AU2004203229B2

AU2004203229B2 - Instruments for use in spinal surgery

Info

Publication number: AU2004203229B2
Application number: AU2004203229A
Authority: AU
Inventors: Gary K Michelson
Original assignee: SDGI Holdings Inc
Current assignee: Warsaw Orthopedic Inc
Priority date: 1999-01-25
Filing date: 2004-07-16
Publication date: 2006-09-28
Anticipated expiration: 2020-01-25
Also published as: AU2004203229C1; AU2004203229A1

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Gary K Michelson Actual inventor(s): Gary K Michelson Address for Service and Correspondence: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: INSTRUMENTS FOR USE IN SPINAL SURGERY Our Ref: 724257 POF Code: 372401/89004 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 6006q INSTRUMENTS FOR USE IN SPINAL SURGERY This application is a divisional of patent application No. 26284/00, (the "Parent Application"), the entire contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to intervertebral spinal surgery, and more particularly to surgical instrumentation and to a method of using such instrumentation for accurately marking a location on the spine for subsequent formation of an implantation space with a bone removal device. Furthermore, the present invention is directed to surgical instrumentation and to a method of using such instrumentation for distracting two adjacent vertebral bodies prior to forming an implantation space.

Description of the Prior Art The spinal disc that resides between adjacent vertebral bodies maintains the spacing between those vertebral bodies and, in a healthy spine, allows for relative motion between the vertebrae. With disease and/or degeneration a disc may become painful and/or mechanically insufficient warranting surgical fusion across the affected disc. Where fusion is intended to occur between adjacent vertebral bodies of a patient's spine, the surgeon typically prepares an opening at the site of the intended fusion by removing some or all of the disc material that exists between the adjacent vertebral bodies to be fused. Because the outermost layers of bone of the vertebral endplate are relatively inert to new bone growth, the surgeon must work on the endplate to remove at least the outermost cell layers of bone to gain access to the blood-rich, vascular bone tissue within the vertebral body. In this manner, the vertebrae are prepared in a way that encourages new bone to grow onto or through an implant that is placed between the vertebrae. An implant or insert may or may not promote fusion of the adjacent vertebral bodies, may be an artificial spinal disc, may permit surface ingrowth, and may be made of bone or inert material, such as titanium. All of these examples and more are implants.

Present methods of forming a space between adjacent vertebrae generally include the use of one or more of the following: hand held biting and grasping instruments known as rongeurs; drills and drill guides, rotating burrs driven by a motor; and osteotomes, chisels, and scraping implements. Surgeons often prefer a drilling technique due to its being ease, quick, and accurate.

Sometimes the vertebral endplate must be sacrificed as occurs when a drill is used to drill across the disc space and deeper into the vertebrae than the thickness of the endplate. Such a surgical procedure is typically used to prepare a space in the spine for an implant having a circular cross-section and necessarily results in the loss of the hardest and strongest bone tissue of the vertebrae, the endplate, and thereby robs the vertebrae of that portion of its structure best suited to absorbing and supporting the loads placed on the spine by everyday activity. Where the surgeon chooses to forego drilling a large bore across the disc space in an attempt to preserve that good bone he must nevertheless use one of the above instruments to work upon the endplates of the adjacent vertebrae to access the vascular, cancellous bone that is capable of participating in the fusion and causing active bone growth, and also to attempt to obtain an appropriately shaped surface in the vertebral bodies to receive the implant, which means and method are unreliable for that purpose.

There exists therefore a need for instrumentation that can be used to accurately mark a location on the spine for subsequent formation of an implantation space with a bone removal device.

There also exists a need for instrumentation that can be used to easily distract two adjacent vertebral bodies prior to forming an implantation space.

SUMMARY OF THE INVENTION In one aspect, the present invention is directed to a distractor for use in spinal surgery, including: a body having a disc penetrating extension extending from the body for insertion into the disc space between the adjacent vertebral bodies and for bearing against the adjacent vertebral endplates of the adjacent vertebral bodies, the disc penetrating extension being hollow and with an open leading end to facilitate insertion of the extension into the disc space and for containing disc material within the extension.

Preferably the body of the distractor includes a shoulder that is adapted to conform at least in part to the exterior of the adjacent vertebral bodies. The shoulder may be curved to correspond to the external curvature of the vertebral bodies.

In another preferred embodiment, the extension of the distractor includes a shaft having one of a rectangular cross-section and a circular cross-section.

It is preferred that the extension includes an end for detachably receiving various sized distractor tips. In this way, the depth of insertion of the tip into the disc space can be controlled to achieve the desired distraction.

The distractor tips may have sharpened surfaces.

In one preferred embodiment, the extension of the distractor converges away from the distractor body. Alternatively, the extension may diverge away from the body.

In another aspect, the present invention is directed to a method for preparing an implantation space at least in part into a disc between two adjacent vertebral bodies of a human spine for receiving a spinal implant, the method including the steps of: providing a distractor having a disc penetrating extension adapted to be inserted into the disc and between the adjacent vertebral bodies, the disc penetrating extension having an upper portion, a lower portion, a hollow interior therebetween, and an open end in communication with the hollow interior; inserting the disc penetrating extension into the disc with the upper portion contacting one of the adjacent vertebral bodies and the lower portion contacting the other of the adjacent vertebral bodies to position the vertebral bodies in a spaced apart relationship; IDadvancing the disc penetrating extension into the disc to incise the disc 0 Sduring the inserting step; retaining a portion of the disc in the hollow interior of the disc penetrating

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extension during the advancing step; and removing the distractor from the disc and from between the adjacent vertebral bodies with a portion of the disc being retained in the hollow interior of the disc penetrating extension to create the implantation space.

(Ni 0In another embodiment the present invention is directed to a method of

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S 10 distracting the disc space between adjacent vertebral bodies, and in particular, 0 including the step of inserting a distractor having a disc penetrating extension into the disc space between adjacent vertebral bodies and against endplates of the adjacent vertebral bodies. The depth of penetration of the distractor into the disc space is preferably controlled. The method may further include the step of changing disc penetrating extension of the distractor in accordance with a desired distractor distance between adjacent vertebral bodies. A guard may be inserted over the distractor in the disc space, and then the distractor may be removed from within the guard.

