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`2
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`

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`NON-PROVISIONAL APPLICATION
`
`FOR UNITED STATES LETTERS PATENT
`
`SYSTEMS AND METHODS FOR SPINAL FUSION
`
`By Inventor:
`
`MATTHEW CURRAN
`
`Filed:
`
`April 4, 2011
`
`3
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`SYSTEMS AND METHODS FOR SPINAL FUSION
`
`CROSS-REFERENCE TO RELATED APPLICATION
`
`This application is continuation of United States Patent Application Serial Number
`
`5
`
`ll/093,409 filed March 29, 2005, now pending, which claims the benefit of the filing date under
`
`35 USC ll9(e) of United States Provisional Application entitled “Systems and Methods for
`
`Spinal Fusion,” serial No. 60/557,536 filed March 29, 2004, the entire contents of which are
`
`incorporated herein by reference.
`
`10
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`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates generally to spinal surgery and, more particularly, to a
`
`system and method for spinal fusion comprising a spinal fusion implant of non—bone construction
`
`releasably coupled to an insertion instrument dimensioned to introduce the spinal fusion implant
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`15
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`into any of a variety of spinal target sites.
`
`11. Discussion of the Prior Art
`
`Currently there are nearly 500,000 spine lumbar and cervical fusion procedures
`
`performed each year in the United States. Such procedures are commonly performed to correct
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`20
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`problems, such as chronic back or neck pain, which result from degenerated intervertebral discs
`
`or trauma. Generally, spinal fusion procedures involve removing some or all of the diseased or
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`damaged disc, and inserting one or more intervertebral implants into the resulting disc space.
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`Introducing the intervertebral implant serves to restore the height between adjacent vertebrae
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`4
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`(“disc height”), which reduces if not eliminates neural impingement commonly associated with a
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`damaged or diseased disc.
`
`Autologous bone grafts are widely used intervertebral implant for lumbar fusion.
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`Autologous bone grafts are obtained by harvesting a section of bone from the iliac crest of the
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`patient and thereafter implanting the article of autologous bone graft to effect fusion. While
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`generally effective, the use of autologous bone grafts suffers certain drawbacks. A primary
`
`drawback is the morbidity associated with harvesting the autologous graft from the patient’s iliac
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`crest. Another related drawback is the added surgical time required to perform the bone-
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`10
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`harvesting.
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`Allo graft bone grafts have been employed with increased regularity in an effort to
`
`overcome the drawbacks of autologous bone grafts. Allograft bone grafts are harvested from
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`cadaveric specimens, machined, and sterilized for implantation. While allograft bone grafts
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`15
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`eliminate the morbidity associated with iliac crest bone harvesting, as well as decrease the overall
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`surgical time, they still suffer certain drawbacks. A primary drawback is supply constraint, in
`
`that the tissue banks that process and produce allo graft bone implants find it difficult to forecast
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`allo graft given the inherent challenges in forecasting the receipt of cadavers. Another related
`
`drawback is that it is difficult to manufacture the allo graft with consistent shape and strength
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`20
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`characteristics given the variation from cadaver to cadaver.
`
`The present invention is directed at overcoming, or at least improving upon, the
`
`disadvantages of the prior art.
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`5
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`

