下颌前突患者下颌神经管的锥状束CT分析

CBCT Analysis of the Position and Course of the Mandibular Canal in Prognathism

目的:本研究通过使用锥状束CT(cone-beam computerized tomography,CBCT)来观察下颌前突患者下颌管的定位与走行,避免术中损伤下颌神经。方法:选取28例骨性Ⅲ类下颌前突患者(男10例,女18例),术前均使用CBCT机拍摄下颌管影像,从下颌孔至第一磨牙区域共分为5个层面测量,在每个层面分别测量下颌管内外径、下颌骨厚度、下颌管至颊舌侧骨皮质及下颌骨下缘的距离。测量结果采用SPSSl7.0软件包进行统计学分析。结果:下颌骨的厚度自下颌升支到下颌角前部呈逐渐增厚趋势,自下颌第一磨牙位置往前牙区方向又有变薄趋势。下颌管入下颌孔后,从下颌升支到下颌体部内外径均呈逐渐变小趋势。下颌升支部颊侧骨皮质厚度呈逐渐增厚趋势,到下颌体部时又呈逐渐变薄趋势。在每一层测量值中,颊侧骨髓腔的宽度均大于舌侧。舌侧骨髓腔的宽度左右差异有显著性,下颌骨厚度、下颌管内外径及颊侧骨髓腔的宽度性别差异有显著性。下颌管与颊侧骨皮质的关系分为3种类型,分开类型占总测量平面(n=280)的92.5%,接触和融合型分别占6.07%和1.43%。结论:使用CBCT能够精确的显示下颌神经管的走行及与周边结构的关系。下颌神经管入下颌孔后先偏颊侧走行,随后再偏向舌侧。建议颊侧骨髓腔缺失的患者可采用垂直截骨术等其他术式,以避免神经损伤的风险。

Objective： The aim of this study was to investigate the position and course of mandibular canal in mandibular prognatbism with cone-beam computerized tomography （CBCT）,and to relate the findings of sagittal split ramus osteotomy, and also describe the anatomical variations of mandibular canal in order to reduce injuries to the inferior alveolar nerve . Methods： 28 patients with skeletal Class m mandibular prognathism （10 males and 18 females） were examined by CBCT. The position and course of mandibular canal from the lowest point of mandibular foramen to the first molar were measured at five specific landmarks. 5 sections from the mandibular foramen to the mandibular first molar area were analyzed, including inner and outer diameter, mandibular bone thickness and the distance between mandibular canal and the buccal and lingual bone cortex, and the inferior border of mandible bone. Statistical analysis was performed using the SPSS 17.0 software package. Results：Mandibular bone became thicker gradually from the mandibular ramus to the forepart of the mandibular angle, and thinner forward to the position where the mandibular first molar projected on the mandibular bone. Cortical bone of buccal side of the mandibular ramus became thicker forward to the mandibular angle and thinner to the mandibular body. At each section, the bone marrow cavity in the buccal side was always lager than in the lingual side. Width difference between left and right Side of lingual bone marrow cavity were statistically significant. The width of buccal bone marrow cavity, thickness and inner and outer diameter of mandibular bone were statistically different between genders. Three types of connections between mandibular canal and buccal bone cortex were demonstrated in CBCT： 92.5% of＇ which were separate type, 6.07% were contact type, and 1.43% were fusion type. Conclusion：This work demonstrates that CBCT can accurately locate the mandibular canal and anatomic structures, which can provide guidance to the design of sagittal split ramus osteotomy for patients with mandibular protrusion.