Embodiments of the distractor of this invention may be used with other surgical instruments in spinal surgery for forming a substantially quadrilateral space in the spine for implanting a spinal implant at least in part into and at least in part across a disc space between adjacent vertebral bodies. Such an instrument set includes an extended guard for providing protected access to the disc space and the adjacent surfaces of the adjacent vertebral bodies, a guide insertable into the guard, and a bone removal device insertable into the guard. This instrument set is described in and is the subject of the Parent Application.

It is understood that both the foregoing general description and the following detailed description are exemplary and exemplary only, and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings Figs 5 to 7, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention. Together with the description, they serve to explain the objects, advantages and principles of the invention. Figs. 1 to 4 and 8 to 51 illustrate other surgical instrumentation that may be utilized in conjunction with the instrumentation of this invention in spinal surgery. In the drawings: Fig. 1 is a leading end side view perspective view of the midline spinal marker of the present invention; Fig. 2 is a leading end view of the midline spinal marker of Figure 1; Fig. 2A is a cross-sectional view along lines X-X of Figure 2; Fig. 2B is a cross-sectional view along lines Y-Y of Figure 2; Fig 3 is a trailing end side perspective view of the midline spinal marker being inserted at the anterior vertebral midline into the disc space between adjacent vertebral bodies of a segment of the spine; Fig. 4 is a cross-sectional view along lines 4--4 of Figure 3 illustrating the spinal marker inserted into the disc space between two adjacent vertebral bodies along the vertebral midline; Fig. 5 is a leading end side perspective view of a spinal distractor of the present invention; Fig. 5A is a cross-sectional view along line 5A--5A of Fig. Fig. 6 is a trailing end side perspective view of the distractor of Figure with an impaction cap for driving the distractor into the disc space lateral to the midline (identified by reference mark) between the adjacent vertebral bodies of the spine; Fig. 7 is a cross-sectional view along line 7--7 of Figure 6 showing the distractor inserted in the disc space between the adjacent vertebral bodies on one side of the vertebral midline; Fig. 8 is an exploded trailing end side perspective view of a guard providing protected access to the disc space and the adjacent surfaces of the vertebral bodies and an impaction cap; Fig. 9 is a leading end side perspective view of the guard of Figure 8; Fig. 10 is an exploded trailing end side perspective view of the guard of Figure 8 for insertion over the distractor of Figure 5 shown inserted in the disc space between two adjacent vertebral bodies and a corresponding impaction cap for seating the guard into the disc space; Fig. 11 is a cross -sectional view along lines 11--11 of Figure 10 showing the guard inserted over the distractor in the disc space between the adjacent vertebral bodies on one side of the vertebral midline; Fig. 12 is a trailing end side perspective view of a guard positioned over the distractor and seated after impaction to the distractor by the impaction cap into the disc space and adjacent vertebral bodies on one side of the vertebral midline; Fig. 12A is a longitudinal cross-sectional view along 12A--12A of Fig. 12 illustrating the guard positioned over the distractor and seated after impaction to the distractor by the impaction cap into the disc space and adjacent vertebral bodies on one side of the vertebral midline; Fig. 13 is a trailing end side perspective view of an extraction instrument to remove the distractor from within the guard; Fig. 14 is an exploded trailing end side perspective view of a drill guide (template) for guiding a drill for insertion into the guard; Fig. 15 is a cross-sectional view along lines 15--15 of Figure 14 illustrating the guard on one side of the vertebral midline; Fig. 16 is an exploded trailing end side perspective view of the guard with the guide and with a large drill bit and a small drill bit used to remove bone from the adjacent vertebral bodies; Fig. 17 is a cross-sectional view along lines 17--17 of Figure 16 illustrating the guard, the large drill bit placed within the guide and extending into the disc space on one side of the vertebral midline; Fig. 17A is a cross-sectional view through the leading end of the drill assembly in the spine along lines 17A--17A of Figure 16 illustrating the guard, the large drill bit placed within the guide and extending into the disc space on one side of the vertebral midline; Fig. 18 is a diagrammatic representation of the hole pattern formed with the guide and large and small drill bits after a first drilling, then rotating the guide 180E and performing a second drilling; 8 Fig. 19 is a leading end side perspective view of a bone compactor; Fig. 20 is an exploded trailing end side perspective view of the compactor of Figure 19 for insertion within the guard shown engaging the spine and inserted in the disc space between two adjacent vertebral bodies with an impaction cap for advancing the compactor into the disc space; Fig. 21 is a cross-sectional view along lines 21--21 of Figure illustrating the compactor placed within the guard inserted into the disc space on one side of the vertebral midline; Fig. 22A is a trailing end perspective view of a universal handle assembly; Fig. 22B is a leading end perspective view of the engagement mechanism of the handle of Figure 22A shown in the locked position; Fig. 22C is a leading end perspective view of the engagement mechanism of the handle of Figure 22A shown in the unlocked position; Fig. 23 is an exploded trailing end side perspective view of the guard in place with a handle for an implant driver and an implant for implanting through the guard and into the space between the two adjacent vertebral bodies; Fig. 24 is a fragmentary leading end view of the implant drive instrument of Figure 23; Fig. 25 is a cross-section view along lines 25--25 of Figure 23 illustrating the implant driver instrument and implant inserted through the guard and into the space created between the two adjacent vertebral bodies on one side of the vertebral midline; Fig. 26 is an exploded side perspective view of the guard, an extraction adapter for engaging the guard and, an extraction instrument for engaging the adapter and for extracting the guard; Fig. 27 is a side perspective view of the operated segment of the spine with the guard removed having a first implant inserted on one side of the midline and between and in part into the adjacent vertebral bodies and with the guard inserted on the opposite side of the vertebral midline next to the implant; Fig. 28 is a cross-sectional view along lines 28--28 of Figure 27 illustrating the implant positioned on one side of the vertebral midline and the guard inserted in the disc space on the opposite side of the vertebral midline and next to the implant; 9 Fig. 29 is an exploded side perspective view of a segment of the spine prepared to receive two implants; Fig. 29A is a top perspective view of the lower vertebral body of the segment of the spine of Fig. 29; Fig. 30 is a trailing end perspective view of a spacer; Fig. 31 is a leading end perspective view of a spacer; Fig. 32 is a side elevational view of two adjacent vertebral bodies in lordosis with an implant inserted into a space created between two adjacent vertebral bodies in which the created space has a lordotic configuration with an implant having parallel upper and lower surfaces maintaining the angular relationship of the adjacent vertebral bodies; Fig. 33 is a side elevational view of two adjacent vertebral bodies in lordosis with a lordotic implant placed between the two adjacent vertebral bodies in a space created between the two adjacent vertebral bodies; Fig. 34 is an exploded trailing end side perspective view of a second embodiment of the guard for placement into a segment of the spine having a removable insertion end and an adapter and a handle assembly; Fig. 35 is a side elevational view of the removable insertion end having extended portions with an anatomical configuration; Fig. 35A is a side elevational view of an alternative embodiment of a removable insertion end; Fig. 35B is a side elevational view of yet another alternative embodiment of a removable insertion end; Fig. 36 is a fragmentary view of the leading end of the guard of Figure 34; Fig. 37 is an exploded trailing end side perspective view of the guard of Figure 34 inserted in the disc space between two adjacent vertebral bodies for receiving a drill (template) guide; Fig. 38 is a cross-sectional view along lines 38-38 of Figure 37 illustrating the guard inserted into the disc space between two adjacent vertebral bodies on one side of the vertebral midline; Fig. 39 is a trailing end side perspective view of the guard with the drill guide inserted into the guard and with a large drill bit and a small drill bit used to remove bone from the adjacent vertebral bodies; Fig. 40 is a trailing end side perspective view of the guard inserted on one side of the vertebral midline and into the disc space between two adjacent vertebral bodies and a central bore guide for insertion therein; Fig. 41 is a trailing end side perspective view of the central bore guide inserted in the guard and the large drill and a handle assembly; Fig. 42 is a diagrammatic illustration of the hole pattern formed with the guide and the large and small drill bits; Fig. 43 is a diagrammatic illustration of the hole pattern formed after the drill guide instrument is flipped 180 degrees and additional holes are drilled with the large and small drill bits; Fig. 44 is a diagrammatic illustration of the space created with the drill guide method of Fig. 43, but where the space to be prepared is wider than in Fig. 43; Fig. 45 is the configuration of the space created with the drill guide instrument and the holes drilled as shown in Fig. 44; Fig. 46 is a diagrammatic illustration of a hole drilled with a central bore drill guide into the space of Fig. Fig. 47 is the configuration of the space created with the drill guide instrument and central bore drill guide instrument of Fig. 46; Fig. 48 is another diagrammatic illustration of a space created with multiple holes drilled with a central bore drill guide to prepare a still wider space; Fig. 49 is a perspective view of a spinal fusion implant oriented in an initial insertion position and configured for clockwise rotation within the disc space, the top and bottom walls thereof being tapered relative to one another for inducing angulation of the adjacent vertebral bodies; Fig. 50 is a side perspective view of a vise adapted to hold the implant of Fig. 49 for loading the implant with fusion promoting substances; and Fig. 51 is a side perspective view of the vise of Fig. 50 holding the implant of Fig. 49.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference will now be made in detail to the present preferred embodiments of the invention, as illustrated in the accompanying drawings Figs. 1 to 7.

