In search of a safe zone for sagittal split ramus osteotomy: a cone-beam computed tomography study of the mandibular...

Unfavourable split is one of the complications of sagittal split ramus osteotomy (SSRO) and anatomical variation has been attributed as one of the factors. This cone-beam computed tomography (CBCT) study aimed to investigate: the ramus thickness; the distance of mandibular lingula (ML) to different ramus landmarks; the horizontal and vertical distance of the ML to the buccal and lingual cortical plates fusion point; and differences between sides of mandible, sex, and ethnicities. This retrospective cross-sectional study consisted of 206 CBCT (412 hemimandibles) of 129 females and 77 males, with a mean age of 33 years. The mandible was slightly thicker at 4 mm above the lingula than at the level of lingula, measuring 6.54 ± 1.52 and 6.53 ± 1.59 mm respectively. The distances of the mandibular lingula (ML) to the borders of mandible were: anterior 17.84 ± 2.25, posterior 14.46 ± 3.44, superior 17.73 ± 3.00, and inferior 27.05 ± 4.40 mm. Buccal and lingual cortical plates fusion point has been found to be approximately 12 mm posterior to and 8 mm above the ML. Mandibular thickness significantly predicted the horizontal distance from the lingula to the cortical fusion point; for every 1 mm increase in thickness, the fusion point lies 0.624 mm further from the lingula. These morphometric data on the mandibular ramus anatomical variables are useful for medial horizontal osteotomy design and placement and may potentially be used as a reference guide for surgical planning in SSRO.