Proximally self-locking long bone prosthesis

A femoral stem hip implant for insertion into a surgically created aperture in a femur, the implant comprising:

• a monolithic femoral stem made of shape memory material, the stem configured to be inserted into the aperture, the stem having a proximal portion and a longitudinal axis, the shape memory material within the proximal portion having a cross-section perpendicular to the longitudinal axis, at least a portion of the shape memory material within the proximal portion being in a compressed state by application of a plurality of compressive forces at a temperature below an austenitic finish temperature of the shape memory material so that the cross-section of the shape memory material expands through shape memory effect via the formation of austenite in response to a temperature increase after insertion into the aperture thereby causing a locking-force to be exerted against an inner surface of the aperture, the locking force being sufficient to stabilize the implant in the aperture, wherein at least 70% of the cross-section is occupied by shape memory material.