The anterior aspect (front) of the spine maybe exposed either by opening a surgical incision large enough to allow direct visualization or laproscopically with a small opening to allow instruments to be placed through the body from outside the body for visualization through an endoscope. The vertebral midline, which bisects the vertebral bodies along the longitudinal axis of the spinal column separating left from right is identified by the surgeon. As shown in Figs. 14, an exemplary embodiment of a midline marker 100 of the present invention preferably is used to create reference marks at the vertebral midline on the disc material and on the adjacent vertebral bodies in a segment of the spine. Marker 100 has a shaft 102 terminating in an insertion tip 104 having a tapered leading edge 106 allowing it to be placed into a multitude of discs having various heights. Tapered leading edge 106 facilitates the insertion of marker 100 into the disc material contained in the disc space between two adjacent vertebral bodies. The juncture of shaft 102 and insertion tip 104 of marker 100 forms a shoulder 108 for butting against the anterior aspect of the adjacent vertebral bodies and thus prevents unwanted over penetration of insertion tip 104 into the disc space. Also located at shoulder 108 at the anterior aspect of shaft 102 are a plurality of dye exit holes 110. Dye exit holes 110 are in communication via a passage 112 with a syringe engaging well 114 located at a trailing end or proximal end 116 of shaft 102. Well 114 is adapted to receive the tip of a syringe (not shown), or any other well-known device for containing and injecting a dye into marker 100. A preferred marker 100 has advantages over a needle due at least in part to having a shoulder for preventing over penetration of the disc space or having the ability to provide multiple marks on the spine via multiple dye exit holes.

After marker 100 is inserted into the disc space, it may have its position confirmed radiographically to make sure that insertion tip 104 is accurately positioned at the vertebral midline and to assess the depth of the disc space relative to the known length of insertion tip 104. After marker 100 is correctly placed at the vertebral midline, a dye such as indigo carmine dye preferably is attached to marker 100 at well 114 at proximal end 116 of shaft 102. With injection, the dye flows through passage 112 within shaft 102 of marker 100 and itgtw 12 exits dye exit holes 110 to create reference marks 118 at the vertebral midline on the adjacent vertebral bodies and on the disc material. The position of reference marks 118 corresponds to dye exit holes 110 at the leading end or distal end 120 of shaft 102 of marker 100. Marker 100 is then removed from the disc space and reference marks 118 remain on the vertebral bodies and disc material. Reference marks 118 are visible to the surgeon and are used as alignment reference points in guiding instruments into the spine.

As embodied herein, and as shown in Figs. 5-7, is a distractor 130 that urges two adjacent vertebral bodies apart and maintains the vertebral bodies in a selected spacial relationship to each other. Distractor 130 comprises a shaft 132 capable of receiving a graduated series of removable, partially hollow tips 134. The junction of shaft 132 and tip 134 forms a shoulder 136 that abuts against the two adjacent vertebral bodies when tip 134 is inserted between the two adjacent vertebral bodies. Shoulder 136 of shaft 132 preferably curves to correspond to the external curvature of the vertebral bodies adjacent the disc space in which distractor 130 is inserted. Tip 134 is preferably, but not requisitely, hollow to facilitate insertion into the disc material and to avoid displacing its own volume that might cause disc protrusion. Tip 134 has a height at its distal end of approximately 4-16 mm that increases to approximately 7at the junction of tip 134 with shoulder 136 of shaft 132 to facilitate insertion of tip 134 into the disc space. When used anteriorly, tip 134 is generally of a lesser height at the leading end. A length of approximately is preferred for use from anterior to posterior. The length of tip 134 is preferably 15-42mm for use translaterally. The increase in height along tip 134 also may be used to position the two adjacent vertebral bodies in an angular spacial relationship, such as to create lordosis. Shaft 132 is preferably hollow to reduce the overall weight of distractor 130.

