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

Abstract

Wearable hip protectors (padded garments) represent a promising strategy to decrease impact force and hip fracture risk during falls, and a wide range of products are currently marketed. However, little is known about how design features of hip protectors influence biomechanical effectiveness. We used a mechanical test system (simulating sideways falls) to measure the attenuation in femoral neck force provided by 26 commercially available hip protectors at three impact velocities (2, 3, and 4 m/s). We also used a materials testing machine to characterize the force-deflection properties of each device. Regression analyses were performed to determine which geometric (e.g., height, width, thickness, volume) and force-deflection properties were associated with force attenuation. At an impact velocity of 3 m/s, the force attenuation provided by the various hip protectors ranged between 2.5% and 40%. Hip protectors with lower stiffness (measured at 500 N) provided greater force attenuation at all velocities. Protectors that absorbed more energy demonstrated greater force attenuation at the higher impact velocities (3 and 4 m/s conditions), while protectors that did not directly contact (but instead bridged) the skin overlying the greater trochanter attenuated more force at velocities of 2 and 3 m/s. At these lower velocities, the force attenuation provided by protectors that contacted the skin overlying the greater trochanter increased with increasing pad width, thickness, and energy dissipation. By providing a comparison Conflict of interestIndependent of this project, SNR has received funding from Tytex A/S (the producer of the Safehip line of hip protectors) in support of hip protector research. SNR is also a co-inventor on a patent licensed to Tytex A/S, and forming the basis of the Safehip Soft product tested in this study. In 2006, ACL received funding from Tytex A/S to support travel to a conference. These relationships had no bearing on any aspect of the study design, data analysis or interpretation of results. No person other than the authors had input into the study design and subsequent reporting of data.

Biomechanical testing of hip protectors following the Canadian Standards Association express document

“…This compares favourably with our study of 3% to 36% at an impact velocity of 3.2 m/s. Our results for the Hipsaver protector (a commonly sold and tested hip protector) also compared favourably with two studies by Laing et al, whereby our study reports 20.26% (Test I) and 18.07% (Test II) compared to 20.9% and 23.5% by Laing et al [20,21]. Other studies which tested the Hipsaver protector, for example, Choi et al, 2010 and van Schoor et al, 2006 report much greater force attenuation of 45% and 45.6 -57.8% [17][18][19].…”

“…The wide range in biomechanical performance observed in this study is in keeping with existing literature. Laing et al, reported a force attenuation range from 2.5% to 40% with an impact velocity of 3 m/s [20]. This compares favourably with our study of 3% to 36% at an impact velocity of 3.2 m/s.…”

“…Previous biomechanical studies have reported a wide range of different values for peak femoral neck force attenuation between 3% and 89% [18][19][20][21] Testing is typically carried out using either a pendulum design system or drop impact tower, but the conditions under which the methods are conducted (e.g. effective mass, impact velocity, pelvic stiffness, geometry of the anatomical femur form etc) vary considerably between studies [15,19,22,23].…”

Three-dimensional knitted textiles

“…Warp-knitted spacer fabrics were proposed to be cushioning materials in developing motorcyclists' protectors, and the results showed that lamination of three layers of spacer fabric with a proper structure can comply with the European standard BS EN 1621-1: 1998 (Liu et al, 2014a,b). Weft-knitted spacer fabrics have also been used for developing hip protectors to reduce the risk of injury from falling accidents for the elderly (Laing et al, 2011).…”

Facilitators of and Barriers to Hip Protector Acceptance and Adherence in Long-term Care Facilities: A Systematic Review

“…However, the hip protector pad utilized in this trial (FallGard) has been shown to have very poor biomechanical performance in a recent laboratorybased study, attenuating only 2.9% and 12.4% of peak forces to the proximal femur at impact velocities of 2 m/s and 3 m/s, respectively. 34 Motivated by the potential benefits of this intervention, many studies have been published to examine the complex factors that influence initial acceptance and continued adherence in the wearing of hip protectors. In 2002, van Schoor et al 46 lead a systematic review of factors that influence acceptance of hip protectors, and adherence with guidelines concerning their use.…”