Assessment of press-fit hip femoral components retrieved at autopsy

Eleven femurs with press-fit titanium hip components were retrieved at autopsy for clinical, radiographic, and histologic evaluation. Back-scattered electron microscopy (BEM), bone densitometry, and appositional bone index studies also were performed. The average patient age was 87 years; the average time in situ was 22 months (range: 2 to 60). All patients were functioning well and pain free. Radiographs and bone mineral density studies (BMD) showed mild proximal stress shielding in five cases. No cases of osteolysis or pedestal formation were observed. Histologic sections revealed an average of 26% bone-prosthesis contact. Bone surrounding the prosthesis appeared viable, and osteoclastic activity in the interfacial bone was minimal; the presence of macrophages and inflammatory cells was rare. The appositional bone index averaged 40%. Bone-prosthesis contact was seen consistently at the corners of the component in the multiple regions, mostly were prosthesis-endosteal cortical contact was made. BEM demonstrated intimate contact of bone with the rough titanium surface. Bone mineral density was lower in the lesser trochanter and medial proximal regions of the implanted femur than in the contralateral femur. Evidence of bone on-growth fixation in 11 femoral components suggests that cementless, stable bone fixation may be achievable in senior individuals and that "complete fit and fill," porous-coated, cementless prostheses may not be required for prosthesis stability.