A spinal distractor

Abstract: An apparatus and a method of inserting spinal implants is disclosed in which an intervertebral space is first distracted, a hollow sleeve having teeth at one end is then driven into the vertebra adjacent that disc space. A drill is then passed through the hollow sleeve removing disc and bone in preparation for receiving the spinal implant which is then inserted through the sleeve. Apparatus and a method of inserting spinal implants is disclosed in which an intervertebral space is first distracted to restore the normal angular relationship of the vertebra adjacent to that disc space. An extended outer sleeve having extended portions capable of maintaining the vertebra distracted in their normal angular relationship is then driven into the vertebra adjacent that disc space. A drill is then passed through the hollow sleeve removing disc and bone in preparation for receiving the spinal implant which is then inserted through the sleeve.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to devices for, inserting spinal implants. 2. Description of the Prior Art For the purpose of achieving long term stability to a segment of injured spine, a fusion (the joining together of two or more bones via a continuous bridge of incorporated bone) may be performed. Well-known to those skilled in such art is the interbody fusion wherein the disc is partially excised and bone placed within that space previously occupied by that disc material (between adjacent vertebrae) for the purpose of restoring a more normal spatial relationship, and to provide for stability; short term by mechanical support, and long term by the permanent cross bonding of bone from vertebra to vertebra. For fusion to occur within the disc space, it is necessary to prepare the vertebrae to be fused by breaking through, or cutting into, the hardened outside plates of bone (the endplates) to allow the interposed bone graft to come into direct contact with the more vascular cancellous (spongy) bone, and to thereby trick the body into attempting to heal this induced, but controlled, "fracturing" by both bone production and the healing of the grafts to both opposed vertebral surfaces such that they become one continuous segment of bone. At present, following the removal of a damaged disc, either bone or nothing is placed into the remaining space. Placing nothing into this space allows the space to collapse which may result in damage to the nerves; or the space may fill with scar tissue and eventually lead to a reherniation. The use of bone to fill the space is less than optimal in that bone obtained from the patient requires additional surgery and is of limited availability in its most useful form, and if obtained elsewhere, lacks living bone cells, carries a significant risk of infection, and is also limited in supply as it is usually obtained from accident victims. Furthermore, regardless of the source of the bone, it is only marginal structurally and lacks a means to either stabilize itself against dislodgement, or to stabilize the adjacent vertebrae. Prior Art Instrumentations And Methods The following is a history of the prior art apparatus and methods of inserting spinal implants: In 1956, Ralph Cloward developed a method and instruments which he later described for preparing the anterior aspect (front) of the cervical spine, and then fusing it. Cloward surgically removed the disc to be fused across and then placed a rigid drill guide with a large foot plate and prongs down over an aligner rod and embedded said prongs into the adjacent vertebrae to maintain the alignment so as to facilitate the reaming out of the bone adjacent the disc spaces. As the large feet plate sat against the front of the spine, it also served as a fixed reference point to control the depth of drilling. The reaming left two opposed resected arcs, one each, from the opposed vertebral surfaces. The tubular drill guide, which was placed only preliminary to the drilling, was thereafter completely removed. A cylindrical bony dowel, significantly larger in diameter than the hole formed, was then pounded into the hole already drilled. Cloward's method of instrumentation was designed for, and limited to, use on the anterior aspect and in the region of the cervical spine only. The hole was midline, which would preclude its use posteriorly where the spinal cord would be in the way. As the bone graft to be inserted in Cloward's method was necessarily larger in diameter than the hole drilled, the graft could not be inserted through the drill guide. This mandated the removal of the drill guide and left the graft insertion phase completely unprotected. Thus Cloward's method and instrumentation was inappropriate for posterior application. In addition, the failure to provide continuous protection to the delicate neural structures from the instruments, as well as the bony and cartilaginous debris generated during the procedure, made Cloward's method inappropriate for posterior application. Also, the drill guide described by Cloward could not be placed posteriorly within the spinal canal, as the foot plate would crush the nerves. Modifying Cloward's drill guide by removing the foot plate completely, would still leave the instrument unworkable as it would then lack stability, and would not be controllable for depth of seating. Nevertheless, Wilterberger, (Wilterberger, B.R., Abbott, K.H., "Dowel Intervertebral Fusion as Used in Lumbar Disc Surgery," The Journal of Bone and Joint Surgery, Volume 39A, pg. 234-292, 1957) described the unprotected drilling of a hole from the posterior into the lumbar spine between the nerve roots and across the disc space, and then inserting a stack of button-like dowels into that space. While Wilterberger had taken the Cloward concept of circular drilling and dowel fusion and applied it to the lumbar spine from a posterior approach, he had not provided for an improved method, nor had he advanced the instrumentation so as to make that procedure sufficiently safe, and it rapidly fell into disrepute. Crock (Crock, H.V., "Anterior Lumbar