PROBLEM TO BE SOLVED: To provide a cervical intervertebral disc protease having facing saddle-shaped joint surfaces having a fixed radius.;SOLUTION: A joints joining implant to be used in the spine has a pair of upper and lower facing members 200 and 300 having engagement joint surfaces which provide the center of rotation of the implant on the upper side of adjoining vertebral end-plate surfaces in a transverse bending mode and provide the center of rotation of the implant on the lower side of the vertebral end-plate surfaces in a bending/extension mode. Furthermore, the facing members can mutually axially rotate without causing the members to move around the longitudinal axis of the spine in the opposite directions along the longitudinal axis across and within an angular range. In a preferable embodiment, the joint faces furthermore cause the facing members to move in the opposite directions when the movement exceeds the range.;COPYRIGHT: (C)2010,JPO&INPIT
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