JP2001524853A - Threaded fusion cage anchoring device and method - Google Patents

Abstract

(57) SUMMARY The present invention is a fixation device and method for stabilizing adjacent vertebral joints. The fixation device (12) includes a fixation plate (26) adapted to be secured to at least one spinal disc having a central portion (32), a protruding end portion (34) and at least one lateral extension (60). )including. The central portion includes fixation nuts (28) that secure the fixation plate to the spinal implant (24), and the end portion includes fixation screws (30) for securing the fixation plate to the spinal disc. The spinal implant is preferably a screwed fusion cage (24), wherein a locking nut is rotatably fixed to both the fixed plate and the screwed fusion cage. The central portion of the locking device and each protruding end portion have at least one locking tab (48, 52) for rotatably locking the locking nut and the locking screw. In addition, the central portion includes a plurality of projecting detents (42) along its outer periphery, which projecting detents engage with corresponding slots (44) provided in the threaded fusion cage.

Description

DETAILED DESCRIPTION OF THE INVENTION Cross Reference for Threaded Fusion Cage Fixation Device and Method Related Application This patent application seeks benefit from US Provisional Application No. 60 / 044,190, filed April 25, 1997. 1. TECHNICAL FIELD The present invention relates to devices and methods for stabilizing a fusion insert placed for the purpose of fusing two adjacent joints (eg, vertebrae of the spinal column), and more particularly to a screwed fusion cage fixation device. 2. Background of the Related Art Degeneration of joints, such as spinal segments, due to deterioration of the hard and soft tissues of the joint complex, can cause severe local or dissipative pain as the segments move. Typically, a joint complex consists of two bone structures and a flexible movable part interposed between them. In the spine, the bone structure is the vertebra and the movable part is the disc. The intervertebral disc consists of a multi-layered outer ligament belt, or annulus, having a concentric laminar structure resembling the layers of an automobile tire. At the core of the disc is a small mass of flexible fibrous gel, which is contained within an annulus ring. The fibrous gel mass, or disc nucleus, is a hydrogel that, when it absorbs water, applies considerable swelling pressure to lift the vertebrae, balancing the forces exerted on the disc by gravity and the contraction of the surrounding muscles. I have. Therefore, hydrogels are important to resist the potentially destructive forces applied to the vertebrae. Unfortunately, as the disc degrades, the hydrogel contained therein begins to lose its water-binding capacity and contracts. This contraction causes loosening of the annulus fibrils, which allows for an abnormal range of movement of the segment with buckling and delamination of the overlapping layers. Even tearing of only a few of the approximately 12-20 concentric laminar structures of the annulus can result in herniation of the compression core material outward through the annulus defect. Conventional procedures for treating degenerative vertebral discs involve fusion of the discs to stop all movement of the bone segments. The most efficient method of fusion is to place the bone or bone-inducing agent inside a support device surgically implanted in the center of the disc. This support device structure eliminates the degenerated nucleus, holds the bone material in place, protects the bone from disintegration, protrusion and invasion by the remaining soft tissue of the disc, and allows the opposing vertebrae to fuse quickly. Has become. A preferred intervertebral fusion device is a vertebral fusion cage. For example, U.S. Patent No. 4,961,740 to Ray, which is incorporated herein by reference, discloses a screwed vertebral fusion cage. The lumen of the cage is used to anchor the bone graft material, allow the bone to grow through and across the surgically evacuated nuclear cavity between adjacent vertebrae. You. Unlike non-threaded fusion cages that are hammered or tapped, insertion of the screwed vertebral fusion cage is more efficient because the threaded outer surface allows for easy adjustment of the cage's penetration depth into the disc space It is a target. The threaded outer surface also prevents the cage from protruding or extruding. In addition, the implanted bone packed into the screwed fusion cage emerges or protrudes through a hole in the cage and comes into close contact with the bone of the adjacent vertebral body. When the cage is inserted into a perforated or internally threaded disc, the side wall of the cage is oriented horizontally and facing the disc space. These cage sidewalls are occluded (i.e., do not include any openings), and thus provide a barrier to the potential implantation of the remaining disc tissue into the contained implant area, as well as the union of adjacent vertebrae. Prevent interference or weakening it. In recent years, the importance of safely securing fusion cages / grafts within vertebrae has increased. During the fusion cage implant procedure, the surgeon may think that implanting the fusion cage alone did not provide sufficient space stabilization. In such situations, additional