US20080058810A1 - Bone screw systems and methods of use - Google Patents

Abstract

A bone plating system is provided that permits maintenance of a compression force while also accommodating bony subsidence, among other features. Methods of implantation are also provided that improve alignment and placement during implantation and avoid maneuvers that weaken the vertebral bodies. A modular distraction screw is placed during the initial stages of surgery when all relevant landmarks are still intact. After completion of the surgical bone work, a proximal end of the distraction screw is detached, leaving a protruding distal segment implanted in the centerline of the vertebral bodies above and below the newly fused disc space. A bone plate is guided into proper position relative to the upper and lower vertebra by attaching the bone plate to the protruding distal segments. The distal segments of the distraction screws are tightened onto the plate and the plate is held stationary while bone screws are placed. The bone plating system is also extendable, allowing additional bone plates to be placed and coupled with existing plate components to create a multi-level plating system. Additional bone plates may be placed contemporaneously or during a subsequent surgical procedure.

Description

REFERENCE TO PRIORITY DOCUMENT
• The present application is a continuation of U.S. patent application Ser. No. 10/755,080, filed Jan. 10, 2004, which claims priority to U.S. provisional patent application Ser. No. 60/439,030 filed on Jan. 10, 2003, and which is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/683,325 filed on Oct. 10, 2003, each of which is incorporated herein by reference in its entirety.
BACKGROUND
• The present invention is directed at skeletal plating systems, components thereof, and method of implant placement. These systems are used to adjust, align and maintain the spatial relationship(s) of adjacent bones or bony fragments during healing and fusion after surgical reconstruction of skeletal segments. Such systems may be comprised of bone distraction devices, skeletal plates, bone screws and/or bone cables, bone screw-to-plate locking mechanisms, and any additional instruments needed for implant placement.
• Whether for degenerative disease, traumatic disruption, infection or neoplastic invasion, surgical reconstructions of the bony skeleton are common procedures in current medical practice. Regardless of anatomical region or the specifics of the reconstructive procedure, many surgeons employ an implantable skeletal plate to adjust, align and maintain the spatial relationship(s) of adjacent bones or bony fragments during postoperative healing. These plates are generally attached to the bony elements using bone screws or similar fasteners and act to share the load and support the bone as osteosynthesis progresses.
• Available plating systems used to fixate the cervical spine possess several shortcomings in both design and implantation protocols. These plates are manufactured and provided to the surgeon in a range of sizes that vary by a fixed amount. This mandates that a large number of different size plates must be made and inventoried—adding to cost for manufacturer, vendor, and end user (hospitals). More importantly, the pre-manufactured sizes may not precisely fit all patients forcing surgeons to choose between a size too small or too large.
• Plates used to attach three or more vertebrae after removal of two or more discs are manufactured with an equal distance between screw holes in the vertical plane. For example, the distance between the pair of C3 (cervical bone #3) and the pair of C4 (cervical bone #4) screws is equal to the distance between the C4 and C5 (cervical bone #5) screws as well as the distance between the C5 and C6 (cervical bone #6) screws and so forth. This not only ignores the known anatomical difference in size between bones at different levels but also fails to anticipate that a patient's unique pathology may require more extensive bony resection at one or more levels, further adding to these differences. Thus, selection of a plate with a suitable total length may still produce improper fit at one or more levels.
• Current cervical plates are not modular, and will not permit addition of one plate to another for extension of the bony fusion at a future date. It is accepted that fusion of a specific spinal level will increase the load on, and the rate of degeneration of, the spinal segments immediately above and below the fused level. As the number of spinal fusion operations have increased, so have the number of patients who require extension of their fusion to adjacent levels. Currently, the original plate must be removed and replaced with a longer plate in order to fixate the additional fusion segment. This surgical procedure necessitates re-dissection through the prior, scarred operative field and substantially increases the operative risk to the patient. Further, since mis-alignment of the original plate along the vertical axis of the spine is common, proper implantation of the replacement plate often requires that the new bone screws be placed in different bone holes. The empty holes that result may act as stress concentration points within the vertebral bodies, as would any empty opening or crack within a rigid structural member, and lead to bone fracture and subsequent screw/plate migration.
• Current plates may provide fixation that is too rigid. Since bone re-absorption at the bone/graft interface is the first phase of bone healing, fixation that is too rigid will not permit the bone fragments to settle and re-establish adequate contact after initial bone absorption. This process is known as “stress shielding” and will lead to separation of the bony fragments and significantly reduce the likelihood of bony fusion. Unsuccessful bone fusion may lead to construct failure and will frequently necessitate surgical revision with a second operative procedure.
• Benzel (U.S. Pat. Nos. 5,681,312, and 5,713,900) and Foley (Pat. Applic. Pub. No. US2001/0047172A1) have independently proposed plating systems designed to accommodate bone settling. In either system, however, bony subsidence can be expected to cause one end of the plate to migrate towards an adjacent, normal disc space. This is highly undesirable since, with progressive subsidence, the plate may overlap the disc space immediately above or below the fused segments and un-necessarily limit movement across a normal disc space. Clearly, accommodation of bone settling at the plate's end is a sub-optimal solution.
• Yuan et al described a multi-segmental plate consisting of two sliding parts in U.S. Pat. No. 5,616,142. While intended to be absorbable, this design may permit excessive play between the sliding segment and encourage bone screw loosening. In addition, this device does not permit application and maintenance of a compressive force across the bony construct. Baccelli noted these deficiencies in U.S. Pat. No. 6,306,136 and proposed a rigid plate capable of maintaining bony compression. However, the latter plate did not permit subsidence.
