Biomechanical properties of trabecular bones in femoral head under loads with different angles / 医用生物力学

ABSTRACT

Objective To investigate the effects from loads with different angles on morphological and biomechanical properties of trabecular bones in femoral head, so as to provide theoretical basis for studying biomechanical mechanism of necrosis and collapse of femoral head. Methods Ninety-four specimens of 12-month-old ovine trabecular bones in femoral head and forty-three specimens of human cadaver trabecular bones in femoral head were prepared. According to different angles between loading direction and principle compression direction, all the trabecular bones were divided into five groups by 10° interval (i.e. varus 10° and 0°, valgus 10°, 20° and 30°) to simulate the reduction condition under different Garden index after internal fixation of femoral neck fractures. Micro-CT scanning and calculation, compression failure test on ovine trabecular bones in femoral head and cyclic compression test on human cadaver trabecular bones in femoral head were performed to investigate morphological and mechanical indices, including BV/TV (bone volume vs. total volume), BS/BV (bone surface vs. bone volume), Tb.Th (thickness of trabecular bone), Tb.N (number of trabecular bone), Tb.Sp (trabecular separation), elastic modulus, ultimate strength, yield strength, initial secant modulus and number of cycles. Results When the angle between loading direction and principle compression direction of trabecular bones was 0°, BV/TV, Tb.Th, elastic modulus, ultimate strength, yield strength, initial secant modulus and number of cycles for trabecular bones were the maximum while BS/BV and Tb.N were the minimum, and all the formers presented decreasing tendency while BS/BV and Tb.N showed increasing tendency along with the angle increasing. ConclusionsAlong with the angle changes, the tendency of BV/TV and ultimate strength for 12-month-old ovine trabecular bones in femoral head displayed as the same as human trabecular bones in femoral head. Both the morphological and biomechanical properties of trabecular bones in femoral head will decrease when the angle between loading direction and principle compression direction of trabecular bones increases. The more the Garden index deviating from 160°, the more likely trabecular bones in femoral head to be damaged.