instruments are needed to improve the stability of the vertebra and cage. Examples where additional stabilization measures should be taken include: Weak vertebrae, cage does not fit tightly into vertebral space, or the central concave surface of the disc space is too deep for good penetration of the cage along the length of the ventral and dorsal sides of the disc space This is the case when it cannot be done. In such cases, the surgeon is usually forced to install additional fusion devices such as pedicle screws, rods or vertebral plates to prevent cage escape and improve the opportunity for good fusion. This additional step in the surgical procedure increases complexity, potential risks and operating costs. Embodiments of the present invention solve these and other related problems and provide a simple, easily adaptable instrument that achieves improved cage fixation and intervertebral disc space stabilization during surgery. SUMMARY OF THE INVENTION An object of the present invention is directed to a fixation device and system for stabilizing adjacent vertebral joints. The fixation device includes a fixation plate adapted to be secured to at least one spinal disc having a central portion, a protruding end portion and at least one lateral extension. The central portion includes fixation nuts for securing the fixation plate to the spinal implant, and the end portion includes fixation screws for securing the fixation plate to at least one spinal disc. The spinal implant is preferably a screwed fusion cage, wherein the fixation nut is rotatably secured to both the fixation plate and the screwed fusion cage. In this locking device, the central portion and each protruding end portion preferably have at least one locking tab for rotatably locking the locking nut and the locking screw. In addition, the central portion further includes a plurality of projecting detents along its outer peripheral surface, which detents engage corresponding slots in the threaded fusion cage. The present invention is also directed to a method of implanting a fixation device in at least one spinal disc having a spinal implant. The method includes providing a fixation plate having a central portion and a protruding end portion. The central portion includes a fixation nut that secures the fixation plate to the spinal implant and at least one locking tab along the circumference. The end portion includes a fixation screw that secures the fixation plate to the at least one spinal disc and at least one locking tab provided along an outer circumference. The method further includes positioning the fixation plate in a corresponding relationship to the at least one spinal disc and the spinal implant, securing the fixation nut to the spinal implant, and securing the fixation screw to the at least one spinal disc. including. Next, the locking tab is positioned by engaging the locking nut and the locking screw. BRIEF DESCRIPTION OF THE DRAWINGS The objects and features of the invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages, both as to its structure and method of operation, may be best understood by referring to the following description, taken in conjunction with the accompanying drawings. In the accompanying drawings: FIG. 1 shows several adjacent vertebral segments and two fixation devices according to the invention mounted on the vertebral segment; FIG. 2 shows a bottom view of the fixation device according to the invention. FIG. 3 is a perspective view showing the rear side of the fusion cage and the associated drive shaft for inserting the fusion cage; FIG. 4 is a plan view of a fixing nut related to the fixing device of the present invention; FIG. 5 is a bottom view showing another embodiment of the fixing device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the devices and methods disclosed herein are described with respect to orthopedic spinal fusion procedures and instruments. However, it is contemplated that the present invention is applicable to a wide variety of procedures, including, but not limited to, joint repair, pseudoarthrosis, facial reconstruction, spinal stabilization, and the like. In addition, the methods and devices of the present invention provide access to the surgical site for both incisional and minimal incisional procedures, including endoscopic and arthroscopic procedures performed through a cannula or small incision. It is thought that it can find a use. The following description describes the screwed fusion cage fixation device utilized in performing spinal fusion, and then describes a preferred method of implanting the screwed fusion cage fixation device according to the present invention. Hereinafter, preferred embodiments of the present invention shown in the accompanying drawings will be described in detail. Turning now to the figures, where like components are designated by like reference numerals throughout the various figures. Attention is first directed to FIGS. 1 and 2. The anterior surface of a fused vertebra 10 having two implanted fixation devices 12 across three adjacent spinal segments 14, 16, 18 is shown schematically in FIG. The vertebral segments 14,16,18, for example the cervical vertebral segments, are separated by two intervening disc spaces 20,22. A threaded fusion cage 24 is implanted between the intervertebral segments 14, 16 and between the intervertebral