Compensatory mechanism involving the hip joint of the intact limb during gait in unilateral trans-tibial amputees

Abstract

Hip dynamics in the intact limb during the beginning of stance phase in unilateral trans-tibial amputees (TTA) was studied to evaluate its contribution to compensatory function. We hypothesized (1) an increase in hip total work during H1 power phase (0-30% of gait cycle) including an initial negative phase and (2) an intensification of the hip work in response to uncomfortable gait induced by prosthesis misalignment. Three-dimensional gait analysis was conducted in 17 unilateral TTA and 15 healthy subjects walking at the same self-selected speed in three prosthetic alignments: initial alignment (IA); IA altered either by 6 degrees of internal rotation (IR) or by 6 degrees of external rotation. Patients reported best comfort of gait in IA condition and discomfort mainly in IR condition. During the H1 power phase, in intact limbs a consistent initial flexion movement of the hip (0-8% gait cycle) was associated to negative work and was followed by hip extension and positive work whereas in both prosthetic and control limbs only hip extension and positive work occurred (except in one healthy individual). Absolute value of hip work during H1 phase was significantly higher in intact and prosthetic limbs compared to control limbs in IA condition and was further significantly increased in IR condition only in intact limbs demonstrating a compensatory function of the latter. In intact limbs, early hip negative work contributed to energy absorption in addition to the knee joint probably to compensate the lower energy absorption exerted by the prosthetic limbs.