US20060247775A1 - Spinal implant - Google Patents

Abstract

An implant to be implanted between a superior vertebra and an inferior vertebra is provided. The implant comprises a main body having a superior surface and an inferior surface that diverge with at least one linear surface protrusion residing on at least one of the superior surface or the inferior surface. The protrusion having a substantially flat bone engaging surface and a generally trapezoidal cross-section.

Description

RELATED APPLICATION
• This application is a continuation of application Ser. No. 11/318,993, which is a continuation-in-part of U.S. patent application Ser. No. 10/680,982, titled SPINAL IMPLANT, filed Oct. 7, 2003, now U.S. Pat. No. 7,041,137.
FIELD OF THE INVENTION
• The present invention relates to apparatuses and methods for implanting a device in the intervertebral space and, more particularly, to an allograft spinal implant.
BACKGROUND OF THE INVENTION
• The vertebrae of the human spine are arranged in a column with one vertebra on top of the next. Between each vertebra exists an intervertebral disc that transmits force between adjacent vertebrae and provides a cushion between the adjacent vertebrae.
• Sometimes, back pain is caused by degeneration or other deformity of the intervertebral disc (“diseased disc”). Conventionally, surgeons treat diseased discs by surgically removing the diseased disc and inserting a bone graft in the space vacated by the diseased disc. The adjacent vertebrae are then immobilized relative to one another. Eventually, the vertebrae grow into one solid piece of bone.
• A variety of different types of bone grafts, also known as intervertebral implants, have been developed to assist in bone growth. These bone grafts can be made out of a number of biocompatible materials, such as, for example, ceramics, metals, bone, and the like. All the various known bone grafts, however, have one or more drawbacks that make the various bone grafts more or less desirable depending on the circumstances.
• Accordingly, a need exists for an improved spinal implant.
SUMMARY OF THE INVENTION
• To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a spinal implant is provided. The spinal implant comprises a main body. The main body has a superior face and an inferior face that diverge in the direction of implantation to distract the disc space. The superior face and the inferior face, each designed with protrusions, to engage superior and inferior vertebral bodies. The main body further comprises an anterior end and a posterior end. The anterior end and posterior end can connected by a straight or curved sidewall. Alternatively, the anterior end and posterior end can be defined portions of a circular sidewall connecting the superior face and the inferior face.
• The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings. Further, the advantages and purpose 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 DRAWING
• The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, serve to explain the principles thereof. Like items in the drawings are referred to using the same numerical reference.
• FIG. 1 shows a front perspective view of a spinal implant constructed in accordance with an embodiment of the present invention;
• FIG. 2 shows a front elevation view of the spinal implant ofFIG. 1;
• FIG. 3 shows a side elevation view of the spinal implant ofFIG. 1;
• FIG. 4 shows a top elevation view of the spinal implant ofFIG. 1;
• FIG. 5 shows a side elevation view of ridges for a spinal implant consistent with an embodiment of the present invention;
• FIG. 6 shows a top elevation view of ridges for a spinal implant consistent with another embodiment of the present invention;
• FIG. 7 shows a top elevation view of a spinal implant constructed in accordance with another embodiment of the present invention;
• FIG. 8 shows a top elevation view of a spinal implant constructed in accordance with another embodiment of the present invention;
• FIG. 9 shows a top elevation view of a spinal implant constructed in accordance with another embodiment of the present invention;
• FIG. 10 shows a top elevation view of a spinal implant constructed in accordance with another embodiment of the present invention; and
• FIG. 11 shows a top elevation view of a spinal implant constructed in accordance with another embodiment of the present invention.
