Biomechanical analysis of postural control of persons with transtibial or transfemoral amputation.

ABSTRACT

OBJECTIVE: In human subjects, leg amputation impairs upright quiet-stance control. The inability to exert appropriate force reactions under the amputated leg and a slight weight-bearing asymmetry cause the amputee to develop compensatory mechanisms through the sound leg. This study is aimed at assessing these mechanisms and the influence of the level of amputation. DESIGN: The postural strategies of transtibial and transfemoral amputees for maintaining quiet stance were investigated using a dual-force platform. With this device, mean body weight distribution and plantar and resultant center of pressure trajectories can be measured and used to assess the likely compensatory mechanisms. RESULTS: Compensatory strategies were found in both transtibial and transfemoral groups, with a forward shift of the mean positions of the center of pressure under the amputated leg and greater resultant center of pressure displacements appearing along the anteroposterior axis, respectively. The transfemoral group presents a larger center of pressure displacements under the amputated leg than the transtibial group. CONCLUSION: These data emphasize the role played by the differences between the center-of-pressure magnitudes intervening under the sound and amputated legs and the size of the prosthesis-stump contact area in these postural strategies.