下颌逐步前伸对阻塞性睡眠呼吸暂停低通气综合征患者舌咽部三维有限元模型的影响
【摘要】
阻塞性睡眠呼吸暂停低通气综合征（obstructive sleep apnea hypopnea syndrome，OSAHS）是以睡眠时反复发生上气道阻塞，进而引起呼吸暂停和通气不足，导致血氧饱和度下降、睡眠结构紊乱、认知功能障碍等一系列临床表现的综合征。OSAHS会导致心、脑、肾等并发症，甚至造成患者生活质量不同程度下降或猝死[1]。目前OSAHS的发病机制尚不十分清楚，多认为上气道相关骨支架刚性异常和局部软组织移位塌陷是阻塞性睡眠呼吸暂停综合征发病机制的重要方面[2-8]。因此，上气道的形态学研究已经成为OSAHS的一大热点，对OSAHS的预防、诊断治疗、预后具有很大的现实意义。目前学者多采用二维影像技术（X线头影测量法）和三维影像技术［包括计算机体层扫描技术（CT）和磁共振技术（MRI）］，对OSAHS患者上气道的形态特点及局部阻塞点进行研究[9-14]，为该疾病诊断、治疗和疗效判断提供一定的客观依据，但将三维有限元方法用于OSAHS的研究仍鲜见报道。
三维有限元法是将形态学和医学生物力学等用于分析研究的一种先进有效的方法。本研究在对OSAHS患者上气道行螺旋CT扫描的基础上，获得DICOM格式的图像信息，采用Mimics和Imageware医学建模软件、Ansys有限元分析软件建立准确、可灵活模拟操作的OSAHS患者上气道及其周围结构的三维有限元模型，通过对有限元模型的加载分析，为OSAHS患者上气道生物力学分析打下基础，以期深入了解OSAHS的发生机制以及为口腔矫治器治疗OSAHS的优化设计等提供理论依据，同时探索一种新的研究OSAHS的方法，为以后OSAHS的研究提供一种新的思路。
目的：建立OSAHS患者上气道、下颌骨、舌骨及其周围结构的三维有限元模型，通过逐步前伸下颌，观察OSAHS患者舌咽部生物力学和形态学改变，为OSAHS的口腔矫治器治疗提供依据。
方法：对OSAHS患者上气道行薄层CT扫描，获得OSAHS患者上气道DICOM格式的图像信息，采用Mimics三维建模软件和Imageware软件、Ansys有限元分析软件建立上气道、下颌骨、舌骨及其周围结构的三维有限元模型，通过逐步前伸下颌骨，观察舌咽部生物力学和形态学的变化及其规律。
结果：建立了OSAHS患者上气道及其周围结构的三维有限元模型，采用10节点的Solid 92四面体单元划分网格后，骨、肌肉、气道得到的单元数和节点数分别为：214725、38826、22590个单元，317305、60018、30720个节点。逐步前伸下颌骨时，舌咽部发生相应的形态变化，主要表现为：上气道舌咽部平面横径和横截面积增加，而上气道舌咽部矢状径减小。气道舌咽会厌尖截面出现在下颌前伸8 mm的情况下；加载模型后，应力分布特征为S1主应力主要分布于上气道前壁区肌肉牵拉处，应力位置未发生明显改变；舌咽部应力值随下颌前伸距离增加而不断增加。
结论：应用螺旋CT技术，并联合使用Mimics三维建模软件、Imageware软件、Ansys有限元分析软件建立OSAHS患者上气道、下颌骨、舌骨及其周围结构三维有限元模型的方法，建模效率高、速度快，模型的几何相似性较好，使用灵活；通过下颌逐步前伸，对OSAHS舌咽部有限元模型进行加载分析，有效展示下颌前伸与舌咽部二者之间的关系，证实了有限元研究方法的可行性，为下颌前伸矫治器治疗OSAHS提供理论依据，同时为后续OSAHS患者上气道生物力学分析打下良好的基础。
【关键词】阻塞性睡眠呼吸暂停低通气综合征；三维有限元法；下颌前伸；生物力学；Mimics软件；Imageware软件；Ansys软件
The change of glossopharyngeal part of the Three-dimensional Finite Element Model of an Obstructive Sleep Apnea Hypopnea Syndrome Patient during titrated mandibular advancement(https://www.daowen.com)
ABSTRACT
Obstructive sleep apnea hypopnea syndrome（OSAHS），is a kind of recurring sleep apnea，oxygen saturation decreased,the upperairway obstructed complex syndrome[1].In the long run，the disease will lead to heart，brain，kidney and other complications,even sudden death.Therefore，OSAHS is a potentially fatal sleep breathing disorder disease.The pathogenesis of OSAHS is not yet very clear，generally considered the upper airway morphology and surrounding tissue abnormalities is important in the pathogenesis[2-8].Therefore,to study the upper airway of an OSAHS patient become an important aspect of the pathogenesis of OSAHS.Currently scholars often use imaging methods to study the upper airway of OSAHS patient including X cephalometric method,computer tomography technology（CT）and magnetic resonance imaging（MRI）to investigate the upper airway of OSAHS patients morphological and anatomical characteristics and position of local obstruction[9-14]，to provide an objective basis for the clinical diagnosis and treatment options，but it is so far rare reported that the method of three-dimensional finite element analysis is used for OSAHS study.