A proximal end 138 of distractor 130 comprises an extraction head 140 for coupling to an extraction instrument 150 described in detail below. While a preferred embodiment is shown, it is appreciated that a variety of configurations at proximal end 138 of distractor 130 could be utilized for the intended purpose, including but not limited to, threads, key-ways that rotate and lock, male and 13 female interlocking parts and the like without departing from the present teaching. Insertion of distractor 130 into the disc space preferably is guided by reference marks 118 created by marker 100. During insertion of distractor 130, shaft 132 of distractor 130 preferably is positioned to one side of the vertebral midline marked by reference marks 118.

Tip 134 of distractor 130 may be driven into the disc space by an impaction force imparted to distractor 130 through an impaction cap 160 which couples to proximal end 138 of distractor 130 and prevents damage to end 138 of distractor 130. In yet another alternative embodiment, an adapter engages distractor removing engagement means and -the adaptor engages at its opposite end to a handle that can be utilized with or without a mallet to install or remove distractor 130, or any of the other instruments that at their trailing ends are similarly configured. The depth of insertion of tip 134 of distractor 130 into the disc space is sufficient to achieve the desired distraction and vertebral alignment and is limited by shoulder 136 that abuts the two adjacent vertebral bodies to prevent any unwanted movement of tip 134 beyond the disc space.

DETAILED DESCRIPTION OF OTHER SPINAL INSTRUMENTS FOR USE WITH THE PRESENT INVENTION As embodied herein, and as shown in Figs. 8-11, an instrument set may include a guard 170 having a hollow body 172 that terminated in an insertion end 174 that preferably curves to correspond to the external curvature of the two adjacent vertebral bodies of the spine. Extending from insertion end 174 of guard 170 are a pair of disc penetrating extensions 176 that are diametrically opposite one another on the sides of guard 170. Each of extensions 176 preferably have a wedged tip to facilitate insertion into the disc material between the two adjacent vertebral bodies. Extensions 176 have a height that preferably is less than the height of guard 170 such that a shoulder 178 is formed at the distal end 180 of guard 170 in which shoulder 178 functions as a depth limiting stop to prevent over penetration of extension 176 into the disc space.

unhIn~o~wpinn4rr1~u7w Preferably, protruding from insertion end 174 of guard 170 also is a pair of prongs 182 for engaging the bone of the vertebral bodies. Prongs 182 function to engage guard 170 to the two adjacent vertebral bodies and to hold the two adjacent vertebral bodies in a selected spacial relationship. A proximal end 184 of guard 170 is open to permit insertion of instruments and implants into guard 170 as described in detail below. The internal opening of guard 170 is suitably dimensioned for receiving distractor 130. For laproscopic use, proximal end 184 of guard 170 can be attached to a laproscopic port allowing for the passage of instruments through the port and guard 170 while effecting a fluid and gas seal.

As embodied herein, and as shown in Figs. 10 and 11, with distractor 130 inserted between the two adjacent vertebral bodies, guard 170 slidably engages proximal end 138 of distractor 130 and advances toward the spine with distractor 130 functioning as a guide post for aligning guard 170. Guard 170 seats into position with an impaction force imparted onto proximal end 184 of guard 170 via a large impaction cap 160. As shown in Figure 12, impaction cap 160 has an internal configuration capable of receiving extraction head 140 of distractor 130 and has a shoulder portion 162 for abutting proximal end 184 of guard 170. Once extraction head 140 contacts the internal part of impaction cap 160, guard 170 can no longer advance and thus serves as a depth limiting stop. Guard 170, like distractor 130 and the bone compactor can also be installed and removed by use of the slap hammer, or an adaptor and mallet.

With particular reference to Figs. 11, 12, and 12A, after guard 170 seats against and engages the spine, extensions 176 are positioned in the disc space at opposite sides of the insertion end of distractor 130. Extensions 176 serve to create or maintain a selected spacial relationship of the two adjacent vertebral bodies and also serve as guards to keep the surgical procedure within the area between extensions 176 and to prevent any unwanted movement of an instrument or implant outside of the area between extensions 176.

in an alternative embodiment, guard 170 may be inserted directly into the spine without recourse to the preliminary use of distractor 130. In that case, it is preferred that the leading end of extensions 176 of guard 170 be configured so as to both facilitate the easy introduction of guard 170 into the disc space, and so as to urge the vertebral bodies apart into a distracted state. For this purpose, the most distal end of extensions 176 themselves would have a lesser height than the remainder of extensions 176 and preferably a pointed, tapered, radiused, or chamfered shape. It should be recognized that while the present instrument set provides means for identifying and achieving the optimal intervertebral distraction prior to the removal of any bone, it also provides for adjusting it later in the procedure via graduated spacer blocks and graduated guards having a variety of heights. While it is believed that the predistraction of the intervertebral space prior to bone removal is desirable, it is not requisite and it is anticipated that the present instrument set allows for the distraction of the intervertebral space later in the procedure, and/or by the insertion of the implant itself.

As shown in Figure 13, once guard 170 is seated, distractor 130 preferably is removed with an extraction instrument 150 which couples to extraction head 140 and may be advanced away from the spine with slap-hammer style advancement or pulled with a handle which couples to an end of extraction instrument 150.

As embodied herein, and as shown in Figs. 14-18, an instrument set may include a guide 190 for creating a quadrilateral space, or more particularly a rectangular space between the two adjacent vertebral bodies. Guide 190 preferably has a large bore 192 and two small bores 194 to one side of large bore 192. Guide 190 has a shaft 196 terminating in an insertion end 198 that is inserted into guard 170. Guide 190 also has a trailing end 200 that preferably has a dimension greater than the inside opening of guard 170 that functions as a depth limiting stop to prevent further insertion of guide 190 into guard 170.

