Injury Prevention and Mobility Laboratory, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.
J Biomech. 2011 Feb 3;44(3):532-9. doi: 10.1016/j.jbiomech.2010.09.011. Epub 2010 Oct 28.
Falls on the outstretched hands are the cause of over 90% of wrist fractures, yet little is known about bone loading during this event. We tested how the magnitude and distribution of pressure over the palm region during a forward fall is affected by foam padding (simulating a glove) and arm configuration, and by the faller's body mass index (BMI) and thickness of soft tissues over the palm region. Thirteen young women with high (n=7) or low (n=6) BMI participated in a "torso release experiment" that simulated falling on both outstretched hands with the arm inclined either at 20° or 40° from the vertical. Trials were acquired with and without a 5 mm thick foam pad secured to the palm. Outcome variables were the magnitude and location of peak pressure (d, θ) with respect to the scaphoid, total impact force, and integrated force applied to three concentric areas, including "danger zone" of 2.5 cm radius centered at the scaphoid. Soft tissue thickness over the palm was measured by ultrasound. The 5mm foam pad reduced peak pressure, and peak force to the danger zone, by 83% and 13%, respectively. Peak pressure was 77% higher in high BMI when compared with low BMI participants. Soft tissue thickness over the palm correlated positively with distance (d) (R=0.79, p=0.001) and force applied outside the danger zone (R=0.76, p=0.002), but did not correlate with BMI (R=0.43, p=0.14). The location of peak pressure was shunted 4 mm further from the scaphoid at 20° than that of 40° falls (d=25 mm (SD 8), θ=-9° (SD 17) in the 20° falls versus d=21 mm (SD 8), θ=-5° (SD 24) in the 40° falls). Peak force to the entire palm was 11% greater in 20° compared with 40° falls. These results indicate that even a 5 mm thick foam layer protects against wrist injury, by attenuating peak pressure over the palm during forward falls. Increased soft tissue thickness shunts force away from the scaphoid. However, soft tissue thickness is not predicted by BMI, and peak pressures are greater in high individuals than that of low BMI individuals. These results contribute to our understanding of the mechanics and prevention of wrist and hand injuries during falls.
跌倒时手掌向外伸展，超过 90%的手腕骨折是由此引起的，但对于这种情况下手掌区域的骨负荷知之甚少。我们测试了在向前跌倒时，泡沫衬垫（模拟手套）和手臂姿势如何影响手掌区域的压力大小和分布，以及跌倒者的身体质量指数（BMI）和手掌区域软组织的厚度。13 名年轻女性（高 BMI 组 7 人，低 BMI 组 6 人）参与了一项“躯干释放实验”，该实验模拟了手臂分别以 20°或 40°从垂直方向伸展时双手着地的情况。试验时手臂上分别带有和不带有 5mm 厚的泡沫衬垫。研究结果变量为相对于舟骨的峰值压力（d，θ）的大小和位置、总冲击力以及施加在三个同心区域上的积分力，包括以舟骨为中心的 2.5cm 半径的“危险区域”。通过超声测量手掌上的软组织厚度。与不使用泡沫衬垫相比，5mm 厚的泡沫衬垫使峰值压力和作用于危险区域的峰值力分别降低了 83%和 13%。与低 BMI 参与者相比，高 BMI 参与者的峰值压力高 77%。手掌上的软组织厚度与距离（d）呈正相关（R=0.79，p=0.001），与危险区域外的受力呈正相关（R=0.76，p=0.002），但与 BMI 无关（R=0.43，p=0.14）。在 20°时，峰值压力的位置比 40°时向远离舟骨的方向移动了 4mm（d=25mm（SD 8），θ=-9°（SD 17）在 20°时跌倒，d=21mm（SD 8），θ=-5°（SD 24）在 40°时跌倒）。与 40°相比，20°时整个手掌的峰值力增加了 11%。这些结果表明，即使是 5mm 厚的泡沫层也可以通过在向前跌倒时减轻手掌上的峰值压力来保护手腕免受伤害。增加的软组织厚度会将力从舟骨处转移开。然而，软组织厚度不能由 BMI 预测，高 BMI 个体的峰值压力大于低 BMI 个体。这些结果有助于我们理解跌倒时手腕和手部受伤的力学机制和预防。
