下顎枝矢状分割法に関連した下顎枝部の解剖学的考察

Abstract

Sagittal splitting ramus osteotomy is a well established method to correct mandibular deformity. However, there still remain some difficulties to accomplish it without any complications because it has a possibility of accidental fracture of mandibular ramus and injury to mandibular canal. Several modifications of technique are reported to reduce these complications.However, the most important thing in ensurring the safety of this operation is having through knowledge about the anatomical and morphological conditions of mandibular ramus.In this report we examined fifteen dried human mandibles and computed tomographies taken from twelve patients who underwent sagittal splitting osteotomy in our department to detect the anatomical properties of mandibular ramus. The following results were obtained:1) The postero-anterior position of mandibular canal was different at the mandibular angle region, where the canal was situated more anteriorly than at mandibular body or mandibular foramen region.2) The bucco-lingual position of mandibular canal was different between the body region and angle region; at the former, all canals lay in lingual portion, at the latter 23% of canals lay just beneath the buccal cortical bone.3) The thickness of cortical bone was thinnest at the posterior half portion of mandibular ramus. The same results were obtained concerning the bucco-lingual thickness of ramus.4) There was no difference between the antero-posterior width of ramus between mandibular protrusion group and normal occlusion group.5) The mean angle between the sagittal plane and the postero-anterior axis of ramus was 10.9 degrees.