Patent ID: 7879101

Claim:
An intervertebral prosthesis comprising: at least one non-spherical core positioned between an upper plate and a lower plate, said at least one core having a plurality of lateral faces, said upper and lower plates respectively comprising inner faces configured for allowing a displacement of said at least one core inside said prosthesis by sliding on the inner faces of said upper and lower plates, a flexible inner casing and at least one flexible outer casing, said at least one flexible outer casing containing a cavity in which said inner casing is positioned and said inner casing having a cavity in which said at least one core is positioned so that said at least one core is surrounded on all said lateral faces by said flexible inner casing, and said inner casing having in horizontal section a shape of a cross formed by four horizontal arms oriented perpendicularly, the arms so arranged defining two favored directions of flexibility oriented perpendicularly to each other.