PROSTHETIC INTERVERTEBRAL DISCS IMPLANTABLE BY MINIMALLY INVASIVE SURGICAL TECHNIQUES
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 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 subject prosthetic discs have shapes, sizes, and other features that make them particularly suitable for deployment using minimally invasive surgical procedures.
1 . A prosthetic intervertebral disc comprising:
a first endplate;
a second endplate;
a compressible core member positioned between said first and second endplates; and
at least one fiber extending between and engaged with said first and second endplates;
wherein said endplates and said core member are held together by said at least one fiber in a manner which substantially mimics the functional characteristics of a natural intervertebral disc; and
wherein at least one of said first endplate and said second endplate includes a plurality of apertures formed therein at locations substantially displaced from the edges thereof.
2 . The prosthetic intervertebral disc of claim 1 , wherein both of said first endplate and said second endplate includes a plurality of apertures formed therein at locations substantially displaced from the edges thereof.
3 . The prosthetic intervertebral disc of claim 2 , wherein said at least one fiber extends through at least one of said apertures of said first endplate and through at least one of said apertures of said second end plate.
4 . The prosthetic intervertebral disc of claim 3 , wherein said at least one fiber extends through each of said plurality of apertures of said first endplate and through each of said plurality of apertures of said second end plate.
5 . The prosthetic intervertebral disc of claim 4 , wherein said at least one fiber is wrapped about said endplates thereby defining a unidirectional wrapping pattern.
6 . The prosthetic intervertebral disc of claim 4 , wherein said at least one fiber is wrapped about said endplates thereby defining a bidirectional wrapping pattern.
7 . The prosthetic intervertebral disc of claim 4 , wherein said at least one fiber is wrapped about said endplates thereby defining a multi-directional wrapping pattern.
8 . The prosthetic intervertebral disc of claim 4 , wherein said at least one fiber defines two or more layers of fibers.
9 . The prosthetic intervertebral disc of claim 8 , wherein the fibers of a first layer and the fibers of a second layer are applied with the same tension.
10 . The prosthetic intervertebral disc of claim 8 , wherein the fibers of a first layer and the fibers of a second layer are applied with different tensions.
11 . The prosthetic intervertebral disc of claim 8 , wherein said fibers of a first layer extend at a first angle relative to at least one of said endplates, and said fibers of a second layer extend at a second angle relative to the same at least one of said endplates, 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.
12 . The prosthetic intervertebral disc of claim 1 , wherein said compressible core member comprises one of either polyurethane or silicone.
13 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber comprises an elastomer.
14 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber comprises a metal.
15 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber comprises a plastic.
16 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber is a multifilament fiber.
17 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber is a monofilament fiber.
18 . The prosthetic intervertebral disc of claim 1 , wherein said at least one fiber is encapsulated.
19 . The prosthetic intervertebral disc of claim 1 , further comprising a fixation member for securing said first endplate to a vertebral body, said fixation member extending from an outer surface of said first endplate.
20 . The prosthetic intervertebral disc of claim 19 , wherein said fixation member comprises at least one anchoring feature.
21 . The prosthetic intervertebral disc of claim 1 , further comprising a capsule encasing said compressible core.
22 . The prosthetic intervertebral disc of claim 21 , wherein said capsule is bellowed.
23 . The prosthetic intervertebral disc of claim 1 , wherein at least one of said first endplate and said second endplate includes a curved bearing surface engaged with said core member.
24 . A prosthetic intervertebral disc comprising:
a first endplate;
a second endplate;
a compressible core member positioned between said first and second endplates; and
at least one fiber extending between and engaged with said first and second endplates;
wherein said endplates and said core member are held together in a manner which substantially mimics the functional characteristics of a natural intervertebral disc; and
wherein at least one of said first endplate and said second endplate includes a curved bearing surface engaged with said core member.
25 . The prosthetic intervertebral disc of claim 24 , wherein both of said first endplate and said second endplate includes a curved bearing surface.
26 . The prosthetic intervertebral disc of claim 24 , wherein said curved bearing surface comprises a generally flat middle section and a raised side on each opposed end of said at least one of said first endplate and said second endplate.