• The implantation procedures of conventional plates in prior art practice have additional shortcomings. Distraction screws are used during disc removal and subsequent bone work and these screws are removed prior to bone plate placement. The empty bone holes created by removal of the distraction screws can interfere with proper placement of the bone screws used to anchor the plate and predispose to poor plate alignment along the long axis of the spine. This is especially problematic since the surgical steps that precede plate placement will distort the anatomical landmarks required to ensure proper plate alignment, leaving the surgeons with little guidance during plate implantation. For these reasons, bone plates are frequently placed “crooked” in the vertical plane and often predispose to improper bony alignment. Correct plate placement in the vertical plane is especially important in plates intended to accommodate bony subsidence, since the plate preferentially permits movement along its long axis. Thus, when the vertical axis of the plate and that of the spine are not properly aligned, the plate will further worsen the bony alignment as the vertebral bones subside.
• The empty bone holes left by the removal of the distraction screws also act as stress concentration points within the vertebral bodies, as would any empty opening or crack within a rigid structural member, and predispose them to bone fracture and subsequent screw/plate migration. Improper plate placement and bony fractures can significantly increase the likelihood of construct failure and lead to severe chronic pain, neurological injury, and the need for surgical revision with a second procedure.
• In view of the proceeding, it would be desirable to design an improved bone plating system and placement protocol. The new device should provide ease of use, reliable bone fixation, adjustable length, modular design, and the ability to accommodate and control bone settling. The design should also maximize the likelihood of proper plate placement and avoid maneuvers that weaken the vertebral bodies. No current plating system addresses all of these concerns. Therefore, what is needed is a system and method that overcomes these significant problems found in the conventional systems as described above.
SUMMARY
• The present invention is that of a modular bone plate of adjustable length. The current invention provides a bone plate that permits maintenance of a compression force while also accommodating bony subsidence, among other features. A modular distraction screw is used for the bone work, including fusion, prior to plate placement. The distraction screw is placed as the first step of surgery when all relevant landmarks are still intact. After completion of the bone work, a proximal end of the distraction screw is detached, leaving a distal segment still implanted in the vertebral bodies above and below the newly fused disc space. The plate is guided to proper position along the upper and lower vertebra by the attached distal segments. The distal segments of the distraction screws are tightened onto the plate and the plate is held stationary while bone screws are placed.
• The distal segments act as an anchor to guide the bone plate into the correct placement position and serve to hold the plate stationary while the plate's bone screws are placed. Since the distraction screws were placed with intact surgical landmarks, use of the distal segments to guide the plate significantly increases the likelihood of proper plate placement. In addition, the distal segments of the distraction screws serve as additional points of fixation for the plate and leave no empty bone holes which give rise to stress concentration points that further weaken the vertebral bodies.
• After the plate is attached to the upper and lower vertebras, the plate is set to the desired length and the two segments are locked together. If application of a compressive force is desired, the plate can be used to maintain the force across the vertebral bodies by simply locking the plate segments after applying compression. Occasionally, surgeons are confronted with a grossly unstable spine from the patient's unique pathology and choose to forgo subsidence in favor of a more fixed and rigid construct. In these situations, plate placement is essentially complete and requires no further steps. More commonly, subsidence is desired and release of a second locking screw permits the plate to accommodate bony subsidence. Unlike current plating systems which provide either a rigid plate or one capable of subsidence, the current invention permits either option by the simple turn of one screw. Further, when subsidence is chosen, this plate will not overlap the adjacent disc space with bone movement, since subsidence is accommodated at the level of settling bone and not at the plate's end.
• Extension of the fusion at a later date is easily accomplished without plate removal. An adapter is placed at either end of the plate that can couple with either a modified distraction screw or an additional bone plate. Fusion extension is started by connecting a modified distraction screw to the coupler at-the end of the plate immediately adjacent to the disc to be removed. A modular distraction screw is inserted into the adjacent vertebra and a discectomy and subsequent fusion are performed within the intervening disc space. After completion of the, bone work, the modified distraction screw is removed leaving the bare coupler on the end of the plate. The proximal segment of the distraction screw is also removed leaving the distal segment attached to the adjacent vertebral body. An extension plate is used to span the space between the distal segment of the distraction screw on the adjacent vertebra and the end-coupler on the original plate. In this way, the fusion is extended and the newly fused segment is fixated without removal of the original plate. Further, the end-coupler can used to correct for any improper (“crooked”) placement of the original plate by rotating the extension plate into the true vertical.
• The preceding discussion has focused on removal of one disc with fusion and plate fixation of the vertebral bodies above and below the evacuated disc space. However, “multi-level” procedures (that is, removal of two or more discs and fusion of three or more bones) can also be addressed with this system. Removal of two or more discs is accomplished by the step-wise removal of individual discs until all pathological levels have been addressed. Modular distraction screws may be used at each vertebral level if desired, but their use is required only at the upper and lower-most vertebras while conventional distraction screws can be used at all intervening levels. After completion of the bone work, the proximal segments of the distraction screws are removed leaving the distal segments attached to the upper and lower-most vertebral bodies. Regardless of the type of distraction screw used at the other levels, that screw is completely removed after the completion of the bone work. The empty bone holes left at these intervening level are far less important than those produced at the upper and lower-most vertebra, since the latter share a disproportionate share of the load.