segments 16, 18, respectively, across the intervening disc spaces 20, 22, with particular reference to FIGS. The fixing device 12 of the present invention generally includes a fixing flute 26, a fixing nut 28 and a fixing screw 30. The fixation plate 26 is substantially in the shape of the numeral eight and includes a large central hole 32 and an extension arm 34. Each extension arm 34 has at least one fixing screw hole 36 for receiving the fixing screw 30. The fixation device 12 disclosed herein is preferably made of a suitable biocompatible rigid material, such as a titanium-titanium alloy, stainless steel, a ceramic material or a rigid polymeric material. The fixation plate 26 includes a fusion cage engagement surface 38 (ie, bottom surface, FIG. 2) and a fixation nut engagement surface 40 (ie, top surface, FIG. 1). The fusion cage engaging surface 38 includes a projecting detent or pin 42 for engaging a slot 44 (FIG. 3) of the fusion cage 24. It is preferable that the projecting detent 42 is provided along the outer peripheral surface of the center hole 32. The fixation device 12 and its associated threaded fusion cage 24 of the present invention can include any number of detents 42 and corresponding slots 44, but the greater the number, the more detents 42 and corresponding slots 44 The fixation relationship between the fusion cage 24 and the fixation plate 26 can be optimized without a large angular change in the position of the graft fusion cage 24. That is, by changing the number of the slots 44 of the fusion cage 24 and the number of the detents 42 of the fixing plate 26, the angular relationship between the fixing plate 26 and the fusion cage 24 is incrementally changed. In this manner, a small change in the angular orientation of the fixation plate 26 relative to the fusion cage 24 is beneficial, and the optimal initial penetration depth of the graft fusion cage 24 into the joint space may be due to implantation of the fixation device 12. There is no need to change significantly for sexual rotation. As best shown in FIG. 1, the orientation or angular displacement of the fixation plate 26 with respect to the longitudinal axis of the spine is adjusted accordingly to provide adequate stability of the fusion cage 24 to adjacent vertebrae. It can vary from 0 degrees to 80 degrees. This wide range of angular displacements allows the fixation plate 26 to be safely positioned with respect to certain anatomical structures, such as vertebral endplates, nearby running nerves or bone obstacles. In this regard, when the pair of fusion cages 24 are implanted at the same level, the fixation plates 26 are preferably set substantially parallel to one another. Therefore, since a wide range of angular displacements can be performed, the formation of the bending angle between the fixing plates 26 can be changed, and the fixing screw 30 can be optimally installed in the vertebral body. Similarly, when two single cages 24 or a pair of cages 24 are placed at adjacent spinal levels, the common flexion angle of the fixation plate 26 is altered to optimally place the fixation screws 30 in adjacent vertebral bodies. Can be. Both the cage 24 and the fixation plate 26 can be set by surgical access to the lumbar spine from anterior or posterior. However, in the thoracic and cervical regions, only the anterior method is recommended. With particular reference to FIGS. 1, 2 and 4, the fixation device 12 of the present invention is installed in an implanted fusion cage 24 and attached to each fusion cage 24 with a threaded locking nut 28. The fixing nut is screwed into a corresponding thread provided on the inner peripheral surface of the fusion cage 24. Once installed, the locking nut 28 is secured against loosening by a plurality of malleable nut locking tabs 48 provided on opposite sides of the center hole 32 of the fixing plate 26. By bending the nut locking tab 48 over the lock nut 28 to engage at least one flat portion of the collar 50 of the lock nut, the lock nut 28 can be prevented from rotating and loosening. The extension arm 34 of the fixation plate 26 includes a fixation screw hole 36 through which a fixation screw 30 having a slotted head is screwed to a vertebral body in a convenient and secure position. Similarly, the fixing screw 30 is prevented from coming off by a plurality of malleable screw locking tabs 52 provided on both sides of the fixing screw hole 36 provided in the extension arm 34. The orientation of the locking tabs 52 is such that when the locking tabs 52 are bent over the locking screws 30, at least one of the locking tabs 52 is securely engaged with at least one slot provided on the head of the locking screws 30. Decide to engage. The fixation device 12 provides the additional support needed to fully stabilize the fusion cage 24 with respect to the spinal segments 14,16,18. By traversing the intervening disc space 20, 22 and attaching the fixation screw 30 to the vertebral body at a location protruding from the fusion cage 24, the mechanical fixation strength is significantly increased. In essence, the fixation device 12 prevents the vertebrae from moving apart when post-operative spinal movement occurs, thus preventing the vertebrae from moving away from the fusion cage 24. In addition, the fixation plate 26 significantly increases the overall initial stiffness of the fusion cage system. FIG. 