A biomechanical analysis of running for trans-femoral amputees

Lower limb amputation results in changes to the usual pattern of human locomotion. Previous research has shown that amputees walk more slowly due to asymmetries In their movement patterns and that trans-femoral amputee gait was also found to be sensitive to the inertia of the prosthesis. As the majority of previous studies on amputee gait have been confined to walking the aim of this study was to develop an understanding of the blomechanical processes that occur when a trans-femoral amputee runs, with the primary objective to enhance performance. The research hypothesis was; "There is a knee axis location which optimizes the inertial characteristics of the trans-femoral amputee's prosthesis, and therefore improves the running performance". With the specific objectives of this study as follows: (a) To collect baseline biomechanical data (kinematic, kinetic and temporal) on the walking and running gait for a group of elite athletes with trans-femoral amputations; (b) To evaluate the performance of the standard prosthesis at walking and running speeds; (c) To develop a mathematical model that simulated the swing phase of the trans-femoral prosthesis, so that the effect of inertial changes to the prosthesis on swing time could be predicted (d) To compare the performance of configurations suggested by the model with physical tests on the modified prosthesis when used for running. The subject group consisted of highly active trans-femoral amputees who were members of the Australian Paralymplc squad for the 1996 Atlanta Paralymplc Games. Their running performance was analysed with their standard prosthesis and then repeated for a total of three modified prosthetic configurations. Each modification was based on the predictions of a mathematlcal model which was developed using the MATALB software. In addition to the objective biomechanical data collection, a subjective written survey was completed by the subjects. With each subject using their same prosthetic components this research found a significantly (p<0.001) faster running velocity for all subjects when they ran with the prosthetic knee axis lower than the standard anatomical configuration. Due to this technological advancement a 15 to 40 percent range of Improvement in running velocity was achieved. This finding was supported by improved indices of symmetry between lnterlimb performance as well as positive subject feedback.