Walking patterns of hip arthroplasty patients: some observations on the medio-lateral excursions of the trunk

PURPOSE: This study examined the angular gait kinematics of the trunk and the pelvis in the frontal plane and their amount of side-to-side asymmetry in patients after total hip replacement arthroplasty. METHOD: The angular gait kinematics of 12 male hip arthroplasty patients (53-70 years) were compared to ten age-matched and ten young (24-35 years) male control subjects. Average step times and medio-lateral oscillation amplitudes of the pelvic and thoracic recordings were calculated for each step. Between successive steps the asymmetry ratio was computed and the mean angle around which the side-to-side oscillations occurred was compared to the angle in a symmetrical standing trial. RESULTS: ANOVA indicated no significant side differences in relative step cycle durations. Patients and senior controls had significantly (p<0.01) less pelvis side-to-side displacements than the younger controls. No significant between-group differences could be detected for the average asymmetry ratio. However, during walking the patients showed a significantly (p<0.01) increased lateral thorax and pelvis deviation. CONCLUSIONS: Hip replacement patients' thoracic and pelvic position is characterized by a lateral shift throughout the gait cycle, while left and right symmetry of angular movements amplitudes remain at about the same value of unimpaired subjects.