The Influence of Fall Direction and Hip Protector on Fracture Risk: FE Model Predictions Driven by Experimental Data

Abstract

Hip fractures in older adults, which often lead to lasting impairments and an increased risk of mortality, are a major public health concern. Hip fracture risk is multi-factorial, affected by the risk of falling, the load acting on the femur, and the load the femur can withstand. This study investigates the influence of impact direction on hip fracture risk and hip protector efficacy. We simulated falls for 4 subjects, in 7 different impact directions (15° and 30° anterior, lateral, and 15°, 30°, 60°, and 90° posterior) at two different impact velocities (2.1 and 3.1 m/s), all with and without hip protector, using previously validated biofidelic finite element models. We found the highest number of fractures and highest fragility ratios in lateral and 15° posterior impacts. The hip protector attenuated femur forces by 23–49 % for slim subjects under impact directions that resulted in fractures (30° anterior to 30° posterior). The hip protector prevented all fractures (6/6) for 2.1 m/s impacts, but only 10% of fractures for 3.1 m/s impacts. Our results provide evidence that, regarding hip fracture risk, posterior-lateral impacts are as dangerous as lateral impacts, and they support the efficacy of soft-shell hip protectors for anterior- and posterior-lateral impacts.

Upright trunk and lateral or slight anterior rotation of the pelvis cause the highest proximal femur forces during sideways falls

“…The results from the current study are supported by several previous studies (Choi and Robinovitch, 2018;Feldman and Robinovitch, 2007;van den Kroonenberg et al, 1995;Galliker et al, 2022). The proximal femur Frontiers in Bioengineering and Biotechnology frontiersin.org forces decrease as the trunk angle changes from 10 to 80 °.…”

“…They found that the 10-degree anterior pelvis rotation leads to the highest load on the femoral neck (Choi and Robinovitch, 2018). A recent subject-specific finite element simulation study (Galliker et al, 2022) indicated that the femoral neck reaction forces which was quantified at the acetabulum were higher in lateral or 15 °anterior pelvis rotations compared to other anterior (30 °) or posterior rotations (15, 30, 60, and 90 °).…”

“…A fall can lead to different body configurations, and each of the body extremities can hit the ground first. However, it is demonstrated that sideways falls are the leading causes of hip fractures (Greenspan et al, 1998;Schwartz et al, 1998;Wei et al, 2001;Ensrud, 2013;Nasiri Sarvi and Luo, 2017;Galliker et al, 2022). Parkkari et al (1999) found a majority of hip fractures occurring as a result of a fall and direct impact on the greater trochanter of the femur.…”

Does hip protector prevent falls and hip fractures? An umbrella review of meta-analyses

“…Fifth, the meta-analysis included in this study did not discuss the effect of the angle at the time of fall on hip fracture incidence. A study using biofidelic finite element models showed that the incidence of hip fractures was highest when the direction of impact was lateral, as was 15 degrees posterior [ 44 ]. And this angle was also in the greatest range of the hip protector attenuation in peak compressive stress [ 45 ].…”