Trost Olivier, Salignon Vivien, Cheynel Nicolas, Malka Gabriel, Trouilloud Pierre
Laboratory of Anatomy, INSERM U-887 Motricité Plasticité, Faculty of Medicine, University of Burgundy, Dijon, France.
Surg Radiol Anat. 2010 Dec;32(10):927-31. doi: 10.1007/s00276-010-0645-1. Epub 2010 Mar 10.
The position of mandibular foramen is variable at the medial aspect of mandibular ramus. Nevertheless its location is useful for the oral and maxillofacial surgeon in orthognatic surgery, especially in vertical ramus osteotomy (VRO) procedure. The aim of our study is to analyse the position of mandibular foramen in order to provide simple and reliable surgical landmarks.
A radio-anatomical study was undertaken on normal mandibular panoramic X-ray examinations. Precise reproductions were outlined on tracing paper. Original orthonormal landmark was designed using posterior border of the ramus, mandibular incisure and anterior border of the ramus. All these elements are visible in the patient in VRO. Measurements of the position of mandibular foramen in horizontal and vertical dimensions were then performed with a ruler by two independent observers: l (width of mandibular branch), x (distance between posterior border of the ramus and mandibular foramen), h (height of mandibular branch) and y (distance between sigmoid notch and mandibular ramus). x/l and y/h ratios were calculated in order to minimise magnifications and image distortions due to the imaging process.
Forty-six panoramic X-rays were analysed, including 24 male and 22 female specimens (sex-ratio 1.1/1) with the mean-age 21 years. In vertical dimension, y/h ratio was distributed on a gaussian mode with a peak around 0.30-0.35, mandibular foramen was located around the midpoint of the inferior two-thirds and the superior third of the ramus, preferentially under this point. In horizontal dimension, x/l ratio observed the same model with a peak around 0.35; mandibular foramen was located around the midpoint of the anterior two-thirds and the posterior third of the ramus, preferentially in front of this point. Mandibular foramen was situated in the ventral and inferior two-thirds of the ramus without difference according to the side, sex or age.
Posterior and superior thirds of the ramus constitute a "safety zone" where mandibular foramen is unlikely to be found. This area can be used by the oral and maxillofacial surgeon in vertical ramus osteotomy of the mandible with low inferior alveolar nerve morbidity probability.
下颌孔在下颌支内侧的位置是可变的。然而，其位置对于口腔颌面外科医生进行正颌手术，特别是在垂直下颌支截骨术（VRO）中很有用。我们研究的目的是分析下颌孔的位置，以提供简单可靠的手术标志。
对正常下颌全景X线检查进行放射解剖学研究。在描图纸上勾勒出精确的复制品。使用下颌支后缘、下颌切迹和下颌支前缘设计原始正交标志。所有这些元素在接受VRO手术的患者中都可见。然后由两名独立观察者用尺子测量下颌孔在水平和垂直方向上的位置：l（下颌支宽度）、x（下颌支后缘与下颌孔之间的距离）、h（下颌支高度）和y（乙状切迹与下颌支之间的距离）。计算x/l和y/h比值，以尽量减少由于成像过程导致的放大和图像失真。
分析了46张全景X线片，包括24例男性和22例女性标本（性别比1.1/1），平均年龄21岁。在垂直方向上，y/h比值呈高斯分布，峰值在0.30 - 0.35左右，下颌孔位于下颌支下三分之二和上三分之一的中点附近，优先位于该点下方。在水平方向上，x/l比值呈现相同模式，峰值在0.35左右；下颌孔位于下颌支前三分之二和后三分之一的中点附近，优先位于该点前方。下颌孔位于下颌支的腹侧和下三分之二处，左右侧、性别或年龄之间无差异。
下颌支的后三分之一和上三分之一构成一个“安全区”，在此区域不太可能找到下颌孔。口腔颌面外科医生在进行下颌垂直下颌支截骨术时可利用该区域，使下牙槽神经损伤概率较低。