• In one embodiment of the present invention, plates used for multi-level procedures will have an expandable/subsidence mechanism overlying each disc space that is fused. The plate is guided to proper position along the upper-most and lower-most vertebra by the attached distal segments—as described above for single level procedures. The distal segments of the distraction screws are tightened onto the plate and the plate is held stationary while bone screws are placed into the upper and lower-most vertebras. In this way, the plate is fixed at each end. Depending on surgeon preference, fixation of the intervening vertebral levels may be started from either end of the plate. For illustration, fixation will be started inferiorly. The plate segment intended to fixate the vertebra immediately superior to the lower-most vertebra is moved into optimal position. The sliding mechanism between this segment and the plate segment attached to the lower-most vertebra is then locked, fixing these two segments together. Bone screws can then be easily and rapidly placed into the vertebra immediately superior to the lower-most vertebra. The process is repeated at each of the remaining vertebra. If compression is desired across the construct, it's applied across the upper and lower-most vertebras prior to placement of the bone screws into any of the intervening vertebra. Compression is maintained until all the vertebra have been fixed to the plate. Once all sliding mechanisms have been locked, the compression device may be released and the force will be maintained by the plate. If a rigid construct/plate is desired, then plate placement is complete. However, if subsidence is needed, the (subsidence) locking screw is opened at each level where bone subsidence is desired. In this way, this plate design permits the surgeon to choose the exact vertebral levels to fixed rigidly and those level that will be allowed to accommodate subsidence. Further, it permits the distance between the bone screws at different levels to be custom fit for the individual patient. These features are not shared by any currently available plating system.
• In other embodiments, multi-level plates will be designed without a sliding/subsidence mechanism at every level. Instead, one or more sliding/subsidence mechanism(s) will be used to affect two or more levels by use of a slotted borehole configuration between levels. At each end, however, the plate will remain rigidly fixed to bone. In this way, subsidence continues to be accommodated at the level of bony movement and the plate remains stationary at each end.
• All embodiments of the multi-level plates will preferentially, but not necessarily, contain central channels to accommodate the distal segment of the modular distraction screw and end-couplers so that extension of the fusion at a future date remains possible.
• In other embodiments of the present invention, additional plate design, different locking mechanisms, and alternative end couplers are shown and described. Other embodiments, in addition to those illustrated, can also be used.
• The plating systems described in the present invention provide ease of use, reliable bone fixation, adjustable length, modular design, and the ability to accommodate and control bone settling. These designs will also maximize the likelihood of proper plate placement, avoid maneuvers that weaken the vertebral bodies, and provide a significant advantage over the current and prior art. These and other features of the present invention will become more apparent from the following description of the embodiments and certain modifications thereof when taken with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• The details of the present invention, both as to its structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which:
• FIG. 1 is a partial side view of a disassembled distraction screw according to an embodiment of the invention;
• FIG. 2 is an assembled distraction screw and a cross sectional side view of the assembled distraction screw according to an embodiment of the invention;
• FIGS. 3A-3B are close up views of the connector portion of the elongated body of a distraction screw according to an embodiment of the invention;
• FIGS. 4A-4B are partial views of a distraction screw removal tool according to an embodiment of the invention;
• FIGS. 5A-5B are exploded perspective views of a bone plate according to alternative embodiments of the invention;
• FIGS. 5C-5D are perspective views of a mounted bone plate according to alternative embodiments of the invention;
• FIGS. 6A-6F are top, bottom, and side views of angled bracket plate components according to an embodiment of the invention;
• FIG. 7A-7C are top, bottom, and side views of square bracket plate components according to an embodiment of the invention;
• FIGS. 8A-8B are top views of a third plate component according to an embodiment of the invention;
• FIGS. 9A-9B are perspective views of a modified distraction screw attached to a bone plate according to an embodiment of the invention;
• FIG. 10A is a partial side view of a modified disassembled distraction screw according to an embodiment of the invention;
• FIGS. 10B-10D are partial side views of a modified assembled distraction screw according to an embodiment of the invention;
• FIG. 10E is a close up view of a modified distraction screw according to an embodiment of the invention;
• FIG. 11A is a perspective view of an offset, modified distraction screw according to an embodiment of the invention;
• FIG. 11B is a perspective view of an offset, modified distraction screw attached to a bone plate according to an embodiment of the invention;
• FIG. 12A is an exploded perspective view of a bone plate according to an embodiment of the invention;
• FIG. 12B is a top view of a first bone plate component according to an embodiment of the invention;
• FIG. 12C is a bottom view of a first bone plate component according to an embodiment of the invention;
• FIG. 12D is a top view of a second bone plate component according to an embodiment of the invention;
• FIG. 12E is a bottom view of a second bone plate component according to an embodiment of the invention;
• FIG. 13A is a sectional view of a bone plate according to an embodiment of the invention;
• FIG. 13B is a close up sectional view of the locking mechanism of a bone plate according to an embodiment of the invention;
• FIG. 14A is a perspective view of a mounted bone plate in an open position according to an embodiment of the invention;
• FIG. 14B is a perspective view of a mounted bone plate in a closed position according to an embodiment of the invention;
• FIG. 15A is an exploded perspective view of a jackscrew bone plate according to an embodiment of the invention;
• FIG. 15B is a sectional view of a jack screw bone plate according to an embodiment of the invention;
• FIG. 15C is a close up sectional view of the locking mechanism of a jack screw bone plate according to an embodiment of the invention;
• FIGS. 16A-16B are top and bottom views of a bone plate component with an open central channel and an alternative end coupler for a modified distraction screw according to an embodiment of the invention; and
• FIGS. 17A-17B are top views of combined bone plates with slotted screw holes and sliding mechanisms according to alternative embodiments of the invention.
DETAILED DESCRIPTION
• Certain embodiments as disclosed herein provide for a modular bone distraction screw and a modular bone fixation plate with an adjustable length to accommodate bone settling. For example, one plating system disclosed herein allows for compression to be set during placement of the plate and also allows subsidence of the bone while maintaining the initial compression.
• After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention as set forth in the appended claims.
