DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Reference will now be made in detail to the present preferred embodiments of this invention, examples of which are illustrated in the accompanying drawings. Similar reference numbers such as 28, 28′ will be used throughout the drawings to refer to similar portions of the same implant.

[0062] With reference to FIG. 1 and FIGS. 2A-2F, an interbody spinal fusion implant in accordance with a preferred embodiment of the present invention is indicated generally as 20. The implant has a body 22 having an insertion end 24, a trailing end 26, opposed side walls 28, 28′ and opposed upper and lower walls 30, 30′. Body 22 has a cross section with side walls 28, 28′ intersecting the upper and lower walls 30, 30′ at junctions that are preferably two diametrically opposed corners 32, 32′ and two diametrically opposed arcs 34, 34′. Fin-like projections 36, 36′ extend outwardly from respective ones of upper and lower walls 30, 30′ and are adapted to penetrate the vertebral endplates of the adjacent vertebral bodies upon rotation of implant 20 while the upper and lower walls 30, 30′ support the vertebral endplates of those adjacent vertebral bodies.

[0063] A brief discussion of a preferred method of use of an embodiment of present invention implant will serve to highlight the function of the structural features of implant 20.

[0064] With reference to FIG. 3A, and with the disc space optimally distracted, implant 20 is advanced linearly until fully contained within the disc space and oriented so that side walls 28, 28′ are opposed to the endplates of the vertebral bodies adjacent the disc space. Arcs 34, 34′ of implant 20 assure that as implant 20 is rotated 90 degrees about its longitudinal axis, the diagonal of this generally cuboid, trapezoid, or otherwise shaped implant body, will not have a dimension substantially greater than the height of body 22 of implant 20, that “height” being the distance between upper and lower walls 30, 30′ of implant 20. This feature, as best shown in FIG. 3B, allows upper and lower walls 30, 30′ to be placed into contact with and to support the vertebral endplates of the adjacent vertebral bodies without over-distracting the disc space or damaging the vertebral bodies. To avoid any ambiguity regarding the phrase “without over-distraction,” this phrase and the individual words contained therein are not being used as they may be in their normal or ordinary use, but are being used as defined in this application only.

[0065] As best shown in the schematic representation of a geometric configuration of a cross-section of a preferred embodiment of body 22 of implant 20 in FIG. 3C, implant 20 has opposed side walls 28, 28′, upper and lower walls 30, 30′, a height “X”, a width “Y”, a hypotenuse “H”, and a reduced or modified hypotenuse “RH”. Reduced hypotenuse RH is much closer to height X of implant 20 than unmodified hypotenuse H. While height X is depicted as being greater than width Y, this schematic is shown by way of example and not limitation, such that it is to be understood that height X could also be equal to or slightly less than width Y along the length of implant 20 or any portion thereof.

[0066] Reduced hypotenuse RH is significantly less than hypotenuse H in this embodiment of the present invention to allow for the rotation of implant 20 from the an insertion position to a deployed position without over-distraction occurring during this process. While reduced hypotenuse RH is illustrated as being arcuate in this preferred embodiment, the configuration of body 22 of implant 20 to form reduced hypotenuse RH can take many forms, including arcuate portions, a radius, a chamfer, a series of angled surfaces, or any other shape so long as a reduced hypotenuse RH of sufficient dimension for the intended purpose of the present invention results therefrom. Reduced hypotenuse RH has a diagonal that does not significantly exceed the height and may be equal to or less than height H of body 22 of implant 20. Reduced hypotenuse RH is preferably substantially the same as the height H of body 22, and in one preferred embodiment reduced hypotenuse RH has a length within 10% of the height H of body 22. Reduced hypotenuse RH also has a diagonal that is less than implant 20 total height “TH” including fins 36, 36′, and more preferably markedly less than the total height TH of implant 20 including fins 36, 36′.

