Department of Orthopaedic Surgery, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
J Shoulder Elbow Surg. 2010 Jan;19(1):86-90. doi: 10.1016/j.jse.2009.05.006.
Throwing fractures of the humerus are well known, but the exact mechanism of injury is not clear. It has been postulated that these may be stress fractures because the forces have not seemed sufficient to cause acute fractures while throwing.
Using finite element analysis, we reproduced fractures of the humerus using 3-dimensional models built from computed tomography images of 5 healthy volunteers. To apply the load during throwing, we assumed that the humeral head was completely fixed, and external rotation torque was applied to the distal end of the humerus until the stress of the bone elements became greater than yield stress. We reproduced the fracture line by removing the bone elements.
The maximum stress concentration was seen in the distal shaft, where a typical spiral fracture was created in all cases. In the humeral models, the torque required to initiate fracture ranged from 51 to 70 Nm. A strong correlation existed between the torque required to initiate fracture and thickness of the humeral cortical bone (R(2) = 0.74).
These results indicate that thickness of the humerus represents one factor contributing to fractures that occur while throwing.
Basic science study.
肱骨投掷骨折众所周知，但确切的损伤机制尚不清楚。有人推测，这些可能是应力性骨折，因为在投掷过程中，这些力似乎不足以导致急性骨折。
使用有限元分析，我们通过对 5 名健康志愿者的计算机断层扫描图像建立三维模型，重现了肱骨骨折。为了在投掷过程中施加负荷，我们假设肱骨头完全固定，并对肱骨远端施加外旋扭矩，直到骨元素的应力超过屈服应力。通过去除骨元素来重现骨折线。
最大的应力集中在远端干骺端，所有情况下均形成典型的螺旋形骨折。在肱骨模型中，引发骨折所需的扭矩范围为 51 至 70Nm。引发骨折所需的扭矩与肱骨皮质骨厚度之间存在很强的相关性（R²=0.74）。
这些结果表明，肱骨的厚度是导致投掷时发生骨折的一个因素。
基础科学研究。
