| 摘要 |
A prosthetic wrist joint for anchoring into the radius and the metacarpals includes a radial component, a metacarpal component and an intermediate component. The radial component has a part-cylindrical bearing surface and a stem portion for insertion into the end of the radius bone. The metacarpal component has a ball-like hinge portion and a pair of outwardly protruding prongs for anchoring into the second metacarpal and the third metacarpal. The intermediate component includes a cylindrical bearing surface which cooperatively engages the part-cylindrical bearing surface of the radial component, and a socket-like recess for receiving the ball-like hinge portion of the metacarpal component for movement in the direction of radial-ulnar deviation. The modified ball and socket arrangement between the metacarpal component and the intermediate component permit limited rotational movement about the longitudinal axis of the arm. The three components are arranged such as to have a full range of motion wherein wrist motion is limited solely by the surrounding soft tissue rather than by the wrist prosthesis components. The calculated rotational motion has an axis which is coincident with the anatomical center of rotation of the wrist rather than being centered about the stem axis of the prosthesis. The intermediate component is arranged relative to the radial component such that when the prosthetic wrist joint is loaded beyond its capacity in one of the various motion planes, the intermediate component will dislocate rather than break or loosen.
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