Effect of compliant flooring on impact force during falls on the hip

Abstract

Compliant flooring represents a promising but understudied strategy for reducing impact force and hip fracture risk due to falls in high-risk environments such as nursing homes, hospitals, gymnasiums, and senior centers. We conducted ''pelvis release experiments'' with young women (n ¼ 15) to determine whether floor stiffness influences peak hip impact force during safe, low-height falls. During the trials, we used a pelvic sling and electromagnet to lift and instantly release the participant from a height of 5 cm above a force plate, which measured the force applied to the hip region during impact. Trials were conducted for rigid floor conditions and with layers of ethylene vinyl acetate foam rubber overlying the floor that we regarded as firm (1.5-cm thick; stiffness ¼ 263 kN/m), semifirm (4.5-cm thick; stiffness ¼ 95 kN/m), semisoft (7.5-cm thick; stiffness ¼ 67 kN/m), and soft (10.5-cm thick; stiffness ¼ 59 kN/m). When compared to the rigid condition, peak hip impact force averaged 8% lower in the firm condition and 15% lower in the semifirm condition. Peak forces were not significantly different between the semifirm, semisoft, and soft floor conditions, indicating that a 4.5 cm-thick foam mat provides nearly the same force attenuation as a 10.5 cm-thick mat. These results support the need for laboratory experiments to measure the effect of floor stiffness on postural stability and for clinical trials to determine the effect of compliant flooring on hip fracture incidence in high-risk environments. ß

The effects of pad geometry and material properties on the biomechanical effectiveness of 26 commercially available hip protectors

“…Increasing the thickness of protective devices has previously been shown to increase force attenuation during sideways falls on the hip (Laing et al, 2006;Nabhani and Bamford, 2004;Parkkari et al, 1994;Robinovitch et al, 1995), likely due to decreased stiffness and increased energy absorption. The observed effect of anterior-posterior pad width on force attenuation is also logical, as a wider pad allows energy to be shunted further from the proximal femur.…”

“…4) through dynamic indentation tests with a servohydraulic testing system (Fas-tTrack ™ 8874, Instron Corporation, Canton, MA, USA). We used a rigid hip-shaped indenter that matched the pelvic surface geometry of a female model of body mass 49.1 kg and height 1.55 m (Laing et al, 2006). Trials were conducted using ramp loading and unloading rates of 35 mm/s to a peak force of 4 kN, the approximate peak load applied to the hip during a sideways fall from standing (Laing and Robinovitch, 2009;Laing et al, 2006).…”

Characterizing the effective stiffness of the pelvis during sideways falls on the hip

“…To conduct a trial, we first positioned the participant lying on her left side, with her left shoulder flexed overhead, hips flexed at 45 degrees, and knees flexed at 75 degrees. This position simulates a sideways fall where the shin and upper extremity contact the ground just before the pelvis (Laing and Robinovitch, 2008a;Laing et al, 2006), as observed in video recordings of real-life falls experienced by older adults in long-term care facilities (Robinovitch et al, 2009b). The participant wore tight-fitting cycling shorts during the trials.…”

The influence of novel compliant floors on balance control in elderly women—A biomechanical study

“…A promising intervention approach that is particularly relevant for high-risk settings is to decrease the stiffness of the floor to attenuate impact forces in the event of a fall (Casalena et al, 1998;Maki and Fernie, 1990;Laing et al, 2006;Laing and Robinovitch, 2009;Laforest et al, 2000;Nevitt and Cummings, 1993;Simpson et al, 2004;Healey, 1994). While the clinical effectiveness of intervention strategies such as exercise, pharmacological agents, and wearable hip protectors depend on active user compliance and adherence, novel compliant floors are a passive intervention approach that may protect against multiple types of fall-related injuries.…”