total hip arthroplasty is the head and proximal neck of the femur and removal of the acetabular cartilage and subchondral bone. An artificial canal is created in the proximal medullary region of the femur and a metal femoral prosthesis, composed of a stem and small-diameter head, is inserted into the femoral medullary canal. An acetabular component composed of a high-molecular weight polyethylene articulating surface is inserted proximally into the enlarged acetabular space (Figures l and 2). To yield successful results. these total hip arthroplasty components must be fixed firmly to the bone, either with polymethylmethacrylate cement or, in more recent uncemented designs. by bony ingrowth into a porous coating on the implant. resulting in "biologic" fixation