[0067] A hypotenuse (true hypotenuse) is a side of a right-angled triangle opposite the right angle. When reference is made herein to a hypotenuse or a reduced hypotenuse, reference is being made to the diagonal dimension of a theoretical line between diagonally opposed points of the implant overlying the true hypotenuse. Side walls 28, 28′ and upper and lower walls 30, 30′ do not need to intersect, but in fact may have a relief, radius, or chamfer by way of example, to form a theoretical line overlying and shorter than a true hypotenuse of a right-angled triangle formed with sides corresponding to side wall 28′ and lower wall 30′, respectively. As shown in FIG. 3C, hypotenuse H represents the dimension of a line between points 32 and 32′ on body 22 across a right angle that would be formed if side wall 28′ and lower wall 30′ were to continue in their respective planes to intersect at a right angle as illustrated by X and Y in FIG. 3C. Reduced hypotenuse RH represents the dimension of a line between points 34 and 34′ on body 22 across a right angle that would be formed by the intersection of side wall 28 and lower wall 30′ because of the radiused junction at the corners of a theoretical right-angled triangle. While reference has been made to a hypotenuse as being the side across a right angle, if the side walls and upper and lower walls were to intersect at an angle other than a right angle, for purposes of this application, a long side of the triangle formed by an angle other than 90 degrees is still referred to herein as a hypotenuse.

[0068] An embodiment of the present invention where reduced hypotenuse RH is slightly greater than height X offers the advantage of an over-center effect that locks implant 20 into place. In this instance, once implant 20 rotates past the diagonal of reduced hypotenuse RH, more force would be required to rotate it back from the final deployed position to its insertion position than in an embodiment where reduced hypotenuse RH is equal to or less than height H.

[0069] Fins 36, 36′ are of greater height than the implant body height as measured between upper and lower walls 30, 30′. Fins 36, 36′ come to reside within the interior of the adjacent vertebral bodies after being driven through the endplates by the act of rotation. This penetration of fins 36, 36′ into the interior, cancellous region of the vertebra allows the implant to access the vascular bone beneath the endplate and further provides for significant stability of implant 20 as each fin 36, 36′ acts as an anchor within the body of the vertebra. It can be seen that the surface area of the vertebral bodies in contact with implant 20 is greatly enhanced by fins 36, 36′ as compared to a flat surface.

[0070] Upper and lower walls 30, 30′ of implant 20 are configured to support the bone of the vertebral endplate region. When implant 20 is inserted into an already distracted disc space corresponding in height to the height of the fusion implant body 22, fins 36, 36′ protruding from implant body 22 will be driven during rotation through the endplates and into the vertebral bodies. This cutting action of fins 36, 36′ can further be enhanced by shaping the leading edges of fins 36, 36′ so they are pointed, sharpened, or both. The leading edge of fins 36, 36′ may additionally have a ramped or sloped profile.

[0071] From the structure of implant 20 it can be appreciated that upper and lower walls 30, 30′ may be configured with a distance between them corresponding to the optimally distracted height of the disc space. The upper and lower walls 30, 30′ may be formed with surface configurations that conform to the vertebral endplates of the adjacent vertebral bodies to provide optimum contact and support between the endplates and the implant. Upper and lower walls 36, 36′ also have at least one, and alternatively a plurality of, openings therethrough so as to allow for the growth of bone in continuity from adjacent vertebral bodies to adjacent vertebral bodies through the implant to permit the vertebral bodies to fuse to one another. Implant side walls 28 and 28′ can have none, one or preferably a plurality of openings.

[0072] As shown in FIG. 1 and FIG. 2A, side walls 28, 28′ preferably have a distance between them so that they contact the adjacent vertebral bodies upon initial insertion of implant 20 into the spine. Each of side walls 28, 28′ lie generally in a plane and, in a preferred embodiment, side walls 28, 28′ are generally parallel to one another.

[0073] Two diametrically opposed arcs 34, 34′ are preferably, but not necessarily, formed as arcs of radii. More preferably, each of the opposed arcs 34, 34′ are of the same radius as shown in FIG. 1 and FIG. 2E and more preferably are arcs of the same circle. The two diametrically opposed arcs 34, 34′ may also include quadrants of the same circle. The distance between opposed arcs 34, 34′ preferably approximates the distance between the upper and lower walls 30, 30′ such that, when implant 20 is rotated from an initial insertion position toward a final deployed position, no over distraction of the space between the adjacent vertebral bodies occurs and no damage to the vertebral bodies occurs.

