The Effect of Fall Biomechanics on Risk for Hip Fracture in Older Adults: A Cohort Study of Video-Captured Falls in Long-Term Care

Abstract

Over 95% of hip fractures in older adults are caused by falls, yet only 1% to 2% of falls result in hip fracture. Our current understanding of the types of falls that lead to hip fracture is based on reports by the faller or witness. We analyzed videos of real-life falls in longterm care to provide objective evidence on the factors that separate falls that result in hip fracture from falls that do not. Between 2007 and 2018, we video-captured 2377 falls by 646 residents in two long-term care facilities. Hip fracture was documented in 30 falls. We analyzed each video with a structured questionnaire, and used generalized estimating equations (GEEs) to determine relative risk ratios (RRs) for hip fracture associated with various fall characteristics. All hip fractures involved falls from standing height, and pelvis impact with the ground. After excluding falls from lower than standing height, risk for hip fracture was higher for sideways landing configurations (RR = 5.50; 95% CI, 2.36-12.78) than forward or backward, and for falls causing hip impact (3.38; 95% CI, 1.49-7.67). However, hip fracture risk was just as high in falls initially directed sideways as forward (1.14; 95% CI, 0.49-2.67), due to the tendency for rotation during descent. Falling while using a mobility aid was associated with lower fracture risk (0.30; 95% CI, 0.09-1.00). Seventy percent of hip fractures involved impact to the posterolateral aspect of the pelvis. Hip protectors were worn in 73% of falls, and hip fracture risk was lower in falls where hip protectors were worn (0.45; 95% CI, 0.21-0.99). Age and sex were not associated with fracture risk. There was no evidence of spontaneous fractures. In this first study of video-captured falls causing hip fracture, we show that the biomechanics of falls involving hip fracture were different than nonfracture falls for fall height, fall direction, impact locations, and use of hip protectors.

Falls and Fall-Related Consequences among Older People Living in Long-Term Care Facilities in a Megacity of China

“…These results indicated that there are different mechanisms underlying different fall scenarios. As suggested in some previous studies, hip protectors [39, 40] which have not become popular in the Chinese mainland are effective in preventing hip fractures, and corner cushions could prevent harm from sharp furniture during falls. The supply of these protective devices should be guaranteed, and the use of them should also be advocated among residents with a high risk of falling.…”

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

“…40 The load that the femur is subjected to depends on factors specific for the faller, such as soft tissue thickness over the greater trochanter, 3,44 stiffness, 42 and shape, 9 but also on biomechanical aspects of the fall such as impact velocity, impact region, and impact direction. 6,14,28,40,50,51 While hip protectors have been implemented to attenuate impact forces in case of a fall, 9,29,42,47,49 clinical studies investigating their effectiveness have revealed conflicting results. 24,45 One contributing factor may relate to hip protector design.…”

Feature Extraction and Evaluation for Classification Models of Injurious Falls Based on Surface Electromyography

“…The purpose of this study was to find a best model to classify injurious versus non-injurious falls using sEMG data of hip muscles during a fall, and the injurious falls were defined based on previous studies, where a. the risk of hip fracture increases Table 3. [7], and b. hip impact force increases 60% (thereby hip fracture risk increases) when the impacting-side knee is free of constraint ("free knee" -neither the ground nor the contralateral knee contacts the impacting-side knee) at the time of hip impact [6]. We found that classification of initial fall direction through sEMG of hip muscles was not promising, and the accuracy of the best model was less than 50%.…”

“…During falls, activity of the iliopsoas, gluteus maximus and medius, and adductor longus were recorded from the EMG electrodes placed on the belly of the muscles. In this study, injurious falls were defined as falls involved "free knee", or "backward initial fall direction" based on two previous studies -Lim and Choi [6] and Yang et al [7], respectively.…”

“…Researchers have shown that the hip fracture risk is affected by knee positions at the time of hip impact, and hip impact force becomes 59% greater when the contactingside knee is free of constraint (i.e., not touching the floor and the contralateral knee) [5,6]. Furthermore, the hip fracture risk increases ten-fold when the fall initiated backward and landed sideways [7].…”