With particular reference to Figs. 17 and 17A, a large drill bit 210 is shown having a longitudinal shaft 212 terminating at one end in a cutting portion 214 16 and having an engagement head 216 at the other end for engaging a rotating device, such as a handle or a power driven motor. A trailing end 218 of large drill bit 210 also includes a stop member 220 for abutting the surface of trailing end 200 of guide 190 to prevent unwanted over penetration of large drill bit 210 into the disc space. Large drill bit 210 is configured and dimensioned for placement through large bore 192 of guide 190.

Similarly, a small drill bit 230 terminates in a cutting end 232 and has an engagement head 234 for engaging a rotating handle or rotating motor. A trailing end 236 of small drill bit 230 also has an enlarged portion 238 for abutting the trailing end 200 of guide 190 to prevent unwanted over penetration of small drill bit 230 into the disc space.

In use, large drill bit 210 passes through large bore 192 in guide 190 to position the cutting portion 214 into the disc space and then is rotated to remove bone from the endplates of the two adjacent vertebral bodies. Large and small drill bits 210, 230 can be turned by a handle or preferably by use of a power drill.

Similarly, small drill bit 230 passes through small bores 194 of guide 190 to position cutting end 232 into the disc space and then rotates to remove bone from the endplates of the adjacent vertebral bodies. As shown in Fig. 17, extensions 176 of guard 170 protect the unwanted movement of large and small drill bits 210, 230 in a lateral or transverse direction and confine the drilling products so that they are evacuated by drill bits 210, 230.

As shown in Fig. 18, the holes created with large drill bit 210 and small drill bit 230 form a pattern as indicated in solid lines in the drawing.

After the first three holes have been drilled, guide 190 is removed from within guard 170. Guide 190 then is rotated 180 degrees and reinserted into guard 170. Guide 190 now is oriented such that large bore 192 is positioned over the area in which the small holes were previously drilled and small bores 194 are positioned over the area in which the large bore was previously drilled. The drilling procedure with large drill bit 210 and small drill bit 230 is repeated to create a pattern of holes as indicated by the dotted lines in Figure 18. The -1- 17 result of this drilling procedure, is the removal of a portion of bone from the endplates of the adjacent vertebral bodies creating a space approximating the configuration of a rectangle.

Although the drilling of the bone of the endplates creates a space with a configuration that approximates the shape of a rectangle, if desired a perfect rectangle may be obtained by use of a rectangular bone compactor.

As shown in Figs. 19-21, a box-shaped bone compactor 240 has a shaft 242 terminating in a compaction end 244. Compaction end 244 of shaft 242 may include beveled, radiused, or thinned edges to ease introduction. Compactor end 244 compresses any remaining boney protuberances into the vertebral bodies achieving a perfectly rectangular space. A trailing end 246 of shaft 242 may include an extraction head 248 for coupling to an extraction instrument 150.

In a preferred embodiment, there is no fixed stop until approximately 32-36 mm, so that a slotted and calibrated impaction cap 260 can be used to predictably and adjustably insert compaction end 244 into the intervertebral space to the desired optimal depth. Alternatively, compactor 240 can have a fixed depth limiting means. As a further alternative, leading edges 250 of compactor 240 can be sharpened so that it functions wholly or in part as a chisel to cut rather than compact the bone. This is considered less desirable, though still workable, than the preferred compaction end 244 by which the density of the bone at the prepared recipient site is actually increased by the compaction process.

Compactor 240 is inserted into guard 170 and advanced by an impaction force imparted to the trailing end 246 of compactor 240 by an impaction cap 260 similar to the impaction cap previously described above. The advancement of compaction end 244 of compactor 240 impacts the remaining portions of the bone that were not removed in the drilling step previously described into the vertebral bodies themselves.

18 As an alternative to compactor 240, trial size spacers 291 resembling implants 290 with either smooth or abraiding surfaces may be impacted into the space to complete the flattening of the opposed bone surfaces.

As show in Figs. 22A-C, a handle assembly 270 is shown for coupling to the drilling instrumentation and other instruments. Compactor 240 is removed from within guard 170 by coupling to extraction instrument 150 and advanced outside of guard 170 with extraction instrument 150 shown in Figs. 13 and 26.

Figs. 23-25 show a driver 280 for inserting an intervertebral implant 290 into the created space between the two adjacent vertebral bodies. Driver 280 has a leading end 282 configured to cooperatively engage an implant 290. As shown in Figure 24, driver 280 has a threaded portion 284 and a non-threaded pin 286 extending from the leading end 282 for insertion into corresponding openings in the trailing end of the implant 290. Threaded portion 284 is rotatable by a knob 288 at the opposite end of driver 280 so as to threadably couple driver 280 to implant 290. Driver 280 has a handle coupling means 289 for coupling to handle assembly 270 for controlling driver 280.

After implant 290 is coupled to driver 280, implant 290 and leading end 282 of driver 280 are inserted into guard 170 and advanced towards and into the created space between the two adjacent vertebral bodies. After implant 290 has been placed within the created space by use of the handle with or without impaction of the slap hammer, or an adaptor and a mallet, knob 288 of driver 280 is rotated to uncouple implant 290 from driver 280. Driver 280 then is removed from within guard 170 leaving implant 290 inserted in the created space.

It is clearly anticipated that while the specific configuration of the preferred ends has been described, that a variety of threaded and non-threaded means for coupling implants 290 to driver 280 could in the alternative be employed.

Fig. 26 shows guard 170 being removed from the disc space and from the adjacent vertebral bodies with extraction assembly 150 which couples to an 19 extraction adapter 152 configured to fit within the proximal end 184 of guard 170. Extraction adapter 152 is locked into place by a spring-biased butterfly member that fits into corresponding notches at the proximal end 184 of guard 170. After extraction assembly 150 is coupled to guard 170, extraction assembly 150 is advanced away from the spine with a slap-hammer style motion or any other suitable means to remove guard 170 from the spine. After guard 170 is removed, implant 290 remains in place in the created space between the endplates of the two adjacent vertebral bodies.

Figs. 27 and 28 show that the procedure being repeated on the opposite side of the vertebral midline. Distractor 130 and guard 170 are rotated 180 degrees to conform to the curvature of the vertebral bodies on the second side of the vertebral midline. The above steps for the present invention are repeated for inserting guard 170 into position on the opposite side of the vertebral midline.

As shown in Fig. 28, first implant 290 is positioned and remains within the created space between the adjacent vertebral bodies and guard 170 is positioned on the opposite side of the vertebral midline to first implant 290.

