Research question:~Description of research question:~P: Population: Patients with facial skeletal deformity and need for mandibular setback using bilateral sagittal split osteotomy (BSSRO) alone or combined with lefort osteotomy.~I: Intervention: Patients with facial skeletal deformity and need and for mandibular setback using low medial cut osteotomy as modification of bilateral sagittal split ramus osteotomy (BSSRO).~C: Comparator: Patients with facial skeletal deformity and need and for mandibular setback using traditional high medial cut osteotomy bilateral sagittal split ramus osteotomy (BSSRO).~O: Outcome: Comparing the post-operative condylar positions changes and TMJ functions of two osteotomies.~Research question:~Is using low medial cut osteotomy modification in BSSRO in mandibular setback will provide more control over proximal segment position than traditional high medial cut through:~limit the segments interference and so maximizes the passive bony contact across the osteotomy site after surgically repositioning the distal segment~Passively positioned the proximal segment without displacement of the condyle from its normal position.
This study hypotheses that using low medial cut osteotomy BSSO in mandibular setback can be an efficient and effective method to limit the bony segment interferences , decreasing muscles stripping during osteotomy ,decrease condylar torque and so securing preoperative condylar position during BSSO in comparison with using high medial cut BSSO.