Systems and methods for spinal fusion

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 into any of a variety of spinal target sites.

BACKGROUND OF THE INVENTION

I. 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 into any of a variety of spinal target sites.

II. 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 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 damaged disc, and inserting one or more intervertebral implants into the resulting disc space. Introducing the intervertebral implant serves to restore the height between adjacent vertebrae (“disc height”), which reduces if not eliminates neural impingement commonly associated with a damaged or diseased disc.

Autologous bone grafts are widely used intervertebral implant for lumbar fusion. Autologous bone grafts are obtained by harvesting a section of bone from the iliac crest of the patient and thereafter implanting the article of autologous bone graft to effect fusion. While 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 crest. Another related drawback is the added surgical time required to perform the bone-harvesting.

Allograft 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 cadaveric specimens, machined, and sterilized for implantation. While allograft bone grafts eliminate the morbidity associated with iliac crest bone harvesting, as well as decrease the overall surgical time, they still suffer certain drawbacks. A primary drawback is supply constraint, in that the tissue banks that process and produce allograft bone implants find it difficult to forecast allograft given the inherent challenges in forecasting the receipt of cadavers. Another related drawback is that it is difficult to manufacture the allograft with consistent shape and strength 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.

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 construction. The non-bone construction of the spinal fusion implant of the present invention overcomes the drawbacks of the prior art in that it is not supply limited (as with allograft) and does not require harvesting bone from the patient (as with autograft). The spinal fusion implant 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.

The spinal fusion implant of the present invention may be provided in any number of suitable shapes and sizes depending upon the particular surgical procedure or need. The spinal fusion implant of the present invention may be dimensioned for use in the cervical and/or lumbar spine without departing from the scope of the present invention. For lumbar fusion, the spinal fusion implant of the present invention may be dimensioned, by way of example only, having a width ranging between 9 and 18 mm, a height ranging between 8 and 16 mm, and a length ranging between 25 and 45 mm. For cervical fusion, the spinal fusion implant of the present invention may be dimensioned, by way of example only, having a width about 11 mm, a height ranging between 5 and 12 mm, and a length about 14 mm.

The spinal fusion implant of the present invention may be provided with any number of additional features for promoting fusion, such as apertures extending between the upper and lower vertebral bodies which allow a boney bridge to form through the spinal fusion implant of the present invention. Such fusion-promoting apertures may be dimensioned to receive any 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. The spinal fusion implant of the present invention is preferably equipped with one or more lateral openings which aid it provides in visualization at the time of implantation and at subsequent clinical evaluations.

The spinal fusion implant of the present invention may be provided with any number of suitable anti-migration features to prevent spinal fusion implant from migrating or moving from the disc space after implantation. Suitable anti-migration features may include, but are not necessarily limited to, angled teeth formed along the upper and/or lower surfaces of the spinal fusion implant and/or spike elements disposed partially within and partially outside the upper and/or lower surfaces of the spinal fusion implant. Such anti-migration features provide the 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.

The spinal fusion implant of the present invention may be provided with any number of features for enhancing the visualization of the implant during and/or after implantation into a spinal target site. According to one aspect of the present invention, such visualization enhancement features may take the form of the spike elements used for anti-migration, which may be manufactured from any of a variety of suitable materials, including but not limited to a metal, ceramic, and/or polymer material, preferably having radiopaque characteristics. The spike elements may also take any of a variety of suitable shapes, including but not limited to a generally elongated element disposed within the implant such that the ends thereof extend generally perpendicularly from the upper and/or lower surfaces of the implant. The spike elements may each comprise a unitary element extending through upper and lower surfaces or, alternatively, each spike element may comprise a shorter element which only extends through a single surface (that is, does not extend through the entire height of the implant). In any event, when the spike elements are provided having radiodense characteristics and the implant is manufactured from a radiolucent material (such as, by way of example only, PEEK and/or PEKK), the spike elements will be readily observable under X-ray or fluoroscopy such that a surgeon may track the progress of the implant during implantation and/or the placement of the implant after implantation.