DETAILED DESCRIPTION
• Some embodiments of the present invention are described with reference to FIGS.1 to11. FIGS.1 to11 are not shown to scale and should be considered exemplary rather than limiting. Referring first to FIGS.1 to4, aspinal implant100 consistent with the present invention is shown. It is contemplated that spinal implants consistent with the present invention could be constructed out of a number of different materials, such as, for example, bone, biocompatible metals, plastics, ceramics, and other synthetics, which may or may not be resorbable.Spinal implant100 comprises amain body102 having asuperior surface104, aninferior surface106, ananterior surface108, aposterior surface110, andsidewalls112 connecting the various surfaces. Extending from thesuperior surface104 and theinferior surface106 exist a plurality oflinear ridges114. One or morelinear ridges114 could extend a majority of the width W of theimplant100 or, alternatively, one or more channels116 (shown in phantom) could separatelinear ridges114 into two or more serial ridges. Eachridge114 could have the same or a different number of optional channels. Further, while the figures are not drawn to scale, it is generally desirable tomill ridges114 such that a majority ofsuperior surface104 andinferior surface106 have ridges.
• Referring now to FIGS.2 to4,ridges114 will be explained in more detail. As shown inFIG. 2,ridges114 have a generally flat vertebralbody engaging surface202 and a generally flat implantengaging surface204. As one of ordinary skill in the art would appreciate on reading the disclosure, generally flat vertebral bodyengaging surface202 may be contoured to match the anatomy of the vertebral body it is engaging, which is shown in phantom onFIG. 2. Notice flat implantengaging surface204 is shown for convenience. Whileridges114 could be individually adhered tomain body102, generallyridges114 are milled out of or molded tomain body102 such that the main body and ridges form a single integral unit.Ridges114 also havelateral sides206 that extend fromsurface202 tosurface204.Lateral sides206 form anacute angle208 withsurface204 and anobtuse angle210 withsurface202. Whilelateral sides206 are shown having equal lengths, the sides can be of differentlengths providing ridges114 with an angled or skewed appearance.FIG. 3 showsridges114 have ananterior side210 and aposterior side212.Sides210 and212 form anacute angle216 withsurface204 and anobtuse angle214 withsurface202. Similar tosides206,sides210 and212 can have different lengths to angle or skew ridge114 (See for exampleFIGS. 5 and 6). As shown,ridges114 have trapezoidal cross-sections in both the anterior to posterior direction as well as the side-to-side (or lateral) direction. Also, as best seen inFIG. 4, a trough216tresides between every tworidges114. As shown, trough216tis shaped similar toridges114, but inverted. Trough216tandridges114 do not need to have identical shapes.Trough216 hassides210 and212 in common withadjacent ridges114 and asurface216sthat coincides with eithersuperior surface104 and/orinferior surface106.
• Referring now toFIG. 5, a side elevation view ofridges500 is shown.Ridges500 are similar toridges114, and the similarities will not be explained herein.Ridges500 haveanterior sides502 andposterior sides504. Unlikeridges114,anterior sides502 andposterior sides504 are different lengths, providing the skewed feature. In this case,anterior side502 is longer thanposterior side504. Alternatively,anterior side502 could be shorter thanposterior side504. Differing the lengths of the sides should make expulsion of the implant by natural body forces more difficult. The sides would be lengthened or shortened based on design choice and the particular forces the implant is to resist. While changing the anterior and posterior side lengths would resist anterior to posterior expulsion forces, changing the lengths ofsides206 such that the implant has a longer side and ashorter side206 would assist in resisting lateral forces. Various combinations of lengthening and shortening could produce many alternative shapes. See, for example,FIG. 6 showingridges600 having generally trapezoidal cross-sections in all directions, but skewed lengths.
