Nagasao Tomohisa, Miyamoto Junpei, Nagasao Maki, Ogata Hisao, Kaneko Tsuyoshi, Tamaki Tamotsu, Nakajima Tatsuo
Department of Plastic and Reconstructive Surgery, School of Medicine, Keio University, Tokyo, Japan.
Plast Reconstr Surg. 2006 Jun;117(7):2373-80; discussion 2381. doi: 10.1097/01.prs.0000218792.70483.1f.
The buckling mechanism is widely accepted as a mechanism of blowout fractures, along with the hydraulic mechanism. Although many studies have been performed related to the buckling mechanism, none of them have taken the direction of the striking force into consideration. As the orbital floor is not parallel to the horizontal plane, a difference in the striking force direction might affect resultant fracture patterns. The present study aims to investigate whether fracture patterns in the orbital floor were influenced by the striking force direction in terms of the buckling mechanism.
The authors produced three-dimensional models on a workstation simulating eight dry skulls and applied striking forces on the orbital rim of each model from three different angles (0, 15, and 30 degrees in the upward direction). Using finite element analysis, the authors calculated the width of the area where the resultant stresses exceed the bone's yielding criterion. The width was termed the "theoretical fracture width" because, theoretically, fracture was expected to occur in the area. Then, the authors compared the theoretical fracture width in groups with the three different striking force angles. Finally, the validity of the theoretical width was verified with an experiment on actual skull models.
The theoretical fracture width was the greatest when the striking force was directed at 30 degrees in the upward direction.
For the buckling mechanism, fracture would occur in a wider area of the orbital floor when striking force was directed upward than when the force was horizontally directed. This finding would be helpful in predicting fracture width in blowout fractures.
除液压机制外，屈曲机制被广泛认为是爆裂性骨折的一种机制。尽管已经进行了许多与屈曲机制相关的研究，但没有一项研究考虑到撞击力的方向。由于眶底不与水平面平行，撞击力方向的差异可能会影响最终的骨折模式。本研究旨在根据屈曲机制探讨眶底骨折模式是否受撞击力方向的影响。
作者在工作站上制作了模拟八个干燥颅骨的三维模型，并从三个不同角度（向上0度、15度和30度）对每个模型的眶缘施加撞击力。作者使用有限元分析计算了合成应力超过骨骼屈服标准的区域的宽度。该宽度被称为“理论骨折宽度”，因为从理论上讲，预计该区域会发生骨折。然后，作者比较了具有三种不同撞击力角度的组中的理论骨折宽度。最后，通过对实际颅骨模型的实验验证了理论宽度的有效性。
当撞击力向上30度方向时，理论骨折宽度最大。
对于屈曲机制，当撞击力向上时，眶底骨折发生的区域比水平方向时更宽。这一发现将有助于预测爆裂性骨折的骨折宽度。
