposed in the first opening and a second screw disposed in the second opening.

8. The spinal implant ofclaim 7, wherein the insert includes a portion for preventing back out of the first and second screws.

9. The spinal implant ofclaim 1, further comprising a third opening extending between the first and second surfaces of the first member, and a fourth opening extending between the third and fourth surfaces of the second member.

10. The spinal implant ofclaim 9, wherein the insert includes a main body, a first portion for covering the first and second openings and a second portion for covering the third and fourth openings.

11. The spinal implant ofclaim 10, wherein the main body of the insert includes an aperture for engagement with a tool.

12. The spinal implant ofclaim 10, further comprising a first screw disposed in the first opening, a second screw disposed in the second opening, a third screw disposed in the third opening, and a fourth screw disposed in the fourth opening.

13. The spinal implant ofclaim 12, wherein the insert includes a first portion for preventing back out of the first and second screws and second portion for preventing back out of the third and fourth screws.

14. The spinal implant ofclaim 13, further comprising a bone growth aperture extending through the first member, the insert, and the second member.

15. The spinal implant ofclaim 1, wherein the first and second surfaces are located in non-parallel planes.

16. The spinal implant ofclaim 15, wherein the insert forces non-parallel relationship between the first and second surfaces.

17. A spinal implant for implantation between first and second vertebral bodies, the implant comprising:

a shell including:

a first plate for engaging the first vertebral body, the first plate including a first hole formed therethrough;

a second plate for engaging the second vertebral body, the second plate including a second hole formed therethrough; and

a resilient member connecting the first and second plates; and

an insert including:

a main body; and

a portion capable of covering at least one of the first or second holes when the insert is disposed between the first and second plates.

18. The spinal implant ofclaim 17, further comprising a first screw disposed in the first hole and second screw disposed in the second hole.

19. The spinal implant ofclaim 18, wherein the portion is capable of preventing back out of both of the first and second screws when the insert is disposed between the first and second plates.

20. The spinal implant ofclaim 17, wherein the insert is constructed at least partially from materials selected from the group consisting of bone, polymer, and metal.

21. The spinal implant ofclaim 17, wherein one of the first or second plates includes a projection for retaining the insert between the first and second plates.

22. The spinal implant ofclaim 21, wherein each of the first and second plates include projections.

23. The spinal implant ofclaim 17, further comprising a third hole formed through the first plate and a fourth hole formed through the second plate.

24. The spinal implant ofclaim 23, furthering comprising a first screw disposed in the first hole, a second screw disposed in the second hole, a third screw disposed in the third hole, and fourth screw disposed in the fourth hole.

25. The spinal implant ofclaim 24, wherein the insert includes a first portion for preventing back out of the first and second screws and second portion for preventing back out of the third and fourth screws.

26. The spinal implant ofclaim 17, further comprising a bone growth aperture extending through the first member, the insert, and the second member.

27. The spinal implant ofclaim 17, wherein the main body of the insert includes an aperture for engagement with a tool.

28. The spinal implant ofclaim 17, wherein the first and second plates are located in non-parallel planes.

29. The spinal implant ofclaim 28, wherein the insert forces non-parallel relationship between the first and second plates.

30. A method of fusing together first and second vertebral bodies, the method comprising:

preparing a space between the first and second vertebral bodies to accept a spinal implant;

implanting a shell, the shell including a first plate, and second plate, and a living hinge connecting the first and second plates;

placing a first screw through the first plate and into the first vertebral body;

placing a second screw through the second plate and into the second vertebral body; and

inserting an insert between the first and second plates, wherein the insert prevents back out of the first and second screws.

31. The method ofclaim 30, wherein the inserting step causes the first and second plates to move with respect to each other, wherein the movement between the first and second plates is translated to the first and second vertebral bodies.

32. The method ofclaim 30, further comprising the step of choosing the insert from a plurality of inserts.

33. The method ofclaim 30, further comprising the steps of placing a third screw through the first plate and into the first vertebral body, and placing a fourth screw through the second plate and into the second vertebral body.

34. The method ofclaim 33, wherein the insert prevents back out of the first, second, third, and fourth screws.

35. The method ofclaim 30, further comprising the step of retaining the insert between the first and second plates.

36. The method ofclaim 35, wherein the retaining step includes engaging the insert with projections formed on the first and second plates.

37. The method ofclaim 30, further comprising the step of allowing bone growth through an aperture formed through the first plate, the insert, and the second plate.

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