MXPA97009599A - Invertebral disk stabilizer and spondiloliste reduction instrument - Google Patents

Abstract

The present invention relates to a spinal disc stabilizer, comprising: an elongated implant having a substantially rectangular cross-sectional shape, perpendicular to its length along, constituted by first, second, third and fourth sides, which provide a minimum height defined by the first and second sides and a maximum width defined by the third and fourth sides, the third and fourth sides being arched from one end of said implant to the other end of said implant to provide the middle portion of said implant with a a bi-convex shape having a width greater than the width of the ends of said implant, the height being less than the width, a lock having a bearing surface formed thereon, and means releasably mounting said lock in a end of said implant to prevent the rotation of said lock in relation to said implant, with the support surface oriented approximately 9 0º with respect to the height of said implan

Description

INTERVERTEBRAL DISK STABILIZER AND INSTRUMENT FOR SPONDILOLYSTIC REDUCTION BACKGROUND OF THE INVENTION The present invention relates to an intervertebral implant and to a method for stabilizing adjacent vertebrae. More specifically, the present invention relates to rectangular shaped disc implants that are expanded in the measured portion used for spinal fusion. If necessary in treating the patient, the present invention also contemplates the reduction of the spondylolisthesis, for example the alignment of the vertebrae comprising the spinal or vertebral column. In this second aspect, the present invention relates to an apparatus that is inserted into the space between adjacent, misaligned vertebrae, links the bodies of the adjacent vertebrae, and pulls the vertebrae back toward alignment. Disorders of the spinal column, especially in the neck or lumbar region, continue to be a challenging field of medicine. Classical treatments for conditions involving sub-dislocation of one vertebra over another, resulting in misalignment of the spinal column, use screws that extend through a plate and are squeezed to bring the misaligned vertebrae back into alignment. However, such conditions often involve damaging the intervertebral disc, for example rupture or herniation, which can result in compression of a nerve root. If the hernia is large, the compression may be bilateral. This condition is usually not corrected by re-aligning the vertebrae with a plate and screws such that surgical removal of the disc, followed by fusion, is often indicated after the reduction of the spondylolisthesis. The classic treatment for a broken disc is the discoctomy, that is, the removal of the disc between the vertebrae. In this process, the entire intervertebral disc, or a part of it, is removed, leaving a defect that bothers the patient for the rest of his life. An additional procedure is to replace the disc space with a bone graft, usually splinters of bone cut from the patient's iliac crest, by fusing the vertebrae above and below the disc and eliminating the space between the vertebrae . However, fusion-enhanced discoctomy is not ideal because the replaced bone does not have the function of the cartilaginous disc tissue, ie it has no cushioning effect and has several complications. First, the conventional bone plugs used to pack the disc space do not conform to the disc space because it is wider in the middle part and narrower in its anterior and posterior ends. For this reason, the bone plugs currently available only have four points of contact, ie in the front and back of the disc space. Second, access to the disc is from the spinal side of the adjacent vertebrae, leaving a space that is "offset from the center" relative to the bodies of the adjacent vertebrae, such that the stability of the implant is even more problematic than what would be evident from the limited contact that results from the shape of the intervertebral space. Another complication is the possibility of infection or other conditions that may require removal of the implant. Also, if the pieces of bone do not melt, they can eventually extrude out of the disc space, causing pressure on the nerve roots. Various prosthetic disc plugs, or implants, have been disclosed in the subject, but all are characterized by limitations in the sense of not being satisfied with the shape of the disc space, the lack of stability when inserted displaced from the center, the difficulty of place them accurately, the inability to remove them, or other disadvantages. For example, United States Patent No. 4, 863,476 (and its European counterpart, EP-A-0260044) discloses an elongated body divided longitudinally into two portions having a cam device to increase the space between the two body portions once it is inserted into the disc space. However, that device is generally cylindrical in shape such that the only points of contact are in the front and back of the disc space, creating the possibility of instability. The technique also discloses intervertebral disc prostheses (e.g., U.S. Patent Nos. 3,867,728; 4,309,777; 4,863,777 and 4,932,969, and French patent application No. 8816184), which may have a more general contact with the adjacent discs, but which are not intended to be used in disc fusion. The material also includes spinal joint prostheses, such as that described in U.S. Patent No. 4,759,769, which again is not indicated for use when fusion is the preferred surgical procedure. SUMMARY OF THE INVENTION Therefore, there is a need