Femoral prosthesis trial fitting device

A trial fitting device for an implantable femoral prosthesis comprising a trial head, a bearing insert removably fitting within said trial head, a trial handle and a button with a spherical surface fitting within said bearing insert, said button and said bearing insert being removably affixed to said trial handle by suitable fastening means, said trial handle having a locking collar movably carried thereon for locking said button and bearing insert onto said trial head, said trial head comprising a substantially spherical body having a flat surface portion formed by removing a segment of a sphere therefrom thereby simulating the natural human femoral head and having a central bore extending axially through the flat surface portion, said bore having an annular groove formed therein adjacent the flat surface portion of said body, said bearing insert comprising a substantially cylindrical body having a plurality of flexible arms depending therefrom and a central bore extending through said cylindrical body, said flexible arms each having an annular ring segment on the exterior surface thereof adjacent its free end for wedging action with the annular groove of said bore, said button having a central bore axially therethrough, a threaded shank at one end and a less than hemispherical surface at its other end, said cylindrical body and the inner surfaces of said flexible arms being formed into a spherical cavity into which the hemispherical surface of the button is fitted, said spherical cavity permitting the free ends of said flexible arms to deflect inwardly to release the annular ring segments from the annular groove when said locking collar on said trial handle is loosened to thereby allow the trial handle and bearing insert and button to be removed from the trial head for replacement with a differently sized trial head.