Prosthetic intervertebral discs having substantially rigid end plates and fibers between those end plates

Abstract

Prosthetic intervertebral discs and methods for using the same are described. The subject prosthetic discs include upper and lower endplates separated by a compressible core member. The prosthetic discs described herein include one-piece, two-piece, three-piece, and four-piece structures. The subject prosthetic discs exhibit stiffness in the vertical direction, torsional stiffness, bending stiffness in the saggital plane, and bending stiffness in the front plane, where the degree of these features can be controlled independently by adjusting the components of the discs. The interface mechanism between the endplates and the core members of several embodiments of the described prosthetic discs enables a very easy surgical operation for implantation.

1 . A prosthetic intervertebral disc for implantation in an intervertebral opening between adjacent first and second vertebral bones in a spine, the disc having an annular region and a nucleus region, the annular region forming an annulus surrounding the nucleus region, the disc comprising:
 a first endplate having an upper surface operable to engage a surface on the first vertebral bone within the intervertebral opening and to secure the first endplate to the first vertebral bone upon said implantation;   a second endplate having a lower surface operable to engage a surface on the second vertebral bone within the intervertebral opening and to secure the second endplate to the second vertebral bone upon said implantation;   a compressible core, said compressible core comprising at least one core member positioned between said first and second endplates and located only in the nucleus region and said compressible core further comprising at least one fiber extending between and engaged with said first and second endplates, the at least one fiber located only in the annular region, and wherein said first and second endplates are held together and said first and second endplates and said core member are held together by the at least one fiber in a manner by which the prosthetic intervertebral disc substantially mimics the functional characteristics of a natural intervertebral disc, the functional characteristics being a.) stiffness in the axial direction, b.) torsional stiffness, c.) bending stiffness in the front plane and in the sagittal plane, d.) range of motion, e.) spacing between vertebrae, f.) degree of flexion, extension, lateral bending, and axial rotation of the prosthetic disc, and g.) axial compressive stiffness.   
     
     
         2 . The prosthetic intervertebral disc of  claim 1  wherein each said endplate comprises a plurality of slots, wherein said at least one fiber extends through at least one of said slots of said first endplate and through at least one of said slots of said second end plate. 
     
     
         3 . The prosthetic intervertebral disc of  claim 2  wherein the at least one fiber comprises a plurality of fibers, wherein each of said plurality of fibers extends through each of said plurality of slots of said first endplate and through each of said plurality of slots of said second end plate. 
     
     
         4 . The prosthetic intervertebral disc of  claim 3  wherein said plurality of fibers define a unidirectional wrapping pattern. 
     
     
         5 . The prosthetic intervertebral disc of  claim 3  wherein said plurality of fibers define a bidirectional wrapping pattern. 
     
     
         6 . The prosthetic intervertebral disc of  claim 3  wherein said plurality of fibers define a multi-directional wrapping pattern. 
     
     
         7 . The prosthetic intervertebral disc of  claim 3  wherein said plurality of fibers define two or more layers of fibers of said compressible core. 
     
     
         8 . The prosthetic intervertebral disc of  claim 7  wherein the fibers of a first layer and the fibers of a second layer are applied with the same tension. 
     
     
         9 . The prosthetic intervertebral disc of  claim 7  wherein the fibers of a first layer and the fibers of a second layer are applied with different tensions. 
     
     
         10 . The prosthetic intervertebral disc of  claim 7  wherein said fibers of a first layer extend at a first angle and said fibers of a second layer extend at a second angle, wherein said first angle is different than said second angle, and further wherein said angles are selected to mimic the fibers of a natural disc. 
     
     
         11 . The prosthetic intervertebral disc of  claim 1  wherein said compressible core member comprises a polymeric material. 
     
     
         12 . The prosthetic intervertebral disc of  claim 1  wherein said compressible core member comprises a hydrogel material. 
     