to treat conditions that involve misalignment and fusion of the spinal column, as specifically of a device capable of aligning and stabilizing the vertebrae adjacent to an intervertebral disc for use in spinal fusion. These needs are met in the present invention by providing a spinal disc stabilizer comprising an elongated implant having first, second, third and fourth readings that provide the implant with a substantially rectangular cross sectional shape of minimal height, defined by the first and second sides. second, and maximum width defined by the third and fourth sides, the third and fourth sides being arched from one end of the implant to the other to provide the portion between the ends with a width greater than the width of the implant at its ends. A lock having a bearing surface formed therein is removably mounted at one end of the implant to prevent rotation of the lock relative to the implant, with the bearing surface oriented at approximately 90 ° with respect to the height of the implant. Also provided is a method of stabilizing two adjacent vertebrae after removing a portion of the intervertebral disc from each other to form a disc space, comprising the steps of inserting an elongate implant, substantially rectangular in shape, having a width greater than its width. height, in the disc space, with the implant oriented so that its upper part and its lower part link the bodies of the adjacent vertebrae, rotating the implant approximately 90 ° in the disc space to make contact with the bodies of the disc. the adjacent vertebrae with the sides of the implant, and subsequently prevent the rotation of the implant relative to the vertebrae. An apparatus for aligning adjacent vertebrae is also provided, comprising an elongated handle having a longitudinal bore therethrough, an implant comprising first and second side members, the first member being integrally mounted to the handle, and means formed in the implant to selectively link adjacent vertebrae to prevent relative movement between the respective first and second members and the adjacent vertebrae. A mandrel is placed in the bore in the handle and is connected to the second member to move the second member relative to the first member in the direction of the longitudinal axis of the handle. To facilitate the precise movement of the second member relative to the first, and to confer the mechanical advantage that may be required to bring the adjacent vertebrae into alignment, the mandrel is preferably threaded and the hole in the handle is provided with an equivalent set of such threads that rotation of the mandrel causes movement of the second member along the longitudinal axis of the handle. A method of aligning adjacent vertebrae after removing a portion of the intervertebral disc from each other to form a disc space is also provided, which comprises the steps of inserting an elongate implant comprising first and second side members with side having means therein. formed to selectively link the adjacent vertebrae to the disc space toward the disc space and move the second member relative to the first member until the first and second members are approximately aligned with the adjacent vertebrae. The implant is rotated approximately 90 ° to cause the means linking the vertebrae to link the vertebrae and the second member is then moved relative to the first member to align the vertebrae to which it is linked with the vertebrae to which the first vertebra is attached. member Brief Description of the Drawings Now referring to the drawings, Figure 1 is a side view of a portion of a human spinal column having the spinal disc stabilizer of the present invention therein inserted and having a portion of the bodies of the vertebrae adjacent to the implant shown cut and / or in phantom line for show the bonding of the vertebral bodies through the spinal disc stabilizer. Figure 2 is an exploded view, in perspective, of the spinal disc stabilizer of Figure 1. Figure 3 is a top plan view of the implant of Figure 1 having a handle mounted therein in place of the lock shown in FIG. Figure 2. Figure 4 is an exploded perspective view of a second preferred embodiment of the spinal disc stabilizer of the present invention. Figure 5 is a longitudinal, sectional view of a preferred embodiment of an apparatus for correcting the misalignment of two adjacent vertebrae, constructed in accordance with the present invention. Figure 6 is an end view of the apparatus of Figure 5. Figure 7 is a view similar to that of Figure 5, but with the mandrel removed therefrom.

Fig. 8 is an end view of the apparatus of Fig. 5. Fig. 9 is a side elevational view of the mandrel after removal of the apparatus of Fig. 5. Fig. 10 is an end view of the mandrel of Fig. 5. Figure 11 is a side view, partially schematic of a portion of the lumbar spine, showing the use of the apparatus of Figure 5 to align the fourth and fifth lumbar vertebrae. Figure 12 is a top plan view of an alternative embodiment of the apparatus of Figure 5, showing the two halves of the body in their first position side by side. Figure 13 is a top plan view of the apparatus of Figure 12, showing the two halves of the body in the second position. DESCRIPTION OF THE FORMS OF CARRYING OUT THE INVENTION In greater detail, a disc stabilizer constructed in accordance with the teachings of the present invention is shown implanted in a human spinal column in Figure 1. The spinal disc stabilizer, generally indicated with the reference number 10, is implanted between the bodies 12 and 14 of two adjacent