3 shows the fusion cage 24 into which a drive shaft 54 is inserted for seating the screwed fusion cage 24 in a hole created between adjacent surfaces of the spinal segment. A plurality of slots 44 provided on the outer edge 62 of the fusion cage 24 correspond to projecting tabs 56 on the drive shaft 54. The fusion cage 24 attaches to a retractable central threaded coupler 58. This coupler rotates freely within the drive shaft 54. The fusion cage slot 44 engages a protruding tab 56 on the drive shaft 54. When the drive shaft 54 rotates, the threaded coupler 58 engages a corresponding fusion cage thread 46 provided along the inner circumference of the fusion cage 24. The engaged slot 44 and projecting tab 56 are used to rotationally drive the fusion cage 24 into position, after which the threaded coupler 58 is loosened to release the drive shaft 54, the threaded coupler 58 from the fusion cage 24. . If the positioning of the fusion cage 24 requires further adjustment, the drive shaft 54 can be engaged with the fusion cage 24 via the protruding tab 56 and the slot 44 and torque can be applied to the fusion cage 24 to move it to its final position. . At this time, it is not necessary to re-attach the threaded coupler 58 to the fusion cage 24 securely. FIG. 5 shows an additional embodiment for the fixing plate 26. In FIG. 5, components similar to those of the previous embodiment are denoted by the same reference numerals. The fixing plate 26 further has an additional lateral extension or tongue 60. The tongues 60 are forcibly pushed into the intervertebral disc spaces 20,22 when the fixation nut 28 is tightened onto the fixation plate 26 and into the fusion cage 24 so that the intervertebral disc spaces 20,22 are forced into place. Can be further stabilized. The space between the edges of the lateral tongue 60 may be additional bone-growth material (allograft) such as cancellous bone or cartilage from another human or additional material such as cancellous bone or cartilage from the same patient. Bone growth material (autograft) can be accommodated. The autograft helps to obtain a better fusion of the spinal segments 14,16,18. Implantation of the Fixation Device In the following, the implantation of the fixation device 12 of the present invention will be described with reference to a single fixation device 12, but with multiple fixation devices 12 across one or more spinal discs or spinal segments 14,16,18. Can be transplanted. Standard surgical techniques are used to access the surface of the vertebral body to be fused. This surgical method includes a method of approaching the cervical spine and thoracic vertebra from anterior, and a method of approaching the lumbar vertebra from anterior or posterior. One or more holes are drilled into the selected intervertebral space and tissue debris is removed therefrom. For certain fusion cage implants, the holes may be tapped to match the threads of the fusion cage. In other cases, a self-tapping fusion cage may be used. In that case, no threading is necessary. As shown schematically in FIG. 3, the threaded fusion cage 24 having a slot 44 in the outer edge 62 engages a protruding tab 56 at the distal end of the drive shaft 54 and is threaded when inserted into the intervertebral space. A coupler 58 is threaded into the inner thread 46 of the fusion cage 24 to secure the fusion cage 24 to the drive shaft 54. Next, the fusion cage 24 is screwed into an optimal position in the prepared intervertebral foramen, and the screw-in coupler 58 and the drive shaft 54 are removed. The placement of the fixation device 12 depends on the actual position of the implanted fusion cage 24. When a single fusion cage 24 or a pair of fusion cages 24 is implanted at multiple vertebral levels, the fixation plate 26 is oriented parallel through multiple fusion vertebral segments. A protruding detent 42 located along the engagement surface 38 of the fixation plate 26 engages equally spaced slots 44 located on the outer edge 62 of the implanted fusion cage 24. The orientation of the fixation plate 26 and the fusion cage 24 relative to the longitudinal axis of the spine is angularly fine-tuned to maintain clearance of any anatomy. This angle adjustment may be a change of only a few degrees from the initial position of the fusion cage 24. Before or after attachment to the fusion cage 24, the fixation plate 26 can be slightly bent to conform to the curved surface of the vertebral body or create clearance from other adjacent structures. Once the fixation plate 26 has been positioned over the graft fusion cage 24, the fixation nut 28 is threaded through the central hole 32 of the fixation plate 26 and threaded into the corresponding thread 46 portion of the graft fusion cage 24. Since the fixation device 12 and the fusion cage 24 can include a plurality of projecting detents 42 and corresponding slots 44, the rotation of the fixation plate 26 is incremented to position the fixation plate 26 in the most advantageous position relative to the fusion case 24 position. You can take it to Rotation or adjustment of the fixation plate 26 with respect to the fusion cage 24 is performed before the fixation nut 28 is tightened to the fixation plate 26 and the fusion cage 24. Next, a pilot hole is drilled in the vertebra through the fixing screw hole 36 of the extension arm 34. The extension arm 