[0074] Fins 36, 36′ have a height H measured from the longitudinal central axis L of implant 20. In a first embodiment, height H may be substantially uniform along a portion or the entire length of implant 20. Alternatively, fins 36, 36′ may have height H′ measured from upper and lower walls 30, 30′ that is substantially constant along the length of implant 20. Other variations on the height and configuration of the fins are readily appreciated by those of skill in the art, i.e., spine surgeons, and are incorporated as part of the present invention. Fins 36, 36′ preferably have a sharp leading edges 40, 40′ for penetrating the vertebral endplates upon rotation of implant 20. The leading edges 40, 40′ may also be pointed, and/or ramped. Fins 36, 36′ may be sharpened along any portion of their length so as to facilitate the penetration of fins 36, 36′ through the vertebral endplates and into the interior, cancellous region of the vertebral bodies. Fins 36, 36′ may be thickened at their trailing end to more tightly lock implant 20 into place. Fins 36, 36′ may be of different shapes and arrangements. By way of example only and not limitation, fins 36, 36′ may be in the shape of fin-like projections evenly spaced along at least a portion of the upper and lower walls 30, 30′. It is also contemplated within the scope of the present invention that fins 36, 36′ may be portions or segments of a helix, or have uneven spacing along the length of the implant. Fins 36, 36′ may have any of a variety of shapes suitable for their intended purpose as stated herein.

[0075] Implant 20 of FIG. 1 is configured to have a single direction of rotation. It can be seen in this exemplary embodiment, as best shown in FIGS. 3A and 3B, that in an appropriately distracted space, rotation of implant 20 in a counterclockwise direction would be blocked due to the fact that the length of the diagonal of implant 20 between the corners 32, 32′ exceeds the height of the disc space. In contradistinction, the implant may be rotated in a clockwise direction because the diagonal between arcs 34, 34′ is less than or equal to the length of the disc space.

[0076] Body 22 of implant 20 preferably includes a hollow portion 42. Hollow portion 42 is adapted to contain fusion promoting material including, but not limited to, bone, in any of its varied forms, hydroxyapatite, coral, bone morphogenetic proteins, and agents with the ability to induce cells to become osteoblasts or to make bone. The implant of the present invention can be made of any material suitable for its purpose and appropriate for implantation in the human spine. Such materials include, but are not limited to, bone itself and particularly human cortical bone as it is obtainable from a cadaver from such areas as the femur, so long as the bone material possesses sufficient strength for the intended purpose. The implants of the present invention can be made of a novel material including an artificial composite of bone and a bioresorbable (broken down and absorbed by the body over time) plastic e.g., from the lactide family including lactones, polylactones, galactone, and so forth, or any such plastic that can be utilized to bind the bone fragments together so that the resultant material is of sufficient strength and for a long enough period of time to work for the intended purpose of being a material for interbody fusion through the implant spinal fusion device. Much like carbon fiber composite, in such a novel material the bone would preferably, but not necessarily, be human bone fragmented into preferably cortical strips having lengths significantly greater than their width so as to take the form of fibrils. These fibrils either randomly disposed, organized in layers or woven together into sheets or pads or meshes would be combined with resorbable plastic to form the material of the implant. The implant could either be molded from the material, machined from the material, or a combination of both.