vertebrae 16 and 18, respectively, in the disc space (not numbered) from which a portion of the intervertebral disc 20 is removed, i.e. by a simple discoctomy and a small laminotomy. Also now referring to Figure 2, the spinal disc stabilizer 10 comprises an elongate implant 22, the lock 24, and means for removably mounting the lock 24 to one end 25 of the implant 22. In the embodiment currently preferred shown, the mounting means is in the form of a bolt 26 passing through a bore 28 in the lock 24, the threads of the bolt 26 engaging complementary threads in the walls of the bore 30 at the end 25 of the implant 22. In greater detail, the implant 22 comprises first and second sides 32 and third and fourth sides 34 defining a substantially rectangular cross section. The height H of the cross section of rectangular shape is defined by first and second sides 32 and the width W is defined by the third and fourth sides 34 and, as will be evident from a comparison of H and, the height H of the implant 22 is smaller than the width W. As will be explained below, H is minimized to facilitate insertion of the second end 36 into and placement of the implant 22 in the disc space from which a portion of the intervertebral disc 20 was removed and W is maximized to provide the desired stabilization to the adjacent vertebrae 16 and 18. The third and fourth sides 34 are arcuate from one end of the implant 22 to the other to provide a portion of the implant 22 between the ends 25 and 36 with a width W that is greater than the width W "at the ends 25 and 36. Because the sides 32 of the implant 22 are substantially flat and the sides 34 are arcuate from one end 25 to the other end 36, the implant 22 is described with an implant 22 bi-planar, bi-convex. The bi-convex sides 34 of the implant 22 are provided with a plurality of teeth 38 for biting the adjacent vertebrae 16 and 18, as will be explained later in detail. The end 36 of the implant 22 is formed in a flat or rounded shape to reduce the possibility of injury to the nerves of the spinal column during insertion into the disc space. In the preferred embodiment shown, the lock 24 is substantially square when viewed from the end 40 along the axis of the bore 28 therethrough and U-shaped when viewed from the side. The internal surfaces 42 of the arms 44 of the U-shaped lock 24 are flat to contact the first and second sides 32 of the implant 22 to prevent rotation of the lock 24 relative to the implant 22, when the lock 24 is mounted to the implant 22 and secured thereto by the pin 26. The surfaces 42 are provided with a slit 46 for receiving a wedge 48 of complementary shape to facilitate the assembly of the lock 24 to the implant 22. The slit 46 can also be placed on the implant 22 and the wedge 48 can be placed on the lock 24 without any difference in the function of those component parts. The perforation 28 in the lock 24 is aligned with the perforation 30 in the implant 22. The sides of the square end 40 of the lock 24 provide surfaces 50 for support against the bodies 12 and 14 of the adjacent vertebrae 16 and 18, as will be explained later in more detail. It will be recognized by those skilled in the art who have the benefit of this disclosure that the bearing surfaces 50 need not be flat and that the end 40 of the lock 24 need not be square. Other shapes and configurations may be used as needed to ensure that the movement of the lock 24 is limited by the bodies of the adjacent vertebrae 16 and 18. The purpose of the bi-planar implant, expanded in the middle, bi-convex 22 is that of allowing the insertion of the implant 22 in the disc space and rotating approximately 90 ° to increase the height of the disc and stabilize the disc space. The purpose of the lock 24 is to lock the implant 22 and against the instability when it is in the vertical position in order to maintain the height of the disc later. Referring now to Figure 3, an applicator 52 mounted on the end 25 of the implant 22 is shown. In the embodiment shown, the applicator 52 is mounted to the implant 22 by screwing its threaded end 54 into the threaded bore 30 in the implant 22. When the end 54 of the applicator 52 is screwed all the way to the perforation 30, so as to prevent relative movement between them, the implant 22 is inserted into the disc space and rotated there using the applicator 52, as will be explained later. The applicator 52 is separated from the implant 22 by rotating in the opposite direction, while the rotation of the implant 22 is restricted. The use of the stabilizer 10 of the present invention, for example, in a lumbar intervertebral disc stabilization method, or LIDS ", is illustrated in Figure 1. The surgery is carried out as a simple discoctomy and the inter-vertebral disc 20 is exposed through a small laminotomy. The disc material is removed and any compression of the nerve root is corrected. The posterior longitudinal ligament (not shown) and the disc cartilage are removed until the surface of the bodies 12 and 14 of the adjacent vertebrae 16 and 18, respectively, is exposed above and below the disc space. Using spreaders, such as those disclosed in international application No. PCT / US95 / 00347, vertebrae 16 and 18 are distracted to open the disc space, and once the desired "spreading" is achieved, the middle portion of the space The disc is packed with cancellous bone chips (not shown). Because the posterior longitudinal ligament is left intact to the opposite side and to the center of the disc space, the bone chips are held in place in the disc space.