Interbody Fusion - Indications for its Use and notes on Surgical Technique," Clinical Orthopedics, Volume 165, pg. 157-163, 1981) described his technique and instrumentation for Anterior Interbody Fusion of the lumbar spine, wherein he drilled two large holes side by side across the disc space from anterior to posterior essentially unprotected and then pounded in two at least partially cylindrical grafts larger than the holes prepared. A review of the prior art is instructive as to a number of significant deficiencies in regard to the method and instrumentation for the performance of Interbody Spinal Fusion utilizing drilling to prepare the endplates. As the great majority of spinal surgery is performed in the lumbar spine and from posteriorly, a review of the prior art reveals a number of deficiencies in regard to the spine in general, and to the posterior approach to the lumbar spine specifically. These deficiencies include the: 1. Failure to protect the surrounding tissues throughout the procedure, specifically, prior to drilling and until after the insertion of the graft; 2. Failure to contain the debris, bony and cartilaginous, generated during the procedure; 3. Failure to optimize the contact of the cylindrical drill hole and bone graft, the mismatch in their diameters resulting in incongruence of fit; 4. Failure to determine the optimal drill size prior to drilling; 5. Failure to determine the optimal amount of distraction prior to drilling; 6. Inability to optimize the amount of distraction so as to restore the normal spatial relationships between adjacent vertebrae; 7. Inability to create sufficient working space within the spinal canal (between the nerve roots and the dural sac) to make the procedure safe; 8. Absent a foot plate on the drill guide, as necessitated by the close tolerances posteriorly, the inability to reliably insure that the drilling is parallel to the vertebral endplates; 9. The inability to insure equal bone removal from the opposed vertebral surfaces; and 10. The inability to determine within the spinal canal, the proper side by side positioning for dual drill holes. BRIEF SUMMARY OF THE INVENTION The apparatus of the present invention for preparing the vertebrae for insertion of the implant allows for the rapid and safe removal of the disc, preparation of the vertebrae, performance of the fusion, and internal stabilization of the spinal segment. The present invention uses novel instrumentation, whereby a protective tubular member, or paired tubular members are placed prior to the drilling part of the procedure and may be left in place until the implant is fully seated. The present invention provides an apparatus for inserting spinal implants from the anterior, posterior and lateral aspect of the spine. The instrumentation of the present invention provides a distractor instrument configured to restore and maintain the normal angular relationship of the vertebrae of the spine, known as lordosis or kyphosis, prior to the completion of the fusion procedure. The present invention also provides an extended outer sleeve that is a combination distractor and outer sleeve used for performing the surgical procedure. The combination distractor and outer sleeve may also be configured to maintain the normal angular relationship of the vertebrae during the surgical procedure. The present invention further discloses a combination distractor outer sleeve that may be used to perform the surgical procedure from the lateral aspect of the spinal column that protects the great vessels and neural structures from being damaged during the surgical procedure. In summary then, the present invention provides for the performance of a total nuclear discectomy, an interbody fusion, a rigid internal fixation of the spine as a single integrated surgical procedure. Discussion of the Instrumentation The apparatus of the present invention provides the following advantages: 1. The present invention is safer by providing protection of the surrounding tissues. An Outer Sleeve places all of the delicate soft tissue structures, nerves, blood vessels, and organs outside of the path of the various sharp surgical instruments and the implant. Further, it is an improvement upon hand held retractors in that it occupies the least possible amount of area, avoids the stretching associated with manual retraction, provides for the retraction and shielding of the surrounding tissues in all directions circumferentially and simultaneously, and it does so exclusively with smooth, curved surfaces. 2. The present invention is safer by providing protection against the danger of instrument or implant overpenetration. 3. The present invention is safer as the surgical site and wound are protected from the debris generated during the procedure. 4. The present invention is safer because it provides for absolute protection to the soft tissues directly and from indirect injury by overpenetration. It makes safe the use of power instrumentation'which is both more effective and efficient. 5. The present invention maintains the vertebrae to be fused rigid throughout the procedure. 6. The present invention holds the vertebrae to be fused aligned throughout the procedure. 7. The present invention holds the vertebrae to be fused distracted throughout the procedure. 8. The present invention assures that all instruments introduced through the Outer Sleeve are coaxial and equally centered through the disc space and parallel the endplates. 9. The present invention facilitates the implant insertion by countering the high compressive forces tending to collapse the interspace, which if left unchecked would resist the introduction and advancement of the implant and make stripping more likely. 10. The present invention extends the range and use of the procedure and similarly the interbody spinal implant itself by making the procedure safe throughout the spine. 11. The present invention increases the ability to use a specifically sized implant. 12. In the present invention the end of all the penetrating instrumentation is blunt faced. 