Three-dimensional fracture pattern analysis of the Obwegeser and Dal Pont bilateral sagittal split osteotomy.

The Obwegeser and Dal Pont modification of the bilateral sagittal split osteotomy (BSSO) is a well-established procedure in orthognathic surgery. The purpose of this retrospective study was to analyze the actual fracture patterns achieved with BSSO by Obwegeser and Dal Pont modification using postoperative cone beam computed tomography (CBCT) datasets from 100 patients. A total of 200 split osteotomies were assessed, which could be categorized into nine different split patterns. Only one of the observed split fractures (0.5%) followed exactly the fracture line described by Obwegeser and Dal Pont, whereas 40% followed the fracture line according to the Hunsuck and Epker modification and 13.5% were seen as unfavourable splits mainly running over the buccal plate. A significant correlation was found between unfavourable buccal splits and both horizontal osteotomies reaching the buccal surface at the dorsal ramus (P=0.001) and a vertical caudal bone cut end at the corpus with a buccal position (P<0.001). These results show that a complete antero-posterior horizontal osteotomy at the mandibular ramus does not lead to the intended fracture pattern, which rebuts the argument of a greater amount of bony overlap using the Obwegeser and Dal Pont modification.