As shown with implant 290 in Fig. 29 and a spacer block 291 in Fig. 31, either of implant 290 or spacer block 291 may be inserted in the space created in the spine. As shown in Figs. 30 and 31, spacer block 291 may have an external configuration similar to that of the implant, except that it may be more or less solid. It is appreciated that spacer blocks 291 and implants 290 may be wedged-shaped or rectangular so as to adjust the angular relationship of the vertebral bodies to each other.

As shown in Figs. 32 and 33, the instrumentation and method may be used to create or maintain lordosis of the spine in at least two ways and to accept both generally rectangular and trapezoidal implants. As shown in Fig. 32, the created space may be formed at an angle to the vertebral endplates, such that the planes of the top and bottom surface of the created space are in an angular relationship to each other. The two adjacent vertebral bodies are positioned in angular relationship to each other with the insertion of implant 290 having parallel upper and lower surfaces within the created space. The insertion of implant 290 into the angular space causes the vertebral bodies to be placed in an angular relationship.

Figs. 32 and 33 show two adjacent vertebral bodies in a desired lordotic angular relationship. In Fig. 32, the space was created by means of the shape of extensions 176 on guard 170 during the drilling and compaction procedure. A rectangular space was formed with more bone removed posteriorly than anteriorly in anticipation of receiving a generally rectangular implant 290. This is a preferred stable configuration as the compressive loads of the spine onto implant 290 are received generally perpendicular to the surface (rather than on an angle that might urge the implant forward or backwards). Additionally, once installed implant 290 is blocked from further penetration by the wall of bone created by the removal of the bone before it, and is blocked from backing out because the implant upper and lower surfaces would need to move against the inclined slanted surfaces of the vertebral bodies in order to move and that would require significantly more energy than remaining in the more stable position of being fully installed.

For the space shown in Fig. 33, extensions 176 of guard 170 were positioned between the vertebral bodies so that the adjacent vertebral surfaces were generally parallel during the creation of the recipient space. This was done in anticipation that the desirable lordosis would be achieved by the use of an implant at least in part generally trapezoidal in shape, or having upper and lower surfaces for engaging the adjacent vertebral bodies, which surfaces are in a non-parallel angular relationship to each other.

While this is theoretically a less stable configuration than that previously described, it offers the advantage that the amount of bone removal is minimal but sufficient for its intended purpose and the thickness of the bone removed is more uniform in thickness.

As shown in Fig. 33 instead of creating an angular space, the created space may have parallel upper and lower surfaces. The two adjacent vertebral bodies 21 are positioned in an angular relationship to each other with the insertion of an implant having upper and lower surfaces that are angled toward each other.

Figs. 34-41 show a second set of instrumentation similar to the first in that it provides both for the creation of a generally rectangular or trapezoidal space in a non-traumatic way and for the insertion of an implant through the same instrumentation, but differs in that the guard is generally cylindrical while the prior guard was generally rectangular. A rectangular shape has less volume and space than a cylindrical shape, which has no corners and is less expensive to manufacture.

Figs. 34-36 show a second embodiment of a guard. Guard 370 has a hollow body 372 that terminates in an insertion end 374, which is removably coupled to body 372. The distal end 380 of guard 370 is curved to correspond to the external curvature of the two adjacent vertebral bodies the spine. Extending from the insertion end 374 are a pair of extensions 376 in a diametrically opposite position on the sides of the insertion end 374. Each of the two extensions 376 have a suitable configuration to facilitate insertion into the disc material between the two adjacent vertebral bodies. As shown in Figure extensions 376 may have an "anatomic" configuration to conform to the contours of the vertebral endplates adjacent to the disc space in which guard 370 is to be inserted. Preferably, but not requisite, also protruding from the insertion end 374 are a pair of prongs 382 for engaging the bone of the adjacent vertebral bodies. Prongs 382 function cooperatively with extensions 376 to engage guard 370 to the adjacent vertebral bodies and to hold the two adjacent vertebral bodies in a selected spacial relationship. The proximate portion of insertion end 374 may include a threaded portion for threadably coupling to body 372 of guard 370.

Fig. 36 shows body 372 having a collar 404 which has a thread to engage the threaded portion of the removable insertion end 374. Guard 370 provides the added advantage of having interchangeable removable insertion ends 374 with different shaped extensions depending on the surgical procedure being employed. For example, instead of having an anatomical configuration, the 22 extensions may have a parallel configuration as shown in Fig. 35A or may have a wedged configuration as shown in Fig. 35B, so as to allow the surgeon to achieve the desired angular relationship of the vertebral bodies to be fused.

Proximal end 384 of hollow guard 370 is open to permit the insertion of other instruments and implants into the guard as described herein. As with the previously described guard, a closeable part may be connected to the proximal end 384 of this guard for laproscopic use allowing for the passing of instruments through guard 370 while providing for a gas and fluid seal.

Guard 370 is seated into the disc space and engaged to the spine by being manually advanced or by imparting an impaction force onto the proximal end 384 of guard 370. As shown in Fig. 34, an insertion and extraction handle assembly 270 is shown with a coupling member for engagement to proximal end 384 of guard 370.

As shown in Fig. 38, after guard 370 is properly seated and engaged to the spine, extensions 376 are positioned in the disc space between the two adjacent vertebral bodies on one side of the vertebral midline. Extensions 376 serve to maintain the spacial relationship of the two adjacent vertebral bodies and also serve as guards to maintain an instrument or implant within the area between extensions 376 and to prevent any unwanted movement of an instrument or implant outside of the area between extensions 376.

Fig. 37 shows a guide 390 for creating a rectangular space between the two adjacent vertebral bodies. Guide 390 comprises a large bore 392 and two small bores 394 to one side of large bore 392. Guide 390 has a shaft 396 terminating in an insertion end 398 that is capable of being inserted into guard 370 and has a trailing end 400 having a dimension greater than the inside opening of guard 370 so as to act as a depth limiting stop to prevent further insertion of 390 guide into guard 370. Moreover, guide 390 is prevented from rotating within guard 370 by pins 402, which fit into the corresponding grooves at the proximal end 384 of the guard 370.

23 Fig. 39 shows a large drill bit 410 and a small drill bit 430 configured similarly to large and small drill bits 210, 230 described above with specific reference to Fig. 16. In use large drill bit 410 is passed through large bore 392 in guide 390 to position cutting end 414 into the disc space and is then rotated to remove bone from the endplates of the two adjacent vertebral bodies. Similarly, small drill bit 430 is passed through the small bores 394 of guide 390 to position cutting end 432 into the disc space and then rotated to remove bone from the endplates of the adjacent vertebral bodies.