• FIG. 1 shows amodular distraction screw110, which comprises adistal segment120 and a removable proximal130 segment. Thedistal segment120 has ahead portion122, and a threadedshank portion124, which can be securely fastened unto bone. Theproximal segment130 comprises anelongated body132 anddeployable member136.Elongated body132 has a smooth-walledinternal bore134 extending through its full length and houses thedeployable member136 within the bore. Thedeployable member136 is adapted to be retractably deployed beyond the distal end of theinternal bore134.FIG. 2 shows the assembled distraction screw.
• FIG. 3 illustratesdistal segment120, which comprises a threadedshank portion124 and ahead portion122.Threads126 of theshank portion124 are preferably self-tapping and/or self-drilling. Depending on the particular application, theshank124 can be of variable lengths and diameter. In one application, the outer diameter of the shank/threads is preferably equal to the widest point ofhead122. One of ordinary skill in the art would understand that the threads can be of any design that is well known to be applicable for screwing placement into mammalian bone.
• Head122 is circular with hollowcentral bore1220. Theupper aspect1222 of the circular head is of uniform diameter but thelower portion1223 of the head is of progressively greater diameter such that the head has a sloping side wall belowedge1224.Threads1225 are located withinbore1220 and are complementary tothreads128 ofdeployable member136.Head122 has a plurality of slots1226 which are engageable by projections1322 of the distal aspect ofelongated body132, as shown inFIG. 3A andFIG. 3B. Slots1226 permit the head to collapse inward when centripetal force is applied to the outer wall of the head.
• Deployable member136 is advanced throughbore134 to engagedistal segment120 with the coupling of thecomplimentary threads128 and1225. Theproximal head1362 ofmember136 permits application of rotational force to deployable member136 (as shown inFIG. 2) further drivingthreads128 and1225 together and lockingmembers132,136 anddistal segment120 together. While depicted as a hex configuration, any engagable configuration may be used to drivedeployable member136.
• The coupledproximal segment130 anddistal segment120 employing the above-described means of engagement provide a modular distraction screw. When fully assembled, the screw functions as a unitary device. In a surgical application, a wrench (not shown) is attached to thetool attachment portion180 of elongated member132 (FIG. 1), and the distraction screw is positioned at a site of a bone. A rotational force is applied toportion180 causing the proximal and distal segments to rotate in unison so thatthread126 of thedistal segment120 engages the underlying bone andshank124 is advanced into the bone.
• After the distraction screw is used to perform the bone work, theproximal segment130 is detached fromdistal segment120. The distraction screw is disassembled into its components by applying a rotational force to head1362 ofmember136 in a direction opposite (usually counter-clock wise) to that required for screw assembly (usually clock-wise). The distal segment is held stationary whilethreads128 and1225 are disengaged by applying a counter force todistal segment120 using theproximal portion180 of theelongated body132. In this way, theproximal segment130 is removed leaving thedistal segment120 attached (implanted) to the bone structure.
• As implanted, thedistal segment120 provides enhanced structural integrity of the bone by reducing the stress concentration generally expected of an empty opening in a structural member. In addition, leaving thedistal segment120 attached to bone eliminates the robust bone bleeding encountered after removal of current, commercially-available distraction screws and obviates the need to fill the empty hole with a hemostatic agent.
• Thedistal segment120 also provides a point of anchoring for a skeletal plate and help insure proper plate placement. Since placement of the distraction screws is performed as the first step in the surgical procedure, the anatomical landmarks required to ensure proper alignment of the plate in the desired anatomical plane are still intact.
• Alternatively, a conventional one-piece distraction can be used to distract the vertebra during discectomy. After the bone work is finished, the conventional distraction screw is removed leaving an empty bone hole. Adistal segment120 is placed into the empty bone hole and provides an anchor point for the skeletal plate.
• FIGS. 5A and 5B show twovertebral bodies2 and4 and theplating system8 of the present invention used to fixate them. The plating system includes slidingplate segments10 and20 and a coupler means or acoupler segment30, which couples the slidingsegments10 and20 and controls their movements.FIGS. 6-7 show the top and, mid-sectional views of the embodiment of the bone fixation plate.
• Theplate segments10 and20 may be curved in either the vertical or horizontal plane in order to conform to the shape of the bone it is designed to fixate. For example, plates designed to attach onto the anterior aspect of the cervical spine are preferentially, but not necessarily, convex in both the vertical and horizontal planes. Further, the plate surface immediately adjacent to the bone surface may contain one or morehorizontal indentations1200 in order to permit the placement of additional curvature in the vertical plane.
• The plating system or any of its components can be made of any biologically adaptable or compatible materials. Materials considered acceptable for biological implantation are well known and include, but are not limited to, stainless steel, titanium, combination metallic alloys, various plastics, resins, ceramics, biologically absorbable materials and the like. It would be understood by one of ordinary skill in the art that any system component can be made of any materials acceptable for biological implantation and capable of withstanding the torque required for insertion and the load encountered during use. Any components may be further coated/made with osteo-conductive (such as deminerized bone matrix, hydroxyapatite, and the like) and/or osteo-inductive (such as Transforming Growth Factor “TGF-B,” Platelet-Derived Growth Factor “PDGF,” Bone-Morphogenic Protein “BMP,” and the like) bio-active materials that promote bone formation. Further, any instrument or device used in implant placement may be made from any non-toxic material capable of withstanding the load encountered during use. Materials used in these instruments need not be limited to those acceptable for implantation, since these devices function to deliver the implatable segments but are not, in themselves, implanted.
• As shown inFIGS. 5-7 slidingsegment10 has twoboreholes1110 which are formed through the plate to accommodate fastening elements, such as bone screw. Each borehole may be oriented in the true vertical plane or form an angle with the vertical. For use in the cervical spine,boreholes1110 will preferentially, but not necessarily, be angled towards each other in the horizontal plane and away from the sliding end in the vertical plane. The top opening of the boreholes may be flush with the plate surface or may be recessed. The distance between the boreholes may also vary depending on the requirement of plate application and design. Adepression1120 is present between the boreholes withslot1130 along the depression. The side walls1132 ofslot1130 are preferentially, but not necessarily, angled with the true vertical such that the top opening ofslot1130 is slightly smaller than the bottom opening.Slot1130 is adapted to accommodate or mate withscrew head122 ofdistal segment120 of the distraction screw. While depicted as an elongated hole,slot1130 may alternatively be a circular hole.
