The viability of the femoral head after resurfacing hip arthroplasty in humans.

Histologic examination of 72 femoral heads retrieved at revision of resurfacing arthroplasties was performed to determine the possible role of generalized osteonecrosis caused by avascular necrosis (AVN) in early loosening of the femoral components. The degree of loosening at the femoral bone-cement interface was correlated with the histologic appearance of the femoral heads. None of the ten femoral heads with solid femoral components and only one of the 15 heads with slight loosening showed evidence of generalized osteonecrosis. The one case might have been attributable to AVN after the resurfacing procedure. In the remaining femoral heads with marked loosening of the femoral component, necrosis of bone was uncommon. When present, it was attributed to loosening. Thickening of bone trabeculae, a fibrovascular marrow, and superficial necrosis of bone of the femoral head are not evidence of generalized AVN caused by the resurfacing arthroplasty procedure, but are the result of remodeling changes and subsequent loosening.