Test Condition Optimization for Testing of Hip Protectors

Abstract

Determining the efficacy of hip protectors designed to reduce the menace of the alarming rise in hip fracture due to fall among the elderly population is particularly challenging. Hip protector evaluation has been done using different soft tissue surrogate and at different energy level to determine the effectiveness of various hip protectors. However, some hip protectors that had been ranked effective in mechanical testing systems proof otherwise when deployed for clinical trials, this may be due to lack of optimization of the testing condition, most notably in testing when the soft tissue surrogate attenuates impacts that may be unduly attributed to the effectiveness of the hip protector. In this study, the performance of a surrogate soft tissue, fabricated from polyethylene, was evaluated at different energy levels (3.68 J - 37.9 J) to ascertain the optimal position for evaluating the efficacy of a hip protector to simulate a representative condition of an actual fall to the sideways by a person. A drop-weight impact testing machine was used to evaluate the impact force response of an employed femoral geometry with and without the soft tissue at various residual impact energy. The result showed that the soft tissue might be responsible for up to about 95.17 % of peak impact force attenuation if not adequately modelled. Therefore various conditions were examined to get representative sideways impact condition where the soft tissue employed do not attenuate beyond 11 - 28 % of the peak impact force. This finding demonstrates that the impact condition is as critical as all other parameters in determining the performance of a hip protector.