Effect of multiple impacts on protective properties of external hip protectors.

A variety of external hip protectors are available on the market but no standards for their performance exist and it is unknown if their properties change after repeated fall impacts. The purpose of this study was to determine if protective properties change in different types of new (unused) hip protectors after repeated, simulated falls. Five hip protector brands were chosen to represent different products available on the market and the two mechanisms employed in reducing the force of an impact (shunting or absorbing). Ten pairs of each type (20 pads for each brand) were tested using a 1.8-m Instron Dynatup 9250 HV vertical impact testing tower. The impact testing system was specifically designed for this study by creating a simulated trochanter to provide more accurately a impact area similar to that of a real hip bone. The hip protectors were impacted once a day for 3 consecutive days. Repeated impacts demonstrated the pads' decreased ability to either absorb or shunt force in all types of hip protectors. However, the mean forces were still in the protective range (force below fracture threshold of 3100 N) for 3 of the 5 brands tested after 3 impacts. The protective properties of external hip protectors do degrade after repeated impacts. The degree of degradation differs from brand to brand. Regardless of type, most pads were still able to bring the force of impact below the fracture threshold of 3100 N. Future studies need to address the issue of durability of different types/brands of hip protectors after repeated laundering and fall impacts to determine when should they be replaced. Additionally, a national or international standard needs to be developed against which the performance of different brands of hip protectors can be compared.