13. In the present invention all of the instruments have been stopped at a predetermined depth to avoid overpenetration. 14. The design of the Outer Sleeve in the present invention conforms to the spacial limitations of the specific surgical site. 15. In the present invention predistraction increases the working space. 16. The Distractor in the present invention is self-orienting acting as a directional finder. 17. The Distractor in the present invention is self-centralizing between the opposed vertebral surfaces acting as a centering post for the subsequent bone removal. 18. In the present invention predistraction assures the equal removal of bone from the adjacent vertebral surfaces. 19. In the present invention predistraction assures the exact congruence between the hole drilled and the device. 20. In the present invention predistraction assures that the drilling is parallel to the vertebral endplates. 21. In the present invention predistraction allows for the determination of the optimal distraction prior to drilling. 22. In the present invention predistraction allows for the verification of the correct prosthesis size prior to drilling. 23. In the present invention predistraction facilitates device insertion by relieving the compressive loads across the interspace which would resist implantation. 24. In the present invention predistraction decreases the likelihood of stripping the bone during insertion. 25. In the present invention predistraction provides for the side by side positioning, spacing, and parallelism required prior to the irrevocable event of drilling. 26. In the present invention predistraction provides for the rigid stabilization of the vertebrae opposed to the disc space throughout the surgical procedure. 27. In the present invention predistraction provides for an implant easier to insert as the compressive loads of the opposed vertebrae are held in check so that the device itself need not drive the vertebrae apart to be inserted. 28. In the present invention predistraction allows for the insertion of a more effective implant as more of the implant can be dedicated to its intended purpose and be full diameter, whereas without the benefit of predistraction and the ability to maintain the same, a significant portion of the forward end of the implant would need to be dedicated to the purpose of separating the opposing vertebrae. 29. The present invention allows for the use of an implant with a sharper thread or surface projections as there is no danger to the surrounding tissues. 30. The present invention allows for the implant to be fully preloaded as provided to the surgeon, or for the surgeon to load it with the material of his choice at the time of surgery. 31. The present invention allows for the loading of a spinal implant outside of the spinal canal and prior to implantation. 32. The present invention provides for Distractors for the restoration of the physiologic amount of lordosis/kyphosis at any given level of the spine. 33. The Distractors of the present invention provide for the restoration of sagittal spinal alignment and the segmental correction of scoliosis. 34. The present invention provides Extended outer Sleeves which are a combined Distractor and Outer Sleeve for the three dimensional segmental restoration of spinal alignment. These and other advantages of the present invention will be apparent from review of the following specification and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevacional view of a Convertible Distractor assembly in relation to the spine. Figure 2 is a side elevational view of a Posterior Long Lordotic Distractor inserted from the posterior aspect of the spine between adjacent vertebrae to restore and maintain lordosis of the spine. Figure 3 is a side elevational view of a Posterior Short Lordotic Distractor of the present invention. Figure 4 is a top plan view along lines 4---4 of Figure 3 of the Posterior Short Lordotic Distractor of the present invention. Figure 5 is a side elevational view of an Anterior Long Lordotic Distractor of the present invention shown inserted between two adjacent vertebrae from the anterior aspect of the spine to restore and maintain lordosis. Figure 6 is a perspective side view of a Posterior Lordotic Extended Outer Sleeve of the present invention having uneven extended members for restoring and maintaining lordosis of the spine and engagement means for engaging the vertebrae. Figure 7 is a side elevational view of a portion of the Posterior Lordotic Extended Outer Sleeve of Figure 6 inserted between adjacent vertebrae from the posterior aspect of the spine to restore and maintain lordosis. Figure 8 is a perspective side view of an Anterior Lordotic Extended Outer Sleeve of the present invention having extended members for restoring and maintaining lordosis of the spine from the anterior aspect of the spine. Figure 9 is a side elevational side view of an alternative embodiment of the Anterior Lordotic Extended Outer Sleeve of Figure 8 absent the engagement means for engaging the vertebrae, inserted between adjacent vertebrae from the anterior aspect of the spine. Figure 10 is a perspective side view of a Dual Extended Outer Sleeve having an uneven extended portion which decreases in height in the direction of insertion. Figure 11 is bottom plan view of the foot plate of the Dual Extended Outer Sleeve of Figure 10. Figure 12 is a perspective side view of a Dual Extended Outer Sleeve having uneven extended portions which decrease in height in the direction insertion. Detailed Description of the Drawings And Detailed Description of a Preferred Use Step 1a. Prior to surgery, translucent implant templates appropriately adjusted for scale are superimposed on AP, lateral, and axial images of the interspace to be fused, for the purpose of selecting the optimal implant size and to determine the desired distraction. Step 1b. The patient is preferably placed onto a spinal surgery frame capable of inducing both distraction and vertebral alignment. Step 2. In a preferred embodiment, a standard bilateral (partial) discectomy is performed and any