Prosthetic intervertebral disk

Abstract

An intervertebral disk prostheses for the total replacement of an intervertebral disk of the lumbar and cervical spine has an upper plate having upwardly projecting formations anchoring it to an upper vertebra on its upper face and a concavity on its inner face surrounded by an edge. A lower plate is provided with downwardly projecting formations anchoring it to a lower vertebra on its lower face and a flat inner face surrounding a groove extending front-to-back. A middle plate between the upper and lower plate has on its upper face a convexity that is identically or differently shaped to the concavity on the inner face of the upper plate and a ridge extending front-to-back surrounded by a flat lower face of the middle plate. The ridge has flanks and the groove houses the ridge of the middle plate and permits the ridge to slide front-to-back in the groove.

1 . An intervertebral disk prosthesis for total replacement of an intervertebral disk of the lumbar and cervical spine, the prosthesis comprising:
 an upper plate having an upper face formed with upwardly projecting formations for anchoring the upper plate to an upper vertebra and a lower face formed with a concavity surrounded by an edge;   a lower plate having a lower face formed with downwardly projecting formations for anchoring the lower plate to a lower vertebra and a flat upper inner face forming and surrounding a groove that extends front-to-back; and   an intermediate sliding plate between the upper and lower plate having an upper face formed with a convexity engaging the concavity on the lower face of the upper plate and a flat lower face formed with and surrounding a guide ridge having flanks, extending front-to-back, and engaging in the guide groove of the upper plate such that the guide ridge can slide in a straight line front-to-back in the guide groove, the convexity of the intermediate sliding plate and the concavity of the upper plate permitting limited extension, flexion, lateral bending to right and left side, and axial rotation to both sides.   
     
     
         2 . The prosthesis defined in  claim 1 , wherein the guide ridge of the intermediate sliding plate ends with outwardly projecting portions and the guide groove of the lower plate has inwardly projecting formations that enclose and capture the portions of the guide ridge, whereby the intermediate sliding plate cannot be separated from the lower plate. 
     
     
         3 . The prosthesis defined in  claim 1 , wherein the guide groove and guide ridge are of complementary dovetail or T-section shape with sharp corners. 
     
     
         4 . The prosthesis defined in  claim 1 , wherein the guide groove and guide ridge are of dovetail or T-section shape with rounded corners. 
     
     
         5 . The prosthesis defined in  claim 1 , wherein the guide ridge comprises a stem and an outer end of the guide ridge has a larger dimension then the stem. 
     
     
         6 . The prosthesis defined in  claim 1 , wherein at least one of the plates is formed of two parts with one part having a fitting for a complementary recess in the other part. 
     
     
         7 . The prosthesis defined in  claim 1 , wherein the guide ridge is of at least semi-elastic composition so that the guide ridge can be elastically deformed and fitted into the guide groove. 
     
     
         8 . The prosthesis defined in  claim 7 , wherein the guide ridge is formed with at least one open slit so that the guide ridge can be deformed by compression. 
     
     
         9 . The prosthesis defined in  claim 1 , wherein an area surrounding the guide groove is at least semi-elastic so that the area surrounding the guide groove can be deformed for accommodating the guide ridge. 
     
     
         10 . The prosthesis defined in  claim 1 , wherein the lower plate or the upper plate or the intermediate sliding plate or the guide ridge are made of different material or the same material with different properties. 
     
     
         11 . The prosthesis defined in  claim 1 , wherein a plurality of the guide grooves and a corresponding plurality of the guide ridges are provided. 
     
     
         12 . The prosthesis defined in  claim 1 , wherein the lower plate is formed in the guide groove with narrow guide rails that fit in complementary guide slots in the guide ridge for guiding of the guide ridge in the guide groove. 
     
     
         13 . The prosthesis defined in  claim 1 , wherein the lower plate comprises a T-section guide ridge formed in the guide groove and the intermediate sliding plate comprises a complementary T-section guide groove formed in the guide ridge. 
     
     
         14 . The prosthesis defined in  claim 1 , wherein one of the plates is formed with at least one recess and is provided therein with an imaging ball. 
     
     
         15 . The prosthesis defined in  claim 14 , wherein the ball is of tantalum or other non-radiolucent material. 
     
     
         16 . The prosthesis defined in  claim 14 , wherein the plates are formed on outer surfaces with tool guides. 
     
     
         17 . The prosthesis defined in  claim 1 , wherein the intermediate sliding plate is exchangeable during revision surgery. 
     
     
         18 . The prosthesis defined in  claim 1 , wherein in sagittal view the intermediate sliding plate or the upper plate or the lower plate is angled. 
     
     
         19 . The prosthesis defined in  claim 18 , wherein the angle of the intermediate sliding plate or the upper plate or the lower plate is selected to avoid kyphosis in the spinal segment comprising the intervertebral disk to be replaced. 
     
     
         20 . The prosthesis defined in  claim 1 , wherein the guide groove comprises only the first body stop or only the second body stop, whereby the lower plate comprises an opening. 
     
     
         21 . The prosthesis defined in  claim 20 , wherein the opening is closed by a detachable covering cap.