Effects of trochanteric soft tissue thickness and hip impact velocity on hip fracture in sideways fall through 3D finite element simulations

A major worldwide health problem is hip fracture due to sideways fall among the elderly population. The effects of sideways fall on the hip are required to be investigated thoroughly. The objectives of this study are to evaluate the responses to trochanteric soft tissue thickness (T) variations and hip impact velocity (V) variations during sideways fall based on a previously developed CT scan derived 3D non-linear and non-homogeneous finite element model of pelvis–femur–soft tissue complex with simplified biomechanical representation of the whole body. This study is also aimed at quantifying the effects [peak impact force (Fmax), time to Fmax, acceleration and peak principal compressive strain (εmax)] of these variations (T, V) on hip fracture. It was found that under constant impact energy, for 81% decrease in T (26–5 mm), Fmax and εmax increased by 38% and 97%, respectively. Hence, decrease in T (as in slimmer persons) strongly correlated to risk for hip fracture (φ) and strain ratio (SR) by 0.972 and 0.988, respectively. Also under same T and body weight, for 75% decrease in V (4.79–1.2 m/s), Fmax and εmax decreased by 70% and 86%, respectively. Hence, increase in V (as in taller persons) strongly correlated to φ and SR by 0.995 and 0.984, respectively. For both variations in T and V, inter-trochanteric fracture situations were well demonstrated by φ as well as by SR and strain contours, similar to clinically observed fractures. These quantifications would be helpful for effective design of person-specific hip protective devices.