An implant 22 having a height H and a width W selected to adjust the disc space is then mounted on the applicator 52 by screwing to the threaded end 54. The appropriately sized implant 22 is then inserted into the disc space using the applicator 52 with the implant 22 oriented so that the upper part and the lower part thereof, ie the first and second sides 32, link the bodies 12 and 14 of the adjacent vertebrae 16 and 18, respectively. Using the applicator 52, the implant 22 is then further moved toward (or back out of) the disc space in an anterior-posterior direction so as to allow the implant 22 to be placed in the disc space at a position in the which the middle portion expanded and the ends of smaller widths 25 and 36 of the third and fourth sides 34 of the implant 22 contact the respective lower and upper surfaces of the bodies 12 and 14 of the adjacent vertebrae 16 and 18 when rotated approximately 90 ° using the applicator 52. To facilitate this rotation, the corners of the implant 22 between the first and second surfaces 32 and the third and fourth surfaces 34 are rounded, as shown at 35, the rounded corners 35, which effectively act as planes or ramps for separating by adjacency the adjacent vertebrae 16 and 18 during rotation. The respective lower and upper surfaces of the vertebra bodies 12 and 14 are slightly concave such that the middle portion "of greatest width of the implant 22 allows the implant 22 to substantially more bond the respective surfaces of the vertebral bodies 12 and 14 than the conventional prosthetic devices, thereby providing increased stability to the fusion once the additional rotation of the implant 22 in the disc space is impeded as will be described later.After the implant 22 is placed in the disc space, the applicator 52 is detached by unscrewing it and disposed rearwardly of the incision in the patient.The lock 24 is then inserted through the same incision and, using the slit 46 and the wedge 48, the perforation 28 in the lock 24 and the perforation 30 in the implant 22 are aligned and the pin 26 is inserted and tightened to hold the lock 24 to the implant 22. Securing the lock 24 to the implant 22 thus prevents relative rotation between the lock 24 and the implant 22 and the bearing surfaces 50 of the lock 24 support against the bodies 12 and 14 of the adjacent vertebrae 16 and 18 to prevent rotation of the lock 24. in relation to the adjacent vertebrae 16 and 18 against which the bearing surfaces 50 abut. The bearing surfaces 50 rest against the cortical end plates of the respective vertebral bodies 12 and 14, which comprise non-cancellous bone, and which provide a hard surface, relatively smooth. The end 40 of the lock 24 is preferably supplied in a plurality of different sizes and shapes other than the square shaped end 40 shown in the drawings, so as to allow the surgeon to select a lock of appropriate size and shape that provides a narrow fit. with the space between the vertebral bodies. If necessary, a small amount of a physiologically compatible adhesive of a type known in the art is applied to the cancellous bone chips just medial to the implant to close the remaining portion of the opening into the disc space. The patient should be able to walk soon after the LIDS procedure due to the stability imparted to the spinal column by the implant of the present invention. Before narrowing of the disc space occurs, the cancellous bone chips will have started the fusion process. The stabilizer 10 is also advantageously used to carry out, for example, an intertransversal, lateral, posterior fusion. The implant 22 is inserted in the region of the disc space from which a portion of the disc has been removed., as described above, with latch 24 and subsequent lateral fusion carried out. Because the implant 22 provides stability to the spine until the posterior lateral fusion is solid, the patient is generally able to walk soon after surgery. This procedure also prevents narrowing of the disc space, which is a common problem with posterior lateral fusion. The removal of the implant 22 is achieved with relative ease compared to conventional implants. The bolt 26 is screwed back out of the implant 22 and the lock 24 is pulled out of the disc space. The applicator 52 is re-inserted and screwed into the bore 30 in the implant 22 and used to rotate the implant 22 by approximately 90 °, causing the first and second sides, having minimum height, to make contact with the bodies 12 and 14 of the adjacent vertebrae 16 and 18 so as to allow directed movement in the posterior direction of the implant 22 out of the disc space. An alternative embodiment of the implant of the present invention is shown in Figure 4, in which the first and second sides 32 'of the implant 22' are substantially flat but not parallel along their longitudinal axes. The wedge shape resulting from the implant 22 'facilitates insertion into the disc space, the rounded end 36 reducing the possibility of injury to the nerves of the spinal column during insertion into the disc space. Similarly, the comparison of widths W, W "and W" 'of implant 22' will show that the width W of implant 22 'at end 36' is less than width W "at end 25. Both widths are smaller that the width "in the middle, expanded portion of the implant 22 '. In another alternative embodiment (not shown), which provides additional resistance to forward or backward movement of the implant 22 in the disc space, the teeth 38 located closer to the end 25 of the implant 22 (e.g. the distal portion of the implant 22) are inclined towards the end 25 and the teeth 38 closer to the end 36 of the implant 22 are inclined towards the end 36. The teeth in the middle portion of the implant 22, for example between the two ends of the inclined teeth, are oriented vertically. Referring now to Figures 5-13, there is shown an apparatus for aligning adjacent vertebrae constructed in accordance with the teachings of the present invention. The apparatus, generally indicated at reference numeral 110, comprises an elongate handle 111 and an elongate body 112. The body 112 comprises first and second side members 113 and 114, respectively, the first member 113 being integrally mounted to the handle 111 and the second member 114 being movable relative to the first member 