Three-dimensional finite element method is the most advanced and effective method of biomechanical analysis in medicine.This study obtained the accurate DICOM format of the image information of OSAHS patient’s upper airway by using spiral CT scan and establish an accurate，flexible simulation OSAHS patient’s upper airway model by using Mimics，Imageware and Ansys software.Through the analysis of finite element model of the load,which lay the foundation for the OSAHS patient’s upper airway biomechanical analysis，in order to understand the pathogenesis of OSAHS，as well as provide a theoretical basis for Oral appliance optimal design for OSAHS therapy，while exploring a new method of OSAHS research in order to provide a new way of thinking for future research of OSAHS.
Objective：To construct a three-dimensional finite element model of the Upper airway and adjacent structure of an Obstructive sleep apnea hypopnea syndrome patient for OSAHS biomechanical analysis.And then titrated mandibular advancement，the changes and the law of glossopharyngeal part observed by biomechanics and morphologic.
Methods：DICOM format image information of an OSAHS patient’s upper airway obtained by thin-section CT scanning and digital image processing were utilized to construct a three-dimensional finite element model by Mimics，Imageware and Ansys software.And then titrated mandibular advancement，the changes and the law of glossopharyngeal part observed by biomechanics and morphologic.
Results：A case of OSAHS and the adjacent upper airway structure of three-dimensional finite element model is constructed which is formed by solid 92 tetrahedral unit of a 10-node mesh.The model has bone:214725 elements，317305 nodes；muscle:38826 elements,60018 nodes；upper airway:22590 elements，30720 nodes.After titrated mandibular advancement，glossopharyngeal part of three-dimensional finite element of OSAHS change signficately.The main manifestations are:After loading model，the transverse diameter and cross-sectional area of tongue pharyngeal were increased significantly，although the sagittal diameter was decreased correspondingly.The cross-sectional area of epiglottis tip of glossopharyngeal airway parts was increased Largest when mandibular advanced at 8 mm.the principal stress is mainly distributed in anterior wall of the upper airway，with the increasing of distance，the location of principal stress concentration did not change significantly.The tongue pharynx stress increased during titrated mandibular advancement.
Conclusion：The joint use of spiral CT technology,Imageware and Mimics software，Ansys software on the establishment of upper airway and vicinity structure of OSAHS patient，which confirmed by CT to establishment accurate,flexible three-dimensional finite element model of the upper airway and vicinity structure of an OSAHS patient.The model has good geometric similarity and good flexibility.The glossopharyngeal part of finite element model of OSAHS was analysises by titrated mandibular advancement,the effective show the relationship between mandibular advancement and the glossopharyngeal part,which confirming that the study is feasibility,providing a theoretical basis for treatment of OSAHS with Mandibular advancement appliance and laying a good foundation.for the follow-up study of upper airway in OSAHS patients with biomechanical analysis.
Key words：three-dimensional finite element method；Obstructive sleep apnea hypopnea syndrome；Mandibular advancement；Biodynamics；Mimics software；Imageware software；Ansys software