Introduction: Avascular necrosis (AVN) of bone is a process that is characterized pathologically by bone marrow ischemia and eventual death of trabecular bone. Following the development of the disease with the remodeling process, the microstructure and corresponding mechanical properties of the trabecular bone changes in different regions with different intensities. Eventually, the lesion leads to collapse of the femoral head and destruction of the hip joint. The most striking finding is the direct relationship between mechanical stress and the progressive collapse of the necrotic region. This study investigated the differences in the mechanical properties from the trabecular bone of the different regions in AVN of the femoral head using microfinite element models.

Materials and Methods: A 20mm cylindrical core sample was obtained from the necrotic zone of the human femoral head with pre-collapse disease throughout the overall head under the fluoroscope and then was scanned using Micro-CT. Region of interest (ROI) was determined in the necrotic, the reactive, and the sub-reactive zone respectively, which were created with the hexahedron mesh model; finite element analysis was performed.

Results: The histomorphology and FE-analysis of three zones revealed that the parameters of Tb. Th, BV/TV, reaction force, ultimated stress, and elastic modulus increase obviously in the reactive zone.

Discussion: The authors conclude that obvious increases of the parameters and the stress concentration in the reactive zone are due to the adaptive remodeling of trabeculae in the boundary zone between the necrotic and the normal zone.