posterior lipping of the vertebral bodies adjacent the interspace is removed. Alternatively, no disc material need be removed. In a preferred embodiment, the interspace is exposed by performing bilateral paired semihemilaminotomies and resecting the inner aspects of the facet joints adjacent the spinal canal while preserving the supra and interspinous ligaments. Step 3. Beginning on the first side, the dural sac and traversing nerve root at that level are retracted medially and a.Long Distractor is then inserted and impacted flush to the posterior vertebral bodies adjacent that interspace. Long Distractors with working ends of increasing diameter are then sequentially inserted until the optimal distraction is obtained. This optimal distraction not only restores the normal height of the interspace, but further achieves a balance wherein the tendency for the space to collapse is resisted, which in urging the vertebral bodies apart is being equally resisted by the powerful soft tissue structures about the spinal segment including the outer casing of the disc (the annulus fibrosus), various ligaments, capsular structures, as well as the muscles and other soft tissue structures. This balanced distraction not only provides for the spatial restoration of the height of the interspace, but for considerable stability as the space now resists further distraction or collapse. In a preferred use, as the desired distraction is approached, the use of the solid bodied Long Distractors is terminated and a disassemblable Convertible Distractor is placed with tactile and/or radiographic confirmation of ideal distraction. The Convertible Distractor is then disassembled such that the Short Distractor portion is left in place and the ultra-low profile head portion being positioned adjacent to the canal floor and safely away from the neural structures. To insure that the Short Distractor remains in place until its removal is desired, various embodiments of the Short Distractor are available with varying degrees of resistance to dislodgment. In the preferred embodiment of the procedure, attention is then directed to the contralateral side of the spine. Step 4. On the contralateral side of the same interspace the Long Distractor having at its working end the diameter matching the Short Distractor already in place, is then inserted. If however, due to an asymmetrical collapse of the interspace if it is then determined that greater distraction is required on the second side to achieve the optimal stability, then the appropriate Short Distractor would be placed on the second side. Then the Short Distractor would be removed from the first side and replaced with a larger Long Distractor so as to bring the interspace into balance. In an alternative use, the entire procedure is performed on the one side of the spine utilizing only the Long Distractor prior to repeating the procedure on the contralateral side of the spine. Step 5. With the Short Distractor in place on the first side of the spine, and the matching Long Distractor in place on the second side of the spine, and with the dural sac and traversing nerve root safely retracted, the Outer Sleeve is placed over the Long Distractor and firmly impacted to its optimal depth using the Impaction Cap and a mallet. The Long Distractor is then removed. Step 6. An Inner Sleeve is then placed within the Outer Sleeve, and the interspace is then prepared on that side by utilizing a boring means such as, but not limited to, a Drill, Endmill, Reamer, or Trephine to drill, ream, or cut out the bone to be removed to either side, as well as any remaining interposed discal material. In a preferred use, utilizing a specially designed Endmill-Drill, it and the Inner Sleeve are removed as a unit, safely carrying away the bone and disc debris trapped within them from the spinal canal. Step 7. If required, a thread forming Tap with penetration limiting means to control the depth of insertion, is then inserted through the Outer Sleeve. Step 8. The prepared implant is then inserted utilizing the specialized Driver unit. It should be noted that the implant may be coated with, and/or made of, and/or loaded with substances consistent with bony fusion which may promote bone growth and/or fusion. However, in the preferred embodiment, the implant is treated with bone promoting and inducing substances, but is loaded with materials suitable for participating in a fusion. While substances both natural and artificial are covered by the present invention, a preferred use is in regard to the use of the patient's own bone by the following method. A hollow Trephine is utilized to harvest a core of bone from the posterior superior aspect of the iliac crest adjacent the sacroiliac joint. This core of bone is at its outside diameter, slightly smaller than the inside diameter of the spinal implant to be loaded, but longer than the spinal implant. Utilizing an instrument designed for that purpose, the core of bone is then injected from within the Trephine into the central cavity of the implant causing a superabundance of the bone material within the implant such that the bone material tends to press out through the openings communicating with the outside surface of the implant. Step 9. Using the Driver Extractor instrument, the prepared implant is threaded into the prepared interspace. The instrumentation is removed from that side of the spine and attention is then redirected to the first side of the spine. A small retractor is utilized to move the dural sac and traversing nerve root medially and to protect them and allowing the direct visualization of the retained Short Distractor unit. Without removing the Short Distractor, it is reassembled to its shaft portion, essentially reconstituting itself into a Long Distractor. With the inserted implant now acting as the distractor on the opposite side, the Long Distractor is utilized to guide the outer Sleeve down where it is impacted as described in Step 5. Steps 6 & 7 are then repeated, completing the procedure at that level. The wound is then irrigated and closed in the routine