Prosthetic Intervertebral Discs Having Substantially Cylindrical Cores Insertable Along Their Axes, That Are Suitable For Implantation By Minimally Invasive Surgical Techniques
The described devices are prosthetic, spinal disc replacement, implants having cores that are insertable after the end plates have been introduced into the intervertebral space. The discs may be surgically implanted into the spine to replace damaged or diseased discs using a posterior approach. The discs are prosthetic devices that approach or mimic the physiological motion and reaction of the natural disc.
1 . A prosthetic intervertebral disc for implantation into an intervertebral space formed by removing a natural disc between two adjacent vertebrae in a spine, comprising:
a.) a first end plate having an anterior end, a posterior end, a first contact surface for contacting a vertebral surface in the intervertebral space, and a first interior surface including a first partial passageway extending from the posterior end towards the anterior end;
b.) a second end plate having an anterior end, a posterior end, a second contact surface for contacting a vertebral surface in the intervertebral space, and a second interior surface including a second partial passageway extending from the posterior end towards the anterior end;
the first interior surface being positioned adjacent the second interior surface and the first partial passageway and second partial passageway being configured to accept at the posterior end a substantially cylindrical compressible core member having a cylindrical axis and to allow passage of that core member towards the anterior end along the core member cylindrical axis,
c.) the cylindrical compressible core member, and
d.) at least one fiber extending between and engaged with said first and second end plates; and wherein said end plates and said core member are held together by said at least one fiber.
2 . The prosthetic intervertebral disc of claim 1 where the compressible core member is positioned between said first and second end plates.
3 . The prosthetic intervertebral disc of claim 1 where the cylindrical compressible core member includes screw threads and where the first partial passageway and second partial passageway are configured with internal screw threads conforming to the screw threads on the cylindrical compressible core member.
4 . The prosthetic intervertebral disc of claim 1 where the cylindrical compressible core member includes one or more circumferential grooves and where the first partial passageway and second partial passageway are configured with internal circumferential ridges conforming with circumferential grooves on the cylindrical compressible core member.
5 . The prosthetic intervertebral disc of claim 1 where the first and second end plates further include openings for the at least one fiber.
6 . The prosthetic intervertebral disc of claim 1 wherein the disc is bullet-shaped.
7 . The prosthetic intervertebral disc of claim 1 wherein the disc is lozenge-shaped.
8 . A kit for surgically replacing a discs in a spine with a posterior approach, comprising exactly two of the prosthetic discs of claim 1 .
9 . The kit of claim 8 further comprising at least one cannula suitable for a posterior approach configured to access a disc to be replaced and to bypass the spinal cord and local nerve roots and further sized for passage of at least one of the two prosthetic discs of claim 1 .
10 . The kit of claim 8 wherein the first and second end plates of each of the prosthetic discs have a length and a width, and wherein the length is greater than the width.
11 . The kit of claim 10 wherein the first and second end plates of the prosthetic discs have a length:width aspect ratio of the first and second end plates is in the range of about 1.5:1 to 5.0:1.