[0077] As previously stated, implant 20 has at least one and, alternatively, a plurality of openings through upper and lower walls 30, 30′ herein shown as openings 38, 38′ passing through the body and in communication with hollow portion 42. These openings provide a passageway through implant 20 and through the upper and lower walls 30, 30′ of implant 20 to allow for the growth of bone in continuity from one adjacent vertebral body through the implant to the other adjacent vertebral body. Side walls 28, 28′ may also include openings 44, 44′ passing therethrough in communication with hollow portion 42. It shall be readily appreciated that openings 38, 38′ in upper and lower walls 30, 30′, as well as openings 44, 44′ in side walls 28, 28′, may have any shape, size, configuration, or distribution suitable for the intended purpose of permitting a fusion to take place through the implant. In the present embodiment, at least some of openings 38, 38′ and 44, 44′ are macroscopic in size, i.e., greater than 1.0 mm in dimension across. However, as will be discussed in more detail in regard to the embodiment of FIGS. 14 and 15A-15D, an implant of the present invention may also comprise extensive surface openings of less than 1.0 mm so as to approximate the structure of human cancellous bone or an implant can combine these features. The implant of the present invention may also include openings 38, 38′ and 44, 44′ that are microscopic in size, that is, less than about 40 □m. Microscopic is defined herein as being of a size sufficiently small that magnification is required to appreciate the fine detail of the structure and as used herein is less than 1 mm in maximum dimension .

[0078] Implant 20 preferably includes a cap 46 with a thread that threadably attaches to insertion end 24 of implant 20. Cap 46 is removable to provide access to hollow portion 42, such that hollow portion 42 can be filled (under compressive load if desired) with any natural or artificial osteoconductive, osteoinductive, osteogenic, or other fusion enhancing material. Some examples of such materials are bone harvested from the patient, or obtained elsewhere, or bone growth inducing material such as, but not limited to, hydroxyapatite, hydroxyapatite tricalcium phosphate, bone morphogenetic proteins, or genes coding for the production of bone.

[0079] Cap 46 and/or implant 20 may be made of any material appropriate for human. implantation including metals such as cobalt chrome, stainless steel, titanium, plastics, ceramics, composites and/or may be made of, and/or filled with, and/or coated with a bone ingrowth inducing material such as, but not limited to, hydroxyapatite or hydroxyapatite tricalcium phosphate or any other osteoconductive, osteoinductive, osteogenic, or other fusion enhancing material, including bone morphogenetic proteins or other genetic material (genes coding for the production of bone) to stimulate the formation of bone making cells and/or the formation of bone by cells. Cap 46 and implant 20 may be partially or wholly bioabsorbable. Cap 46 is not limited, however, to a threaded coupling, which is offered only by way of example. Implant 20 and cap 46 may each be adapted to cooperatively engage the other in any manner suitable for the intended purpose and as known to those skilled in the art. The implant does not require an end opening and may in various embodiments, including a single opening being easily loaded through the opening. Cap 46 may also be configured to cooperatively engage a driver for engaging cap 46 to implant 20 or for inserting and rotating implant 20 into the disc space and adjacent vertebral bodies. Cap 46 may also be perforate so as to retain fusion promoting substances within implant 20 while providing for vascular access and growth therethrough.

[0080] In a preferred embodiment, for use in the lumbar spine when oriented front to back or back to front, implant 20 has an overall length in the range of approximately 20 mm to 34 mm with 26 mm to 28 mm being the preferred length. Body 22 of implant 20, as defined by the distance between the upper and lower walls 30, 30′, has a height from about 6-20 mm when for use in the lumbar spine, which height can vary over the length of the implant. Fins 36, 36′ have a preferred height when measured from body 22 in the range of from 1-5 mm. Side walls 28, 28′ are preferably spaced apart from each other a distance in the range of from 6-20 mm. Fins 36 extend from upper and lower walls 30, 30′ such that the distance measured from the tip of fin 36 to the tip of fin 36′ is greater than the distance between upper and lower walls 30, 30′. An implant for use in the cervical spine preferably has a length from 10-22 mm, a body height from 5-12 mm, a fin height from 0.5-2.5 mm, and a body width from 5-12 mm.