The spinal implant of the present invention may be introduced into a spinal target site 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, direct, accurate placement of the spinal implant of the present invention into the intervertebral space. According to one embodiment, the insertion instrument includes a threaded engagement element dimensioned to threadably engage into a receiving aperture formed in the spinal fusion implant of the present invention. According to another embodiment, the insertion instrument includes an elongate fork member and a generally tubular lock member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1illustrates, by way of example only, a spinal fusion system5for performing spinal fusion between adjacent lumbar vertebrae, including an exemplary spinal fusion implant10and an exemplary insertion instrument20provided in accordance with the present invention. The spinal fusion implant10may 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 implant10of the present invention may be dimensioned, by way of example only, having a width ranging between 9 and 18 mm, a height ranging between 8 and 16 mm, and a length ranging between 25 and 45 mm.

As will be described in detail below, the insertion instrument20is configured to releasably maintain the exemplary spinal fusion implant10in the proper orientation during insertion into a lumbar disc space and thereafter released to deposit the implant10. The exemplary spinal fusion implant10, 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 implant10, resulting in the formation of a honey bridge extending between the adjacent vertebral bodies. The implant10is particularly suited for introduction into the disc space via a lateral (trans-psoas) approach to the spine, but may be introduced in any of a variety of approaches, such as posterior, anterior, antero-lateral, and postero-lateral, without departing from the scope of the present invention (depending upon the sizing of the implant10).

The spinal fusion implant10of the present invention may be provided with any number of additional features for promoting fusion, such as apertures2extending between the upper and lower vertebral bodies which allow a boney bridge to form through the spinal fusion implant10. 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 apertures2and/or adjacent to the spinal fusion implant10. Such osteoinductive materials may be introduced before, during, or after the insertion of the exemplary spinal fusion implant10, and may include (but are not necessarily limited to) autologous bone harvested from the patient receiving the spinal fusion implant10, 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.

The spinal fusion implant10of the present invention is preferably equipped with one or more visualization apertures4situated 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 implant10, the visualization apertures4provide the ability to visualize the interior of the implant10during X-ray and/or other suitable imaging techniques which are undertaken from the side (or “lateral”) perspective of the implant10. If fusion has taken place, the visualization apertures4will 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 implant10. Further, the visualization apertures4will provide an avenue for cellular migration to the exterior of the spinal fusion implant10. Thus the spinal fusion implant10will serve as additional scaffolding for bone fusion on the exterior of the spinal fusion implant10.

FIGS. 2-5depict various embodiments of the exemplary spinal fusion implant10. Some common attributes are shared among the various embodiments. More specifically, each spinal fusion implant10has a top surface31, a bottom surface33, lateral sides14, a proximal side22, and a distal side16. In one embodiment, the top and bottom surfaces31,33are generally parallel. It can be appreciated by one skilled in the art that although the surfaces31,33are 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 surfaces31,33may better match the natural contours of the vertebral end plates. Although not shown, it will be appreciated that the top and bottom surfaces31,33may be angled relative to one another to better match the natural lordosis of the lumbar and cervical spine or the natural kyphosis of the thoracic spine.

The exemplary spinal fusion implant10also preferably includes anti-migration features designed to increase the friction between the spinal fusion implant10and the adjacent contacting surfaces of the vertebral bodies so as to prohibit migration of the spinal fusion implant10after implantation. Such anti-migration features may include ridges6provided along the top surface31and/or bottom surface33. Additional anti-migration features may also include a pair of spike elements7disposed within the proximal region of the implant10, a pair of spike elements8disposed within the distal region of the implant10, and a pair of spike elements9disposed within the central region of the implant10. Spike elements7,8,9may extend from the top surface31and/or bottom surface33within the respective proximal, distal and central regions of the implant10. The spike elements7,8,9may be manufactured from any of a variety of suitable materials, including but not limited to a metal, ceramic, and/or polymer material, preferably having radiopaque characteristics. The spike elements7,8,9may also take any of a variety of suitable shapes, including but not limited to a generally elongated element disposed within the implant10such that the ends thereof extend generally perpendicularly from the upper and/or lower surfaces31,33of the implant10. As best appreciated inFIG. 4, the spike elements7,8,9may each comprise a unitary element extending through upper and lower surfaces31,33. Alternatively, each spike element7,8,9may comprise a shorter element which only extends through a single surface31,33(that is, does not extend through the entire height of the implant10). In any event, when the spike elements7,8,9are provided having radiodense characteristics and the implant10is manufactured from a radiolucent material (such as, by way of example only, PEEK and/or PEKK), the spike elements7,8,9will be readily observable under X-ray or fluoroscopy such that a surgeon may track the progress of the implant10during implantation and/or the placement of the implant10after implantation.