manner. Referring to Figure 1, in the preferred embodiment, a Convertible Long Distractor 113 is used on the first side of the spine. The Convertible Long Distractor 113 has a barrel portion 152 separable from the Short Distractor portion . While the initial distraction may be performed with a solid Long Distractor, as the optimal distraction is approached the appropriate Convertible Long Distractor is utilized. The Convertible Long Distractor 113 consists of a Short Distractor portion and a barrel 152 having a rectangular projection 134 at one end. The Short Distractor has an increased diameter head 128, a rectangular slot 118 and an internal threaded opening 114. The barrel 152 is hollow and has an internal shaft 111 terminating in a large diameter hexagonal crown 115 at one end and a reduced diameter portion 112. The crown 115 has a detent portion 117 in its flat surface. The other end of the shaft 111 has a threaded working end screw 116 that corresponds to threaded opening 114. The shaft 111 is prevented from removal from the barrel 152 by set pin 119 passing through the wall of barrel 152 in a convenient manner. The Short Distractor portion is removably attached to the barrel portion 152 via the mating of female rectangular slot 118 and the male mating member 134. The mating held together by utilizing knob 135 to drive the crown 110 connected to interior shaft 111 having a threaded working end screw 116 that threads into the female rectangular slot 118 of the Short Distractor portion. Knob 135 has an open socket 138 for fitting around crown 115 and engages the reduced diameter hexagonal portion 112 so as to permit the rotation of shaft 111 and threaded working end screw 116. A detent ball 150 in the inside of the socket 138 engages detent 117 in the crown 115, holding them together. The Short Distractor portion is designed to provide for high stability when temporarily situated so as to resist inadvertent migration while the surgeon is working on the second side. To that end, the embodiment of the Short Distractor shown in Figure 1 has a pair of sharp pegs 126, to embed into the opposing vertebral bodies and forward facing ratchetings, that further resist backward movement. The Short Distractor may have knurling to increase the interference with the bone surface so as to add stability to the unit and to resist dislodgment. To this end, it is apparent that the working ends of both the Long and Short Distractors can have a variety of configurations consistent with their purpose, and that surface irregularities as well as the shape of the ends themselves, with or without prongs 126, may be utilized to make the Short Distractor more resistant to migration. Once the ideal distraction has been achieved on the first side of the spine, the Convertible Distractor is dissociated, leaving Short Distractor in place with its rounded external end 128, safely on the canal floor and deep to the dural sac and nerve root. Referring to the Figures, the front end of the Outer Sleeve is metal and has sharp teeth that are capable of penetrating into and holding fast the two adjacent vertebrae (V). Interrupting the circumferential sharp teeth are flat, planar areas which serve to resist the further insertion of the sharp teeth into the vertebral bodies. The sharp teeth of the Outer Sleeve are a continuation of the tubular shaft , which in turn is connected to circumferentially enlarged tubular back end having a knurled outer surface for easier manipulation. Referring to Figure 2, an alternative embodiment of the instrumentation of the present invention comprising a Posterior Long Lordotic Distractor 400 capable of restoring and maintaining lordosis of adjacent vertebrae V from the posterior approach of the spine is shown. The Posterior Long Lordotic Distractor 400 is inserted from the posterior aspect of the spine and comprises a barrel portion 410 terminating at its distal end 412 in a disc penetrating portion 420 which is shown interposed within the disc space between two adjacent vertebrae V. The disc penetrating portion 420 terminates distally into a leading bullet-shaped front end 422 which facilitates the insertion of the disc penetrating portion 420 between the adjacent vertebrae V. The disc penetrating portion 420 is configured to have an uneven diameter such that it has a lesser diameter, and thus a lesser height within the disc space proximate the distal end 412 of the barrel portion 410 and has a greater diameter, and thus greater height within the disc space, in the direction of the front end 422. This configuration of the disc penetrating portion 420 serves to not only restore the intervertebral disc space height upon insertion of the disc penetrating portion 420 of the Posterior Long Lordotic Distractor 400, but also serves to restore and maintain the normal lordosis between the adjacent vertebrae V. The leading bullet-shaped front end 422 is of particular importance in regard to the Posterior Long Lordotic Distractor 400 where the largest diameter portion of the disc penetrating portion 420 would otherwise be entering the disc space first. The widest diameter of the disc penetrating portion 420 is less than the diameter of the barrel portion 410, such that a circumferential shoulder 424 is formed at the distal end 412 of the barrel portion 410 which prevents over penetration into the disc space of the Posterior Long Lordotic Distractor 400. It can readily be appreciated that such a configuration of the disc penetrating portion 420 renders the Posterior Long Distractor 400 quite stable within the disc space and resistant to backing out as the compressive forces of the spine upon the disc penetrating portion 420 tend to urge it forward, while simultaneously the circumferential shoulder 424 makes such further motion impossible, thus making the Posterior Long Distractor 400 exceedingly stable. Referring to Figures 3 and 4, an elevational side view and a top plan view, respectively, of a Posterior Short Lordotic Distractor 500 for posterior use generally referred to by the numeral 500 is shown. The Posterior Short