单侧冠状缝早闭症整复手术的三维有限元生物力学分析

Three dimensional finite element biomechanical analysis of unilateral coronal synostosis and reconstruction

目的建立单侧冠状缝早闭症的头颅、额眶前移截骨术以及额眶牵引的有限元模型,分析颅面、颅底及额眶前移术的力学特征,以期指导后期牵引器的应用。方法选取1例2015年10月在中国医学科学院整形外科医院就诊的6岁单侧冠状缝早闭症男性患儿,通过头颅CT扫描获得DICOM数据,将数据输入Mimics17.0中进行轮廓提取,重建完整的三维头颅骨组织,通过Mimics、GeomagicStudio12.0、Hypermesh12.0等软件处理后建立三维有限元模型,分别对单侧和双侧额眶截骨牵引模型的额部截骨线近中点A和颞部截骨线近中点B施加3组不同的载荷:(1)A点50N,B点50N;(2)A点80N,B点50N;(3)A点100N,B点50N。在牵引力施加点进行力学分析。结果成功建立了患儿头颅、单侧及双侧额眶前移有限元模型。应力分析结果表明,术前患儿的前颅窝及中颅窝的应力分布比较集中。单侧额眶前移模拟截骨后,可见前颅窝尤其靠近患侧应力降低,双侧额眶截骨前移后前颅窝的应力降低。A点和B点施加载荷后,眶上切迹、眶上缘中点、额颞点与额颧缝点在三维平面方向的最佳偏差结果:X值偏差率分别为-29.4%、-20.5%、-8.6%、-9.3%,Y值偏差率分别为20.9%、31.5%、73.0%、539.4%,Z值偏差率分别为4.4%、1.9%、0.1%,11.8%,说明牵引力的施加可以使得骨瓣向内侧、下方、前方移动,初步得出最佳的牵引力为A点80N,B点50N。结论通过额眶前移截骨模拟有限元分析可以更加精细地进行术前手术模拟,明确额眶前移对颅面和颅底形态及发育的影响,也为后期牵引器的设计和植入提供指导。

Objective To establish finite element models of skull, fronto-orbital advancement and fronto-orbital distraction osteogenesis of craniosynostosis, to analyze the mechanical characteristics of skull base and fronto-orbital operation area, so as to guide the later application of tractors. Methods One 6-year-old male patient with unilateral coronal synostosis was enrolled in October 2015. Three-dimensional (3D) computed tomography (CT) scan of skull was performed. DICOM data was imported into Mimics 17.0 for contour extraction and cranial 3D reconstruction. The skull model was processed by Mimics, Geomagic Studio 12.0, Hypermesh 12.0 and other software to establish a three-dimensional finite element model. The unilateral and bilateral fronto-orbital anterior osteotomy models were simulated respectively. The mechanical analysis was performed at point A in forehead area and point B in temporal area. Three different groups of traction forces were loaded:(1) 50 Newton for point A, 50 Newton for point B;(2) 80 Newton for point A and 50 Newton for point B;(3) 100 Newton for point A and 50 Newton for point B, to obtain the optimized traction force. Results Stress analysis was performed on established cranial finite element model, as well as unilateral and bilateral fronto-orbital advancement procedures. The stress distribution of the anterior and middle cranial fossae was found to be concentrated. After unilateral fronto-orbital advancement, the stress of anterior cranial fossa, especially the affected side, was decreased. The stress on both side in anterior cranial fossa was decreased after bilateral fronto-orbital advancement. After force was applied to point A and point B, the optimum deviation result at supraorbital notch point, midpoint of supraorbital margin, frontal temporal point and frontal zygomatic suture point in 3D (Deviation result of X value:-29.4%,-20.5%,-8.6%,-9.3%;Deviation result of Y value: 20.9%, 31.5%, 73.0%, 539.4%;Deviation result of Z value: 4.4%, 1.9%, 0.1%, 11.8%) demonstrated the application of traction force can inwardly, downwardly and forwardly move the bone flap. The optimized traction was 80 Newton at point A and 50 Newton at point B by preliminary assessment. Conclusions The finite element analysis of the fronto-orbital advancement can be used for more accurate preoperative simulation, to clarify the influence of fronto-orbital advancement on craniofacial morphology and development, as well as skull base. It also facilitates surgical decision and predicts the postoperative distraction vectors.