[0081] A preferred embodiment of the present invention includes means for engaging an implant driver. Preferably, but not by way of limitation, the engaging means is located at trailing end 26 of implant 20 allowing for the full loading of implant 20 prior to insertion. It is also preferable that the driver engaging means allows implant 20 to be secured to the implant driver such that it can be pulled or pushed as well as rotated without inadvertent disengagement of the driver. One such engaging means is shown in FIG. 2D wherein implant 20 has a recessed slot 48 formed at its trailing end 26 for receiving insertion instrumentation. Recessed slot 48 has a threaded opening 50 for threadably attaching implant 20 to instrumentation for use in inserting implant 20. Numerous other types of engaging means will be readily contemplated by those of skill in the art, and such alternative mechanisms are within the scope of the present invention.

[0082] In accordance with another preferred embodiment of the present invention, and with further reference to FIGS. 4 and 5A-5E and with particular attention being drawn to FIG. 5A, the implant 120 includes upper and lower walls 130,130′ disposed in a diverging angular relationship to each other from insertion end 124 to trailing end 126 of body 122. This angular relationship preserves and/or restores lordosis in a segment of the lumbar or cervical spinal column when inserted from the anterior (front) aspect of the spine. Implant 120 of FIG. 4 has fins 136, 136′ having a substantially uniform height H measured from the central longitudinal axis L of implant 120 such that the overall height of fins 136, 136′ has an overall dimension that is substantially parallel to the longitudinal axis L. Fins 136, 136′ as measured from upper and lower walls 130, 130′ have a height H′ that varies along the length of implant 120. Alternatively, fins 136,136′ can have a height H measured from the longitudinal central axis L of implant 120 wherein the height H is variable along the length of implant 120.

[0083] In accordance with yet another preferred embodiment of the present invention, and with further reference to FIGS. 6 and 7A-7E, implant 220 includes upper and lower walls 230, 230′ disposed in a converging angular relationship to each other from insertion end 224 to trailing end 226 of body 222. In this embodiment, when implant 220 is inserted from the posterior aspect of the spine, body 222 of implant 220 has a maximum height at a point nearest to insertion end 224 and a minimum height at a point nearest trailing end 226 so as to restore the natural lordosis of the spine at that spinal segment. This is facilitated by the fact that implant 220 is introduced in the disc space lying on its side, and the side to side dimension of body 222 is preferably uniform.

[0084] In accordance with yet another embodiment of the present invention, and with further reference to FIGS. 8 and 9A-9E, implant 320 includes upper and lower walls 330, 330′ having a generally anatomical shape configured to substantially match the natural contours of the endplates of the adjacent vertebral bodies to be fused. This anatomical shape is best observed in FIGS. 8 and 9A wherein upper and lower walls 330, 330′ are shown having a curvature oriented from insertion end 324 to trailing end 326. The generally anatomical shape may also include a contour of upper and lower walls 330, 330′ from side to side of implant 320.

[0085] In accordance with yet another embodiment of the present invention, and with reference to FIGS. 10 and 11A-11D and FIGS. 12 and 13A-13D, implant 420 may comprise four diametrically opposed junctions that are radiused so as to permit rotation of the implant in both clockwise and counterclockwise directions. The specialized junctions of implant 420 need not be limited to portions of a circle. Alternatively, the junctions can be tapered, or in some other manner have a relief or cut out area to serve in a manner similar to the radiused areas previously described so that the reduced hypotenuse is substantially less than the other hypotenuse between the other diagonally opposed junctions, which is an unreduced, an unmodified, or a theoretical hypotenuse or at least a hypotenuse reduced to a lesser extent than the reduced hypotenuse, and thus the reduced hypotenuse is closer in height to the body of the implant.

[0086] Implant 420 of FIGS. 12 and 13B shows use of three large openings 438 passing through upper wall 430, into the implant, and through openings 438′ in lower wall 430′. These openings allow for the growth of bone in continuity from adjacent vertebral body to adjacent vertebral body through implant 420. It is understood that upper and lower walls 430, 430′ can have fewer than or more than the number of openings 438, 438′ herein shown. Such an alternative embodiment readily lends itself to being loaded with osteogenic material such as bone without resort to an end opening to the implant which is not an essential feature of the implant.

