Funk James R, Crandall Jeff R, Tourret Lisa J, MacMahon Conor B, Bass Cameron R, Patrie James T, Khaewpong Nopporn, Eppinger Rolf H
Automobile Safety Laboratory, Department of Mechanical, Aerospace, and Nuclear Engineering, University of Virginia, 1011 Linden Avenue, Charlottesville, VA 22902, USA.
J Biomech Eng. 2002 Dec;124(6):750-7. doi: 10.1115/1.1514675.
Axial loading of the foot/ankle complex is an important injury mechanism in vehicular trauma that is responsible for severe injuries such as calcaneal and tibial pilon fractures. Axial loading may be applied to the leg externally, by the toepan and/or pedals, as well as internally, by active muscle tension applied through the Achilles tendon during pre-impact bracing. The objectives of this study were to investigate the effect of Achilles tension on fracture mode and to empirically model the axial loading tolerance of the foot/ankle complex. Blunt axial impact tests were performed on forty-three (43) isolated lower extremities with and without experimentally simulated Achilles tension. The primary fracture mode was calcaneal fracture in both groups. However, fracture initiated at the distal tibia more frequently with the addition of Achilles tension (p < 0.05). Acoustic sensors mounted to the bone demonstrated that fracture initiated at the time of peak local axial force. A survival analysis was performed on the injury data set using a Weibull regression model with specimen age, gender, body mass, and peak Achilles tension as predictor variables (R2 = 0.90). A closed-form survivor function was developed to predict the risk of fracture to the foot/ankle complex in terms of axial tibial force. The axial tibial force associated with a 50% risk of injury ranged from 3.7 kN for a 65 year-old 5th percentile female to 8.3 kN for a 45 year-old 50th percentile male, assuming no Achilles tension. The survivor function presented here may be used to estimate the risk of foot/ankle fracture that a blunt axial impact would pose to a human based on the peak tibial axial force measured by an anthropomorphic test device.
足部/踝关节复合体的轴向负荷是车辆创伤中的一种重要损伤机制，可导致跟骨和胫骨平台骨折等严重损伤。轴向负荷可通过鞋头和/或踏板从外部施加于腿部，也可在碰撞前支撑时通过跟腱施加的主动肌肉张力从内部施加。本研究的目的是调查跟腱张力对骨折模式的影响，并通过实验模拟足部/踝关节复合体的轴向负荷耐受性。对43个孤立的下肢进行了钝性轴向冲击试验，试验时分别施加和不施加实验模拟的跟腱张力。两组的主要骨折模式均为跟骨骨折。然而，增加跟腱张力后，骨折更频繁地始于胫骨远端（p<0.05）。安装在骨头上的声学传感器表明，骨折始于局部轴向力峰值时。使用威布尔回归模型对损伤数据集进行生存分析，将标本年龄、性别、体重和跟腱张力峰值作为预测变量（R2 = 0.90）。开发了一个封闭形式的生存函数，以根据胫骨轴向力预测足部/踝关节复合体的骨折风险。假设没有跟腱张力，与50%损伤风险相关的胫骨轴向力范围为，65岁第5百分位女性为3.7 kN，45岁第50百分位男性为8.3 kN。这里给出的生存函数可用于根据拟人测试装置测量的胫骨轴向力峰值，估计钝性轴向冲击对人体造成足部/踝关节骨折的风险。
