Intervertebral Prosthesis with Self-Tapping Fixing Projections

Abstract

An intervertebral prosthesis, in particular for the cervical spine, has two attachment plates connected in an articulated manner. The attachment surfaces of the attachment plates, which are configured for attachment to adjacent vertebral bodies have a base surface configured to bear on the surface of the vertebral bodies, and self-tapping fixing projections rising from the base surface. These fixing projections are formed by at least one pair of ribs which extend in opposite directions obliquely with respect to a predetermined implantation direction and whose side faces oriented more away from the implantation direction are steeper than their side faces oriented more in the implantation direction. The ribs can be toothed.

What is claimed is: 
     
         1 . An attachment plate forming part of an intervertebral prosthesis including two attachment plates arranged in an articulating manner, the attachment plate comprising:
 an attachment surface configured for attachment to an adjacent vertebral body having a base surface configured to bear on a endplate of the adjacent vertebral body;   fixing projections rising from the base surface wherein the fixing projections are arranged symmetrically about a medial plane in at least two rows with an interspace opening between the rows, the rows extending outwardly and obliquely in a V-shape with respect to an implantation direction;   wherein the fixing projections are configured with a first limit surface formed by a lateral-facing side surface, a second limit surface formed by a medial-facing side surface, a third limit surface formed by a steep ventral-facing surface, and a fourth limit surface formed by an inclined dorsal-facing surface; and   wherein the fixing projections are self-tapping and configured to penetrate into the endplate of the adjacent vertebral body.   
     
     
         2 . The attachment plate of  claim 1 , wherein the inclined dorsal-facing surface encloses an angle of approximately 45° or less with respect to the base surface, measured in a plane extending parallel to the implantation direction and perpendicular to the base surface, wherein the steep ventral-facing surface is substantially perpendicular to the base surface, wherein the medial-facing side surface and lateral-facing side surface are substantially perpendicular to the base surface, and wherein the medial-facing side surface and lateral-facing side surface are substantially parallel to one another and to the implantation direction. 
     
     
         3 . The attachment plate of  claim 1 , wherein the inclined dorsal-facing surface has a surface that is configured with a fine toothing. 
     
     
         4 . The attachment plate of  claim 1 , wherein the fixing projections have a height that (a) does not exceed about 2 mm above the base surface, (b) does not exceed about 1.6 mm above the base surface, or (c) is between about 0.7 mm to 1.5 mm above the base surface. 
     
     
         5 . The attachment plate of  claim 1 , wherein an angle a formed by the V-shape extending outwardly and obliquely with respect to the implantation direction has an angle: (a) smaller than 60°, (b) smaller than 30°, or (c) approximately 20°. 
     
     
         6 . The attachment plate of  claim 1 , wherein at least one row reaches at least as far as one fifth of an anterior to posterior dimension of the attachment surface from a dorsal boundary thereof relative to the implantation direction. 
     
     
         7 . The attachment plate of  claim 1 , wherein the base surface is provided with a surface structure permitting in-growth of bone tissue that bears substantially across the endplate of the vertebral body and wherein the surface structure is one or more of: (a) an arrangement of rows of serrations, (b) a porous coating, or (c) an arrangement of rows of serrations and a porous coating. 
     
     
         8 . An attachment plate forming part of an intervertebral prosthesis including two attachment plates connected in an articulating manner, the attachment plate comprising;
 a base surface configured with serrated ridges for attachment to an endplate of an adjacent vertebral body; and   cutting teeth configured to penetrate the endplate of the adjacent vertebral body, each of the cutting teeth extending from the base surface and defined by an inclined posterior-facing surface having a stair-stepped toothing, a steep anterior-facing surface, a medial-facing side surface, and a lateral-facing side surface, wherein the cutting teeth are arranged in at least two rows arranged with an interspace opening between the rows, the rows arranged symmetrically in a V-shape about a median plane in an anterior to posterior direction wherein the at least two rows converge in the posterior direction and open outward in the anterior direction.   
     
     
         9 . The attachment plate of  claim 8  wherein the angle of inclination of the inclined posterior-facing surface is approximately 45° or less. 
     
     
         10 . The attachment plate of  claim 8 , wherein the steep anterior-facing surface is substantially perpendicular to the base surface, wherein the medial-facing side surface and lateral-facing side surface are substantially perpendicular to the base surface, and wherein the medial-facing side surface and lateral-facing side surface are substantially parallel to one another and to the median plane. 
     
     
         11 . The attachment plate of  claim 8 , wherein the cutting teeth have a height that (a) does not exceed about 2 mm above the base surface, (b) does not exceed about 1.6 mm above the base surface, or (c) is between about 0.7 mm to 1.5 mm above the base surface. 
     
     
         12 . The attachment plate of  claim 8 , wherein an angle α formed by the converging rows in the posterior direction has an angle that is: (a) smaller than 60°, (b) smaller than 30°, or (c) approximately 20°. 
     
     
         13 . The attachment plate of  claim 8 , wherein the base surface is substantially covered with a porous coating to promote bone tissue ingrowth to the attachment plate. 
     
     
         14 . The attachment plate of  claim 8 , wherein the cutting teeth are arranged in a central area of the attachment plate, the central area being at a distance of more than one sixth of an anterior to posterior dimension from a nearest edge. 
     
     
         15 . The attachment plate of  claim 8 , wherein both attachment plates of the intervertebral prosthesis are configured identically.