FATIGUE TESTING OF ENERGY-STORING PROSTHETIC FEET

This paper describes a simple approach to the fatigue testing of prost hetic feet. A fatigue testing machine for prosthetic feet was designed as part of the programme to develop an energy storing prosthetic foot (ESPF). The fatigue tester does not simulate the loading pattern on t he foot during normal walking. However, cyclic vertical loads are appl ied to the heel and forefoot during heel-strike and toe-off respective ly, for 500,000 cycles. The maximum load applied was chosen to be 1.5 times that applied by the bodyweight of the amputee and the test frequ ency was chosen to be 2 Hz to shorten the test duration. Four prosthet ic feet were tested: two Lambda feet (a newly developed ESPF), a Kings ley SACH foot and a Proteor SACH foot. It was found that the Lambda fe et have very good fatigue properties. The Kingsley SACH foot performed better than the Proteor model, with no signs of wear at the heel. The results obtained using the simple approach was found to be comparable to the results from more complex fatigue machines which simulate the load pattern during normal walking. This suggests that simple load sim ulating machines, which are less costly and require less maintenance, are useful substitutes in studying the fatigue properties of prostheti c feet.