As shown in Fig. 42, the holes created with large drill bit 410 and small drill bit 430 form a pattern as indicated in the dotted lines. After the first three holes have been drilled to provide a large hole L and two small holes S, guide 390 is removed from within guard 370 and guide 390 is rotated a 180 degrees and reinserted into guard 370. Guide 390 is now oriented such that large bore 392 is positioned over the area in which the small holes S were drilled and small bores 394 are positioned over the area in which the large hole L was drilled.

The drilling procedure with large drill bit 410 and small drill bit 430 is repeated to create a pattern of holes as indicated by the dotted lines in Fig. 43. As a result of this drilling procedure, a substantial portion of bone is removed from the endplates of the adjacent vertebral bodies creating a space approximating the configuration of a rectangle.

As shown in Fig. 40, as the central portion of the space created may not have all of the bone removed from the drilling procedure through guide 390, a central bore guide 500 may be inserted into guard 370. Central bore guide 500 has a large bore 502 that is centrally placed, such that when large drill bit 410 is passed through central bore guide 500, the portion of bone remaining in the central portion of the space being created can be removed. As shown in Fig.

44, the use of central bore guide 500 may be of particular value in removing remaining bone where guide 390 has a hole pattern that when reversed provides for a lesser amount of overlap of bores formed through large bore 392.

Fig. 45 shows the space created with the drilling procedure through Fig. 44.

Central hole C created with central bore guide 500 is shown in dotted line in Fig.

46.

As shown in Fig. 47, the space created with the drilling procedure results in a substantial portion of bone being removed from the endplates of the adjacent vertebral bodies creating a space that more closely approximates the configuration of a rectangle.

Fig. 48 shows a space created with the drilling procedure to prepare a still wider space with a template pattern for the guide having a hole pattern that uses an offset central drill guide to drill two additional large bores to remove additional bone to form the space.

By way of example only, impacted implant 290 has been illustrated as one type of implant that could be inserted into the opening formed in the spine by the various embodiments of instrumentation and methods of the present invention.

By way of another example, without limitation to use of any other type of implant, a self-broaching, rotatable impacted implant such as disclosed in U.S.

application serial number 09/429,628, now US Patent No. 6,537,320 which is hereby incorporated by reference herein, could also be inserted into the opening formed in the spine by the instrumentation and methods disclosed herein.

With reference to Fig. 49, an interbody spinal fusion implant is indicated generally as 600. The implant has a body 602 having an insertion end 604, a trailing end 606, opposed side walls 608, and opposed upper and lower walls 610. Body 602 has a cross section with side walls 608 intersecting the upper and lower walls 610 at junctions that are preferably two diametrically opposed corners and two diametrically opposed arcs. Fin-like projections 612 extend outwardly from respective ones of upper and lower walls 610 and are adapted to penetrate the vertebral endplates of the adjacent vertebral bodies upon rotation of implant 600 while the upper and lower walls 610 support the vertebral endplates of those adjacent vertebral bodies. Body 602 of implant 600 preferably includes a hollow portion that may be accessed through a cap 614 that is preferably located on an end of implant 600. The hollow portion is adapted to contain fusion promoting material including, but not limited to, bone, in any of its varied forms, hydroxyapatite, coral, bone morphogenetic proteins, genes coding for the production of bone, and agents with the ability to induce cells to become osteoblasts or to make bone.

As shown in Figs. 50 and 51, a vise 700 has surfaces 702 adapted to cooperatively receive fins 612 and thereby cover the openings between fins 612. While holding implant 600 in vise 700 with cap 614 removed from implant 600, fusion promoting material may be compressively loaded into implant 600.

Fusion promoting material may be loaded into implant 600 until the material is extruded from openings in side walls 608.

Having described certain preferred embodiments of the surgical instrument set, the method for creating a substantially quadrilateral space in a spine will now be described in more detail. A method for creating a substantially quadrilateral space in a spine for inserting a spinal implant into a disc space between adjacent vertebral bodies, comprises the steps of: positioning guard 170 into contact with the adjacent vertebral bodies for protecting access to the disc base and the adjacent vertebral bodies; and boring, through guard 170, a plurality of bores across the disc space to form the substantially quadrilateral space across the height of the disc space and into the adjacent surfaces of the adjacent vertebral bodies.

The method may include the step of marking the spine for guiding, by reference marks, the proper location of guard 170. The step of marking preferably includes inserting a penetrating extension of a spinal marker 100 into a central point of the disc space between the adjacent vertebral bodies. The method may include the step of placing dye spots on the spine by injecting the dye through openings in a shaft 102 of spinal marker 100. The depth of penetration of marker 100 into the disc space is controlled.

The method may also include the step of distracting the disc space between adjacent vertebral bodies, and in particular, the distracting step may include the step of inserting a distractor 130 having a disc penetrating extension into the disc space between adjacent vertebral bodies and against endplates of the Ufl~D*SS7WWW 26 adjacent vertebral bodies. The depth of penetration of distractor 130 into the disc space is preferably controlled. The method may further include the step of changing disc penetrating extensions of distractor 130 in accordance with a desired distractor distance between adjacent vertebral bodies. Guard 170 may be inserted over distractor 130 and the disc space, and then distractor 130 may be removed from within guard 170.The positioning step may include inserting at least one disc penetrating extension 176 extending from guard 170 into the disc space between the adjacent vertebral bodies for bearing against endplates of the adjacent vertebral bodies. The insertion of disc penetrating extension 176 into the disc space distracts the adjacent vertebral bodies. Another method further includes the step of controlling a depth of penetration of extension 176 into the disc space. Another method includes the step of engaging guard 170 with the adjacent vertebral bodies through prongs 182 extending from guard 170 and into the adjacent vertebral bodies.