[0087] In accordance with yet another preferred embodiment of the present invention, and with further reference to FIGS. 14 and 15A-15D, implant 520 comprises a porous material with a plurality of openings 538, 538′ within a surface and generally being 1.0 mm or less in diameter. Openings 538, 538′ are the ends of channelings passing entirely through implant 520 such that there are passageways from upper wall 530 to lower wall 530′ to allow the growth of bone from vertebral bodies to vertebral bodies through the implant. Because of its porous nature, implant 520 is able to hold fusion promoting materials and further provides for an increased surface area of contact and engagement when opposed to the adjacent vertebral bodies By increasing both surface area and contact, implant 520 further promotes the process of interbody fusion. In this particular implant at least a significant portion of the pores of the outer surface 552 are in the range of 50-500 microns with a significant portion of those in the range of 250-500 microns in diameter. Because of its porous nature, implant 520 also lends itself well to being coated with bioactive fusion promoting substances such as bone morphogenetic proteins or genetic material to induce bone formation in the recipient. Such materials include sequences of nucleic acids comprised of cytosine guanine adenine thymine (CGAT). While implant 520 in FIGS. 14 and 15A-15D are shown as being solid, it should be appreciated that implant 520 can be made to be substantially hollow or hollow in part.

[0088] FIGS. 16A and 16B show an alternative embodiment of the present invention that has previously been referred to as third implant 820 or the middle implant. This third implant is for use between first implant 620 and second implant 720 in accordance with the embodiments described above. Within the preferred embodiment of the implant set, first implant 620 is configured to rotate, by preference only, in a first direction while second implant 720 is configured, again as a matter of preference only to rotate in a second direction opposite the first direction. Each of first and second implants 620, 720 rotate from a more central to a more lateral position. Thus, as best shown in FIG. 16C, in this embodiment, first implant 620 rotates clockwise while second implant 720 rotates counterclockwise. Third implant 820 is configured for placement between first and second implants 620, 720 and has contacting surfaces 860, 860′ for contacting the adjacent side walls 628, 728′ of first and second implants 620, 720, respectively.

[0089] As best seen in FIGS. 17 and 18A-18D, third or middle implant 820 has openings 838, 838′ for permitting bone growth from vertebral body to vertebral body and preferably openings 844, 844′ in the side walls 828, 828′ of the implant 820 to allow for the growth of vascularity and bone through implant 820 and adjacent implants 620 and 720. Implant 820 is not configured to facilitate rotation since it is inserted into the spine already correctly oriented with upper and lower walls 830, 830′ to contact the adjacent vertebral bodies. Upper wall 830 and lower wall 830′ preferably include ridges 864 or other surface projections for engaging the adjacent vertebral bodies. Side walls 828, 828′ of implant 820 include surface projections for engaging complementary surface projections on the side walls 628, 728′ of implants 620 and 720, respectively. The present embodiment preferably includes ridges 860 formed of forward facing ratchetings that permit implant 820 to be easily slid between implants 620 and 720 but resists its dislodgement in a direction counter to its insertion. It can be seen in FIGS. 16B and 18E how the forward facing side wall ratcheting of implant 820 cooperate with the reversed side wall ratchetings of implants 620 and 720 to bind the three implants together side by side.

[0090] In accordance with yet another preferred embodiment of the present invention, and with further reference to FIGS. 20A and 20B, implant 920 is configured to rotate less than 90 degrees from an initial insertion position to a final, deployed position. This embodiment of the present invention preferably has a rotation of approximately 70 degrees. An implant configured for less than 90 degrees of rotation can have larger contact areas for upper and lower walls 930 and 930′ than a comparable height 90 degree rotation implant.