Lordotic Distractor 500 is similar to the Short Distractor described above in reference to the Convertible Distractor and comprises a disc penetrating portion 520 identical to that of the Posterior Long Lordotic Distractor 400 and an increased diameter head 128. As discussed above for the Posterior Long Distractor 400, the configuration of the disc penetrating portion 520 renders the Posterior Short Lordotic Distractor 500 quite stable. This is an especially important feature for the Posterior Short Lordotic Distractor 500 because it is left under the delicate dural sac and nerves while work is being performed on the contralateral side of the spine. If the Posterior Short Lordotic Distractor 500 were other than stable, injury to these structures might result. To further prevent unwanted backing out of the Posterior Short Lordotic Distractor 500, the bone engaging surface 530 may be knurled or otherwise roughened, or have forward facing ratchetings. Referring to Figure 5, an Anterior Long Lordotic Distractor 600 for use anteriorly within the spine is shown. It can be seen that the configuration of the disc penetrating portion 620 is the reverse of the disc penetrating portion 420 of the Posterior Long Lordotic Distractor 400 in that the disc penetrating portion 620 is of greatest diameter and height proximate the barrel portion 610 and that the diameter and height are diminished more distally in the direction towards the front end 622 along the disc penetrating portion 620. The Anterior Long Lordotic Distractor 600 serves to restore and maintain lordosis of the spine by distraction of the adjacent vertebrae V. As described above for the Posterior Short Lordotic distractor 500, it is appreciated that an Anterior Short Lordotic Distractor (not shown) having a disc penetrating portion 520 may be similarly devised. It can be seen that all of the lordotic distractors, both the anterior and the posterior embodiments, have specialized leading bullet-shaped or nosecone-shaped portions so as to facilitate the insertion of the disc penetrating portions within the disc space. This is of particular importance in regard to the Posterior Lordotic Distractors where the largest diameter portion of the disc penetrating portion 420 would otherwise be entering the disc space first. Referring to Figures 6 to 9, a preferred embodiment of the present invention for maintaining distraction during the surgical procedure is shown. The Extended Outer Sleeve is entirely a new invention such as has never existed in the art or science of surgery, the Extended Outer Sleeve offers numerous advantages over all previously described drilling sleeves. The Extended Outer Sleeve by dint of its extended portions which are inserted between the adjacent vertebrae does itself act as an intervertebral distractor and is therefore essentially a combination outer sleeve and distractor. The Extended Outer Sleeve is exceedingly stable as the extended portions are trapped within the disc space and further held there by the considerable compressive loads within the spine. Because of the stability thus provided, a further derivative advantage is that the teeth on the distal end of the Extended Outer Sleeve may either be eliminated or be made of a lesser size. Further, it should be noted that teeth when present would be confined to the area directly in line with the vertebrae V and the extended portions would ensure the proper rotatory alignment. A further advantage, to be discussed in more detail subsequently, is that the extended portions confine the surgery to the area within and between the extended portions and protect all other tissues external to the extended portions. Having now described the novel concept of the Extended Outer Sleeve, attention may now be directed to further variations of the Extended Outer Sleeve capable of not only restoring and maintaining the appropriate intervertebral disc space height, but additionally being able to restore and maintain anatomic lordosis or kyphosis, as desired, throughout the surgical procedure. Referring to Figure 6, a Posterior Lordotic Extended Outer Sleeve 800 for use from the posterior approach of the spine is shown. The Posterior Lordotic Extended Outer Sleeve 800 comprises a hollow tubular member 802 having a distal end 810 which has been extended such that a pair of extended portions 820 and 822, which are essentially a continuation of the tubular member 802, are opposed 180 degrees from each other. Extended portions 820 and 822 are configured to restore and maintain lordosis of the spine similar to the disc penetrating portion 420 of the Posterior Long Lordotic Distractor 400, the features of which are herein incorporated by reference. The extended portions 820 and 822 each have a height that is lesser at a point proximate the distal end 810 of the tubular member 802 that increases in the direction away from the tubular member 802. The extended portions 820 and 822 are tapered at their leading edges 824 and 826, respectively to facilitate insertion into the disc space. Between the extended portions 820 and 822, may be a plurality of teeth 812 for engaging the bone of the vertebrae V when the Extended Outer Sleeve 800 is inserted within the disc space between the adjacent vertebrae V. Referring to Figure 7, a Posterior Lordotic Extended Outer Sleeve 800' in place within the intervertebral disc space is shown. Referring to Figure 8, an Anterior Extended Outer Sleeve 900 for use from the anterior approach of the spine is shown. The Anterior Lordotic Extended Outer Sleeve 900 comprises a hollow tubular member 902 having a distal end 910 which has been extended such that a pair of extended portions 920 and 922 which are essentially a continuation of the tubular member 902 and are opposed 180 degrees from each other. The extended portions 920 and 922 differ from the extended portions 820 and 822 in that the extended portions 920 and 922 are configured to restore and maintain lordosis of the spine from the anterior approach similar to the disc penetrating portion 620 of the Anterior Long Lordotic Distractor 