113 in the direction of the longitudinal axis of the arrow 115 of the handle 111. Means, in the shape of the teeth 138, are provided on the body 112 to selectively link the vertebrae adjacent 133, 137 when the body 112 is inserted therebetween to prevent relative movement between the respective first and second members 113 and 114 and the adjacent vertebrae 137 and 133 to which the first and second members 113 and 114. are attached. Arrow 115 of the handle 111 is provided with a longitudinal perforation 116 therethrough having a mandrel 117 there placed, the second member 114 being mounted on the mandrel 117 '. At the opposite end to the first member 113, the arrow 115 is provided with a tubular barrel 118 having a collar 119 there positioned. The collar 119 is also provided with a longitudinal bore 116 ', the longitudinal axis of which is aligned with the longitudinal axis of the bore 116 in the mandrel 117, which is provided with a set of threads 120 for receiving the threaded end 121 of the mandrel 117. The collar 119 is retained within the barrel 118 by the follower 122, which is retained at the end of the barrel 118 by means of screws 23. An adjustment knob 124 is integrally mounted on the collar 119 by screws 126. As a result of this construction, when the mandrel 117 is rotated by turning the knob Adjustment 124, the second member 114 moves relative to the first member 113 from a first position in which the members 113 and 114 are in a parallel relationship side by side with each other to a second position along the longitudinal axis of the arrow 115 of the handle 111 in which the two members remain parallel to each other but are no longer side by side, as shown in Figure 11. Referring to Figures 7-10, it can be seen that a surface of the first member 113 is formed in the form of a semi-round recess 127 for receiving the round mandrel 117 to retain the two members 113 and 114 in side-by-side, parallel, tight engagement when the second member 114 is moved from the first to the second position.

When the first and second members 113 and 114 are in the first side-by-side position shown in Figures 5 and 6, for example when the mandrel 117 is rotated to bring the end 136 of the second member 114 against the end 154 of the handle 111 , the two members 113 and 114 form an elongate body 112 having a shape that is similar to the shape of the monolithic implant 22 shown in Figures 1-4. However, referring to the body 112 for the time being, the two members 113 and 114 side by side form a body 112 comprising the first and second sides 132 and the third and fourth sides 134, providing a cross section of substantially rectangular shape. The height H6 of the cross section of rectangular shape is defined by first and second sides 132 and the width W6 is defined by the third and fourth sides 134 and, as evidenced by the comparison of H6 and W6, the height H6 of the body 112 is less than width 6. As will be explained below, H6 is minimized to facilitate insertion of second end 136 toward and placement of body 112 in the disc space from which a portion of intervertebral disc 130 was removed and s maximized to provide the desired stabilization to the adjacent vertebrae 133 and 137. The third and fourth sides 134 are arched from one end of the body 112 to the other to provide the body portion 12 between the ends 125 and 136 with a width W'6 that is larger than the width W "6 at the ends 125 and 136. Because the sides 132 of the body 112 are substantially flat and the sides 134 are arched from one end 125 to the other end 136, the body 112 is of written as a bi-planar, bi-convex body. The convex or arched sides 134 of the body 112 are provided with a plurality of teeth 138 to bite into the adjacent vertebrae 133 and 137, as will be explained below in greater detail. The end 136 of the body 112 is formed in a flat or rounded shape to reduce the possibility of injury to the nerves of the spinal column during insertion into the disc space. Referring now to Figure 11, the use of the apparatus 110 for the reduction of the spondylolisthesis is shown. In figure 11, the fourth lumbar vertebra (L4) 133 is shown as displaced in the anterior direction, leaving that vertebra out of alignment with the fifth lumbar vertebra (L5) 137 and the vertebra comprising the sacrum 135. To correct this misalignment, surgery is performed as in a simple discoctomy and the intervertebral disc (not shown) is exposed through a small laminotomy. The disc material is removed and any understanding of the nerve root is corrected. The posterior longitudinal ligament (not shown) and the disc cartilage are removed until the surface of the bodies 129 and 131 of the adjacent vertebrae (L4 and L5) 133 and 137, respectively, are exposed above and below the disc space. Using spreaders such as those disclosed in the international application No. PCT / US95 / 00347, the adjacent vertebrae 133 and 137 are distracted to open the disc space. The body 112 of the apparatus 110, having the first and second members 113 and 114 initially in the side-by-side relationship described above, is then inserted into the disc space with the upper part and the upper part thereof, i.e. the sides substantially first and second planes 132 linking the adjacent vertebrae 133 and 137 so that the teeth 138 formed on the third and fourth sides 134 of the body 112 extend into the disc space without linking the adjacent vertebrae 133 and 137. The implant is oriented in the disc space so that, when rotated as described below, the first member 113 is the portion of the body 112 that makes contact with the body 131 of L5 137 and the second member makes contact with the body 129 of L4 133 In other words, the body 112 is oriented so that the first member 113 is positioned in close proximity to the body 131 of the vertebra 137 which is aligned with the axis, or central line CL, of the spinal column, and the second member 114 is positioned in close proximity to the axis of the body 129 of the vertebra 133 that is out of alignment. The body 112 of the apparatus 110 is inserted until the middle portion of the first member 113 is positioned adjacent the concavity on the upper surface of the body 131 of L5 137. Using the adjustment knob 124, the mandrel 117 is then rotated to advance the second