Department of Mechanical Engineering, Johns Hopkins University, USA.
Department of Mechanical Engineering, Johns Hopkins University, USA; Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, USA.
J Biomech. 2014 Aug 22;47(11):2626-32. doi: 10.1016/j.jbiomech.2014.05.019. Epub 2014 Jun 6.
A novel reconstructive alternative for patients with severe facial structural deformity is Le Fort-based, face-jaw-teeth transplantation (FJTT). To date, however, only ten surgeries have included underlying skeletal and jaw-teeth components, all yielding sub-optimal results and a need for a subsequent revision surgery, due to size mismatch and lack of precise planning. Numerous studies have proven swine to be appropriate candidates for translational studies including pre-operative planning of transplantation. An important aspect of planning FJTT is determining the optimal muscle attachment sites on the recipient's jaw, which requires a clear understanding of mastication and bite mechanics in relation to the new donated upper and/or lower jaw. A segmented CT scan coupled with data taken from literature defined a biomechanical model of mandible and jaw muscles of a swine. The model was driven using tracked motion and external force data of one cycle of chewing published earlier, and predicted the muscle activation patterns as well as temporomandibular joint (TMJ) reaction forces and condylar motions. Two methods, polynomial and min/max optimization, were used for solving the muscle recruitment problem. Similar performances were observed between the two methods. On average, there was a mean absolute error (MAE) of <0.08 between the predicted and measured activation levels of all muscles, and an MAE of <7 N for TMJ reaction forces. Simulated activations qualitatively followed the same patterns as the reference data and there was very good agreement for simulated TMJ forces. The polynomial optimization produced a smoother output, suggesting that it is more suitable for studying such motions. Average MAE for condylar motion was 1.2mm, which reduced to 0.37 mm when the input incisor motion was scaled to reflect the possible size mismatch between the current and original swine models. Results support the hypothesis that the model can be used for planning of facial transplantation.
一种用于严重面部结构畸形患者的新型重建方法是基于 Le Fort 的面颌牙移植术（FJTT）。然而，迄今为止，只有十例手术包括了潜在的骨骼和颌牙成分，由于大小不匹配和缺乏精确的规划，所有手术结果都不理想，需要后续进行修正手术。许多研究已经证明猪是转化研究的合适候选者，包括移植前的规划。计划 FJTT 的一个重要方面是确定受者颌骨上的最佳肌肉附着点，这需要清楚地了解咀嚼和咬合力学与新捐赠的上下颌之间的关系。分段 CT 扫描结合文献中获取的数据定义了猪下颌骨和颌骨肌肉的生物力学模型。该模型使用先前发表的咀嚼一个周期的跟踪运动和外部力数据进行驱动，并预测了肌肉激活模式以及颞下颌关节（TMJ）反作用力和髁突运动。使用多项式和最小/最大值优化两种方法解决肌肉募集问题。两种方法的性能相似。平均而言，所有肌肉的预测和测量激活水平之间的平均绝对误差（MAE）<0.08，TMJ 反作用力的 MAE<7N。模拟激活与参考数据的模式大致相同，并且模拟 TMJ 力的一致性非常好。多项式优化产生了更平滑的输出，表明它更适合研究此类运动。髁突运动的平均 MAE 为 1.2mm，当输入切牙运动被缩放以反映当前和原始猪模型之间可能的大小不匹配时，MAE 降低至 0.37mm。结果支持该模型可用于面部移植规划的假设。