• Plate segment10 has three projections, consisting of twoside projections1140,1160 and acentral projection1150. Twoindentations1180 and1190 are formed between these three projections. The inside wall of eachprojection1140 and1160 containindentations1142 and1162, respectively. While depicted as “V” shaped, these indentations may be made of any geometric configurations including, but not limited, square, oval, circular, and hybrid designs which are complimentary to the sliding portion of theother plate segment20. Thecentral projection1150 has a partial thicknessmiddle segment1152 and twofull side walls1154. Anopening1156 with internal threads1158 is provided onsegment1152. The top surface ofmiddle segment1152 is preferentially textured so as to permit superior contact with the undersurface of the complementary plate component.
• The other end portion of theplate segment10 has aprojection1170, which is preferentially, but not necessarily, position in the midline of the plate segment. The projection has acentral hole1172 with threads1174.Spines1176 may be placed along the top of the projection to mate with complimentary spines on the add-on attachments, as shown inFIG. 4. These spines may be placed on any one or combination of surfacesadjacent projection1170. These surfaces may be textured or left smooth.
• FIGS. 6D, 6E,6F &7 illustrate the complementary slidingplate segment20 to slidingsegment10. Again, twoboreholes210 are vertically formed through the plate to accommodate fastening elements. As with slidingplate segment10, these boreholes may be oriented in the true vertical plane or form an angle with it, may be flush with the plate surface or further recessed, and the distance between these holes may vary depending on the requirement of the plate application. Adepression220 is formed between the boreholes with aslot230 whoseside walls232 are preferentially angled with the true vertical such that the top opening of the slot is slightly smaller than the bottom opening.Slot230 is adapted to mate with and accommodate the distal segment of a distraction screw.
• Slidingplate segment20 has twoprojections240,260 andcentral connection250.Projection240 has an extension242 which is complementary toindentations1142 ofprojections1140. Likewise,projection260 has an extension262 that is adapted to be received byindentations1162 ofprojection1160.Projections240 and260 may be of any geometric configuration and cross-section including, but not limited, square, oval, circular, truncated triangular, modified rectangular and hybrid designs that are complimentary to the corresponding sliding portions of thesegment10. Further,projections240 and260 may be of differing designs that are complimental toprojections1140 and1160. Thecentral connection250 has a partial thickness middle segment252 and two side walls254. Anopening256 with internal threads258 is located on segment252.Openings256 and1156 may be aligned with the direction of bone subsidence.
• On its opposite end,plate segment20 has apartial thickness projection270 that is preferentially, but not necessarily, in the midline of the plate.Projection270 has acentral hole272 withthreads274.Spines276 may be placed along the top of the projection to mate with complimentary spines of the add-on attachments. These spines may be placed on any one or combination of surfacesadjacent projection270. These surfaces may be textured or left smooth.
• FIG. 8 illustrates top and oblique views of coupling means orsegment30. Twofull thickness channels310 and320 are formed withinsegment30. The channels are preferentially, but not necessarily, of different lengths andwalls312 and322 ofchannels310 and320 are preferentially angled with the vertical plane. The top surface ofcoupling segment30 is smooth while the bottom surface is preferentially textured in the portion of the segment with thelarger channel320. The bottom of the segment with thesmaller channel310 is smooth. Couplingsegment30couples plate segments10 and20 as depicted inFIG. 5 withscrews40 and41. While not depicted, each screw has threads on which are complimentary to threads158 ofsegment10 and threads258 ofsegment20. The screws havetop depressions414 and404 for engagement by a screwdriver or other driving instrument. While both screws are depicted as being identical, each may be of any of the many well known fastener designs and may be inserted using any complimentary driver.
• Projections1150 and250 of slidingplate segment10 and20 respectively may be of equal or different lengths. When unequal,central projection1150 is made longer thanprojection250 as a matter of preference. (Alternatively, the longer projection may be placed withinsegment20.) Thelonger channel320 ofsegment30 engages the longer central projection (element1150 of segment10) byscrew41 while theshorter channel310 engages the shorter central projection (element250 of segment20) byscrew40.
• The bone screws and the screw for thecoupler segment30 may be of any of the many well known designs considered acceptable for implant attachment to the bony skeleton and made from any material intended for biological implantation.
• As an option, any portion of the plating segments may be made of radiolucent materials (such as PEEK, PEAK, and the like) so that unfettered x-ray examination of the underlying bone can be performed in the post-operative period. Thus,projections1150,250 andsegment30 can be made from radiolucent materials so as to provide a window for x-ray examination of the bone without decreasing the overall strength of the plate.
• After completion of the bone work and detachment of the proximal portions of the distraction screws, the distal segments are left attached to the vertebra above and below the newly fused disc space. The bone plate is fully assembled before implantation.Screw40 is fully seated at theoutside edge312 ofchannel310 so thatplate segment20 andcoupler segment30 are fixed relative to one another. However, screw41 is partially seated on theoutside edge320 ofchannel320 so thatplate segment10 andcoupler segment30 are free to slide relative to each other.Slot1130 and230 are aligned with thedistal segments120 which are implemented on the bone structure following bone work upon which theheads122 ofdistal segments120 are snapped into the slots. As thehead122 spring back, the plate segments are held between the screw heads122 and theunderlying bone2 and4.
• If the plate is poorly positioned because of bony irregularity, it can be removed to permit additional bone work.FIGS. 4a&4billustrate ascrew head remover300, which can be used to remove the plate segments. When pushed ontohead122 ofdistal segment120, the screw head remover applies a centripetal force to the side walls, causing them to move inward, and permitting plate removal. Alternatively, if the plate is well positioned, the boreholes are moved into optimal position for bone screw placement. A screw driver is used to drivedistal segment120 further into the bone, thereby holding the plate stationary. The bone screws are then easily placed into the underlying bone.
