Biomechanical investigation of ambulatory training in patients with acetabular dysplasia

The purpose of this study was to investigate the effectiveness and safety of ambulatory training in patients with acetabular dysplasia. To achieve this, we studied the hip joint moment in subjects walking with laterally and horizontally elevated arms and changing speeds as a form of training to strengthen hip joint abductor muscles. We studied eight women with pre- or early stage hip disease (center–edge angle of Wieberg 18.5° to −3.0°) and six healthy women. In exercise task 1 the subjects walked at a rate of 90 steps/min, with abduction of 90° in the shoulder joint ipsilateral or contralateral to the affected hip joint, and either no load or a 1 kg weight in either hand. In exercise task 2, walking speed was changed in three stages from 60 steps/min (s-gait), 90 steps/min (n-gait), and 120 steps/min (f-gait), with both hands swinging freely. Using results from a three-dimensional motion analysis system, the hip joint moments were calculated. In both the healthy and the acetabular dysplasia groups, the abduction moment of the hip joint decreased significantly with ipsilateral elevation and increased significantly with contralateral elevation. There was no significant change in hip flexion moment in either group. The hip extension moment decreased significantly with contralateral elevation, but no significant changes were seen in ipsilateral elevation. In the walking rate variation, the extension hip moment in fast gait was higher than in slow gait. It was concluded that ambulatory training with contralateral horizontal arm elevation may be an effective way of increasing hip joint abductor muscle strength. Ipsilateral arm elevation decreases gluteus medius muscle tension and is an effective way of ambulatory training for people with compensated trendelenburg gait. Variable speed walking is an effective exercise method that can strengthen extensor muscles. Therefore, these ambulatory training methods are useful for acetabular dysplasia patients.