下颌骨受力时颅底的保护因素分析

Study of protection factors of skull base with loaded mandible

目的:利用有限元方法分析下颌骨受外力作用时,下颌骨与颞骨的应力分布,推断颅底的保护因素。方法:对1名健康成年男性头部进行CT扫描,根据扫描图像与相关解剖研究,对下颌骨、颞骨以及两者之间的颞下颌关节进行有限元模型重建,同时重建约束下颌骨运动范围的主要附着韧带和肌肉。对此模型颏部正中施加后上方向的力,角度分别为与下颌体水平成0°、30°、54°,施加力为1000N、2000N、3000N,观察施加不同大小与方向的外力作用时下颌骨与颞骨的应力分布情况。结果:无论外力方向与大小如何变化,颞骨应力总是小于下颌骨应力。随着外力方向的变化,下颌骨的应力集中部位亦发生变化,主要集中于髁突与下颌体前部内侧;颞骨的应力集中部位没有发生明显改变,主要集中于外耳道前壁,而不在颞骨关节窝顶。随着外力角度的增大,下颌骨与颞骨应力集中部位的应力与应变均减小。随着施加力值的增大,下颌骨与颞骨应力亦逐渐增大。结论:本模型能真实准确地计算出下颌颏部受矢状方向力作用时,下颌骨与颞骨的应力分布情况。颞下颌关节的缓冲使颞骨应力始终小于下颌骨的应力。在受到正中方向的力打击时,颞骨应力多数集中于外耳道前壁,并非关节窝顶部的薄弱部位,避免了颞骨受到严重破坏。

PURPOSE： The stress distribution of the mandible and temporal bone under impact loading was analyzed by finite element method for investigating the protection factors of skull base.METHODS： According to the obtained CT image of the head from a healthy male adult and the related anatomic studies,a 3-D finite element model with the anatomic structures of the temporal bone,mandible,temporomandibular joint,main ligaments and masticatory muscles was established.A concentrated force was applied to the chin of mandible.The angle of the force with the horizontal line was 0°,30°,54° and the magnitude of the force was 1000N,2000N,3000N,respectively.The stress distribution of the mandible and temporal bone under different loading conditions was analyzed.RESULTS： The stress of temporal bone was always less than that of mandible whatever the direction or the magnitude of the force was.With the alteration of force directions,the region of peak stress in mandible changed,which mainly lied on the condyle and the interior surface of anterior part of the mandible,while the region of peak stress in the temporal bone did not change,which lied on the anterior wall of external acoustic meatus.The stress of the roof of the glenoid fossa was not the largest in the temporal bone.CONCLUSIONS： Due to the buffer effect of the disc,the stress of temporal bone was always less than that of the mandible.When the chin was loaded in the sagittal direction,the region of peak stress in the temporal bone was the anterior wall of external acoustic meatus,not the weak part of the roof of glenoid fossa,so as to avoid the temporal bone being destructed severely.