Stress transmission anomalies in femoral heads altered by aseptic necrosis.

Abstract The effects of aseptic necrosis upon load transmission patterns in the adult femoral head are explored by means of a two-dimensional finite element model. Experimental measurements of the modulus reductions of necrotic human cancellous bone are incorporated in the computation, by reducing the elasticity matrix values within the simulated infarct regions. Stress distribution patterns characterizing the effects of parametric variations of the stiffness deficit, and the lesion base width, depth, and apex width are presented. The data show that the intact viable bone surrounding a weakened infarct preferentially takes up additional load, but that the degree of stress relief achieved is a strong function of the infarct geometry. The results indicate that osteotomies undertaken to provide stress relief are likely to be most effective for narrow infarcts, and that achieving stress relief for the superior aspect of the lesion should be the principal objective of such procedures.