Total wrist prosthesis

Abstract

A total wrist prosthesis which has a metacarpal component and a radial component having ellipsoidal articulating surfaces. The metacarpal component and the radial component each have a fixation stem for insertion into the third metacarpal and the radius respectively. The fixation stem of the metacarpal component is curved dorsally to volarly so as to approximate the natural curvature of the third metacarpal and capitate of the human hand. The fixation stem of the metacarpal component has a center line which attaches to the head of the metacarpal component which contains the articulating surface dorsally from the minor axis of the ellipsoidal articulating surface. The fixation stem and the head of the metacarpal component have a plurality of wings attached thereto and a spur to prevent rotation of the device once inserted into the metacarpal. Also, the surface area of the metacarpal component proximal to the ellipsoidal articulating surface is coated with porous coating to aid in cement fixation. The radial component of the wrist prosthesis also has a fixation stem which is fixedly attached to a holder which receives a bearing member that defines a concave ellipsoidal articulating surface which is complimentary to the convex articulating surface of the metacarpal component. The center line of the fixation stem of the radial component is displaced dorsally from the minor axis of the concave articulating surface and also radially from the minor axis. A porous coating is also present about the base of the holder and the fixation stem. The curvature of the metacarpal fixation stem and the displacement of the center lines of both fixation stems relative to the minor axis of the ellipsoidal surfaces to which they are attached cause the center of rotation and flexion-extension motion and radial-ulnar-deviation to approximate the natural centers of rotation of flexion-extension motion and radial-ulnar-deviation.

Dependencies are inferred from the claim text.