Smeesters Cécile, Hayes Wilson C, McMahon Thomas A
Department of Mechanical Engineering, Université de Sherbrooke, 2500 boul. de l'Université, Sherbrooke (Quebec) J1K 2R1 Canada.
J Biomech Eng. 2007 Jun;129(3):393-9. doi: 10.1115/1.2737432.
Because fall experiments with volunteers can be both challenging and risky, especially with older volunteers, we wished to develop computer simulations of falls to provide a theoretical framework for understanding and extending experimental results. To perform a preliminary validation of the articulated total body (ATB) model for passive falls, we compared the model predictions of fall direction, impact location, and impact velocity as a function of disturbance type (faint, slip, step down, trip) and gait speed (fast, normal, slow) to experimental results with young adult volunteers. The three-dimensional ATB model had 17 segments and 16 joints. Its physical characteristics, environment definitions, contact functions, and initial conditions were representative of our experiment. For each combination of disturbance and gait speed, the ATB model was left to fall passively under gravity once disturbed, i.e., no joint torques were applied, until impact with the floor occurred. Finally, we also determined the sensitivity of the model predictions to changes in the model's parameters. Our model predictions of fall angles and impact angles were qualitatively in agreement with those observed experimentally for ten and seven of the 12 original simulations, respectively. Quantitatively, the model predictions of fall angles, impact angles, and impact velocities were within one experimental standard deviation for seven, three, and nine of the 12 original simulations, respectively, and within two experimental standard deviations for ten, nine, and 11 of the 12 original simulations, respectively. Finally, the fall angle and impact angle region did not change for 92% and 95% of the 74 input variation simulations, respectively, and the impact velocities were within the experimental standard deviations for 78% of the 74 input variation simulations. Based on our simulations and a sensitivity analysis, we conclude that our preliminary validation of the ATB model for passive falls was successful. In fact, these ATB model simulations represent a significant step forward in fall simulations. We believe that with additional work, the ATB model could be used to accurately simulate a variety of human falls and may be useful in further understanding the etiology and mechanisms of fall injuries such as hip fractures.
由于涉及志愿者的跌倒实验既具有挑战性又存在风险，尤其是对于老年志愿者而言，因此我们希望开发跌倒的计算机模拟，以提供一个理论框架来理解和扩展实验结果。为了对被动跌倒的关节全身体（ATB）模型进行初步验证，我们将该模型关于跌倒方向、撞击位置和撞击速度的预测作为干扰类型（昏厥、滑倒、下台阶、绊倒）和步态速度（快、正常、慢）的函数，与年轻成年志愿者的实验结果进行了比较。三维ATB模型有17个节段和16个关节。其物理特性、环境定义、接触函数和初始条件均代表了我们的实验。对于每种干扰和步态速度的组合，一旦受到干扰，ATB模型在重力作用下被动跌倒，即不施加关节扭矩，直到与地面发生撞击。最后，我们还确定了模型预测对模型参数变化的敏感性。我们对跌倒角度和撞击角度的模型预测在定性上分别与12个原始模拟中的10个和7个实验观测结果一致。在定量方面，跌倒角度、撞击角度和撞击速度的模型预测分别在12个原始模拟中的7个、3个和9个的一个实验标准差范围内，以及分别在12个原始模拟中的10个、9个和11个的两个实验标准差范围内。最后，在74个输入变化模拟中，分别有92%和95%的跌倒角度和撞击角度区域没有变化，并且在74个输入变化模拟中的78%，撞击速度在实验标准差范围内。基于我们的模拟和敏感性分析，我们得出结论，我们对被动跌倒的ATB模型的初步验证是成功的。事实上，这些ATB模型模拟代表了跌倒模拟方面的显著进步。我们相信，通过进一步的工作，ATB模型可用于准确模拟各种人类跌倒情况，并且可能有助于进一步理解诸如髋部骨折等跌倒损伤的病因和机制。
