Early Subchondral Cortical Bone Biomechanical Changes in Relation to the Pre-Collapse Osteonecrosis of the Femoral Head-A Three-Dimensional Finite-Element Simulation

摘要

Background: This paper presents evidence to support a hypothesis that the biomechanical changes of subchondral cortical bone in the osteonecrosis of the femoral head (ONFH) are prior to articular cartilage, and subchondral cortical bone damage is one of the initial mechanisms involving the development of osteoarthritis which is related to the reduced load-bearing ability of the necrotic bone. Methods: A healthy hip model was developed from CT scans of a 23-year old male volunteer by Mimics software. Four parametric models were developed to simulate different classifications of ONFH based on Japanese Investigation Committee (JIG) classification criterion and healthy hip model. Load share relation and stress transfer pattern (STP) were selected for quantitative and qualitative studies. Results: The results showed that as the size of necrotic segment increased and located more laterally, load share ratio (LSR) of subchondral cancelous to cortical bone dropped significantly. There was no significant difference on contact stress between the normal femoral head and four subtypes of ONFH. Conclusions: This study indicates that early subchondral cortical bone damage is correlated significantly with the JIG classification of ONFH. The biomechanical changes in the subchondral cortical bone may precede cartilage degeneration. Subchondral cortical bone changes are not the etiology of osteoarthritis, but non-physiologic mechanical changes may affect the joint homogeneous and lead to subchondral cortical bone failure and osteoarthritis.