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`SUMMARY OF THE INVENTION
`
`The present invention overcomes the drawbacks of the prior art by providing a spinal
`
`fusion system and related methods involving the use of a spinal fusion implant of non—bone
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`construction. The non—bone construction of the spinal fusion implant of the present invention
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`overcomes the drawbacks of the prior art in that it is not supply limited (as with allograft) and
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`does not require harvesting bone from the patient (as with auto graft). The spinal fusion implant
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`of the present invention may be comprised of any suitable non—bone composition, including but
`
`not limited to polymer compositions (e. g. poly—ether—ether—ketone (PEEK) and/or poly—ether—
`
`ketone—ketone (PEKK)), ceramic, metal or any combination of these materials.
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`The spinal fusion implant of the present invention may be provided in any number of
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`suitable shapes and sizes depending upon the particular surgical procedure or need. The spinal
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`fusion implant of the present invention may be dimensioned for use in the cervical and/or lumbar
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`spine without departing from the scope of the present invention. For lumbar fusion, the spinal
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`fusion implant of the present invention may be dimensioned, by way of example only, having a
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`length ranging between 9 and 18 mm, a height ranging between 8 and 16 mm, and a width
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`10
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`15
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`ranging between 25 and 45 mm. For cervical fusion, the spinal fusion implant of the present
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`20
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`invention may be dimensioned, by way of example only, having a length about ll mm, a height
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`ranging between 5 and 12 mm, and a width about 14 mm.
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`6
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`The spinal fusion implant of the present invention may be provided with any number of
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`additional features for promoting fusion, such as apertures extending between the upper and
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`lower vertebral bodies which allow a boney bridge to form through the spinal fusion implant of
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`the present invention. Such fusion—promoting apertures may be dimensioned to receive any
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`number of suitable osteoinductive agents, including but not limited to bone morphogenic protein
`
`(BMP) and bio—resorbable polymers, including but not limited to any of a variety of poly (D,L—
`
`lactide—co—glycolide) based polymers, such as disclosed in U.S. Patent No. 6,013,853. The spinal
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`fusion implant of the present invention is preferably equipped with one or more lateral openings
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`which aid it provides in visualization at the time of implantation and at subsequent clinical
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`10
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`evaluations.
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`The spinal fusion implant of the present invention may be provided with any number of
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`suitable anti—migration features to prevent spinal fusion implant from migrating or moving from
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`the disc space after implantation. Suitable anti—migration features may include, but are not
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`necessarily limited to, angled teeth formed along the upper and/or lower surfaces of the spinal
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`fusion implant and/or spike elements disposed partially within and partially outside the upper
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`and/or lower surfaces of the spinal fusion implant.
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`Such anti—migration features provide the
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`additional benefit of increasing the overall surface area between the spinal fusion implant of the
`
`present invention and the adjacent vertebrae, which promotes overall bone fusion rates.
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`15
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`20
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`The spinal implant of the present invention may be introduced into a spinal target site
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`through the use of any of a variety of suitable instruments having the capability to releasably
`
`engage the spinal implant. In a preferred embodiment, The insertion instrument permits quick,
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`7
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`direct, accurate placement of the spinal implant of the present invention into the intervertebral
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`space. According to one embodiment, the insertion instrument includes a threaded engagement
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`element dimensioned to threadably engage into a receiving aperture formed in the spinal fusion
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`implant of the present invention. According to another embodiment, the insertion instrument
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`includes an elongate fork member and a generally tubular lock member.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Many advantages of the present invention will be apparent to those skilled in the art with
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`10
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`a reading of this specification in conjunction with the attached drawings, wherein like reference
`
`numerals are applied to like elements and wherein:
`
`Figure l is a perspective view of a spinal fusion system of the present invention,
`
`including a lumbar fusion implant releasably coupled to an insertion instrument according to one
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`15
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`embodiment of the present invention;
`
`Figure 2 is a perspective view of the lumbar fusion implant of FIG. 1, illustrating (among
`
`other things) fusion apertures extending between top and bottom surfaces, a plurality of
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`visualization apertures extending through the side walls, and a variety of anti—migration features
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`20
`
`according to one embodiment of the present invention;
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`8
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`Figure 3 is a top View of the lumbar fusion implant of FIG. 1, illustrating (among other
`
`things) the fusion apertures and the anti—migration features according to one embodiment of the
`
`present invention;
`
`Figure 4 is a side View of the lumbar fusion implant of FIG. 1, illustrating (among other
`
`things) the visualization apertures, the anti—migration feature, and a receiving aperture for
`
`releasably engaging the insertion instrument of FIG. 1 according to one embodiment of the
`
`present invention;
`
`Figure 5 is an end view of the lumbar fusion implant of FIG. 1, illustrating (among other
`
`things) the receiving aperture formed in the proximal end, the anti—migration features, and the
`
`visualization apertures according to one embodiment of the present invention;
`
`Figure 6 is an enlarged side view of the lumbar fusion implant of FIG. 1 releasably
`
`coupled to the distal end of the insertion instrument of FIG. 1 according to one embodiment of
`
`the present invention;
`
`Figure 7 is a perspective view of the insertion instrument of FIG. 1 in a fully assembled
`
`form according to one embodiment of the present invention;
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`10
`
`15
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`20
`
`Figure 8 is an enlarged perspective view of the distal region of the insertion instrument of
`
`FIG. 1 according to one embodiment of the present invention;
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`9
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`