[0091] In accordance with another preferred embodiment of the present invention, and with further reference to FIG. 21, implant 1020 has at least one side wall 1028 that is configured to mate with another implant 1120. In particular, FIG. 21 illustrates a trailing end view of an embodiment of the present invention having a concave side wall 1028 to cooperatively mate with either of a cylindrical, partial cylindrical, tapered, threaded or push-in interbody implant 1120. Sidewall 1028 may be concave or be incomplete providing an opening to accommodate implant 1120 or otherwise relieved to allow for implants 1020 and 1120 together to have a width less than the sum of their maximum widths apart. Alternatively, yet another embodiment of the present invention is shown in FIG. 22, and includes an implant 1220 having grooves 1280 in at least one side wall 1228 for cooperatively receiving threads from an adjacent threaded interbody implant 1320. While implant 1320 is of a tapered design it could be more or less cylindrical and its surface projections could be other than a thread. Also, implant 1220 may have an incomplete sidewall 1228 with openings therein to accommodate the projections or thread of implant 1320.

[0092] Having described certain preferred embodiments of the implant of the present invention, the method for deploying this implant will now be described in more detail. The method comprises the steps of: removing at least a portion of the disc from between the adjacent vertebral bodies so as to at least in part expose the vertebral endplates of those adjacent vertebral bodies; providing a first implant having an insertion end, a trailing end, side walls, upper and lower walls, and protrusions, which protrusions are preferably but not necessarily in the form of fins extending outwardly from the opposed upper and lower walls. Preferably, the upper and lower walls have at least one, or alternatively a plurality of openings passing therethrough so as to allow for the growth of bone in continuity from one of the adjacent vertebral bodies to the other of the adjacent vertebral bodies through the spinal fusion implant. The implant includes a cross-section with the side walls intersecting the upper and lower walls at opposed junctions, two of which are preferably diametrically opposed arcuate portions. The method also includes the steps of inserting the first implant by linearly advancing it between the adjacent vertebral bodies with the side walls facing the endplates of the adjacent vertebral bodies, and then rotating the first implant 90 degrees into a deployed position such that the fins penetrate the endplates of the adjacent vertebral bodies. When the implant is deployed, the upper and lower walls from which the fins extend will then be placed into contact and support through the endplate regions of the adjacent vertebral bodies the vertebral endplates themselves.

[0093] The inserting step may include positioning the adjacent vertebral bodies in relative angular position to each other by the step of rotating the implant 90 degrees about its longitudinal axis. The method may further comprise of the step of loading the first implant with osteogenic material prior to insertion of the implant. The method may further comprise compressibly loading fusion promoting materials within the interior of the implant prior to its insertion. The rotating step may further include the sub-step of initiating rotation in a direction so that the two diametrically opposed arcs of radii rotate toward the nearest of the adjacent vertebral bodies respectively. Additionally, the rotating step may include the sub-step of rotating the first implant from its position after the insertion step to a deployed position without substantial additional distraction of the adjacent vertebral bodies.

[0094] The method may further comprise of the step of attaching a driver to the first implant, the preferred driver being capable of both pushing and pulling the implant while rotating the implant both clockwise and counterclockwise. The method may further comprise using the driver to insert the implant through a guard either with or without disc penetrating extensions or in combination with a distractor as disclosed in U.S. Pat. Nos. 5,484,437 and 5,797,909, which are hereby incorporated by reference.

[0095] The method may further comprise the steps of providing a second implant having an insertion end, a trailing end, side walls, upper and lower walls, and fins extending outwardly from the upper and lower walls. The upper and lower walls preferably have openings which pass therethrough that are configured to allow for the growth of bone therethrough and from vertebral body to vertebral body through the implant. The second implant has a cross-section with the side walls intersecting the upper and lower walls at junctions, two of which are preferably diametrically opposed arcuate portions. The second implant is inserted between the adjacent vertebral bodies with the side walls directed toward the adjacent vertebral bodies and then rotated 90 degrees into a deployed position such that the upper and lower walls then contact and support each of the adjacent vertebral endplate regions while the fins extending from the upper and lower walls are then penetrably driven through the vertebral endplates. The implant is rotated to drive the fins into the substance of the vertebral bodies.

[0096] As a substep of that method, the first implant may be deployed by rotating it 90 degrees in a first direction while the second implant may be deployed by rotating it in either the same direction or in the opposite direction.