The spinal fusion implant10has two large fusion apertures2, separated by a medial support50, extending in a vertical fashion through the top surface31and bottom surface33. The fusion apertures2function primarily as an avenue for bony fusion between adjacent vertebrae. The fusion apertures2may be provided in any of a variety of suitable shapes, including but not limited to the generally rectangular shape best viewed inFIG. 3, or a generally circular, oblong and/or triangular shape or any combination thereof. The spinal fusion implant10may have a plurality of visualization apertures4which allow a clinician to make visual observations of the degree of bony fusion un-obscured by the lateral side14to facilitate further diagnosis and treatment. The visualization apertures4may be provided in any of a variety of suitable shapes, including but not limited to the generally oblong shape best viewed inFIG. 4, or a generally circular, rectangular and/or triangular shape or any combination thereof.

The spinal fusion implant10may be provided with any number of suitable features for engaging the insertion instrument20without departing from the scope of the present invention. As best viewed inFIGS. 4-6, one engagement mechanism involves providing a threaded receiving aperture12in the proximal sidewall22of the spinal fusion implant10of the present invention. The threaded receiving aperture12is dimensioned to threadably receive a threaded connector24on the insertion instrument20(as will be described in greater detail below). The receiving aperture12extends inwardly from the proximal side22in a generally perpendicular fashion relative to the proximal side22. Although shown as having a generally circular cross-section, it will be appreciated that the receiving aperture12may be provided having any number of suitable shapes or cross-sections, including but not limited to rectangular or triangular. In addition to the receiving aperture12, the spinal fusion implant10is preferably equipped with a pair of grooved purchase regions60,61extending generally horizontally from either side of the receiving aperture12. The grooved purchase regions60,61are dimensioned to receive corresponding distal head ridges62,63on the insertion instrument20(as will be described in greater detail below), which collectively provide an enhanced engagement between the implant10and instrument20.

FIGS. 6-9detail the exemplary insertion instrument20according to one embodiment of the invention. The exemplary insertion instrument20includes an elongate tubular element28and an inserter shaft44. The elongate tubular element28is constructed with a distal head26at its distal end, distal head ridges62,63on the distal end of the distal head26, a thumbwheel housing38at its proximal end and a handle42at its proximal end. The elongate tubular element28is generally cylindrical and of a length sufficient to allow the device to span from the surgical target site to a location sufficiently outside the patient's body so the handle42and thumbwheel housing38can be easily accessed by a clinician or a complimentary controlling device.

The elongate tubular element28is dimensioned to receive a spring46and the proximal end of the inserter shaft44into the inner bore64of the elongate tubular element28. The inserter shaft44is dimensioned such that the threaded connector24at the distal end of the inserter shaft44just protrudes past the distal head ridges62,63to allow engagement with the receiving aperture12of the spinal fusion implant10. It should be appreciated by one skilled in the art that such a construction allows the inserter shaft44to be able to rotate freely within the elongate tubular element28while stabilized by a spring46to reduce any slidable play in the insertion instrument20.

The handle42is generally disposed at the proximal end of the insertion instrument20. The handle42is fixed to the thumbwheel housing38allowing easy handling by the clinician. Because the handle42is fixed the clinician has easy access to the thumbwheel34and can stably turn the thumbwheel34relative to the thumbwheel housing38. Additionally, the relative orientation of the thumbwheel housing38to the handle42orients the clinician with respect to the distal head26and distal head ridge62. By way of example, the thumbwheel housing38holds a thumbwheel34, a set screw32, and a spacer36. The inserter shaft44is attached to the thumbwheel34and is freely rotatable with low friction due to the spacer36. One skilled in the art can appreciate myriad methods of assembling a housing similar to the above described.