• WhileFIGS. 1-6 are generally described as cubic implants, alternative shapes are possible. For example,superior surface104 andinferior surface106 could converge on one end and diverge towards the other forming a wedge shape. In this case, generally, a distance da separating thesuperior surface104 andinferior surface106 atanterior side108 would be larger than a distance dp separatingsuperior surface104 andinferior surface106 at posterior side110 (seeFIG. 1).
• FIG. 7 shows animplant700.Implant700 is similar toimplant100, and the similarities will not be further explained, but sides712 are curve to provide a concave shape to implant. While not specifically shown,implant700 would have ridges similar toimplant100.FIG. 8 shows still anotherimplant800. In this case,implant800 has an anterior side width dimension Wa and a posterior width dimension Wp, which forms a somewhat conical shape. Various combinations of da, dp, Wa, and Wp could be combined with parallel or substantially parallel sidewalls (FIGS. 1-4), or arched sidewalls (FIG. 7).
• Generally, the spinal implants shown above are useful in the posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) techniques. However, using the TLIF techniques, implants are generally inserted at an angle and rotated in the intervertebral space.FIGS. 9 and 10 show top elevation views ofimplants900 and1000 useful in TLIF techniques, althoughimplants900 and1000 could be used in PLIF technique as well. Referring first toFIG. 9,implant900 has a series ofsurface protrusions902. Aleading edge904 ofsurface protrusions902 is angled with respect toanterior surface906. As shown inFIG. 10,implant1000 has a series ofsurface protrusions1002. Aleading edge1004 ofsurface protrusion1002 is perpendicular toside1006, in other words, the surface protrusions are arranged along the longer dimension L of the implant rather than the shorter dimension S of the implant. Conventionally, surface protrusions are aligned along the shorter dimension S. Whileprotrusions902 and1002 are shown as generally trapezoidal shapes,protrusions902 and1002 could be conical or triangular in shape. In other words, the bone engaging surface associated withimplants900 and10000 could form a cutting edge instead of a flat engaging surface.
• While usable in all spinal regions, the implants shown and described with respect to FIGS.1 to10 are generally used as implants for the lumbar or thorax regions of the spine.FIG. 11 shows a top elevation view of animplant1100 more suitable for the cervical region of the spine, althoughimplant1100 could be used in the lumbar or thorax region as well. While not shown,implant1100 would be milled to have surface protrusions similar to the protrusions shown inFIGS. 1-6,9 and10.Implant1100 comprises amain body1102, asuperior surface1104, aninferior surface1106 that is generally oppositesuperior surface1104, and aannular sidewall1108 surroundingmain body1102 and connectingsuperior surface1104 andinferior surface1106.Annular sidewall1108 is used generically and should not be limited to circular, but rather includes other geometric shapes, such as, for example, oval, elliptical, trapezoidal, or the like. Ahollow region1110 may reside internal to implant1100 giving implant1100 a doughnut like shape.Hollow region1110 may be the intramedullary canal of a conventional bone. Moreover,hollow region1110 could be milled out from a solid implant, such as a solid bone piece. Further,hollow region1110 is used generically to mean a lack of cortical bone in the region, other substances, such as, for example, cancellous bone, may reside inregion1110. Instead of specific anterior and posterior sides,sidewall1108 has ananterior region1112 and aposterior region1114. While shown as a circular cross section,implant1100 could be flattened overposterior region1114 oranterior region1112 to more conform to a patient's anatomy. Further,implant1100 could be a wedge shape withsuperior surface1104 andinferior surface1106 converging atposterior region1114 and diverging atanterior region1112.
• While particular shapes and designs for the implants shown inFIGS. 1-11 are shown and described, one of ordinary skill in the art would recognize on reading the disclosure that other shapes and designs are possible. In particular, the implants could be cubic, oval, elliptical, triangular, trapezoidal, conical, or the like.
• While the invention has been particularly shown and described with reference to some embodiment thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention.