34 is then screwed into the vertebra and mated with a suitable length of the fixation screw 30 through the fixed hole 36. At this time, the nut locking tab 48 and the screw locking tab 52 are bent with respect to the edge of the fixing nut 28 and the slot of the fixing screw 30, respectively, to prevent any of them from being loosened or removed. Next, the bone inducing material is packed into the fusion cage 24 through the center hole 32 and the center of the fixation nut 28. Alternatively, the bone inducing material may be packed into the fusion cage 24 prior to insertion. With respect to the alternative embodiment of the anchoring device 12 shown in FIG. 5, similar components and methods are consistent with those of the previously described embodiment and are indicated by similar reference numerals. In the implantation of the fixation plate 26 in the body, a bone inducing material placed laterally along the fusion cage 24 before attaching the fixation plate 26 to the fusion cage 24 is further added. It should be understood that various modifications may be made to the embodiments disclosed herein. For example, the locking device 12 of the present invention may include any number of nut locking tabs 48 and screw locking tabs 52 to better secure each nut 28 and screw 30 respectively. The fixation device 12 also includes one or more extension arms 34 that are radially displaced in an angular relationship from the central hole 32 to better enhance the fixation device 12, the fusion cage 24 and the associated bone segments 14,16,18. May be stabilized. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the appended claims.

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Claims (1)

[Claims] 1. A fixation device for use with a spinal implant, the device comprising:     A fixation plate having a central portion and at least one protruding end portion,     The central part can be attached to the spinal implant,     Each end portion includes an anchoring fastener that is coupled to the bone segment.   A fixing device, characterized in that: 2. The fixing device according to claim 1,     A fixation device comprising two protruding end portions. 3. The fixing device according to claim 1,     The fixation device wherein the spinal implant is a screwed fusion cage. 4. The fixing device according to claim 1,     A fixing device, wherein the fixing fastener is a bone screw. 5. The fixing device according to claim 1,     The central portion and each protruding end portion further include at least one locking tab.   Characteristic fixing device. 6. The fixing device according to claim 1,     The center portion further includes a plurality of projecting detents along its outer peripheral surface.   And fixing device. 7. The fixing device according to claim 1,     The fixing plate further comprises at least one lateral extension   Fixing device. 8. A system for stabilizing adjacent vertebral parts,     A spinal implant adapted to anchor between adjacent vertebral portions;     A central portion and a protruding end portion adapted to adhere to adjacent vertebrae   And a fixing plate having     Central portion includes fixation nut for fixing fixation flute to spinal implant   Yes,     End portion includes fixation screws to secure fixation plate to adjacent vertebral portion   A fixing device, characterized in that the fixing device is provided. 9. An anchoring system according to claim 8, wherein     The fixation device wherein the spinal implant is a screwed fusion cage. Ten. The anchoring system according to claim 9, wherein:     Locking nut is rotatably secured to the locking plate and screwed fusion cage.   A fixing device, characterized in that it is fixed. 11． An anchoring system according to claim 8, wherein     A fixation device wherein each end portion is secured to a spinal disc. 12． An anchoring system according to claim 8, wherein     The central portion and each protruding end portion may further include at least one locking tab.   And a fixing device. 13. An anchoring system according to claim 8, wherein     The center portion further includes a plurality of projecting detents along its outer peripheral surface.   And fixing device. 14. 9. The fastening system according to claim 8, wherein     The fixing plate further comprises at least one lateral extension   Fixing device. 15． A method of implanting a spinal implant, comprising:     Inserting a spinal graft between adjacent vertebrae;     Position the fixation plate in a corresponding relationship to the spinal implant and adjacent vertebrae   The fixing plate includes a central portion and a protruding end portion.   The central part of the body contains one fixation nut to secure the fixation flute to the spinal implant.   End portion includes fixation screws to secure fixation plate to adjacent vertebral portions   Process and     Securing the fixation nut to the spinal implant;     Securing the fixation screw to an adjacent vertebral portion.   . 16． The spinal column graft transplantation method according to claim 15,     The fixing plate has at least one at least one along an outer peripheral surface of the central portion and the protruding end portion.   Includes two locking tabs, and     The step of positioning the locking tab in a state engaged with the fixing nut and the fixing screw is described.   A method, further comprising: