Development of a CT-based finite element analysis model for verifying the effect of shock-absorbing floors on hip fracture prevention

Abstract text (incl. references and figure legends)
Introduction

Drug/exercise therapy and hip protector have been reported to be effective in preventing fragility hip fractures. Shock-absorbing mats lack evidence, and are too soft and unstable during walking/moving. In Japan, the floor "Coroyawa" (Magic Shields Inc.), which has a structure that achieves both stability and shock absorption, has been launched and is expected to be incorporated into government-led fragility fracture precautions. Here, we developed a CT-based finite element analysis (CT/FEA) model to determine the effectiveness of shock-absorbing floors at falling.

Material & Methods

CT/FEA model was constructed using physical property values of three types of floors (vinyl sheet, 2mm thick; sponge mat, 40mm thick; Coroyawa, 22mm thick). From CT DICOM data of the contralateral femur of an 83-year-old woman with a trochanteric fracture, a falling model was configured in which greater trochanter collided with the floor. Concrete was placed below each floors. Load cells were placed on the femoral head and diaphysis, and elastic materials were constructed on the contact surface of the femoral head and greater trochanter. The external reaction stress that cause a fracture was extracted by static analysis, and the effect of preventing fracture was evaluated by dynamic analysis that reproduced drop-weight impact test (mass, 11kg; drop height, 230mm) equivalent to backward falling energy.

Results

Static analysis showed that trochanteric fracture occurred at 1400N. Dynamic analysis showed that stress attenuated at a peak of 1200N for sponge mat and Coroyawa, and the floor bounced without causing fractures, while bone geometry of the proximal femur was completely destroyed with vinyl sheet.

Conclusion

CT/FEA model developed in the present study can verify the effect of shock-absorbing floors on hip fracture prevention and be useful for product improvement.

References

Hirabayashi S, et al. Simulation study on mechanisms of hip fractures in backward falls. J Biomech Sci Eng 2013:8;328-343.

Tatemoto T, et al. Shock-absorbing effect of flooring-adopted mechanical metamaterial technology and its influence on the gait and balance of older adults. Inj Prev. 2022;28:410-414.

Disclosure: Do you have a significant financial interest, consultancy or other relationship with products, manufacturer(s) of products or providers of services related to this abstract? (If not, please enter "No" in the text field.)

The department to which the presenter (Yoto Oh) belongs has received funding for operating costs from Saku Central Hospital of the Nagano Prefectural Federation of Agricultural Cooperatives for Health and Welfare, Suwa Central Hospital, Doujin Hospital, Medtronic Sofamor Danek Co., Ltd., Stryker Japan K.K., HOYA Technosurgical Co., Ltd. and NuVasive Japan K.K.

Physical property values of flooring materials were provided from Magic Shields Inc. (gratuitous research collaboration agreement: Jul 24, 2021).