Artificial discs

Abstract

A four-component artificial intervertebral disc may provide six degrees of movement: flexion, extension, lateral bending, axial rotation, axial deflection, and anterior/posterior translation. The disc may include a superior endplate, a superior core, an inferior core, and an inferior endplate. The superior endplate may include a concave mating surface, and the inferior endplate may include a spherical mating surface. The superior endplate may roll across the superior core to provide flexion, extension, and lateral bending. The superior endplate may twist or rotate atop the superior core to provide axial rotation, and the superior endplate may slide over the superior core to provide anterior/posterior translation. The superior core may be connected to the inferior core, and the inferior core may be connected to the inferior endplate. The inferior core may be made from a flexible material that may enable the artificial disc to expand or compress vertically.

What is claimed is: 
     
         1 . An artificial disc comprising:
 a first endplate having a first surface and an opposite second surface, and a round first recess;   a first keel extending from the first surface of the first endplate and defining a longitudinal axis, wherein a center of the upper recess is laterally offset from the longitudinal axis;   a second endplate having a third surface and an opposite fourth surface, and a round second recess;   a second keel extending from the fourth surface of the second endplate;   an insert disposed in the first and second recesses.   
     
     
         2 . The artificial disc of  claim 1 , wherein:
 the endplates are elongate endplates shaped to lie in a medial-lateral direction;   the center of the first recess is disposed posteriorly from the longitudinal axis.   
     
     
         3 . The artificial disc of  claim 1 , wherein the first endplate includes a second insert defining the round second recess and adapted to receive a portion of the insert. 
     
     
         4 . The artificial disc of  claim 1 , wherein the insert has a domed surface adapted to be received in the first recess. 
     
     
         5 . The artificial disc of  claim 4 , wherein the insert contains a plurality of tabs configured to be snap fit into the second recess. 
     
     
         6 . The artificial disc of  claim 5 , wherein the second recess comprises a circular side wall divided into a superior portion and an inferior portion by a lip. 
     
     
         7 . The artificial disc of  claim 6 , wherein the plurality of tabs each contain a hook configured to grip the lip to secure the insert to the second endplate. 
     
     
         8 . The artificial disc of  claim 1 , wherein the first and second keels each include at least one hole perpendicular to the longitudinal axis to promote bony in-growth. 
     
     
         9 . The artificial disc of  claim 1 , wherein the first and second endplates are made of metallic material and the insert is made of thermoplastic material. 
     
     
         10 . The artificial disc of  claim 9 , wherein the first and second endplates are made of either titanium or cobalt material, and the insert is made of PEEK material. 
     
     
         11 . A lateral artificial disc comprising:
 an elongate superior endplate having a superior surface and an inferior surface, and a round upper recess formed on the inferior surface;   an upper keel extending upwardly from the superior surface of the superior endplate and defining a longitudinal axis, wherein a center of the round recess is laterally offset from the longitudinal axis;   an elongate inferior endplate having a superior surface and an inferior surface, and a round lower recess formed on the superior surface;   a lower keel extending downwardly from the inferior surface of the inferior endplate;   an insert disposed in the upper and lower recesses.   
     
     
         12 . The artificial disc of  claim 1 , wherein the elongate endplates are shaped to lie in a medial-lateral direction and the center of the upper recess is disposed posteriorly from the longitudinal axis. 
     
     
         13 . The artificial disc of  claim 1 , wherein the superior endplate includes a second insert defining the round upper recess and adapted to receive a portion of the insert. 
     
     
         14 . The artificial disc of  claim 1 , wherein the insert has a domed upper surface. 
     
     
         15 . The artificial disc of  claim 14 , wherein the insert contains a plurality of tabs configured to be snap fit into the lower recess. 
     
     
         16 . The artificial disc of  claim 15 , wherein the lower recess comprises a circular side wall divided into a superior portion and an inferior portion by a lip. 
     
     
         17 . The artificial disc of  claim 16 , wherein the plurality of tabs each contain a hook configured to grip the lip to secure the insert to the inferior endplate. 
     
     
         18 . The artificial disc of  claim 11 , wherein the superior and inferior keels each include at least one hole perpendicular to the longitudinal axis to promote bony in-growth. 
     
     
         19 . The artificial disc of  claim 1 , wherein the superior and inferior endplates are made of metallic material and the insert is made of thermoplastic material. 
     
     
         20 . The artificial disc of  claim 19 , wherein the superior and inferior endplates are made of either titanium or cobalt material, and the insert is made of PEEK material.