Massive osteolysis due to failure of a unipolar endoprosthesis.

Unipolar endoprostheses are commonly used for the treatment of displaced femoral neck fractures in the elderly. Failure due to polyethylene wear, which has been well documented in bipolar endoprostheses, is not a commonly reported problem with unipolar prostheses. We present 2 cases of a particular unipolar design that failed due to polyethylene wear. We report these cases to promote awareness of this particular reason for failure in this design. We also question the need for polyethylene in any prosthetic, when it is not indicated for the bearing surface.