`
`Figure 9 is a perspective exploded View of the insertion instrument of FIG. 1, illustrating
`
`the component parts of the insertion instrument according to one embodiment of the present
`
`invention;
`
`Figure 10 is a perspective View of a spinal fusion system of the present invention,
`
`including a cervical fusion implant releasably coupled to a cervical insertion instrument
`
`according to one embodiment of the present invention;
`
`10
`
`15
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`Figure ll is a perspective view of the proximal side of the cervical fusion implant of FIG.
`
`10, illustrating (among other things) fusion apertures extending between top and bottom surfaces,
`
`a plurality of visualization apertures extending through the lateral walls, a plurality of receiving
`
`apertures, and a variety of anti—migration features according to one embodiment of the present
`
`invention;
`
`Figure 12 is a perspective view of the distal side cervical fusion implant of FIG. 10,
`
`illustrating (among other things) the visualization apertures and anti—migration features;
`
`Figure 13 is a top view of the cervical fusion implant of FIG. 10, illustrating (among
`
`other things) the fusion apertures and anti—migration features according to one embodiment of the
`
`20
`
`present invention;
`
`Figure 14 is a side view of the cervical fusion implant of FIG. 10, illustrating (among
`
`other things) the visualization apertures, the anti—migration features, and one of two receiving
`
`10
`
`10
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`

`
`apertures provided in the proximal end for releasably engaging the cervical insertion instrument
`
`of FIG. 10 according to one embodiment of the present invention;
`
`Figure 15 is a perspective view of the cervical fusion implant of the present invention just
`
`prior to attachment to the cervical insertion device according to one embodiment of the present
`
`invention;
`
`Figure 16 is a perspective view of the insertion instrument of FIG. 10 in a fully assembled
`
`form according to one embodiment of the present invention;
`
`10
`
`Figure 17 is a perspective exploded view of the insertion instrument of FIG. 10,
`
`illustrating the component parts of the insertion instrument according to one embodiment of the
`
`present invention.
`
`15
`
`DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`Illustrative embodiments of the invention are described below. In the interest of clarity,
`
`not all features of an actual implementation are described in this specification. It will of course
`
`be appreciated that in the development of any such actual embodiment, numerous
`
`implementation—specific decisions must be made to achieve the developers’ specific goals, such
`
`20
`
`as compliance with system—related and business—related constraints, which will vary from one
`
`implementation to another. Moreover, it will be appreciated that such a development effort
`
`might be complex and time—consuming, but would nevertheless be a routine undertaking for
`
`those of ordinary skill in the art having the benefit of this disclosure. The system to facilitate
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`ll
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`11
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`

`
`bone fusion and related methods disclosed herein boasts a variety of inventive features and
`
`components that warrant patent protection, both individually and in combination.
`
`FIG. 1 illustrates, by way of example only, a spinal fusion system 5 for performing spinal
`
`fusion between adjacent lumbar vertebrae, including an exemplary spinal fusion implant l0 and
`
`an exemplary insertion instrument 20 provided in accordance with the present invention. The
`
`spinal fusion implant 10 may be comprised of any suitable non—bone composition having
`
`suitable radiolucent characteristics, including but not limited to polymer compositions (e.g. poly-
`
`ether—ether—ketone (PEEK) and/or poly—ether—ketone—ketone (PEKK)) or any combination of
`
`PEEK and PEKK. The spinal fusion implant 10 of the present invention may be dimensioned, by
`
`way of example only, having a length ranging between 9 and 18 mm, a height ranging between 8
`
`and 16 mm, and a width ranging between 25 and 45 mm.
`
`As will be described in detail below, the insertion instrument 20 is configured to
`
`releasably maintain the exemplary spinal fusion implant 10 in the proper orientation during
`
`insertion into a lumbar disc space and thereafter release to deposit the implant 10. The
`
`exemplary spinal fusion implant 10, having been deposited in the disc space, facilitates spinal
`
`fusion over time by maintaining a restored disc height as natural bone growth occurs through
`
`and/or past the implant 10, resulting in the formation of a boney bridge extending between the
`
`10
`
`15
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`20
`
`adjacent vertebral bodies.
`
`The spinal fusion implant 10 of the present invention may be provided with any number
`
`of additional features for promoting fusion, such as apertures 2 extending between the upper and
`
`10
`
`12
`
`12
`
`

