Intervertebral Prosthetic Disc
A prosthetic disc for insertion between adjacent vertebrae includes upper and lower plates, a core disposed between the plates, and at least one projection extending from at least one of the upper and lower curved surfaces of the core into at least one recess of one of the inner surfaces of the plates. The recess is oversize with respect to the projection to allow sliding movement of the plate over the core while retaining the core between the plates during such sliding movement. The projection(s) may include a rod extending through an axial hole in the core, multiple surface features of the core, or the like.
1 . An intervertebral prosthetic disc for insertion between adjacent vertebrae, the disc comprising:
upper and lower plates having outer surfaces locatable against the respective vertebrae and inner bearing surfaces;
a core between the plates, the core having upper and lower surfaces complementary in shape to the inner bearing surfaces of the plates to allow the plates to slide over the core, the core including a lateral surface between the upper and lower surfaces; and
a retaining assembly to hold the core captive between the plates when the plates slide over the core, the retaining assembly including a core retainer that projects from the lateral surface of the core in diametrically opposite directions, and fasteners carried by one of the plates to fasten the core retainer on diametrically opposite regions of the plate.
2 . The prosthetic disc of claim 1 , wherein at least one of the inner bearing surfaces is a concave surface.
3 . The prosthetic disc of claim 1 , wherein the core retainer extends into a channel in the core.
4 . The prosthetic disc of claim 3 , wherein the channel is tapered with the channel being wider at the lateral surface of the core.
5 . The prosthetic disc of claim 1 , wherein the core retainer extends through the core.
6 . The prosthetic disc of claim 1 , wherein the fasteners are imbedded within one of the plates.
7 . The prosthetic disc of claim 1 , wherein the core retainer comprises a cable.
8 . The prosthetic disc of claim 1 , wherein the plates and the core are formed of rigid materials.
9 . A method of retaining a core in a prosthetic disc, the method comprising:
providing upper and lower plates and a core having a lateral surface;
positioning the core between the upper and lower plates; and
providing a retaining assembly to hold the core captive between the plates when the plates slide over the core, the retaining assembly including a core retainer that projects from the lateral surface of the core in diametrically opposite directions.
10 . The method of claim 9 , further comprising fastening the core retainer on diametrically opposite regions of the plate.
11 . The method of claim 9 , wherein the retaining assembly projects into a channel in the core.
12 . The method of claim 9 , wherein core has two bearing surfaces which cooperate with bearing surfaces on the on the upper and lower plate to allow the core to slide and translate with respect to the upper and lower plates.
13 . The method of claim 9 , wherein at least one of the bearing surfaces on the upper or lower plates is a curved bearing surface.