下顎枝矢状分割を安全に行うための力学的研究 ヒト乾燥下顎骨における静的荷重下のひずみ分布による検討

Abstract

Sagittal splitting ramus osteotomy is frequently performed during orthognathic surgery for mandibular deformity. However, misapplication of instruments such as an osteotome and a splitter in bone splitting may result in accidental fracture in areas other than the desired line of splitting. The areas most prone to accidental fracture were determined by measuring the strain distribution during sagittal splitting of the ramus in a simulation experiment by the Obwegeser-Dal Pont technique using air-dried human mandibles fixed firmly at its posterior end and lower border.The following results were obtained:1) A large amount of strain was exerted in the vicinity of the mylohyoid sulcus irrespective of the direction or angle from which the osteotome was applied.2) Application of the osteotome parallel to the sagittal plane and at an angle almost parallel from the anterior to the occlusal plane was shown in general to be the safest with the minimum degree of strain.3) Application of the osteotome at an angle 60 degree from the anterior to the occlusal plane and approximately 15 degree lingually from the sagittal plane generated a large strain in the center of the external aspect of the mandibular ramus.4) As judged from the shape of the split segments, application of the osteotome parallel to the sagittal plane and degree from the anterior to the occlusal plane frequently enabled splitting in the desired shape.5) The maximum load during complete splitting was lowest when the splitter was applied parallel to the sagittal plane and 60 degree from the anterior to the occlusal plane. However, a large amount of strain was generated.