`
`lower vertebral bodies which allow a boney bridge to form through the spinal fusion implant 10.
`
`According to a still further aspect of the present invention, this fusion may be facilitated or
`
`augmented by introducing or positioning various osteoinductive materials within the apertures 2
`
`and/or adjacent to the spinal fusion implant 10. Such osteoinductive materials may be introduced
`
`before, during, or after the insertion of the exemplary spinal fusion implant 10, and may include
`
`(but are not necessarily limited to) autologous bone harvested from the patient receiving the
`
`spinal fusion implant 10, bone allograft, bone xenograft, any number of non—bone implants (e. g.
`
`ceramic, metallic, polymer), bone morphogenic protein, and bio—resorbable compositions,
`
`including but not limited to any of a variety of poly (D,L—lactide—co—glycolide) based polymers,
`
`10
`
`such as disclosed in U.S. Patent No. 6,013,853.
`
`The spinal fusion implant 10 of the present invention is preferably equipped with one or
`
`more visualization apertures 4 situated along the lateral sides, which aid in visualization at the
`
`time of implantation and at subsequent clinical evaluations. More specifically, based on the
`
`generally radiolucent nature of the implant 10, the visualization apertures 4 provide the ability to
`
`visualize the interior of the implant 10 during X—ray and/or other suitable imaging techniques
`
`which are undertaken from the side (or “lateral”) perspective of the implant 10. If fusion has
`
`taken place, the visualization apertures 4 will provide a method for the surgeon to make follow
`
`up assessments as to the degree of fusion without any visual interference from the spinal fusion
`
`implant 10. Further, the visualization apertures 4 will provide an avenue for cellular migration to
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`15
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`20
`
`the exterior of the spinal fusion implant 10. Thus the spinal fusion implant 10 will serve as
`
`additional scaffolding for bone fusion on the exterior of the spinal fusion implant 10.
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`11
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`13
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`13
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`
`FIGS. 2-5 depict various embodiments of the exemplary spinal fusion implant 10. Some
`
`common attributes are shared among the various embodiments. More specifically, each spinal
`
`fusion implant 10 has a top surface 31, a bottom surface 33, lateral sides 14, a proximal side 22,
`
`and a distal side 16. In one embodiment, the top and bottom surfaces 31, 33 are generally
`
`parallel. It can be appreciated by one skilled in the art that although the surfaces 31, 33 are
`
`generally parallel to one another, they may be provided in any number of suitable shapes,
`
`including but not limited to concave and/or convex. When provided as convex shapes, the top
`
`and bottom surfaces 31, 33 may better match the natural contours of the vertebral end plates.
`
`10
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`15
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`The exemplary spinal fusion implant 10 also preferably includes anti—migration features
`
`designed to increase the friction between the spinal fusion implant 10 and the adjacent contacting
`
`surfaces of the vertebral bodies so as to prohibit migration of the spinal fusion implant 10 after
`
`implantation. Such anti—migration features may include ridges 6 provided along the top surface
`
`31 and/or bottom surface 33. Additional anti—migration features may also include a pair of spike
`
`elements 7 disposed within the proximal region of the implant 10, a pair of spike elements 8
`
`disposed within the distal region of the implant 10, and a pair of spike elements 9 disposed
`
`within the central region of the implant 10. Spike elements 7, 8, 9 may extend from the top
`
`surface 31 and/or bottom surface 33 within the respective proximal, distal and central regions of
`
`the implant 10. The spike elements 7, 8, 9 may be manufactured from any of a variety of suitable
`
`20
`
`materials, including but not limited to a metal, ceramic, and/or polymer material, preferably
`
`having radiopaque characteristics. The spike elements 7, 8, 9 may also take any of a variety of
`
`suitable shapes, including but not limited to a generally elongated element disposed within the
`
`implant 10 such that the ends thereof extend generally perpendicularly from the upper and/or
`
`12
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`14
`
`14
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`

`
`lower surfaces 31, 33 of the implant 10. As best appreciated in FIG. 4, the spike elements 7, 8, 9
`
`may each comprise a unitary element extending through upper and lower surfaces 31, 33.
`
`Alternatively, each spike element 7, 8, 9 may comprise a shorter element which only extends
`
`through a single surface 31, 33 (that is, does not extend through the entire height of the implant
`
`10).
`
`The spinal fusion implant 10 has two large fusion apertures 2, separated by a medial
`
`support 50, extending in a vertical fashion through the top surface 31 and bottom surface 33.
`
`The fusion apertures 2 function primarily as an avenue for bony fusion between adjacent
`
`vertebrae. The fusion apertures 2 may be provided in any of a variety of suitable shapes,
`
`including but not limited to the generally rectangular shape best viewed in FIG. 3, or a generally
`
`circular, oblong and/or triangular shape or any combination thereof. The spinal fusion implant
`
`10 may have a plurality of visualization apertures 4 which allow a clinician to make visual
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`observations of the degree of bony fusion un—obscured by the lateral side 14 to facilitate further
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`diagnosis and treatment. The visualization apertures 4 may be provided in any of a variety of
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`suitable shapes, including but not limited to the generally oblong shape best viewed in FIG. 4, or
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`a generally circular, rectangular and/or triangular shape or any combination thereof.
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`10
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`15
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`The spinal fusion implant 10 may be provided with any number of suitable features for
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`20
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`engaging the insertion instrument 20 without departing from the scope of the present invention.
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`As best viewed in FIGS. 4-6, one engagement mechanism involves providing a threaded
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`receiving aperture 12 in the proximal sidewall 22 of the spinal fusion implant 10 of the present
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`invention. The threaded receiving aperture 12 is dimensioned to threadably receive a threaded
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`13
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`15
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`15
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`

