Xing Zhang, Chen Ling Song, Peng Wei, Chen Ling Jian
*Department of Stomatology, Guangdong Provincial Hospital of Traditional Chinese Medicine †Department of Oral and Maxillofacial Surgery, First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
J Craniofac Surg. 2017 Mar;28(2):e117-e120. doi: 10.1097/SCS.0000000000003305.
A mathematical simulation of stress distribution around orbital implants was used to determine which length and diameter of implants would be best to dissipate stress.
An integrated system for computed tomography data was utilized to create a 3-dimensional model of craniofacial structures. The model simulated implants placed in the 7, 11, and 12 o'clock positions of the orbital rim. A load of 2 N was applied to the model along the long axis of the implant (model 1) and an angle of 45° with the long axis of the implant (model 2). A model simulating an implant with a diameter of 3.75 mm and lengths of 3, 4, 6, 8, and 10 mm was developed to investigate the influence of the length factor. The influence of different diameters was modeled using implants with a length of 6 mm and diameters of 3.0, 3.75, 4.2, 5.0, and 6.0 mm. Values of von Mises equivalent stress at the implant-bone interface were computed using the finite element analysis for all variations.
The elements exposed to the maximum stress were located around the root of the orbital implant in model 1 or between the neck and the first thread of the orbital implant in model 2. An increase in the orbital implant diameter led to a decrease in the maximum von Mises equivalent stress values. In model 1, the reductions were 45.2% (diameter of 3.0-3.75 mm), 25.3% (diameter of 3.75-4.2 mm), 17.2% (diameter of 4.2-5.0 mm), and 5.4% (diameter of 5.0-6.0 mm). In model 2, the reductions of the maximum stress values were 51.9%, 35.4%, 19.7%, and 8.1% respectively. However, the influence of orbital implant length was not as pronounced as that of diameter. In model 1, the reductions were 28.8% (length of 3-4 mm), 19.2% (length of 4-6 mm), 9.6% (length of 6-8 mm), and 4.3% (length of 8-10 mm). In model 2, the reductions of the maximum stress values were 35.5%, 21.1%, 10.9%, and 5.4% respectively.
An increase in the implant diameter decreased the maximum von Mises equivalent stress around the orbital implant more than an increase in the implant length. From a biomechanical perspective, the optimum choice was an orbital implant with no less than 4.2 mm diameter allowed by the anatomy.
通过对眼眶植入物周围应力分布进行数学模拟，以确定何种长度和直径的植入物最有利于分散应力。
利用计算机断层扫描数据集成系统创建颅面结构的三维模型。该模型模拟了放置在眶缘7点、11点和12点位置的植入物。沿植入物长轴（模型1）以及与植入物长轴呈45°角（模型2）向模型施加2 N的载荷。开发了一个模拟直径为3.75 mm、长度分别为3、4、6、8和10 mm的植入物的模型，以研究长度因素的影响。使用长度为6 mm、直径分别为3.0、3.75、4.2、5.0和6.0 mm的植入物对不同直径的影响进行建模。对所有变体使用有限元分析计算植入物 - 骨界面处的冯·米塞斯等效应力值。
在模型1中，承受最大应力的单元位于眼眶植入物根部周围；在模型2中，位于眼眶植入物颈部与第一螺纹之间。眼眶植入物直径的增加导致最大冯·米塞斯等效应力值降低。在模型1中，降低幅度分别为45.2%（直径从3.0 - 3.75 mm）、25.3%（直径从3.75 - 4.2 mm）、17.2%（直径从4.2 - 5.0 mm）和5.4%（直径从5.0 - 6.0 mm）。在模型2中，最大应力值的降低幅度分别为51.9%、35.4%、19.7%和8.1%。然而，眼眶植入物长度的影响不如直径明显。在模型1中，降低幅度分别为28.8%（长度从3 - 4 mm）、19.2%（长度从4 - 6 mm）、9.6%（长度从6 - 8 mm）和4.3%（长度从8 - 10 mm）。在模型2中，最大应力值的降低幅度分别为35.5%、21.1%、10.9%和5.4%。
植入物直径的增加比植入物长度的增加更能降低眼眶植入物周围的最大冯·米塞斯等效应力。从生物力学角度来看，最佳选择是解剖结构允许的直径不小于4.2 mm的眼眶植入物。