600, the features of which are herein incorporated by reference. The extended portions 920 and 922 each have a height that is greater at a point proximate to the distal end 910 of the tubular member 902 that decreases in the direction away from the tubular member 902. The extended portions 920 and 922 are tapered at their leading edges 924 and 926, respectively to facilitate insertion into the disc space. While the Lordotic Extended Outer Sleeve for use anteriorly is shown in the singular form and in use in the lumbar spine, it is understood that it may take a double barrelled form and in either form, be used throughout the spine. Referring to Figures 10 and 11, a Lumbar Dual Extended Outer Sleeve is shown and generally referred to by the numeral 1100. The Dual Extended Outer Sleeve 1100 comprises two hollow tubular members 1101 and 1102. The two hollow tubular members 1101 and 1102 have a distal end 1104 which has been extended co form an extended portion 1121 which is essentially a continuation of the hollow tubular members 1101 and 1102 joined together. The extended portion 1121 is similar in shape and function to the extended portions 920 and 922 described above in reference to Figure 8. The extended portion 1121 has a height that is greater at a point proximate the distal end 1104 and decreases in the direction away from the hollow tubular members 1101 and 1102, in order to maintain the normal curvature of the spine by correcting the angular relationships of the vertebrae V. The extended portion 1121, is tapered at its leading edge 1124 to facilitate insertion of the extended portion 1121 into the disc space between two adjacent vertebrae V. Located at the distal end of the tubular members 1101 and 1102 are sharpened teeth 1130 for engaging the vertebrae V. Each of the hollow tubular members 1101 and 1102 are displaced from each other ideally the sum of the difference between the minor and major diameters of two threaded spinal implants I combined, but not less than that difference for one implant I, as it is possible to have the threads of one implant I nest interposed to the threads of the other implant I such that they both occupy a common area between them. Typically, the walls of each hollow tubular members 1101 and 1102 have a combined thickness at the point which the walls of the hollow tubular members 1101 and 1102 are in contact with each other which is approximately 2.0 mm. This is achieved by machining away part of each hollow tubular member 1101 and 1102 to reduce the wall thickness of each hollow tubular member 1101 and 1102 prior to joining them together. In this manner, the two hollow tubular members 1101 and 1102 may be placed closer together so that two . spinal implants I may be placed closer together when inserted within the disc space between adjacent vertebrae W. The hollow tubular member 1101 and 1102 can be overlapped or displaced from each other so as to control the distance between implants when the Dual Extended Outer Sleeve is utilized and two implants implanted The hollow tubular members 1101 and 1102 may be bridged in part or wholly throughout their length, but are typically fixed by a foot plate 1110. Referring specifically to Figure 11, the foot plate 1110 has an oval configuration that contours and hugs the vertebrae and has a plurality of prongs 1112-1115 extending from the bottom of the foot plate 1110 is shown. The prongs 1112-1115 are sufficiently long to engage the bone of adjacent vertebrae V, but limited in length so as not to over penetrate beyond the vertebrae once inserted. Referring to Figure 12, a second Dual Extended Outer Sleeve 1200, is shown. The Dual Extended Outer Sleeve 1200 is similar to the Dual Extended Outer Sleeve 1100, except that it has additional extended portions 1220 and 1222 which have a height that is greater near the distal end 1204 of the hollow tubular members 1201 and 1202 and decreases in the direction away from the hollow tubular members 1201 and 1202. The extended portions 1220-1222 are similar in shape and function to the extended portions 920 and 922 described above in reference to Figure 8. Moreover, as the foot plate 1210 is rectangular and larger than foot plate 1110, additional prong 1216 and 1217 may be added. Further, it should be appreciated that the lordotic distractor for use posteriorly when referring to their use in the lumbar spine, would be used anteriorly if applied to the thoracic spine, either in the single or double-barrel form. This is because the thoracic spine is normally curved into kyphosis which is the reverse of lordosis. That is, in approaching the thoracic spine anteriorly, it would be desirable to distract the back of the disc space more than the front, and that would require an Extended Outer Sleeve which would resemble that seen in Figure 7; though when used in this new context, it would more correctly be referred to as an Anterior Thoracic Kyphotic Extended Outer Sleeve. It can readily be appreciated that the described Expended Outer Sleeves may be used with the Short and Long Distractors having a disc penetrating portion of uniform diameter or in combination with the lordotic and kyphotic distractors of complimentary configuration. It is readily appreciated that the tubular members can be of a variety of shapes and sizes. Further, the removal of disc and bone may be accomplished by the use of a burr, or a chisel of appropriate shape for that purpose and with or without the use of a drill. The implants would then have shapes appropriate for use in the spaces so formed. While the present invention has been described in association with the implant of a threaded spinal implant, it is recognized that other forms of implants may be used with the present method. For example, dowels, made from bone or artificial materials, knurled or irregularly shaped cylinders or partial cylinders, or any other shaped implants that can be introduced through the outer sleeve may be used. Being able to perform the procedure through the outer sleeve permits the procedure to be performed safely and quickly, and more accurately.

