INFLUENCE OF THIGH MUSCLES ON THE AXIAL STRAINS IN A PROXIMAL FEMUR DURING EARLY STANCE IN GAIT

This work is focused on the in vitro simulation of the loads occurring in the femur during early stance in gait, for hip prostheses stress s hielding test purposes. Ten thigh muscles (the three gluteal muscles, the three vasti, rectus femoris, adductor longus and magnus, biceps fe moris), simulated by nylon straps, were tested in order to establish t heir influence on the strains in the proximal femur. Axial and hoop st rains were recorded from 16 strain gauges for the effect of each muscl e and compared to the strains recorded as a result of the hip joint re action force only (i.e. without muscle simulation). It appears that th e three glutei are the principal muscles in determining the vertical s trains, however the rectus femoris, biceps femoris and the adductors w ere also seen to significantly affect the strain pattern. The inadequa cy of increasing the adduction angle and applying the resultant force at the hip joint to simulate the abductors was also confirmed.