Abstract
Falls to the side are the leading cause of hip fractures in the elderly. The load that a person experiences during a fall cannot be measured with volunteers for ethical reasons. To evaluate injurious loads, while considering relevant energy input and body posture for a sideways fall, a subject-specific cadaveric impact experiment was developed. Full cadaveric femur-pelvis constructs (N = 2) were embedded in surrogate soft tissue material and attached to metallic surrogate lower limbs. The specimens were then subjected to an inverted pendulum motion, simulating a fall to the side with an impact to the greater trochanter. The load at the ground and the deformation of the pelvis were evaluated using a 6-axis force transducer and two high-speed cameras. Post-test, a trauma surgeon (PG) evaluated specimen injuries. Peak ground contact forces were 7132 N and 5641 N for the fractured and non-fractured specimen, respectively. We observed a cervical fracture of the femur in one specimen and no injuries in a second specimen, showing that the developed protocol can be used to differentiate between specimens at high and low fracture risk.
Highlights
Among fragility fractures, hip fracture is the most devastating type. [1, 2] They are associated with a high risk of morbidity [3, 4] and mortality, [5, 6] and an immense financial burden on the health care system. [7] State of the art screening for hip fracture risk is based on areal bone mineral density
More than 50% of hip fractures occur in people that are not identified by this metric. [8,9,10] An alternative metric for femur is quantitative computed tomography (CT) based finite element analysis (FEA). [11,12,13] this metric performs better than areal bone mineral density (aBMD) against cadaveric femoral strength measures, in cohort studies, FEA-based femoral strength prediction demonstrated only marginal improvement over aBMD-based risk assessment, [14,15,16,17,18,19,20,21,22,23] suggesting that both metrics may not account for all relevant biomechanical factors
[29] Previous cadaveric studies focused on the femur [12, 30,31,32] or placed the femur-pelvis construct into boundary conditions that simulated car crash scenarios. [33,34,35] Fall simulators that modelled the pelvic compliance [32, 36] used springs with characteristics based on the average compliance of the whole pelvic region at low force levels, neglecting subject specific variability in pelvic compliance and non-linearity of the pelvic response
Summary
Hip fracture is the most devastating type. [1, 2] They are associated with a high risk of morbidity [3, 4] and mortality, [5, 6] and an immense financial burden on the health care system. [7] State of the art screening for hip fracture risk is based on areal bone mineral density (aBMD). [11,12,13] this metric performs better than aBMD against cadaveric femoral strength measures, in cohort studies, FEA-based femoral strength prediction demonstrated only marginal improvement over aBMD-based risk assessment, [14,15,16,17,18,19,20,21,22,23] suggesting that both metrics may not account for all relevant biomechanical factors Another important aspect affecting the risk of hip fracture is the load experienced by the femur due to a fall. A combination of the sDOF models and dual energy x-ray absorption (DEXA) based FEA to predict femoral strength have been used to assess fracture risk. [41] These studies showed that incorporating the prediction of impact loads can affect the fracture risk prediction
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