NATURAL COURSE AND PREDICTION OF PROGNOSIS OF FEMORAL HEAD OSTEONECROSIS

Regional Comparison of the Mechanical Characteristic of the Trabecular Bone in Avascular Necrosis of the Femoral Head Using Micro-finite Element Models
YY Won¹, MH Beak¹, WQ Cui1, HS Kim^2
1Department of Orthopaedic Surgery, School of Medicine, Ajou University, Suwon, Korea, and ²Department of Biomedical Engineering, Collage of Health Science, Yonsei University, Seoul, Korea

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

Coring 20mm cylindrical sample was obtained from the necrotic zone of the human femoral head with pre-collapse throughout overall head under the fluroscope 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 then performed finite element analysis.

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

We suppose that obvious increases of the parameter and the stress concentration in the reactive zone due to the adaptive remodeling of trabeculae in the boundary zone between the necrotic and the normal zone.