University of Virginia, Center for Applied Biomechanics, Charlottesville, Virginia.
Autoliv Research, Vårgårda, Sweden.
Traffic Inj Prev. 2020 Oct 12;21(sup1):S168-S170. doi: 10.1080/15389588.2020.1829919. Epub 2020 Nov 12.
This study aims to evaluate the assumption of geometric similitude inherent to equal-stress equal-velocity scaling by determining if scale factors created with different anthropometry metrics result in different scaled injury tolerance predictions. This assumption will be evaluated when equal-stress equal-velocity scaling is employed across dissimilar (e.g., 50 male to small female) and similar (e.g., small female to a reference small female anthropometry) anthropometries.
Three average male and three small female lower extremity specimens that were tested in ankle inversion/eversion were selected for scaling analysis. Three additional female specimens were selected as a reference dataset, such that the accuracy of the scaled data could be compared to an independent measured dataset. The failure moments, total height and total weight for these donors were determined from literature. Additional anthropometry metrics (leg length, calcaneus height, and bimalleolar width) were taken from each of their respective CT scans. Scale factors were calculated from these previously determined anthropometric metrics for the six donors selected for scaling analysis by targeting the averaged anthropometry metrics of the reference small female dataset. Equal-stress equal-velocity scaling was applied to the failure moments from literature using different scale factors. The mean predicted failure tolerance and standard deviation for scaled data using different scale factors were compared to one another and to the mean failure tolerance from the reference (unscaled) small female dataset.
When using average male data to predict ankle failure moment for a small female anthropometry, scaled moments were statistically significantly different from measured small female failure moment. Furthermore, scaled failure moments predicted using scale factors based on different anthropometry metrics were found to be significantly different from one another. Conversely, predicted mean failure moment using scaled female data of a similar size to the reference data was not significantly different from measured female failure moment, and the predicted failure moments were not significantly affected by choice of scale factor.
This study shows that an injury metric predicted with equal-stress equal-velocity scaling is sensitive to choice of scale factor when employing scaling across occupants of dissimilar size and sex. This conclusion suggests error can be introduced into scaled response due to choice of anthropometry metric used to create a scale factor, and therefore, anthropometry metrics used to create scale factors should be justified mechanistically and shown to apply across size and sex before being employed.
本研究旨在通过确定使用不同人体测量学指标创建的比例因子是否会导致不同比例的损伤耐受预测结果，来评估等应力等速度比例所固有的几何相似性假设。当在不同（例如，50 名男性到小女性）和相似（例如，小女性到小女性参考人体测量学）人体测量学之间使用等应力等速度比例时，将评估此假设。
选择三个进行踝关节内翻/外翻测试的平均男性和三个小女性下肢标本进行比例分析。选择另外三个女性标本作为参考数据集，以便可以将比例数据的准确性与独立测量数据集进行比较。从文献中确定了这些供体的失效力矩、总高度和总重量。从各自的 CT 扫描中获取了这些供体的其他人体测量学指标（腿长、跟骨高度和双踝宽度）。通过针对参考小女性数据集的平均人体测量学指标，从六个用于比例分析的供体中确定的这些先前确定的人体测量学指标计算出比例因子。使用不同的比例因子，通过文献中的失效力矩应用等应力等速度比例。比较使用不同比例因子的比例数据的平均预测失效容限和标准偏差，以及与参考（未缩放）小女性数据集的平均失效容限。
当使用平均男性数据预测小女性人体测量学的踝关节失效力矩时，比例矩与测量的小女性失效力矩有统计学显著差异。此外，基于不同人体测量学指标的比例因子预测的比例失效力矩彼此之间也存在显著差异。相反，使用与参考数据相似大小的女性比例数据预测的平均失效力矩与测量的女性失效力矩没有显著差异，并且比例因子的选择对预测失效力矩没有显著影响。
本研究表明，在跨不同尺寸和性别的乘员使用比例缩放时，使用等应力等速度比例预测的损伤度量对比例因子的选择很敏感。这一结论表明，由于用于创建比例因子的人体测量学指标的选择，可能会在缩放响应中引入误差，因此，在使用之前，应从机械角度证明用于创建比例因子的人体测量学指标的合理性，并证明其在尺寸和性别上的适用性。