     
         13 . The prosthetic intervertebral disc of  claim 1  wherein said compressible core member comprises an elastomeric material. 
     
     
         14 . The prosthetic intervertebral disc of  claim 1  wherein said compressible core member comprises one of either polyurethane or silicone. 
     
     
         15 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber comprises an elastomer. 
     
     
         16 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber comprises a metal. 
     
     
         17 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber comprises a plastic. 
     
     
         18 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber comprises a polymer selected from the group consisting of polyester (e.g., Dacron), polyethylene, polyaramid, carbon or glass fibers, polyethylene terephthalate, arcrylic polymers, methacrylic polymers, polyurethane, polyurea, polyolefin, halogenated polyolefin, polysaccharide, vinylic polymer, polyphosphazene, polysiloxane, and the like. 
     
     
         19 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber comprises polyethylene. 
     
     
         20 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber is a multifilament fiber. 
     
     
         22 . The prosthetic intervertebral disc of  claim 1  wherein said at least one fiber is a monofilament fiber. 
     
     
         23 . The prosthetic intervertebral disc of  claim 1  wherein the upper surface of the first endplate and the lower surface of the second endplate each include a mechanism for securing the endplates to vertebral surfaces. 
     
     
         24 . The prosthetic intervertebral disc of  claim 23  wherein the mechanism for securing the endplates to vertebral surfaces comprises at least one fin. 
     
     
         25 . The prosthetic intervertebral disc of  claim 1  further comprising an annular capsule having a generally cylindrical body extending from the first endplate to the second endplate and sealing an interior space between the first endplate to the second endplate containing the compressible core and at least one fiber. 
     
     
         26 . The prosthetic intervertebral disc of  claim 25  wherein the generally cylindrical body of the annular capsule is bellowed. 
     
     
         27 . A prosthetic intervertebral disc comprising:
 a first substantially rigid endplate having an upper surface for engaging an upper vertebral bone and a lower surface opposite the upper surface and further comprising a plurality of slots passing through the first endplate from the upper surface to the lower surface;   a second substantially rigid endplate having a lower surface for engaging a lower vertebral bone and an upper surface opposite the lower surface and further comprising a plurality of slots passing through the second endplate from the upper surface to the lower surface;   a compressible core comprising, a.) at least one polymeric core member positioned between the first and second endplates and b.) at least one fiber passing through more than one of the first endplate plurality of slots and passing through more than one of the second endplate plurality of slots to hold the upper endplate to the lower endplate, and   an annular capsule having a generally cylindrical body extending from the first endplate to the second endplate and sealing an interior space between the first endplate to the second endplate containing the compressible core and at least one fiber.   
     
     
         28 . The prosthetic intervertebral disc of  claim 27  wherein the at least one fiber passes multiple times through the first endplate plurality of slots and through the second endplate plurality of slots. 
     
     
         29 . The prosthetic intervertebral disc of  claim 27  wherein the at least one fiber comprises multiple fibers. 
     
     
         30 . The prosthetic intervertebral disc of  claim 28  wherein the at least one fiber comprises multiple fibers. 
     
     
         31 . The prosthetic intervertebral disc of  claim 27  wherein the upper surface of the first endplate and the lower surface of the second endplate each include a mechanism for securing the endplates to vertebral surfaces. 
     
     
         32 . The prosthetic intervertebral disc of  claim 31  wherein the mechanism for securing the endplates to vertebral surfaces comprises at least one fin. 
     
     
         33 . The prosthetic intervertebral disc of  claim 32  wherein the upper surface of the first endplate and the lower surface of the second endplate each include a mechanism for securing the endplates to vertebral surfaces. 
     
     
         34 . The prosthetic intervertebral disc of  claim 33  wherein the mechanism for securing the endplates to vertebral surfaces comprises at least one fin. 
     
     
         35 . The prosthetic intervertebral disc of  claim 27  wherein the generally cylindrical body of the annular capsule is bellowed.