| Artificial expansile total lumbar and thoracic discs for posterior placement without supplemental instrumentation and its adaptation for anterior placement of artificial cervical, thoracic and lumbar discs -> Monitor Keywords |
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Artificial expansile total lumbar and thoracic discs for posterior placement without supplemental instrumentation and its adaptation for anterior placement of artificial cervical, thoracic and lumbar discsRelated Patent Categories: Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor, Implantable Prosthesis, Bone, Spine Bone, Having A Fluid Filled ChamberArtificial expansile total lumbar and thoracic discs for posterior placement without supplemental instrumentation and its adaptation for anterior placement of artificial cervical, thoracic and lumbar discs description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050256576, Artificial expansile total lumbar and thoracic discs for posterior placement without supplemental instrumentation and its adaptation for anterior placement of artificial cervical, thoracic and lumbar discs. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to artificial discs, and more specifically relates to artificial expansible total lumbar and thoracic discs for posterior placement without supplemental instrumentation, and to anterior placement of artificial discs for the cervical, thoracic and lumbar spine. [0003] 2. Description of the Relevant Art [0004] Cervical and lumbar total artificial discs are entering the clinical neurosurgical and orthopedic markets. The benefits of these artificial discs are well known. They replace diseased discs, and preserve motion segment mobility. Discogenic and radicular pain are relieved without forfeiting segmental mobility, which is typical of traditional anterior or posterior lumbar fusions. Total artificial disc replacements aim to cover the entire expanse of the disc space because restoration of range of motion is reportedly greatest when roughly 80% of the vertebral endplate is covered. Thus it is only rational, currently to place prosthetic discs anteriorly where access can be easily obtained, and they can be secured by a variety of anterior screw fixations. This technology is adequate for single level disc replacement in the cervical spine. However based on the current anterior cervical prosthetic disc screw fixation methodology its implantation is periodically complicated by screw failures e.g. partial or complete screw pullouts or breaks, and in most designs it is limited to single level replacement. Furthermore, for lumbar total artificial discs, placement is limited to only the L4/5 and L5/S1 disc spaces, and not above, secondary to aortic and vena caval anatomical restraints. Likewise, for the thoracic spine. Thus far no type of thoracic prosthetic disc device has been reported or described. Furthermore, despite the purported safety of placement of the current total lumbar artificial discs, there is a significant risk of retrograde ejaculations in males, and the risk of vascular injury, which although small, is potentially catastrophic if it occurs. [0005] The design of total artificial discs, which began in the 1970's, and in earnest in the 1980's, consists essentially of a core (synthetic nucleus pulposus) surrounded by a container (pseudo-annulus). Cores have consisted of rubber (polyolefin), polyurethane (Bryan-Cervical), silicon, stainless steel, metal on metal, ball on trough design (Bristol-Cervical, Prestige-Cervical), Ultra High Molecular Weight Polyethylene (UHMWPE) with either a biconvex design allowing unconstrained kinematic motion (Link SB Charite-Lumbar), or a monoconvex design allowing semiconstrained motion (Prodisc-Lumbar). There is also a biologic 3-D fabric artificial disc interwoven with high molecular weight polyethylene fiber, which has only been tested in animals. Cervical and lumbar artificial discs are premised on either mechanical or viscoelastic design principles. The advantages of mechanical metal on metal designs including the stainless steel ball on trough design and the UHMWPE prostheses include their low friction, and excellent wear characteristics allowing long term motion preservation. Their major limitation is the lack of elasticity and shock absorption capacity. The favorable features of the viscoelastic prosthetics include unconstrained kinematic motion with flexion, extension, lateral bending, axial rotation and translation, as well as its cushioning and shock absorption capacity. On the other hand, their long term durability beyond ten years is not currently known. Containers have consisted of titanium plates, cobalt chrome or bioactive materials. This history is reviewed and well documented in Guyer, R. D., and Ohnmeiss, D. D. "Intervertebral disc prostheses", Spine 28, Number 15S, S15-S23, 2003; and Wai, E. K., Selmon, G. P. K. and Fraser, R. D. "Disc replacement arthroplasties: Can the success of hip and knee replacements be repeated in the spine?", Seminars in Spine Surgery 15, No 4: 473-482, 2003. [0006] It would be ideal if total lumbar artificial discs could be placed posteriorly allowing access to all levels of the lumbar spine. Also one could place these devices posteriorly in thoracic disc spaces through a transpedicular approach. Similarly if these devices can be placed anteriorly particularly in the cervical spine without anterior screw fixation, and custom-fit it for each disc in each individual, the ease of placement would reduce morbidity and allow for multi-level disc replacement. Placement of an artificial disc in the lumbar spine if inserted posteriorly through a unilateral laminotomy by using a classical open microscopic approach or by using a minimally invasive tubular endoscopic approach would significantly reduce the possibility of recurrent disc herniation. If placed without facet joint violation, or with only unilateral mesial facetectomy, and the device can purchase the endplates with spikes there would be no need for supplemental posterior pedicle screw fixation, thus obviating the