Biomechanical and computational investigation of the hip protector design and function

and related hip fracture in the elderly population are a serious problem in health care. It is widely documented that prevention of hip fracture has the potential to improve the quality of life and substantially decrease health care costs, and the methods aimed at prevention of hip fracture are of considerable interest. Hip protectors have been identified as one of the noninvasive preventative methods that have been proven to be effective. However, due to lack of compliance among their recipients, questions have arisen as to the directions of improvements of this type of protective device to improve outcomes. This study investigates a new padding material for these protective devices that is expected to be effective in attenuating the impact force as well as being light weight and more elastic to improve the comfort for users. As part of this study the factors influencing low user compliance with hip protectors among aging adults at risk of falling and incurring hip fracture were identified through a new descriptive compliance study aimed at the aging adults themselves and at the health care professionals involved in the patient treatment. Four types of polyurethane gel elastomers were selected for this study. Uniaxial tensile, biaxial tensile, simple compression and stress relaxation tests were carried out to establish a comprehensive definition of the complex mechanical properties of the chosen materials. The experimental testing proved that, the material behaviour is viscoelastic in nature and is sufficient for an energy absorption application. Additionally, the experiments provided a set of data that were used in Finite Element Analysis (FEA) for satisfactory representation of these properties by computational model. This FEA study lead to the development of a predictive numerical model for impact test of hip protectors. An axisymmetric drop-weight impact test model for impact resistance behaviour of four chosen PU gels was developed. Such numerical models required experimental validation. All materials were experimentally assessed for their suitability in hip fracture protection. Although differences in performance of four chosen PU gels occur, they all have been found effective in attenuating the impact force below the fracture threshold. The results from FEA simulations of impact test show very good compatibility with experimental data and therefore the FEA model can be utilised to enable very precise, cost and time effective assessment of various designs and material properties for impact protection products. These design features may lead to enhanced user compliance. A range of design modifications was developed and assessed with the newly established numerical model. One of the modified designs was selected as exceptionally light in weight and effective in attenuating the impact force below the fracture threshold and is recommended for application in hip protection garments.