• Once the plate segments are set to the desired length, screw41 is tightened. If desired, compression can be placed across the bony construct and maintained with closure ofscrew41. The inferior surface ofsegment30 around thelonger channel320 and the superior surface ofprojection1150 is preferentially, but not necessarily, textured so as to promote greater frictional contact betweensegments10 and30. At this point, the plate is rigid. If accommodation of bony subsidence is desired, screw40 is unlocked, permitting movement ofsegments20 towards each other as bone settling occurs. The extent of subsidence permitted is governed by the length ofchannel310.
• Extension of the fusion at a future date can be easily accomplished without plate removal. Incorporation of the vertebral body immediately above or below into the fusion mass is started by placement of amodular distraction screw110 into that adjacent vertebra. A modified distraction screw is used to engage the end-coupler of the existing plate as shown inFIG. 10. As shown inFIGS. 9, 10 and11, the modifieddistraction screw500 comprises anelongated body510 with an internal bore512 extending through its entire length todistal end portion516. Theelongated body510 houses adeployable member530, which is disposed within the internal bore512. Thedeployable member530 is adapted to be retractably deployed beyond theopening516 of internal bore512.Threads532 are located on one end ofmember530 andhead534 is formed on the other end.Head534 has diameter greater than that of the internal diameter of bore512.Depression536 is formed withinhead534 so as to permit engagement and rotation ofdeployable member530 with a complimentary screwdriver. While depicted as a hexagonal depression intended to receive an Allen's wrench, any alternative means and arrangements for engaging and rotating thedeployable member530 can be employed including. Likewise, the engageable surface may be placed on the outer surface ofhead534 or extend from it.
• Adjacent todistal end516 ofelongated body510, spines are placed which are adaptable to compliment and engage withspines270 and1176 ofend coupler270 and1170 respectively. The spines may be placed on any surfaces of thedistal portion516 of theelongated body510 or both.Threads532 ofdeployable member530 are engageable to threads1174 ofend coupler1170 orthreads274 ofend coupler270, thus firmly affixing the modified distraction screw to the plate. The modified distraction screw and the modular distraction screw previously affixed to the adjacent vertebra are used to distract the vertebral bodies, permitting work on the intervening disc space. When the discectomy and subsequent bone work are finished, the modular distraction screw is separated leaving the distal segment attached to vertebral body. The modified distraction screw is removed leaving a bare end-coupler. A separate plate is used to span the distance between the distal segment and the end coupler. In this way, the fusion is readily extended to an adjacent level.
• Occasionally, placement of the plating segments might result in the end coupler being too close to the adjacent disc space such that placement of the modified distraction screw onto the coupler could hinder surgical access to the disc space.FIG. 11A shows an offset modified distraction screw which may be used in this setting andFIG. 11B illustrates its placement. The screw components are similar to those described above and as shown inFIG. 10.
• A further embodiment of the present invention is illustrated inFIGS. 12-16. As in the embodiments described above, the plating segments may be curved in either the vertical or horizontal plane, may contain one or more horizontal indentations in order to permit the placement of additional curvature in the vertical plane (not shown), and may be made of any biologically adaptable or compatible materials.
• Each of theplate segments140 and150 possess two boreholes to accommodate bone fasteners, a central channel to couple withdistal segment120 of the modular distraction screw and an end-coupler.
• A slidingend portion80 ofplate segment140 is formed by twoside projections840,860 and acentral opening850.Projection840 is an extension of theplate segment80 withside indentation842.Indentation842 may be made of any geometric configurations including, but not limited, square, oval, circular, and hybrid designs which is complimentary to wall942 ofprojection940 ofplate segment150.Projection860 has atop wall862, aside wall864 and aninferior wall866. Preferably, both top and side walls are straight while the inferior wall is triangular. One of ordinary skill in the art would recognize that any geometric configurations may be used for the walls ofprojection860 as long as they compliment the interacting surface ofslide portion90 ofplate segment50. Top surface ofwall862 has opening8620 which is key-hole shaped and composed of a larger, full thicknesscircular opening8622 at one end and a partial thickness,slot8624. The inferior surface ofwall862 has a partial thickness channel withopening8622 at one end and achannel8626. The latter is set beneathslot8624, is of the same length asslot8624 and of the same width as the diameter ofopening8622.
• As shown inFIG. 12, the slidingend portion90 ofplate segment50 is adapted to fit snuggly withincentral opening850 and slidingly engages the inner walls ofprojections840 and860 ofplate segment140. The slidingend portion90 is formed byprojection940 which hasside walls942 and946.Wall942 is depicted as projecting in a “>” fashion but any geometric configuration may be used that compliments surface842 ofplate segment80. Likewise,wall946 is configured to compliment860 ofplate segment80. Preferably,wall946 has slopingsurface9462 and thepartial thickness projection9464 which has upper wall9470 andlateral wall9472. The inferior aspect ofwall9472 is preferably slopped.Partial thickness projection9464 haschannel9465 and a cross-sectional exploded view is shown inFIG. 13B. The width ofchannel9465 is preferably equal to the diameter of opening8622 of theplate segment140. Acentral ridge9466 is formed along the walls ofchannel9465 which is preferably rectangular.Ridge9466 does not extent to the bottom ofchannel9465, leavingchannel9467 beneath the ridge. Preferably,ridge9466 does not extent to the top ofchannel9465, leaving anothersecond channel9468 above the ridge. The width of the opening formed at the level ofridge9466 is less than the width ofopening8622.
• Plate segments140 and150 are coupled in assembly withchannel9465 andopening8620 overlapping each other by a suitable coupler means. Coupler means incorporates abolt element96, which comprises ascrew960 and lockingnut980.Screw960 hashead962 which is preferably square or hex shaped and fits snuggly beneathridge9466 and withinchannel9465. The thickness ofhead962 is sufficiently thin so as not to extent beyond the inferior surface ofprojection9464. Shank964 ofscrew960 is circular and fits within the channel formed at the level ofridge9466. The shank has a flat end and total length greater than the thickness ofprojection9464 but less than the combined thickness ofprojection9464 andchannel8626. Shank964 also has threads966 (not depicted) which engagesnut980.Nut980 has a central full thickness bore982 with threads984 (not depicted) adapted to compliment and engage threads966. The threads may be of any available and recognized thread design.Nut980 fits snuggly within opening8622 ofsegment140, but has diameter greater than that ofchannel8624. Preferably, the top surface ofnut980 has indentations986 which can be engaged by the driving tool.