member 114, for example the portion having the width "6 greater in the anterior direction until the middle portion, for example the portion having the greater width" 6 of the second member 114, is positioned adjacent to the concavity of the surface bottom of the body 129 of L4 133. As noted above, the widest middle portion "6" of each of the members 113 and 114 comprising the body 112 of the apparatus 110 provides maximum bonding of the concavely shaped surface of the body of the body. vertebra when the body 112 is rotated approximately 90 °, as described below.According to the circumstances of each surgery, it may also be advantageous to "pre-adjust" the body 112 advancing the second member 114 to the second position in the amount of misalignment before inserting the body 112 of the apparatus 110 into the disc space. The magnitude of the patination of L4 133 relative to L5 137 is calculated using known methods and / or estimated from X-ray films or other images. Once the first and second members 113 and 114 are approximately aligned with each of the adjacent vertebrae 133 and 137 by placing the wide middle portion of each member in the respective concavities of the vertebrae, using the barrel 118 of the handle 111, the body 112 of apparatus 110 is rotated by approximately 90 ° to cause teeth 138 formed on surfaces 134 of first and second members 113 and 114 to link bodies 129 and 131 of respective adjacent vertebrae 133 and 137, as shown in FIG. Figure 11. Using the adjustment knob 124, the mandrel 117 is then rotated in the opposite direction to bring the second member 114 back toward the first parallel relationship, side by side with the first member 113, pulling the vertebra to which it is attached. linked, ie L4 133, back towards alignment with L5 137. The discoctomy and the laminotomy are preferably carried out bilaterally. In other words, the surgical procedure described above is carried out adjacent to the center line of the adjacent vertebrae such that the portion of the intervertebral disc that is withdrawn is "off center" relative to the bodies 129 and 131 of the vertebrae adjacent 133 and 137 respectively. An identical surgery is carried out on the other or second side of the center line of the adjacent vertebrae and the body 112 of a second apparatus 110 (not shown in the drawings for clarity) is inserted into the disc space after that second process. The adjacent vertebrae 133 and 137 are then aligned by rotation of the respective adjustment knobs 124 of both apparatuses 110 until the vertebrae are aligned. In this way, the body 112 of one of the two apparatuses 110 retains the adjacent vertebrae in alignment even after the removal of the other implant. Removal of the body 112 is achieved by rotation approximately 90 ° (preferably in the direction opposite to the direction of rotation which was used to cause the teeth 138 to link the respective adjacent vertebrae 133 and 137) so as to disengage the teeth 138 from L4 133 and L5 137. Although the body of the second apparatus remains in the disc space on the second side of the center line, an implant such as implant 22 (see Figures 1-4) is inserted into the disc space from which the body 112 was removed at the end of the applicator 52 with the flat surfaces 32 adjacent the bodies 129 and 131 of the adjacent vertebrae 133 and 137 and moved in an anterior-posterior direction so as to allow the implant 22 to be placed in the disc space in a position in which the middle portion, expanded and the ends of smaller widths 25 and 36 of the third and fourth sides 34 of the implant 22 contact the respective lower and upper surfaces of the bodies 129 and 131 of the adjacent vertebrae 133 and 137 when rotated approximately 90 ° using the applicator After rotation, the applicator 52 is detached from the implant 22 by unscrewing and throwing it back and out of the incision. The lock 124 is then inserted through the same incision and, using the slit 46 and the wedge 48, the bore 28 in the lock 24 and the bore 30 in the implant 22 are aligned, and the pin 26 is inserted and tightened to fastening the lock 24 to the implant 22, all as previously described. Once the monolithic implant 22 is locked in place on the first side of the center line of adjacent vertebrae 133 and 137, the body 12 of the second apparatus 10 on the second side of the center line, which has remained in its place through all this procedure, is then withdrawn. The disc space is then packed with chips of cancellous bone through this second side and a second monolithic implant 22 (also not shown) is inserted, placed, rotated and locked in place in the same manner as described above. If necessary, a small amount of a physiologically compatible adhesive of a type known in the art is applied to the cancellous bone chips just medial to the implants to close the remaining portion of the openings into the disc space. Referring now to Figures 12 and 13, there is shown an alternative embodiment of the spondylolisthesis reduction apparatus, generally indicated in reference numeral 110a of the present invention. Wherever possible, the component parts of the apparatus 110a are labeled with the reference number (and the designation "a") of the corresponding parts of the apparatus 110. The apparatus 110a comprises a handle Illa and a body 112a, the body 112a comprising members first (fixed) and second (movable) 113a and 114a, respectively. The second member 114a is mounted on a mandrel 117a placed in a longitudinal bore 116a in the arrow 115a by an oscillating joint 140a and moves relative to the first member 113a by the action of the threads 121a formed on the outer surface of the mandrel 117a, in the threads 120a formed in the arrow 115a of the handle Illa. The body 112a of the apparatus 110a is configured in the same substantially rectangular shape in cross section as the body 112 of the apparatus 110 and the component parts of the apparatus 110a operate in the same manner as the parts of the apparatus 110. The apparatus 110a also includes a plurality of fine serrations 142a formed on the opposing surfaces 144a and 146a of the first and second members 113a and 114a, respectively. The serrations 142a act to resist longitudinal movement of the second member 114a relative to the first member 113a.

