Aix Marseille Univ, CNRS, ISM, Marseille, France.
PLoS One. 2019 Mar 5;14(3):e0213100. doi: 10.1371/journal.pone.0213100. eCollection 2019.
Looking for new opportunities in mechanical design, we are interested in studying the kinematic behaviour of biological joints. The real kinematic behaviour of the elbow of quadruped animals (which is submitted to high mechanical stresses in comparison with bipeds) remains unexplored. The sheep elbow joint was chosen because of its similarity with a revolute joint. The main objective of this study is to estimate the effects of elbow simplifications on the prediction of joint reaction forces in inverse dynamic simulations. Rigid motions between humerus and radius-ulna were registered during full flexion-extension gestures on five cadaveric specimens. The experiments were initially conducted with fresh specimens with ligaments and repeated after removal of all soft tissue, including cartilage. A digital image correlation system was used for tracking optical markers fixed on the bones. The geometry of the specimens was digitized using a 3D optical scanner. Then, the instantaneous helical axis of the joint was computed for each acquisition time. Finally, an OpenSim musculoskeletal model of the sheep forelimb was used to quantify effects of elbow joint approximations on the prediction of joint reaction forces. The motion analysis showed that only the medial-lateral translation is sufficiently large regarding the measuring uncertainty of the experiments. This translation assimilates the sheep elbow to a screw joint instead of a revolute joint. In comparison with fresh specimens, the experiments conducted with dry bone specimens (bones without soft tissue) provided different kinematic behaviour. From the results of our inverse dynamic simulations, it was noticed that the inclusion of the medial-lateral translation to the model made up with the mean flexion axis does not affect the predicted joint reaction forces. A geometrical difference between the axis of the best fitting cylinder and the mean flexion axis (derived from the motion analysis) of fresh specimens was highlighted. This geometrical difference impacts slightly the prediction of joint reactions.
我们在机械设计方面寻找新的机会，对研究生物关节的运动学行为很感兴趣。四足动物肘部（与二足动物相比，它承受着更高的机械应力）的实际运动学行为仍未被探索。羊肘关节因其与转动关节相似而被选中。本研究的主要目的是估计在反向动力学模拟中，简化肘部对预测关节反作用力的影响。在五个尸体标本上进行了全屈伸运动，记录了肱骨和桡尺骨之间的刚性运动。实验最初是在有韧带的新鲜标本上进行的，然后在去除所有软组织（包括软骨）后重复进行。使用固定在骨骼上的光学标记的数字图像相关系统用于跟踪。使用 3D 光学扫描仪对标本的几何形状进行数字化。然后，为每个采集时间计算关节的瞬时螺旋轴。最后，使用羊前肢的 OpenSim 肌肉骨骼模型来量化肘部关节近似对预测关节反作用力的影响。运动分析表明，只有内侧-外侧平移相对于实验的测量不确定性足够大。这种平移将羊肘等同于螺旋关节，而不是转动关节。与新鲜标本相比，在干燥骨标本（无软组织的骨骼）上进行的实验提供了不同的运动学行为。从我们的反向动力学模拟结果中注意到，将内侧-外侧平移包含在具有平均弯曲轴的模型中不会影响预测的关节反作用力。在新鲜标本中，最佳拟合圆柱的轴和平均弯曲轴（从运动分析中得出）之间存在几何差异。这种几何差异对关节反应的预测略有影响。
