A new design of the Christiansen endoprosthesis. Report of two cases in which separation of the two components of the prosthetic head occurred.

Primary prosthetic replacement in elderly patients with displaced intracapsular fracture of the femoral neck has been used during the last few years with encouraging early results. The prosthetic device preferred has been Christiansen's endoprosthesis. During the past year a new type with separable plastic head and metallic cap has been used. This modification has resulted in the occurrence of a previously unknown complication, a separation of these two parts, necessitating reoperation and insertion of a new head piece. The possible mechanisms causing this separation are discussed.