Pre-collapse stress redistributions in femoral head osteonecrosis--a three-dimensional finite element analysis.

Three-dimensional finite element analysis is used to explore the influence of several lesion characteristics upon mechanical stress distributions in segmentally necrotic human femoral heads. Variables studied parametrically included apparent modulus deficits within the lesion proper, as well as the depth, width, and location of the infarcted head regions. The detailed patterns of stress redistribution were complex and were found to be a strong function of the specific lesion characteristics. The salient phenomenon, however, was one of preferential load uptake by the stiffer bone surrounding the lesion. Since computed stress reductions within the infarctions were usually much smaller than experimentally observed strength reductions, the data suggest a strong tendency for an elevated incidence of trabecular fatigue fractures in the affected regions.