The purpose of this research was to test in vitro the energy (or force) absorbing characteristics of the foams that are used inside various industry produced hip protectors. Hip protectors are medical devices sold as undergarments (usually) that protect the hip during a fall. When worn correctly, the energy absorbing material, typically a polyurethane/polyethylene foam or a hard shell or a combination of both, covers the hip so that any impact will be reduced to safer levels such that a hip fracture will be averted

The experiments were conducted using a drop weight apparatus that simulated the dynamic forces transferred to the greater trochanter area of the femur during a typical fall. Impacts were conducted using an Instron 8250 DynaTup apparatus. A surrogate hip model (Fig. 1) was fabricated and impact conditions were simulated for an elderly female subject. The average energy introduced into the apical surface of the substrate was 80 J, with an impact velocity of 2.14 m/s. The crosshead was outfitted with the approximate effective mass (35 kg) during a fall onto the lateral side of a patient, specifically the greater trochanter of the femur. Details of the experimental setup and the results on tests done on the foams inside various commercial hip protectors can be found in the MS thesis of Bimal Gandhi.

Figure 1. A surrogate hip model