FIG. 6details the distal head ridge of the exemplary insertion instrument20coupled to the spinal fusion implant10through the purchase regions60,61. The distal head ridges62,63are dimensioned to fit slidably into the purchase regions60,61with low friction to allow accurate engagement of the threaded connector24to the receiving aperture12of the spinal fusion implant10. In the presented embodiment, the outer dimension of the threaded connector24is smaller than the largest outer dimension of the distal head26and elongate tubular element28. Alternatively, other methods of creating a gripping surface are contemplated including but not limited to knurling or facets.

In order to use the system to perform a spinal fusion procedure, the clinician must first designate the appropriate implant size. After the spinal fusion implant10is chosen, the distal head ridges62,63of the inserter shaft44are inserted into the purchase regions60,61of the spinal fusion implant10. At that time the spinal fusion implant10and insertion instrument20are slidably engaged with one another. Before the clinician can manipulate the combined spinal fusion implant10and insertion instrument20, they must be releasably secured together. In order to secure the spinal fusion implant10onto the threaded connector24of the inserter instrument20, the clinician employs the thumbwheel34to rotate the inserter shaft44and threaded connector24. The rotation of the threaded connector24will releasably engage the receiving aperture of the spinal fusion implant10and stabilize the insertion instrument20relative to the spinal fusion implant10.

A clinician can utilize the secured system in either an open or minimally invasive spinal fusion procedure. In either type of procedure, a working channel is created in a patient that reaches the targeted spinal level. After the creation of that channel, the intervertebral space may be prepared via any number of well known preparation tools, including but not limited to kerrisons, rongeurs, pituitaries, and rasps. After preparation, the insertion instrument20is used to place a spinal fusion implant10into the prepared intervertebral space. Once the implant10is inserted into the prepared space, the implant10is released from the insertion instrument20by rotating the thumbwheel34to disengage the threaded connector24from the receiving aperture12. That motion removes the compressive force on the purchase regions60,61between the distal head26and the distal head ridges62,63of the spinal fusion implant10and allows the insertion instrument to be slidably removed from the implant10. After the threaded connector24is disengaged from the implant10, the insertion instrument20is removed from the working channel and the channel is closed. As previously mentioned, additional materials may be included in the procedure before, during or after the insertion of the spinal fusion implant10to aid the natural fusion of the targeted spinal level.

FIG. 10illustrates a spinal fusion system105for performing spinal fusion between adjacent cervical vertebrae, including an exemplary spinal fusion implant110and an exemplary cervical insertion instrument120provided in accordance with the present invention. The spinal fusion implant110may comprise 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 implant110may be provided in any number of suitable sizes, such as, by way of example only, a width ranging between 11 to 14 mm, a height ranging between 5 and 12 mm, and a length ranging from 14 and 16 mm.

As will be described in detail below, the cervical insertion instrument120is configured to releasably maintain the exemplary cervical fusion implant110in the proper orientation for insertion. The cervical fusion implant110may be simultaneously introduced into a disc space while locked within the cervical insertion instrument120and thereafter released. The exemplary cervical fusion implant110, having been deposited in the disc space, effects spinal fusion over time as the natural bone healing process integrates and binds the implant with the adjacent vertebral bodies. This fusion may be facilitated or augmented by introducing or positioning various materials in a space created within or adjacent to the cervical fusion implant110. Those materials may be introduced before, during, or after the insertion of the exemplary cervical fusion implant110. The additional material may include bone autograft harvested from the patient receiving the spinal fusion implant10, one or more additional bone allograft, bio-resorbables or xenograft implants, any number of non-bone implants, and any number of fusion promoting compounds such as bone morphogenic protein.

FIGS. 11-14depict various embodiments of the exemplary cervical fusion implant110. Some common attributes are shared among the various embodiments. More specifically, each cervical fusion implant110has a top surface31, a bottom surface33, lateral sides14, a proximal side22, and a distal side16. In one embodiment, the top and bottom surfaces31,33are generally parallel. It can be appreciated by one skilled in the art that although the surfaces are generally parallel, that the top31and bottom33surfaces may be angled with respect to one another to match the natural curve of the spine (i.e. lordosis or kyphosis). By way of example, implants for the cervical or lumbar regions of the spine will have anterior height greater than the posterior height to match the natural lordosis in those regions. Inversely, the implants designed for implantation into the thoracic region will be manufactured with a posterior height greater than the anterior height to match the natural kyophosis in that region. Additionally, the angled surface can aid in overall fit within the vertebral disc space.