• FIGS. 14A and 14B illustrate the coupler means in the open and closed positions. When open,nut980 ofbolt element96 is held withinopening8622 such that it cannot move relative toplate segment140. However, since thebolt element96 is not fixed toplate segment150, theplate segments140 and150 can continue to move relative to one another in either direction. When the plate is set to the desired length,nut980 is rotated untiledge9466 rests tightly betweennut980 andhead962. Thenut980 also leavesopening8622 and coming to rest withinchannel8626. In this way,bolt element96 is fixed toplate segment150 and freed fromplate segment140. If desired, compression may be applied across the fused disc space prior to lockingnut980. Sincebolt element96 rests at the far end ofopening8620, any applied compressive force is maintained with closure of the locking mechanism. After closure,plate segments140 and150 can only move towards each other, thus accommodating subsidence. The length ofopening8620 determines the amount of subsidence permitted.
• As shown in the drawings, each of the plate segments of the present invention have two boreholes to accommodate bone fasteners, a central channel to couple withdistal segment120 of the modular distraction screw and an end-coupler. These features have been described above and will not be illustrated further.
• The plating system of the present invention can be applied, by way of a multilevel plating configuration to fixate three or more bones after the removal of two or more discs. As in the embodiments previously illustrated for single level plate, “multilevel” plates may be curved in either the vertical or horizontal plane, may contain one or more horizontal indentations in order to permit the placement of additional curvature in the vertical plane, and may be made of any biologically adaptable or compatible materials. Each of the upper and lower ends of the plates will contain two boreholes to accommodate bone fasteners, a central slot to anchor thedistal segment120 of the modular distraction screw and an end-coupler to accommodate possible modular extension of the fusion at a later date.
• FIG. 17 shows an exemplary embodiment of the multi-level plates, where one of the number of sliding mechanisms can be used at each level such that the total number of sliding mechanisms is equal to the number of discs removed and fused. Longer plates can be made by the sequential addition of other levels. While the illustrated plate present only one exemplary embodiment of the sliding mechanism and coupler means, it is understood that any of the previously discussed embodiments may be used in any combination to produce these plates. Further, different sliding mechanism designs can be used at different levels, if desired.
• With the exception of the two ends, asegment300 with two full thickness bore holes is placed between each of the sliding portions. These boreholes may be oriented in the true vertical plane or form an angle with the vertical. The boreholes will be angled towards each other in the plate's short axis (horizontal plane) and form a right angle with the body of the plate in the long axis (vertical plane). The top opening of the boreholes may be flush with the plate surface or may be recessed. The distance between the boreholes may also vary depending on the requirement of plate application and design.
• Removal of two or more discs is accomplished by the step-wise removal of individual discs until all pathological levels have been addressed. Modular distraction screws may be used at each vertebral level if desired, but their use is required only at the upper and lower-most vertebras while conventional distraction screws can be used at all intervening levels. After completion of the bone work, the proximal segments of the distraction screws are removed leaving the distal segments attached to the upper and lower-most vertebral bodies. At other disc levels, the distraction screw can be completely removed after the completion of the bone work.
• The plate is guided to proper position along the upper-most and lower-most vertebra by the attached distal segments—as described above for single level procedures. The distal segments of the distraction screws are tightened onto the plate after selection of optimal bone screw position. In this way, the plate is held stationary while the bone screws are placed into the upper and lower-most vertebras and the plate is fixed at each end. Depending on surgeon preference, fixation of the intervening vertebral levels may be started from either end of the plate. For illustration, fixation will be started inferiorly. The plate segment intended to fixate the vertebra immediately superior to the lower-most vertebra is moved into a desired position. The sliding mechanism between this segment and the plate segment attached to the lower-most vertebra is then locked. Once these segments are immobilized, bone screws are placed into the vertebra immediately superior to the lower-most vertebra. The process is repeated at each of the remaining vertebra. If compression is desired across the construct, it's applied across the upper and lower-most vertebras prior to placement of the bone screws into any of the intervening vertebra. Compression is maintained until all the vertebras have been fixed to the plate. Once all sliding mechanisms have been locked, the compression device may be released and the force will be maintained by the plate.
• Alternatively, one or more sliding mechanisms can be used to accommodate boney subsidence at two or more fused levels. This is accomplished by using a slotted borehole between levels.FIG. 17A illustrates this design feature in a two level plate in which only one sliding mechanism is employed. Again, the plate is placed after completion of the bone work and plate placement is started by fixation of the plate at each end using the distal segments of the distraction screws. The plate is set to the desired length and the sliding mechanism is locked. If desired, compression may be applied prior to closure of the mechanism. The bone screw is placed at the end of the slotted borehole immediately adjacent to the sliding mechanism and the subsidence screw is opened. In this way, the plate's adjustable length and subsidence can be accomplished using a single sliding mechanism. While the second embodiment of the sliding mechanism as well as the alternative embodiments of the end-coupler and central channel are illustrated, it is understood that any of the previously discussed embodiments may be used in any workable combination to produce these plates.
• FIG. 17B demonstrates the other potential designs that can be used for a three level plate. Other possible variations that can be used in creating a other multi-level plating system. Longer plates can be made by the sequential addition of other levels.
• While the particular systems and methods herein shown and described in detail are fully capable of attaining the above described objects of this invention, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.