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`connector 24 on the insertion instrument 20 (as will be described in greater detail below). The
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`receiving aperture 12 extends inwardly from the proximal side 22 in a generally perpendicular
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`fashion relative to the proximal side 22. Although shown as having a generally circular cross-
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`section, it will be appreciated that the receiving aperture 12 may be provided having any number
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`of suitable shapes or cross—sections, including but not limited to rectangular or triangular. In
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`addition to the receiving aperture 12, the spinal fusion implant 10 is preferably equipped with a
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`pair of grooved purchase regions 60, 61 extending generally horizontally from either side of the
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`receiving aperture 12. The grooved purchase regions 60, 61 are dimensioned to receive
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`corresponding distal head slots 62, 63 on the insertion instrument 20 (as will be described in
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`greater detail below), which collectively provide an enhanced engagement between the implant
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`10 and instrument 20.
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`FIGS. 6-9 detail the exemplary insertion instrument 20 according to one embodiment of
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`the invention. The exemplary insertion instrument 20 includes an elongate tubular element 28
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`and an inserter shaft 44. The elongate tubular element 28 is constructed with a distal head 26 at
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`its distal end, a distal head slot 62 at it s distal end, a thumbwheel housing 38 at its proximal end
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`and a handle 42 at its proximal end. The elongate tubular element 28 is generally cylindrical and
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`of a length sufficient to allow the device to span from the surgical target site to a location
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`sufficiently outside the patient’s body so the handle 42 and thumbwheel housing 38 can be easily
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`10
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`15
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`20
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`accessed by a clinician or a complimentary controlling device.
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`The elongate tubular element 28 is dimensioned to receive a spring 46 and the proximal
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`end of the inserter shaft 44 into the inner bore 64 of the elongate tubular element 28. The inserter
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`14
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`16
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`16
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`

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`shaft 44 is dimensioned such that the threaded connector 24 at the distal end of the inserter shaft
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`44 just protrudes past the distal head slots 62, 63 to allow engagement with the receiving aperture
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`12 of the spinal fusion implant 10. It should be appreciated by one skilled in the art that such a
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`construction allows the inserter shaft 44 to be able to rotate freely within the elongate tubular
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`element 28 while stabilized by a spring 46 to reduce any slidable play in the insertion instrument
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`20.
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`The handle 42 is generally disposed at the proximal end of the insertion instrument 20.
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`The handle 42 is fixed to the thumbwheel housing 38 allowing easy handling by the clinician.
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`10
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`15
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`Because the handle 42 is fixed the clinician has easy access to the thumbwheel 34 and can stably
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`turn the thumbwheel 34 relative to the thumbwheel housing 38. Additionally, the relative
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`orientation of the thumbwheel housing 38 to the handle 42 orients the clinician with respect to
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`the distal head 26 and distal head slot 62. By way of example, the thumbwheel housing 38 holds
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`a thumbwheel 34, a set screw 32, and a spacer 36. The inserter shaft 44 is attached to the
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`thumbwheel 34 and is freely rotatable with low friction due to the spacer 36. One skilled in the
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`art can appreciate myriad methods of assembling a housing similar to the above described.
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`FIG. 6 details the distal head slot of the exemplary insertion instrument 20 coupled to the
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`spinal fusion implant 10 through the purchase regions 60, 61. The distal head slots 62, 63 are
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`20
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`dimensioned to fit slidably into the purchase regions 60, 61 with low friction to allow accurate
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`engagement of the threaded connector 24 to the receiving aperture 12 of the spinal fusion implant
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`10.
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`In the presented embodiment, the outer dimension of the threaded connector 24 is smaller
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`than the largest outer dimension of the distal head 26 and elongate tubular element 28.
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`15
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`17
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`17
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`Alternatively, other methods of creating a gripping surface are contemplated including but not
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`limited to knurling or facets.
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`In order to use the system to perform a spinal fusion procedure, the clinician must first
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`designate the appropriate implant size. After the spinal fusion implant 10 is chosen, the distal
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`head slots 62, 63 of the inserter shaft 44 are inserted into the purchase regions 60, 61 of the
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`spinal fusion implant 10. At that time the spinal fusion implant 10 and insertion instrument 20
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`are slidably engaged with one another. Before the clinician can manipulate the combined spinal
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`fusion implant 10 and insertion instrument 20, they must be releasably secured together. In order
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`to secure the spinal fusion implant 10 onto the threaded connector 24 of the inserter instrument
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`20, the clinician employs