The cervical fusion implant110preferably includes two receiving apertures12which are centrally aligned on the proximal side22. The receiving apertures12extend inwardly from the proximal side22in a generally perpendicular fashion relative to the proximal side22. Although shown as having a generally circular cross-section, it will be appreciated that the receiving aperture12may be provided having any number of suitable shapes or cross-sections, including but not limited to rectangular or triangular.

The exemplary cervical fusion implant110also preferably includes anti-migration features such as anti-migration teeth6along the top surface31and bottom surface33. Additional anti-migration features may include a plurality of proximal anti-migration spikes68and/or distal anti-migration spikes70integrated vertically through the cervical fusion implant110. The anti-migration features increase the friction between the cervical fusion implant110and the adjacent contacting surfaces of the vertebral bodies. That friction prohibits migration of the cervical fusion implant110during the propagation of natural bony fusion. It should be appreciated by one skilled in the art that such anti-migration teeth6can be oriented in a any manner other than generally vertically (as shown) without departing from the scope of the present invention. Moreover, as described above, the spikes68,70may be constructed from any of a variety of radiopaque materials, including but not limited to a metal, ceramic, and/or polymer material. When the spike elements68,70are provided having such radiodense characteristics, and the implant110is manufactured from a radiolucent material (such as, by way of example only, PEEK and/or PEKK), the spike elements68,70will be readily observable under X-ray or fluoroscopy such that a surgeon may track the progress of the implant110during implantation and/or the placement of the implant110after implantation.

The cervical fusion implant110has one large fusion aperture2, extending in a vertical fashion through the top surface31and bottom surface33which will function primarily as the avenue for bony fusion between adjacent vertebrae. The cervical fusion implant110may have a plurality of visualization apertures4which can also serve as an avenue of bony fusion on the lateral sides14via cell migration or additional adjuvants. The visualization apertures4serve an additional function of allowing a clinician to make visual observations of the degree of bony fusion un-obscured by the lateral side14to facilitate further diagnosis and treatment.

FIG. 15illustrates, by way of example, the orientation of the cervical fusion implant110prior to attachment to the cervical insertion instrument120by a clinician. One skilled in the art would appreciate that although the current embodiment shows a slidable engagement, various other methods of engagement are contemplated, such as, threadable or hooking features.

FIGS. 16-17detail the tubular lock member21of the exemplary cervical inserter instrument110. The tubular lock member21includes a central bore25dimensioned to receive the proximal end of the elongate fork member11therein. The internal dimension of the central bore25is smaller than the largest freestanding outer dimension of the taper feature19. As a result, the portion of the elongate fork member11that may be received by the central bore25of the tubular lock member21is limited by interference between the distal end of the tubular lock member21and the taper feature19of the elongate fork member11. In the present embodiment, the outer dimension of the threaded feature13of the elongate fork member11is smaller than the largest outer dimension of the taper feature19on the elongate fork member11. A thread feature23(not shown) at the proximal end of the tubular lock member21is situated inside the central bore25. The thread feature23matches the thread feature13on the elongate fork member11so that they can be threadably attached to one another. To ease the rotation of the tubular lock member21by hand, two semi-circular wings27may be provided protruding laterally outward from either side of the tubular lock member21. Alternatively, other methods of creating a gripping surface are contemplated including but not limited to knurling or facets.

