Hip fractures, which represent a severe health problem for the elderly, typically result in sideways falls with a direct impact to the hip. One possibility to prevent hip fractures is the use of hip protectors. An experimental test device was developed which consists of anatomically shaped structures that represent the hard and soft tissues of the femur and the hip. In parallel to the development of the experimental set-up, a finite element model of the device was established. On the one hand the model was used during the design process to investigate several design aspects like the positioning of the load cell or the choice of materials for the soft tissue surrogate. On the other hand, as the final model matches exactly the test device, it was used to study different hip protector design strategies and can serve as a design tool for the development of new hip protectors. By means of finite element modelling, a detailed stress analysis of the device under impact was performed to ensure that the tri-axial load cell of the experimental set-up was positioned reasonably, i.e. at the position where the maximum stress can be expected in the femoral neck. The mechanical hip model was used to investigate ten different types of hip protectors, including three energy-shunting systems with hard shells and seven energy-absorbing systems consisting of soft foam pads. The anatomically shaped hip model which was developed in this study is suitable to investigate the effect of hip protectors with respect to femoral neck loading. Different design strategies of hip protectors as well as different positioning (out-of-position problem) can be analysed. Hence it is possible to use the test device plus a standardised test procedure as basis for a quality assessment scheme to rate the performance of commercially available hip protectors. In addition, the device is helpful for the optimisation and development of future protectors. Correlating the load recorded to the actual risk of sustaining femoral neck fractures, a Swiss certificate will be issued which allows the consumer to assess the protective potential of a hip protector. For the covering abstract see ITRD E141807.
Samenvatting