Patent ID: 8790404

Claim:
An intervertebral disk prosthesis, comprising: an upper plateau ( 16 ) having i) an upper external surface ( 16 a ) capable of bearing on an upper vertebra, ii) a lower surface ( 16 b ) directed downwardly, and iii) a upwardly convex depression within the lower surface ( 16 b ); a lower plateau ( 18 ) having i) a lower external surface ( 18 a ) capable of bearing on a lower vertebra, ii) an upper bearing surface ( 18 b ) directed upwardly towards the lower surface ( 16 b ) of the upper plateau ( 16 ), the upper bearing surface ( 18 b ) being comprised of an upwardly concave-shaped surface part ( 22 ) surrounded by a flat part ( 23 ), and iii) an upwardly extending edge ( 19 ) delimiting the flat part ( 23 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ), a region open to an environment outside of the intervertebral disk prosthesis being present between the lower surface ( 16 ) of the upper plateau ( 16 ) and the top edge surface of the upwardly extending edge ( 19 ) such that a part of the flat part ( 23 ) delimited by the upwardly extending edge ( 19 ) is open to the environment outside of the intervertebral disk prosthesis; and an intermediate part ( 20 ) comprising an upper surface defined by a spherical upwardly convex domed part ( 27 ) and a lower surface, the intermediate part ( 20 ) being located between the lower surface ( 16 b ) of the upper plateau and the upper bearing surface ( 18 b ) of the lower plateau, the upwardly convex domed part ( 27 ) being in movable contact with the upwardly convex depression within the lower surface ( 16 b ) of the upper plateau ( 16 ), the lower surface of the intermediate part ( 20 ) being carried by direct contact with the flat part ( 23 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ), the intermediate part ( 20 ) being laterally movable on an area of the flat part ( 23 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ) delimited by the upwardly extending edge ( 19 ); and a lumen ( 25 ) defined by the upwardly concave-shaped surface part ( 22 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ) and a portion of the lower surface of the intermediate part ( 20 ), wherein upon a vertical impact on the upwardly convex domed part ( 27 ) of the intermediate part ( 20 ) during sudden or vibratory movements in everyday life, elasticity of the intermediate part ( 20 ) allows deformation of the upwardly convex domed part ( 27 ) of the intermediate part ( 20 ) to at least partial fill the lumen; and wherein the flat part ( 23 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ) is located around the upwardly concave-shaped surface part ( 22 ) of the upper bearing surface ( 18 b ) of the lower plateau ( 18 ), and a surface ratio between the upwardly concave-shaped concave part ( 22 ) and the flat part ( 23 ) of the upper bearing surface ( 18 b ) is in a range between 1/4 and 3/4.