Claims (20)

1. An implant for insertion into a space between a superior vertebra and an inferior vertebra, the implant comprising:

a main body, the main body comprising at least a superior surface and an inferior surface;

the superior surface and the inferior surface diverging along an axis to form a wedge shape;

a plurality of surface protrusions residing on at least one of the superior surface or the inferior surface; and

a plurality of spaces residing on at least one of the superior surface or the inferior surface separating the plurality of surface protrusions, wherein

the plurality of surface protrusions comprise:

an anterior facing surface,

a posterior facing surface,

a plurality of laterally facing surfaces, and

a vertebral body engaging surface, such that

the anterior facing surface and the posterior facing surface converge from the main body to the vertebral body engaging surface and the plurality of laterally facing surfaces converge from the main body to the vertebral body engaging surface, wherein the implant shape facilitates distracting the space between the superior vertebra and the inferior vertebra.

2. The implant ofclaim 1, wherein the vertebral body engaging surface is substantially shaped to conform to at least one of an inferior surface of the superior vertebra or the superior surface of the inferior vertebra.

3. The implant ofclaim 2, wherein the implant comprises bone and wherein the plurality of linear surfaces are milled from the bone.

4. The implant ofclaim 2, wherein the implant comprises a biocompatible material.

5. The implant ofclaim 1, further comprising a plurality of troughs separating the plurality of surface protrusions.

6. The implant ofclaim 5, wherein the plurality of troughs reside in the plurality of spaces.

7. The implant ofclaim 1, further comprising at least one bore through the main body.

8. The implant ofclaim 1, wherein one of the anterior facing surface or the posterior facing surface is substantially vertical.

9. The implant ofclaim 1, further comprising at least one channel in each of the plurality of surface protrusions.

10. The implant ofclaim 1 wherein the anterior facing surface and the posterior facing surface converge between the plurality of laterally facing surfaces.

11. An implant for insertion into a space between a superior vertebra and an inferior vertebra, the implant comprising:

a main body, the main body comprising at least a superior surface and an inferior surface, the superior surface and the inferior surface diverge to form the main body as a wedge shape;

a plurality of surface protrusions residing on at least one of the superior surface or the inferior surface; and

a plurality of spaces residing on at least one of the superior surface or the inferior surface separating the plurality of surface protrusions, wherein

the plurality of surface protrusions comprise:

an anterior facing surface,

a posterior facing surface,

a plurality of laterally facing surfaces, and

a vertebral body engaging surface shaped to substantially conform with a superior vertebra or an inferior vertebra.

12. The implant ofclaim 11, further comprising at least one channel in each of the plurality of surface protrusions.

13. The implant ofclaim 11, wherein the implant comprises bone.

14. The implant ofclaim 11, wherein the implant comprises resorbable material.

15. The implant ofclaim 11, wherein the anterior facing surface and the posterior facing surface converge from the main body to the vertebral body engaging surface, and the plurality of laterally facing surfaces converge from the main body to the vertebral body engaging surface.

16. The implant ofclaim 11, further comprising at least one space residing on at least one of the superior surface or the inferior surface separating the plurality of surface protrusions.

17. The implant ofclaim 11, further comprising a plurality of troughs residing between the plurality of surface protrusions.

18. The implant ofclaim 11, wherein the main body is substantially circular.

19. The implant ofclaim 11, wherein the main body diverges from an anterior portion to a posterior portion.

20. An implant for insertion into a space between a superior vertebra and an inferior vertebra, the implant comprising:

a main body;

a superior surface residing on the main body and an inferior surface residing on the main body opposite the superior surface, the superior surface and the inferior surface diverging from an anterior end to a posterior end to self distract the space during implantation;

at least one sidewall about the main body connecting the superior surface and the inferior surface;

an anterior region residing on the main body and a posterior region residing on the main body opposite the anterior region and connected by the at least one sidewall;

a plurality of linear surface protrusions residing on at least one of the superior surface and the inferior surface, the linear surface protrusions comprising:

an anterior facing surface,

a posterior facing surface,

a plurality of laterally facing surfaces,

a substantially flat main body engaging surface,

a substantially flat bone engaging surface opposite the main body engaging surface, and

the anterior facing surface and the posterior facing surface converging between the substantially flat main body engaging surface to the substantially flat bone engaging surface and the plurality of laterally facing surfaces converging between the substantially flat main body engaging surface to the substantially flat bone engaging surface, such that

the linear surface protrusion has a generally trapezoidal cross-section in both an anterior to posterior direction and a lateral direction.

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