Improving the prediction of sideways fall-induced impact force for women by developing a female-specific equation

Impact force induced in sideways falls is an important determinant of hip fracture risk. While body parameters may differently affect the magnitude of impact force in men and women, the effect of sex is not considered in existing impact force predictors. The objective of this study was to construct a female-specific equation to predict the fall-induced impact force applied to the hip and evaluate whether it could improve hip facture risk assessment. A previously developed human-body dynamic model was used to simulate falling of 80 women and determine the hip impact force. Results were then used to derive a female-specific equation between impact force and body parameters. The proposed female-specific equation and available non-sex-specific impact force predictors in the literature were integrated with a finite element model to discriminate hip fracture patients among 393 women (99 hip fractures; 294 non-fracture controls). Results of the implemented methods were compared to evaluate whether considering the effect of sex could improve the discrimination of females with and without a hip fracture. The area under the curve (AUC) and odds ratio (OR) for the assessed hip fracture risk by the proposed female-specific method (AUC = 0.799, OR = 4.22) were significantly (p<0.001) greater than those of non-sex-specific methods (the most accurate: AUC =0.750, OR =3.62). This study indicates that the proposed equation may be useful to improve hip fracture risk assessment for women.