A clinician can utilize the secured system in either an open or minimally invasive spinal fusion procedure. In either type of procedure, a working channel is created in a patient that reaches the targeted spinal level. After the creation of that channel, the intervertebral space would be prepared (via known instruments as described above). After preparation, the insertion instrument120is used to place a cervical fusion implant110into the prepared intervertebral space. Once the cervical fusion implant110is inserted into the prepared space, the implant110is released from the cervical insertion instrument120by retracting the tubular lock member21from the elongate fork member11by rotating the tubular lock member21with respect to the elongate fork member11in the opposite direction from that used to initially secure the implant110. That motion removes the compressive force on the purchase region39between the apertures12of the cervical fusion implant110and allows the engagement features17to be slidably removed from the apertures12. After the engagement features17are disengaged from the cervical fusion implant110, the cervical inserter instrument120is removed from the working channel and the channel is closed. As previously mentioned, additional materials may be included in the procedure before, during or after the insertion of the cervical fusion implant110to aid the natural fusion of the targeted spinal level.

In order to use the system to perform a spinal fusion procedure, the clinician must first designate the appropriate implant size. After the cervical fusion implant110is chosen, the engagement features17of the elongate fork member11are inserted into the apertures12on the implant110. At that time the cervical fusion implant110and elongate fork member11are slidably engaged with one another. Before the clinician can manipulate the combined cervical fusion implant110and elongated fork member11, they must be releasably secured together. In order to secure the cervical fusion implant110onto the elongate fork member11, the clinician would next employ the tubular lock member21. The clinician would insert the proximal end of the elongate fork member11into the central bore25of the tubular lock member21at its distal end. The tubular lock member21would then be advanced over the elongate fork member11until the thread feature13of that member and the thread feature23of the tubular lock member21become engaged.

Once engaged, advancement of the tubular lock member requires rotation of the tubular lock member21with respect to the elongate fork member11. Preferably, after only a small amount of engagement of the thread features the distal end of the tubular lock member21would contact the taper feature19of the elongate fork member11. The tubular lock member21would be advanced creating greater interference as the distal end approaches the distal end of the taper feature19which has the larger outer dimension. The increasing interference would laterally displace the clamping arms15of the elongate fork member11towards each other. Since the engagement features17of the elongate fork member11were initially inserted into the apertures12of the exemplary cervical fusion implant110, the displacement of the clamping arms15would create a compressive force on the purchase region39separating the apertures12of the exemplary cervical fusion implant110. That compressive force allows a clinician to manipulate the system without the exemplary cervical fusion implant110becoming disengaged from the cervical inserter instrument120.

The enhanced visualization features of the implants10,110are explained in greater detail with reference toFIGS. 18-23.FIG. 18illustrates an implant10dimensioned particularly for use in a posterior approach (PLIF) having (by way of example only) a width ranging between 9 and 11 mm, a height ranging between 8 and 14 mm, and a length ranging between 25 and 30 mm.FIG. 19illustrates the implant10ofFIG. 18from a side perspective via as taken via X-ray or fluoroscopy techniques, clearly showing the location of the spike elements7and8(there is no central spike element9as withFIG. 1) relative to the implant10and visualization apertures4.FIG. 20illustrates an implant10dimensioned particularly for use in a lateral approach (XLIF™ by NuVasive) having (by way of example only) a width of approximately 18 mm, a height ranging between 8 and 16 mm, and a length ranging between 40 and 45 mm.FIG. 21illustrates the implant10ofFIG. 20from a side perspective via as taken via X-ray or fluoroscopy techniques, clearly showing the location of the spike elements7,8,9relative to the implant10and visualization apertures4.FIG. 22illustrates an implant110dimensioned particularly for use in the cervical spine having (by way of example only) a width of approximately 11 mm, a height ranging between 5 and 12 mm, and a length of approximately 14 mm.FIG. 23illustrates the implant110ofFIG. 22from a side perspective via as taken via X-ray or fluoroscopy techniques, clearly showing the location of the spike elements66relative to the implant110and visualization apertures4. In this fashion, a surgeon may easily track the progress of the implant10,110during implantation and/or after implantation by visualizing the spike elements7,8,9and66, respectively, under X-ray and/or fluoroscopy according to the present invention.

For example, while described herein primarily with reference to the lumbar and cervical spinal surgery, it is to be readily appreciated that the spinal fusion implants of the present invention may be suitable for accomplishing fusion in the thoracic spine without departing from the scope of the present invention. Moreover, it is to be readily appreciated that the insertion tools described herein may be employed with implants of any number of suitable constructions, including but not limited to metal, ceramic, plastic or composite.