Claims (33)

1. CLAIMS 1. A spinal disc stabilizer, comprising: an elongate cuboid implant having first, second, third, fourth, fifth and sixth sides that provide said implant with a substantially rectangular shape in cross section of minimum height defined by the sides first and second and maximum width defined by the third and fourth sides, the third and fourth sides being arched from one end of said implant to the other end of said implant to provide the middle portion of said implant with a width greater than the width of the ends of said implant; characterized in that said first, second and / or fifth or sixth sides define surfaces for linking a lock having a vertebra carrier surface therein formed; and means being provided for releasably mounting said lock at one end of said implant to prevent rotation of said lock relative to said implant, in use.
2. 2. The stabilizer of claim 1, wherein the third and fourth sides of said implant are provided with teeth.
3. The stabilizer of claim 1, wherein said lock is provided with a substantially planar implant bearing surface for contacting either the first or second side of said implant to prevent rotation of said lock relative to said implant.
4. 4. The stabilizer of claim 1, wherein the corners of said implant between the first, second, third and fourth sides are rounded.
5. The stabilizer of claim 1, wherein the end of said implant opposite the end where said lock is mounted is rounded.
6. The stabilizer of claim 1, wherein said bearing surface is oriented at an angle of approximately 90 ° to the first and second sides of said implant when secured thereto.
7. 7. The stabilizer of any of claims 1-6, in combination with an applicator for releasably mounting said implant.
8. 8. Apparatus for insertion between and alignment of adjacent vertebrae, comprising: a body formed of elongate members first and second side with side; an elongated handle having said first member mounted thereon; an elongate mandrel having said second member mounted therein and movable relative to and along the longitudinal axis of said handle to move said first member relative to said second member along its longitudinal axis; and a plurality of teeth formed on said body to link adjacent vertebrae when said body is inserted therebetween using said handle.
9. The apparatus of claim 8, wherein said body is substantially rectangular in cross section, the sides of said rectangular body forming the width of said body having a larger dimension than the sides of said body that they form the height of said body.
10. The apparatus of claim 8, wherein said teeth are formed on the sides of said body that form the height of said body.
11. The apparatus of claim 8, wherein the width of said body is smaller at the ends of said body than in the middle part of said body.
12. The apparatus of claim 11, wherein the teeth are formed on the sides of said body forming the height of said body and on the portion of said body forming the middle part of said body.
13. The apparatus of claim 8, wherein said handle is provided with a longitudinal bore and said mandrel is placed there.
14. The apparatus of claim 8, wherein said second member is provided with a rounded surface to receive a surface of complementary shape on said first member to hold said first and second members in alignment side by side during the movement of said first member with relationship to said second member.
15. 15. Apparatus for aligning adjacent vertebrae, comprising: an elongated handle having a longitudinal bore through it; a mandrel placed in the bore in said handle and movable therein; a body composed of first and second side with side members, the first member being mounted on the end of said handle and the second member being mounted on the end of said mandrel; and means formed in said body to selectively link adjacent vertebrae when said body is inserted therebetween to prevent relative movement between the respective first and second members and the respective adjacent vertebrae to which the first and second members are linked.
16. 16. The apparatus of claim 15, wherein said body is formed in a cross-section of substantially rectangular shape, said means linking vertebrae being formed on their opposite sides.
17. The apparatus of claim 16, wherein the height of said rectangular shaped body is less than the width of said body.
18. The apparatus of claim 16, wherein the sides of said rectangular body defining the height of said body are arched from the first end of said body to the second end of said body to provide said body with a width in the intermediate portion. at its ends which is greater than the width at the ends of said body.
