Model for Calculating Impact Force for Individualized Hip Fracture Prediction During a Fall

Osteoporotic-related weakening of bone is a common cause of hip fractures. The standard of care for the diagnosis and management of osteoporosis is the dual-energy x-ray absorptiometry bone mineral density T-scores. Many individuals considered nonosteoporotic, however, still sustain fractures since these tools do not incorporate vital bone parameters and subject-specific characteristics. The purpose of this work was to (1) develop a simple analytical model for estimating the force exerted on the femur during a fall (i.e., impact force) based on measurable patient metrics and (2) define a quantifiable fracture risk index by comparing finite-element-derived bone strength and impact force, which could be validated in a cohort of human subjects. Aggregated regression models were derived for estimating impact force based on patient age, weight, height, and soft tissue thickness. Patients with a history of hip fractures were then compared to a matched nonfracture group via the bone strength index (BSI), defined as the ratio between bone strength and maximum impact force. The BSI was lower in the fracture group compared to the control group by 0.23 (p = 0.045). The combination of patient-specific impact force on the femur during a fall and bone strength could provide additional insights into osteoporotic hip fracture risk alongside standard risk assessments.