Choi W J, Russell C M, Tsai C M, Arzanpour S, Robinovitch S N
Department of Physical Therapy, Chapman University, Irvine, CA, USA.
Deptarment of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.
J Biomech. 2015 Feb 26;48(4):695-700. doi: 10.1016/j.jbiomech.2014.12.026. Epub 2014 Dec 16.
Hip fracture risk increases dramatically with age, and 90% of fractures are due to falls. During a fall on the hip, the soft tissues overlying the hip region (skin, fat, and muscle) act as shock absorbers to absorb energy and reduce the peak force applied to the underlying bone. We conducted dynamic indentation experiments with young women (aged 19-30; n=17) and older women (aged 65-81; n=17) to test the hypothesis that changes occur with age in the stiffness and damping properties of these tissues. Tissue stiffness and damping were derived from experiments where subjects lay sideways on a bed with the greater trochanter contacting a 3.8cm diameter indenter, which applied sinusoidal compression between 5 to 30Hz with a peak-to-peak amplitude of 1mm. Soft tissue thickness was measured using ultrasound. On average, stiffness was 2.9-fold smaller in older than young women (5.7 versus 16.8kN/m, p=0.0005) and damping was 3.5-fold smaller in older than young women (81 versus 282Ns/m, p=0.001). Neither parameter associated with soft tissue thickness. Our results indicate substantial age-related reductions in the stiffness and damping of soft tissues over the hip region, which likely reduce their capacity to absorb and dissipate energy (before "bottoming out") during a fall. Strategies such as wearable hip protectors or compliant flooringmay compensate for age-related reductions in the shock-absorbing properties of soft tissues and decrease the injury potential of falls.
髋部骨折风险会随着年龄急剧增加，且90%的骨折是由跌倒所致。在髋部发生跌倒时，髋部区域上方的软组织（皮肤、脂肪和肌肉）充当减震器，吸收能量并降低施加于下方骨骼的峰值力。我们对年轻女性（年龄19 - 30岁；n = 17）和老年女性（年龄65 - 81岁；n = 17）进行了动态压痕实验，以检验这些组织的刚度和阻尼特性会随年龄发生变化这一假设。组织刚度和阻尼源自实验，实验中受试者侧身躺在床上，大转子接触直径为3.8厘米的压头，压头在5至30赫兹之间施加正弦压缩，峰 - 峰值振幅为1毫米。使用超声测量软组织厚度。平均而言，老年女性的刚度比年轻女性小2.9倍（5.7对16.8kN/m，p = 0.0005），老年女性的阻尼比年轻女性小3.5倍（81对282Ns/m，p = 0.001）。这两个参数均与软组织厚度无关。我们的结果表明，髋部区域软组织的刚度和阻尼随年龄大幅降低，这可能会降低它们在跌倒时（在“触底”之前）吸收和消散能量的能力。诸如可穿戴髋部保护器或柔性地板等策略可能会弥补与年龄相关的软组织减震性能下降，并降低跌倒造成损伤的可能性。