Claims: A spinal distractor (600, 900, 1100, 1200) for use in spinal fusion surgery for positioning two adjacent vertebrae (V) in selected relationship to each other, said spinal distractor comprising: a body (610, 902, 1101, 1102, 1201) having a distal end (910, 1104) with a shoulder (1110, 1210) configured to prevent said body from entering the disc space; and a disc penetrating extension (620, 920, 922, 1121, 1220, 1222) extending from said distal end of said body for insertion into the disc space between the two adjacent vertebrae and for bearing against adjacent endplates of the two adjacent vertebrae, said disc penetrating extension having a first portion for bearing against one of the adjacent endplates and a second portion for bearing against the other of the adjacent endplates, said first and second portions converging away from said body. A spinal distractor (400, 500, 800) for use in spinal fusion surgery for positioning two adjacent vertebrae (V) in selected relationship to each other, said spinal distractor comprising: a body (410, 802); and a disc penetrating extension (420, 520, 820, 822) extending from said body for insertion into the disc space between the two adjacent vertebrae and for bearing against adjacent endplates of the two adjacent vertebrae, said disc penetrating extension having a first portion for bearing against one of the adjacent endplates and a second portion for bearing against the other of the adjacent endplates, said first and second portions diverging away from said body, said disc penetrating extension having a tapered leading end (422, 824, 826) to facilitate placement of said disc penetrating extension into the disc space. The spinal distractor of claim 1, wherein said disc penetrating extension has a tapered front end (422, 622, 824, 826, 924, 926, 1124) to facilitate insertion of said disc penetrating extension into the disc space. The spinal distractor of claim 2, further comprising means (424, 128) for limiting the penetration of said disc penetrating extension into the disc space. The spinal distractor of claim 4, wherein said limiting means (424, 128) comprises a shoulder on said body (410, 802) at the juncture of said disc penetrating extension and said body for preventing said body from entering the disc space. The spinal distractor of any one of the preceding claims, wherein said body is removably attached to said disc penetrating extension. The spinal distractor of either claim 5 or 6, wherein said disc penetrating extension includes a head proximate the juncture of said disc penetrating extension and said body. The spinal distractor of any one of the preceding claims, further comprising means (812, 1130, 1112-1115, 1216, 1217) for engaging the two adjacent vertebrae. The spinal distractor of claim 8, wherein said engaging means includes a prong (1112-1115, 1216, 1217). The spinal distractor of claim 6, further comprising means for limiting the depth of insertion of said disc penetrating extension into the disc space. The spinal distractor of claim 10, wherein said limiting means comprises a head associated with said disc penetrating extension, said head being dimensioned to prevent entry into the disc space. The spinal distractor of claim 11, wherein said head has a low profile so as to minimize protrusion of said head from the two adjacent vertebrae. The spinal distractor of claim 10, further comprising an impacting surface at the juncture of said head and said disc penetrating extension for flattening portions of the exterior surface of the two adjacent vertebrae. The spinal distractor of either claim 6 or 10, wherein said disc penetrating extension (420, 520, 620, 820, 822, 920, 922, 1121, 1220, 1222) comprises means for engaging an extraction device for extracting said disc penetrating extension from the disc space. The spinal distractor of any one of the preceding claims, wherein said body is a barrel member. The spinal distractor of any one of the preceding claims, wherein said disc penetrating extension (420, 520, 620, 820, 822, 920, 922, 1121, 1220, 1222) has surface irregularities. The spinal distractor of claim 16, wherein said surface irregularities include ratchetings. The spinal distractor of claim 16, wherein said surface irregularities include knurling. The spinal distractor of any one of the preceding claims, wherein said body (410, 610, 802, 902, 1101, 1102, 1201) has means for engaging an extraction device for extracting said disc penetrating extension from the disc space. The spinal distractor of claims 19, wherein said engaging means for engaging an extraction device includes a mating member for mating with an extraction device. The spinal distractor of either claim 1 or 2, further comprising an impacting surface proximate the juncture of said body and said disc penetrating extension for flattening portions of the exterior surface of the two adjacent vertebrae. The spinal distractor of any one of the preceding claims, in combination with a guard member having an opening for providing protected access to the disc space and the adjacent vertebrae, said spinal distractor passing through said opening. The spinal distractor of claim 22, wherein said opening is sized to permit passage of said disc penetrating extension of said spinal distractor through said opening. The spinal distractor of either claim 22 or 23, further comprising bone removal means having a portion sized for passage through said opening for forming through said guard member an implantation space across the disc space. The spinal distractor of any one of claims 22-24, further comprising an implant driver having means for engaging an implant, said implant driver having a portion sized for passage through said opening for passing an implant through said guard member

Inventors: MICHELSON GARY KARLIN, MICHELSON, GARY KARLIN
Applicants: MICHELSON GARY K, MICHELSON, GARY KARLIN
Application year: 1996
Main classification: A61B17
IPC codes: A61B17, A61F2, A61B19