[0097] The method may further comprise of lateralizing (moving lateral) the first and second implant to provide a space between the first and second implants. The method may still further comprise placing within that space a third specialized implant different in structure from the first and second implants in that while it is designed to be inserted by linear advancement, it is not designed to be rotated into place. Further, the specialized third implant preferably includes protrusions or ratchetings on its outer walls so as to engage the implant to the adjacent vertebral bodies and to the first and second implants. This specialized third implant preferably has upper and lower walls for contacting each of the adjacent vertebral bodies. The upper and lower walls preferably have at least one opening to allow for the growth of bone in continuity from a first adjacent vertebral body through the implant to the second adjacent vertebral body. A third implant preferably is inserted between the first and second implant and between the adjacent vertebral bodies with opposed upper and lower walls directed towards the adjacent vertebral bodies. The step of inserting the third implant may include a substep of contacting the first and seconds implants with the side walls of the third implant and a substep of securing the third implant to the first and second implants. The securing substep preferably includes a substep of providing the first, second, and third implants with cooperating engaging surfaces along the side walls of each implant at least where the implants are in contact with one another.

[0098] When the implants are rotated approximately 90 degrees, while they do not cause an over distraction of the inner space, they nevertheless create a path through the adjacent vertebral endplates of the fins that may be approximately one and a half times the width of the implant itself. When a first, second, and third implants are inserted into the disc space, the first and second implants migrate as described above, approximately 50 percent of their width laterally to create room for the third implant with a width the same as the first and second implants. The third implant uses the 50 percent extra area cut by of each of the first and second implants. The track that is cut in each of the adjacent vertebral bodies by the fins of the first and second implants acts as a pathway of less resistance to allow these implants to slide laterally. A third implant with a width greater than or lesser than that of said first and second implants may also be utilized without departing from the scope of the present invention.

[0099] The method for inserting these implants may also include use of a cutting tool patterned like the implant but made of a material either stronger than or sharper than the implant. For example, if the implant were made of a carbon fiber or resorbable plastic, or bone, it may be desirable to utilize a cutting tool such as a rotary broach to cut the path that the fins of the implant would than occupy but not use the fins of the implant to do the actual cutting work.

[0100] The method may further include the step of scrapping or otherwise working upon the endplates until at least partially decorticated, i.e. worked upon to access the vascularity deep to the outer most aspect of the endplates itself prior to the step of inserting the implant. The step of removing may include the step of exposing the endplates of the adjacent vertebral bodies by removing sufficient disc material including both annulus fibrosus and nucleus pulposus from between the adjacent vertebral bodies. The providing step may include providing the first implant with at least one of the leading end and the trailing end of the body with an opening in communication with a hollow portion and adapted to cooperatively engage a cap. The providing step may also include providing the first implant in combination with a removable cap for closing the opening in at least one of the leading end and the trailing end of the body. The method may further include the step of loading or compressively loading the implant with osteogenic material.

[0101] The inserting step includes the sub-step of linearly advancing the implant between the adjacent vertebral bodies. The linearly advancing step includes the substeps of pushing the implant between the adjacent vertebral bodies or driving the implant between the adjacent vertebral bodies with percussion. The method may further include the step of distracting the adjacent vertebral bodies sufficiently for insertion of the implant prior to the inserting step. The method may further include the step of retracting the dural sac on the posterior side the adjacent vertebral bodies prior to the inserting steps. The step of inserting the implant may occur from an anterior aspect of the spine in which case the great blood vessels on the anterior side the adjacent vertebral bodies are retracted prior to the inserting step. The method may further include the step of inserting a rotary broach between the adjacent vertebral bodies, the broach having opposed sides for sliding against the adjacent vertebral bodies and a cutting portion for broaching into each of the adjacent vertebral bodies transverse to the long axis of said broach. The step of rotating includes rotating the broach so as to the drive cutting elements along the length of cutting portion of the broach into each of the adjacent vertebral bodies transverse to the long axis of the broach.

[0102] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples may be considered as exemplary only, and the true scope and spirit of the invention be indicated by the following claims.