associated morbidity associated with pedicle screws and bone harvesting. To take it one step further, if artificial lumbar discs can be posteriorly placed successfully and safely throughout the entire lumbar spine, every routine lumbar discectomy could be augmented by artificial disc placement which would simultaneously eliminate discogenic and radicular pain while preserving flexibility. Furthermore by so doing, the probability of recurrent herniation plummets, and subsequently the need for posterior pedicle instrumentation plummets, thereby diminishing overall spinal morbidity, expenditure, and leading to the overall improvement in the quality of life. [0007] Presumably up to now, technology is not focusing on posterior placement of total lumbar prosthetic discs because of inadequate access to the disc space posteriorly. To circumvent this problem others have been working on the posterior placement, not of a total prosthetic disc but of a prosthetic disc nucleus (PDN), or essentially a core without a container (pseudo annulus). PDNs, which are considered post-discectomy augmentations, have consisted of one of the following materials: 1) hydrogel core surrounded by a polyethylene jacket (Prosthetic Disc Nucleus). Two of these devices have to be put in. There is a very high, 38% extrusion rate, 2) Polyvinyl alcohol (Aquarelle), 3) polycarbonate urethane elastomer with a memory coiling spiral (Newcleus), 4) Hydrogel memory coiling material that hydrates to fill then disc space, 5) Biodisc consisting of in-situ injectable and rapidly curable protein hydrogel, 6) Prosthetic Intervertebral Nucleus (PIN) consisting of a polyurethane balloon implant with in-situ injectable rapidly curable polyurethane and 7) thermopolymer nucleus implant. (See the two publications identified above). The approach of posteriorly placing artificial disc cores appears to be flawed in that: 1) there is a high extrusion rate, 2) it lacks good fixation as does total prosthetic devices that are placed anteriorly, 3) it is restricted only to early symptomatically disrupted discs which have only nucleus pulposus but not annulus or endplate pathology, and 4) are contraindicated in discs with an interspace height of less than 5 mm. DESCRIPTION OF THE DRAWINGS [0008] FIG. 1 illustrates a cross-section of the, expansile total lumbar/thoracic implant upon initial posterior insertion into the lumbar (or thoracic) disc space against the background of a vertebral body, i.e., this illustrates a three-dimensional expandable elastic polymer nucleus design (Embodiment I); [0009] FIG. 2 illustrates ratcheting of the three-dimensional expansile total lumbar/thoracic titanium shells to conform to the length of the vertebral body (Embodiment I); [0010] FIG. 3 illustrates the dorsal view of the three-dimensional expansile total lumbar/thoracic construct from the surgeon's perspective (Embodiment I); [0011] FIGS. 4A-M illustrate in detail the mechanical cylinder-spur-gear-spring (CSGS) system incorporated into the cross-connecting 8 titanium shells of the three-dimensional Lumbar/Thoracic prosthesis which enable expansion of the device in x, y and z dimensions. A system of springs is incorporated into the y-axis of the CSGS so as not to hinder the flexibility of the inner core. [0012] FIGS. 5A and 5B illustrate a second embodiment of the three-dimensional expansile lumbar/thoracic disc invention, i.e., these illustrate an in-situ injection/expansion elastic polymer nucleus design (Embodiment II); [0013] FIGS. 6A, 6B and 6C illustrate a third embodiment of the expansile total lumbar/thoracic artificial disc implant, i.e., this illustrates a mechanical metal on metal, stainless steel, ball on trough design (Embodiment [0014] FIGS. 7A, 7B and 7C illustrate a fourth embodiment of the three-dimensional expansile total lumbar/thoracic artificial disc implant, i.e., this illustrates a mechanical metal on metal, biconvex ultra high molecular weight polyethylene (UHMWPE) design (Embodiment IV); [0015] FIG. 8 illustrates a fifth embodiment of the three-dimensional expansile total lumbar/thoracic artificial disc implant, i.e., this illustrates a mechanical metal on metal, monoconvex UHMWPE design (Embodiment V); [0016] FIGS. 9A-E illustrates a sixth embodiment of the expansile total lumbar/thoracic artificial disc implant. This simpler design expands in two not three dimensions (height and width). FIGS. 9A-E therefore represent a two-dimensional expansile prosthesis, using the elastic polymer nuclear design as the prototype. [0017] FIG. 10A represents an endoscope variant of the present invention inserted unilaterally into the disc space to inspect the disc space circumferentially; [0018] FIG. 10B represents a specifically designed pituitary rongeur endoscopic attachment with a light source emanating from the junction of the adjoining dorsal and ventral cup forceps. This significantly aids in performing a complete circumferential discectomy necessary for adequate prosthesis implantation. [0019] FIG. 10C illustrates a right-angled ratchet driver integrated into an endoscope to assist in visualization of screws beneath the caudal aspect of the spinal cord or thecal sac, if necessary. [0020] FIGS. 11A, 11B, 11C and 11D illustrate a cross-section of the prostheses adapted for anterior implantation into the cervical disk space. FIG. 11A illustrates the expandable elastic polymer nucleus design (Embodiment I). FIG. 11B illustrates the in-situ injection/expansion elastic polymer nucleus design (Embodiment II). FIG. 11C illustrates the mechanical, metal on metal, stainless steel, ball on trough design (Embodiment II). FIG. 11D illustrates the mechanical, metal on metal, UHMWPE biconvex or monoconvex design (Embodiments IV and V). DESCRIPTION OF THE PREFERRED EMBODIMENTS [0021] The Medical Device Continue reading about Artificial expansile total lumbar and thoracic discs for posterior placement without supplemental instrumentation and its adaptation for anterior placement of artificial cervical, thoracic and lumbar discs... 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