The boring step may include the sub-step of using a template in association with guard 170. The template may be rotated 180 degrees along its longitudinal axis. The boring step may include the sub-step of using either of a drill, mill, laser, or grinder to bore the plurality of bores. The plurality of bores may be overlapping, circular, or both. The boring step may include forming at least three bores in the spine to form a first bore pattern, and in particular may include forming at least a main bore and at least two secondary bores located to a side of the main bore. The main bore has a diameter that is preferably greater than a diameter of each of the two secondary bores. The main bore in the spine is preferably positioned to form a portion of three sides of the substantially quadrilateral space formed in the spine. Each of the two secondary bores are preferably positioned to form a portion of two adjacent sides of the substantially quadrilateral space formed in the spine. A second bore pattern having at least three bores in the spine may be formed such that the first and second bore patterns defined the substantially quadrilateral space.

The substantially quadrilateral space may be one of a substantially rectangular shape and a substantially trapezoidal shape.

27 Further the method may comprise the step of inserting a multiple passage drill guide 190 into guard 170. Guide 190 may be inserted into guard 170 for guiding the forming of the first bore pattern. The method may further include the steps of removing guide 190 from guard 170, rotating guidel90 one hundred-eighty degrees along its longitudinal axis, reinserting guide 190 into guard 170, and forming, through the plurality of openings in guide 190, a second bore pattern, the first and second bore patterns defining the substantially quadrilateral space. The method may further include the step of controlling the depth of penetration of guide 190 into guard 170.

The method may also include the step of boring a centralized bore within the substantially quadrilateral space. The centralized bore preferably forms a portion of opposite sides of the substantially quadrilateral space. Further the method may include the step of inserting a secondary guide 500 into guard 170 and further forming, through an opening in secondary guide 500, a centralized bore within the substantially quadrilateral space.

The method may include the step of compressing outer edges of the substantially quadrilateral space. The step of compressing preferably includes inserting a compactor 240 having a compaction end 244 through guard 170 and into the substantially quadrilateral space formed in the spine. The step of compressing preferably includes inserting compactor 240 having compaction end 244 having a sharpened cutting edge for cutting bone. The depth of penetration of compactor 240 into the disc space is preferably controlled. The step of compressing may include the sub step of inserting a spinal implant through guard 170 and into the substantially quadrilateral space formed in the spine to compress the outer edges on the substantially quadrilateral space.

Also described is a surgical method to prepare a segment of a human spine having a disc and two vertebral bodies adjacent the disc for fusion between body portions of the adjacent vertebral bodies and through the space previously occupied by the disc, each of the adjacent vertebral bodies to be fused including a vertebral body having an endplate outer surface adjacent the disc space, and a subchondral zone immediately internal to each endplate, the vrsMfl'~44Th47 Ipois

S

28 method comprising: positioning a guard 170 into contact with the adjacent vertebral bodies for protecting access to the disc space and the adjacent vertebral bodies; and forming, through guard 170, a plurality of bores to form a substantially quadrilateral space in the spine across the height of the disc space and into the adjacent endplates of the vertebral bodies adjacent the disc space, the quadrilateral space being formed by the removal of at least bone from at least the adjacent endplates as deep as with, and generally not deeper than, the subchondral zone of each of the adjacent endplates.

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 be considered as exemplary only, and a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A distractor for use in spinal surgery, including: a body having a disc penetrating extension extending from said body for insertion into the disc space between the adjacent vertebral bodies and for bearing against the adjacent vertebral endplates of the adjacent vertebral bodies, said disc penetrating extension being hollow and with an open leading end to facilitate insertion of said extension into the disc space and for containing disc material within said extension.

2. The distractor of claim 1 wherein said body includes a shoulder adapted to conform at least in part to the exterior of the adjacent vertebral bodies.

3. The distractor of either claim 1 or 2, wherein said extension includes a shaft having one of a rectangular cross-section and a circular cross-section.

4. The distractor of any one of claims 1 to 3, wherein said extension includes an end for detachably receiving variously sized distractor tips.

5. The distractor of claim 4, wherein said distractor tips have sharpened surfaces.

6. The distractor of any one of claims 1 to 5, wherein said extension converges away from said body.

7. The distractor of any one of claims 1 to 5, wherein said extension diverges away from said body.

8. A distractor substantially as hereinbefore described as illustrated in any one of the figures.

9. A method for preparing an implantation space at least in part into a disc between two adjacent vertebral bodies of a human spine for receiving a spinal implant, the method including the steps of: providing a distractor having a disc penetrating extension adapted to be inserted into the disc and between the adjacent vertebral bodies, the disc penetrating extension having an upper portion, a lower portion, a hollow interior therebetween, and an open end in communication with the hollow interior; inserting the disc penetrating extension into the disc with the upper portion contacting one of the adjacent vertebral bodies and the lower portion contacting the other of the adjacent vertebral bodies to position the vertebral bodies in a spaced apart relationship; advancing the disc penetrating extension into the disc to incise the disc during the inserting step; retaining a portion of the disc in the hollow interior of the disc penetrating extension during the advancing step; and removing the distractor from the disc and from between the adjacent vertebral bodies with a portion of the disc being retained in the hollow interior of the disc penetrating extension to create the implantation space.

The method of claim 9, wherein the inserting step includes the sub-step of imparting an impaction force to the distractor.

11. The method of claim 10, wherein the imparting sub-step includes imparting the impaction force to the distractor through an impaction cap.

12. The method of claim 9, wherein the removing step includes removing the distractor by coupling an extraction instrument to a proximal end of the distractor.

13. The method of claim 12, wherein the coupling sub-step includes the use of at least one of a thread, a keyway, a lock, and interlocking parts.

14. The method of claim 9, wherein the providing step includes providing the distractor with a shoulder proximate the disc penetrating extension to prevent over-insertion of the disc penetrating extension into the disc.

The method of claim 14, wherein the shoulder is adapted to conform, at least in part, to the exterior of the adjacent vertebral bodies.

16. The method of claim 9, further including the step of inserting over the distractor a guard for providing protected access to the disc and the adjacent vertebral bodies.

17. The method of claim 16, wherein the removing step is performed through the guard.

18. The method of claim 16, wherein the guard includes at least one extension for insertion into the disc and for bearing against the end plates of the adjacent vertebral bodies.

19. The method of claim 9, further including the step of inserting an implant into the implantation space.

The method of claim 9, wherein the providing step includes providing the distractor with a distal edge configured to cut the disc during the advancing step.

21. The method of claim 9, wherein the inserting step includes the sub-step of inducing angulation of the adjacent vertebral bodies.

22. A method for preparing an implantation space at least in part into a disc between two adjacent vertebral bodies of a human spine for receiving a spinal implant, the method substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings.