IMPROVED JOINT ENDOPROSTHESIS

摘要

Joint endoprosthesis for the total replacement of degenerate joints such as the andle, knee, elbow, wrist and finger. When embodied as an ankle endoprosthesis (10), the device comprises a tibial component (11) which provides a first bearing surface (21a); a talar component (13) which provides a second bearing surface (34) which is at least a segment of a surface of revolution about a first axis (2); and a tibial insert (12) intermediate the tibial and talar components (11 and 13) which provides a third bearing surface (26a) which provides area contact with the first bearing surface (21a) to permit relative rotation between the tibial component (11) with respect to the tibial insert (12) and the talar component (13) about a second axis (1) that is substantially parallel to the shaft of the tibia and which relative rotation provides one of only two degrees of freedom of rotational movement of said tibia with respect to said talus, and wherein the tibial insert (12) is further provided with a fourth bearing surface (29) in area contact with the second bearing surface (34) that is in sliding engagement therewith to permit relative rotational movement of the tibial component (11) and tibial insert (12) with respect to the talar component (13) about the first axis (2) which relative rotation thereby provides the second of only two degrees of freedom of rotational movement of said tibia with respect to said talus. The joint endoprosthesis overcomes the problem of poor wear characteristics on parts due to high stresses and pressures resulting from normal joint loads and avoids bone fushion techniques.