Hip cartilage supported by methacrylate in canine arthroplasty.

A theoretically attractive approach to femoral head arthroplasty would be the preservation of a"biologic" bearing surface composed of autogenous articular cartilage and subchondral bone, supported by a prosthetic material with mechanical properties similar to those of trabecular bone. The substitution of such a material for bone would preclude incomplete revascularization of the femoral head and eventual bony collapse. The advantages of preserving the patient's hip joint, even in the face of a fracture that has caused the loss of vascular supply to the femoral head, are self-evident. To test this hypothesis, seven dogs underwent hip arthroplasty, whereby the trabecular bone of the femoral head was replaced with polymethylmethacrylate. When killed 2 1/2 years after operation all of the dogs demonstrated injury or loss of articular cartilage in the superior aspect of the femoral head. The lesions are consistent with advanced osteoarthritis by gross and histologic examination. These lesions apparently were produced by changing either the geometry or stiffness, or both, of the material supporting the articular cartilage. Supporting human articular cartilage with methacrylate for joint arthroplasty is not recommended.