Spacerless artificial disc replacements

Abstract

Spacerless artificial disc replacements (ADR) are disclosed. One preferred embodiment includes two saddle-shaped components to facilitate more normal spinal flexion, extension, and lateral bending while limit axial rotation, thereby protecting the facet joints and the annulus fibrosus (AF). Either or both of the superior and inferior components are made of a hard material such as chrome cobalt, titanium, or a ceramic including alumina, zirconia, or calcium phosphate. The articulating surfaces of the ADR are also preferably highly polished to reduce friction between the components. Metals, alloys or other materials with shape-memory characteristics may also prove beneficial.

1 . An artificial disc replacement comprising: 
 a first component having a first articulating surface, said first articulating surface being a single saddle-shaped surface; and    a second component having a second articulating surface in contact with said first articulating surface, said second articulating surface being a single saddle-shaped surface,    wherein said first and second components are operable to articulate relative to one another about at least one of (i) a first center of rotation located above said first and second articulating surfaces for one of flexion/extension or lateral bending, and (ii) a second center of rotation located below said first and second articulating surfaces for the other of flexion/extension or lateral bending.    
   
   
       2 . The artificial disc replacement of  claim 1 , wherein said first and second articulating surfaces engage one another.  
   
   
       3 . The artificial disc replacement of  claim 1 , wherein said first and second articulating surfaces include substantially congruent surfaces.  
   
   
       4 . The artificial disc replacement of  claim 1 , wherein said first articulating surface includes a single substantially continuous concave surface and a single substantially continuous convex surface, and said second articulating surface includes a single substantially continuous concave surface and a single substantially continuous convex surface.  
   
   
       5 . The artificial disc replacement of  claim 4 , wherein the concave surface of said first articulating surface engages the convex surface of said second articulating surface, and the convex surface of said first articulating surface engages the concave surface of said second articulating surface.  
   
   
       6 . The artificial disc replacement of  claim 4 , wherein the single concave and convex surfaces of said first articulating surface extend between outer edges of said first articulating surface, and the single concave and convex surfaces of said second articulating surface extend between outer edges of said second articulating surface.  
   
   
       7 . The artificial disc replacement of  claim 1 , wherein said first articulating surface is defined by a concave arc having a substantially constant radius of curvature A about a first axis, and a convex arc having a substantially constant radius of curvature B about a second axis perpendicular to the first axis, and said second articulating surface is defined by a convex arc having a substantially constant radius of curvature C about a third axis, and a concave arc having a substantially constant radius of curvature D about a fourth axis perpendicular to the third axis.  
   
   
       8 . The artificial disc replacement of  claim 7 , wherein said radius of curvature A is substantially equal to said radius of curvature C and said radius of curvature B is substantially equal to said radius of curvature D.  
   
   
       9 . The artificial disc replacement of  claim 7 , wherein at least one of: (i) said first and third axes are coaxial; and (ii) said second and fourth axes are coaxial.  
   
   
       10 . The artificial disc replacement of  claim 7 , wherein at least one of: (i) said first and third axes are coplanar; and (ii) said second and fourth axes are coplanar.  
   
   
       11 . The artificial disc replacement of  claim 1 , wherein said first and second member further include projections for engaging a vertebral body.  
   
   
       12 . The artificial disc replacement of  claim 11 , wherein said projections are keels.  
   
   
       13 . The artificial disc replacement of  claim 11 , wherein said projections are selected from the group consisting of flanges, keels and spikes.  
   
   
       14 . The artificial disc replacement of  claim 1 , wherein said first and second components are constructed of hard materials.  
   
   
       15 . The artificial disc replacement of  claim 14 , wherein said hard materials are selected from the group consisting of chrome cobalt, titanium, alumina, zirconia, and calcium phosphate.  
   
   
       16 . The artificial disc replacement of  claim 1 , wherein said first and second components each further include vertebral surfaces for contacting vertebral bodies.  
   
   
       17 . The artificial disc replacement of  claim 16 , wherein said vertebral surfaces have plasma spray or beads thereon.  
   
   
       18 . The artificial disc replacement of  claim 1 , wherein said first component is cemented to a first vertebral body and said second component is cemented to a second vertebral body.