Qiu Shuang, Gui Lai, Wang Meng, Chen Ying, Niu Feng, Liu Jianfeng, Liu Wei, Zhang Yankun
Department of Craniomaxillofacial Surgery, Plastic Surgery Hospital, Chinese Academy of Medical Science, Peking Union Medical College, Beijing, China.
J Craniofac Surg. 2012 May;23(3):749-54. doi: 10.1097/SCS.0b013e31824dbd49.
Reduction malarplasty with L-shaped osteotomy is widely used for surgical correction of prominent zygoma and bilateral zygomatic asymmetry. One of the keys to this surgery is the formation of the greenstick fracture on the root of the zygomatic arch. However, the greenstick fracture cannot be seen directly both in the postoperative x-ray films and three-dimensional computed tomography images, and it is unknown how the greenstick fracture forms biomechanically. So it is of great concern to both the doctors and patients whether the greenstick fracture can really take place on the root of the zygomatic arch. This study focused on the biomechanism and deformation effects of the surgery by using the method of finite element (FE) analysis.
Computed tomography data of 2 patients with prominent malar complex were obtained for three-dimensional reconstruction. The FE models of the zygomatic complex with L-shaped osteotomy were established by using Mimics via thresholding, segmentation techniques, and material properties assignment with gray value conversion. Then simulations including the boundary conditions and the forces of the surgery were performed in ABAQUS.
The FE models have fine quality; the first one contains 63,053 units and 100,995 nodes, and the other one contains 70,238 units and 136,219 nodes. Under the loading of pressures, the zygoma and the zygomatic arch inward have deformation displacement. Maximum stress concentration was found just at the root of the zygomatic arch.
A appropriate zygomatic pressure will generate a stress concentration to form the greenstick on the root of the zygomatic arch. This study can help surgeons understand and conduct the reduction malarplasty with L-shaped osteotomy from a biomechanical insight.
L形截骨颧骨缩小整形术被广泛用于突出颧骨和双侧颧骨不对称的手术矫正。该手术的关键之一是在颧弓根部形成青枝骨折。然而，术后X线片和三维计算机断层扫描图像中均无法直接看到青枝骨折，且青枝骨折在生物力学上如何形成尚不清楚。因此，颧弓根部是否真的能发生青枝骨折是医生和患者都非常关心的问题。本研究采用有限元分析方法，聚焦于该手术的生物力学机制及变形效果。
获取2例颧骨复合体突出患者的计算机断层扫描数据进行三维重建。利用Mimics通过阈值化、分割技术以及灰度值转换进行材料属性赋值，建立L形截骨颧骨复合体的有限元模型。然后在ABAQUS中进行包括边界条件和手术力的模拟。
有限元模型质量良好；第一个模型包含63053个单元和100995个节点，另一个模型包含70238个单元和136219个节点。在压力加载下，颧骨和颧弓向内有变形位移。最大应力集中恰好出现在颧弓根部。
适当的颧骨压力会产生应力集中，在颧弓根部形成青枝骨折。本研究有助于外科医生从生物力学角度理解并实施L形截骨颧骨缩小整形术。
