We employed an anatomically realistic three-dimensional finite-element
model to explore several biomechanical variables involved in coring or
bone-grafting of a segmentally necrotic femoral head. The mechanical
efficacy of several variants of these procedures was indexed in terms of
their alteration of the stress:strength ratio in at-risk necrotic
cancellous bone. For coring alone, the associated structural compromise was
generally modest, provided that the tract did not extend near the
subchondral plate. Cortical bone-grafting was potentially of great
structural benefit for femoral heads in which the graft penetrated deeply
into the superocentral or lateral aspect of the lesion, ideally with
abutment against the subchondral plate. By contrast, central or lateral
grafts that stopped well short of the subchondral plate were
contraindicated biomechanically because they caused marked elevations in
stress on the necrotic cancellous bone. Calculated levels of stress were
relatively insensitive to variations in the diameter of the graft.