19. 19. The apparatus of claim 15, wherein said vertebral linking means comprises teeth formed on the surface of said body.
20. The apparatus of claim 15, wherein the side of said second member that abuts said first member when said first and second members are side by side is provided with a semi-round recess to retain said first and second members in side relation with side, parallel, tight.
21. 21. A method of stabilizing two adjacent vertebrae after removal of a portion of the intervertebral disc to form a disc space therebetween, comprising the steps of: inserting an elongate, substantially rectangular implant, having a width greater than the height of the disc. implant towards the disc space with the implant oriented so that its upper part and its lower part connect with the bodies of the adjacent vertebrae; rotating the implant approximately 90 ° in the disc space to contact the bodies of the adjacent vertebrae with the sides of the implant; and securing a lock to the implant to prevent rotation of the implant relative to the lock, the lock having a surface to support against the body of the adjacent vertebrae to prevent rotation of the lock relative to the body of the adjacent vertebrae against which supports the surface of the lock.
22. 22. The method of claim 21, further comprising assembling an applicator at one end of the implant before inserting the implant into the disc space.
23. 23. The method of claim 22, wherein the implant is rotated by rotating the applicator.
24. 24. The method of claim 23, further comprising detaching the applicator from the implant prior to securing the lock to the implant.
25. 25. The method of any of claims 21-24, further comprising preventing the movement of the implant in the disc space along the axis of rotation of the implant.
26. 26. A method of aligning adjacent vertebrae after removing a portion of the intervertebral disc from each other to form a disc space, comprising the steps of: inserting an elongated body having means formed on its opposite sides to selectively link the adjacent vertebrae to the disk space towards the disk space, the body comprising first and second side members, the linking means extending into the disk space without linking the adjacent vertebrae; moving the second member relative to the first member until the first and second members are aligned approximately with each of the adjacent vertebrae; rotating the elongate body approximately 90 ° to cause the means of attachment of vertebrae therein to link the vertebrae; and moving the second member relative to the first member to align the vertebrae to which each member is linked.
27. The method of claim 26, wherein the first and second members are moved by moving a mandrel on which the second member is mounted.
28. The method of claim 26, wherein the body is elongated and wider in the middle portion than at its ends and the first and second members are aligned with the adjacent vertebrae by positioning at the point relative to the adjacent vertebrae in which the respective wider median portions link the respective adjacent vertebrae maximally.
29. 29. The method of claim 26, wherein the body is inserted into the disc space on one side of the center line of the adjacent vertebrae.
30. The method of claim 29, further comprising inserting a second body into a second side of the center line of the adjacent vertebrae.
31. The method of claim 30, further comprising replacing the first body with a monolithic body after aligning the adjacent vertebrae.
32. 32. The method of claim 31, further comprising replacing the second body with a monolithic body. The method of claim 26, further comprising removing the elongate body from the disc space and inserting an elongate, substantially rectangular implant having a width greater than the height of the implant into the disc space with the implant oriented in a manner that its upper part and its lower part link the vertebrae, rotate the implant, and secure a lock to the implant to prevent further rotation of the implant. Summary A removable, expanded, medium (22) disc implant with a substantially rectangular cross-sectional shape with a minimum height (H) and a width (W) greater than height, which is removably mounted to an applicator (52) for insertion in the anatomical region between two adjacent vertebrae (16, 18) from which a portion of the intervertebral disc has been removed. The implant is placed by means of anterior-posterior movement in the disc space to the position in which both the expanded middle portion and the smaller diameter end portions (25, 36) of the implant link the bodies (12, 14) of the adjacent vertebrae and then rotated to bring the sides (34) of the implant defining the height of the implant to be linked with the bodies of the adjacent vertebrae. A lock (24) is then secured to the implant to prevent its further rotation. In the event that the adjacent vertebrae need to be aligned prior to fusion, an elongated implant (112) is provided, which is longitudinally divided into side-by-side members (113, 114) movable relative to each other and being inserted into the disc space between two misaligned vertebrae (133, 137). The members are provided with teeth (138) to link the adjacent vertebrae and the implant formed by the two members side by side is rectangular in cross section, the height (H6) of the cross section rectangular being less than the width (W6) so that the implant can be inserted between the adjacent vertebrae with the dimension of least height oriented in the same direction as the axis of the spinal column and the dimension of greatest width at approximately right angle with that axis. One member is then moved relative to the other from the first position side by side along the longitudinal axis of the implant to a second position in which the members are aligned with the respective misaligned, adjacent vertebrae and the implant is rotated 90 ° to link the teeth to the bodies of the adjacent vertebrae. The two members are then brought back to the first position side by side to bring the vertebrae into alignment and the implant is rotated approximately 90 ° to disengage the teeth of the vertebrae for removal of the disc space.