三维有限元模型分析OSAHS患者下颌逐步前伸引起的关节盘位移和表面应力分布变化的研究
【摘要】
目的：建立阻塞性睡眠呼吸暂停低通气综合征（OSAHS）患者的下颌骨、颞下颌关节、上气道及其周围结构的三维有限元模型，通过软件设计定量的加载，下颌逐步前伸；观察患者因下颌前伸引起的关节盘位移和表面应力分布变化，及关节盘整体位移与下颌前伸量之间的关系，为今后下颌前伸类口腔矫治器治疗OSAHS机理研究提供一定生物力学依据，并从颞颌关节关节盘形态学变化方面提供基础理论参数。
方法：对OSAHS患者颞下颌关节和上气道行薄层CT扫描，获得患者下颌骨、颞下颌关节、上气道及其周围结构的三维影像信息，影像信息以DICOM格式输入至相关联合建模软件：Mimics三维建模软件、Imageware逆向工程学软件、Ansys有限元分析软件之中，最终建立了实验所需的OSAHS患者的下颌骨、颞下颌关节、上气道及其周围结构的三维有限元模型，然后通过软件加载下颌骨定量的逐步前伸，观察关节盘位移和表面生物力学改变的变化及趋势。
结果：建立了实验所需的OSAHS患者相关解剖部位结构的三维有限元模型，所建模型单元采用10节点的Solid 92四面体单元，得到包含骨密质、骨松质、肌肉和气道的单元总数和节点总数共为：280 360个单元和590 195个节点。通过逐步前伸下颌骨，关节盘三维方向上的位移逐渐增大，关节盘整体位移逐渐增大，发生向前向下的移动。经统计学回归分析，下颌骨前伸与关节盘整体位置变化两者之间相关，并得出回归系数方程：y=0.018 85x-0.000 56。整个加载过程中，关节盘应力分布除去4.4 mm和11.00 mm这两个位点差距较大外，其他位点应力变化较为平均，且在11.00 mm时应力达到最大。
结论：在螺旋CT扫描图像的基础上，并联合使用相关建模软件Mimics、Imageware和Ansys，建立了实验所需的OSAHS患者相关解剖部位的三维有限元模型，通过软件验证模型真实有效，使用灵活。通过逐步前伸下颌骨，对关节盘位移和表面应力分布变化进行分析发现，关节盘三维方向均发生位移的改变，均随下颌前伸量的增加而增加，不同距离的下颌骨前伸关节盘最大应力的分布区域基本不变，关节盘应力在下颌骨前移时不同距离的应力数值在4.4 mm与11.00 mm时变动较大时临床中需考虑到患者的耐受度。下颌前伸与关节盘向前向下移动正相关，证实关节盘的位置可作为判定下颌前伸大小的重要参考指标。
【关键词】阻塞性睡眠呼吸暂停低通气综合征；下颌前伸；颞下颌关节；关节盘；三维有限元法
The three-dimensional Finite Element analysis of an Obstructive Sleep Apnea Hypopnea Syndrome Patient’s hyoid bone position changement with titrated mandibular advancement(https://www.daowen.com)
ABSTRACT
Objective：Construct a three-dimensional finite element model of the mandible，temporomandibular joint，the upper airway and the adjacent structure of an Obstructive sleep apnea hypopnea syndrome patient and regulate protrusion of mandibular，Articular disc displacement and surface stress distribution changes observed OSAHS patients due to mandibular advancement By gradually loaded quantitative mandibular advancement.the position changes of articular disc and its relationship with the mandibular protrusion can be observed and analysized which providing theoretical basis for mechanism studies of treatment to OSAHS with mandibular protraction.And provide the basis for theoretical aspects of parameters from the temporomandibular joint.
Methods：DICOM format image information of an OSAHS patient’s upper airway and temporomandibular joint obtained by thin-section CT scanning and digital image processing were utilized to construct a three-dimensional finite element model by Mimics and Ansys software.And then titrated mandibular advancement，the changes and the law of articular disc observed by biomechanics and displacement.
Results：Construct a three-dimensional finite element model of the mandible，temporomandibular joint，the upper airway and the adjacent structure of an Obstructive sleep apnea hypopnea syndrome patient and regulate protrusion of mandibular，which is formed by solid92 tetrahedral unit of a 10-node mesh.The model has cluded cortical bone，the total number of units and the total number of nodes in cancellous bone，muscle and airway total：280，360 units and 590，195 nodes.Protrusive mandible by gradual displacement of the articular disc dimensional direction increases，Overall articular disc displacement increases，the occurrence of a downward move forward.The statistical regression analysis between the mandible and the articular disc protrusion overall position related changes，and draw the regression coefficient equation：y=0.01885x-0.00056.The entire loading process，the articular disc stress distribution which is substantially removed 4.4mm 11.00mm and a larger gap between the two sites，other sites of stress more evenly，and the stress reaches a maximum when 11.00mm.
Conclusion：Application of spiral CT combined use Mimics，Imageware and Ansys finite element analysis software to establish OSAHS patients under the jaw，temporomandibular joint，upper airway dimensional finite element model of the structure and its surroundings.Through real and effective software validation model，the use of flexible，By gradually lower jaw protrusion，articular disc displacement in three dimensions were changed，and the inconsistencies in the lateral direction，and the surface of the articular disc displacement changes the stress distribution analysis found that the mandible forward articular disc distribution area of maximum stress at different distances basically unchanged，Stress values at different distances when articular disk stress mandible forward when 4.4mm and 11.00.mm larger changes，taking into account the clinical need of the patient’s tolerance.Mandibular joint disc protrusion and move forward down a positive correlation，confirmed：articular disc position as mandibular advancement determine the size of the important reference index.
Key words：Obstructive sleep apnea syndrome；mandibular advancement；temporomandibular joint；articular disc；three-dimensional finite element method