Claims (8)

1. An orthopedic implant adapted to fixate at least three skeletal bones of a human or animal subject, comprising:

a connector adapted to connect a plurality of bone anchors, the connector having a slotted bore hole, wherein at least one bone anchor is positioned into each of a skeletal bone, wherein the connector is adapted to allow movement between at least three skeletal bones wherein movement between at least one set of immediately adjacent bones is provided by movement between a connector segment attached to a first bone and another connector segment attached to a second bone,

and wherein movement between at least a second set of immediately adjacent bones is provided by movement of at least one bone anchor within the slotted bore hole wherein the bore is contained within a single plate segment that inter-connects both bones of the second set of adjacent bones.

2. A method for the manipulation and movement of a first vertebral bone relative to an adjacent set of vertebral bones that have been collectively inter-connected by a first orthopedic implant at a first operation, comprising:

coupling an extension member to an aperture of the first orthopedic implant while the first orthopedic implant remains attached to the inter-connected set of vertebral bodies; and

applying a force onto the extension member so as to produce collective movement of the set of inter-connected vertebral bodies relative to the first vertebral body.

3. A method as inclaim 2, further comprising:

distracting a disc space that is anatomically positioned between the first vertebral body and the adjacent set of inter-connected vertebral bodies; and

producing a bone fusion across the disc space.

4. A method as inclaim 2, further comprising:

placing a second orthopedic implant between the first vertebral body and the adjacent set of inter-connected vertebral bodies.

5. A method for the positioning of a vertebral bone connector that is used to fixate at least two vertebral bones wherein at least one bone distraction screw is placed into each of an upper most and a lower most of the fixated vertebral bones, the method comprising:

actuating a bone distraction screw to position the bones in a desired spatial configuration relative to one another;

positioning at least one end of the vertebral bone connector onto a distraction screw so that a segment of the distraction screw transverses a slotted bore hole contained on an end of the connector, wherein the slotted bore hole is adapted to interact with at least a segment of the distraction screw to permit the connector to move relative to the underlying bone in a first plane while limiting movement in a second plane;

moving the connector in the first plane until a desired connector position is achieved; and

actuating a distraction screw segment so as to immobilize the connector relative to the underlying bone.

6. A method as inclaim 5, further comprising:

surgically manipulating at least one disc space that is positioned between an upper most vertebral bone that is attached to a distraction screw and a lower most vertebral bones that is attached to a distraction screw, wherein the manipulation is performed prior to placement of the connector device.

7. A method for the attachment of a vertebral bone connector that is used to fixate at least two vertebral bones wherein at least one bone distraction screw is placed into each of an upper most and a lower most of the fixated vertebral bones, the method comprising:

actuating bone distraction screws to position the bones in a desired spatial configuration relative to one another;

positioning at least one end of the vertebral bone connector onto a distraction screw so that a segment of the distraction screw transverses a slotted bore hole contained on an end of the connector, wherein the distraction screw segment is adapted to transverse the slotted bore hole from an inferior to superior direction and to reversibly capture and retain the connector in the seated position.

9. An orthopedic implant adapted to fixate at least two skeletal bones of a human or animal subject, comprising:

a connector adapted to connect a plurality of bone anchors, wherein at least one bone anchor is adapted to be positioned into each of a skeletal bone;

a slotted bore hole that is contained within at least one end of the connector and is adapted to interact with at least a segment of a distraction screw so as to permit the connector to move relative to the underlying bone in a first plane while limiting movement in a second plane, wherein the slotted bore hole is has a vertical thickness less than that of the surrounding connector so as form a recess at a superior slot surface, wherein the recess provides a bearing surface against which an anchor may be forcibly seated to immobilize the connector relative to the underlying bone.

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