Centre for Anatomical and Human Sciences, Hull York Medical School, University of York, UK.
J Anat. 2012 Jul;221(1):55-68. doi: 10.1111/j.1469-7580.2012.01516.x.
Biomechanical analyses are commonly conducted to investigate how craniofacial form relates to function, particularly in relation to dietary adaptations. However, in the absence of corresponding muscle activation patterns, incomplete muscle data recorded experimentally for different individuals during different feeding tasks are frequently substituted. This study uses finite element analysis (FEA) to examine the sensitivity of the mechanical response of a Macaca fascicularis cranium to varying muscle activation patterns predicted via multibody dynamic analysis. Relative to the effects of varying bite location, the consequences of simulated variations in muscle activation patterns and of the inclusion/exclusion of whole muscle groups were investigated. The resulting cranial deformations were compared using two approaches; strain maps and geometric morphometric analyses. The results indicate that, with bite force magnitude controlled, the variations among the mechanical responses of the cranium to bite location far outweigh those observed as a consequence of varying muscle activations. However, zygomatic deformation was an exception, with the activation levels of superficial masseter being most influential in this regard. The anterior portion of temporalis deforms the cranial vault, but the remaining muscles have less profound effects. This study for the first time systematically quantifies the sensitivity of an FEA model of a primate skull to widely varying masticatory muscle activations and finds that, with the exception of the zygomatic arch, reasonable variants of muscle loading for a second molar bite have considerably less effect on cranial deformation and the resulting strain map than does varying molar bite point. The implication is that FEA models of biting crania will generally produce acceptable estimates of deformation under load as long as muscle activations and forces are reasonably approximated. In any one FEA study, the biological significance of the error in applied muscle forces is best judged against the magnitude of the effect that is being investigated.
生物力学分析常用于研究颅面形态与功能的关系，尤其是在与饮食适应有关的方面。然而，在缺乏相应的肌肉活动模式的情况下，通常会用实验记录的不同个体在不同摄食任务下的不完整肌肉数据来替代。本研究使用有限元分析（FEA）来检验通过多体动力学分析预测的不同肌肉活动模式对猕猴颅骨机械响应的敏感性。与改变咬合位置的影响相比，本研究还研究了模拟肌肉活动模式变化和包括/排除整个肌肉群的影响。使用两种方法比较了由此产生的颅骨变形：应变图和几何形态测量分析。结果表明，在控制咬合力大小的情况下，颅骨对咬合位置的机械响应的变化远远超过由于肌肉活动变化而观察到的变化。然而，颧骨变形是一个例外，浅层咬肌的激活水平对此影响最大。颞肌的前部使颅穹窿变形，但其余肌肉的影响较小。本研究首次系统地量化了 FEA 模型对广泛变化的咀嚼肌活动的敏感性，发现除了颧骨弓外，对于第二磨牙咬合的合理肌肉加载变体对颅骨变形和由此产生的应变图的影响远小于磨牙咬合点的变化。这意味着只要肌肉活动和力得到合理近似，FEA 模型在负载下的颅骨变形通常会产生可接受的估计值。在任何一项 FEA 研究中，应用肌肉力的误差的生物学意义最好根据正在研究的效应的大小来判断。
