Accuracy of Lateral Mandibular Landmarks in Defining a Safe Zone for Intraoral Vertical Ramus Osteotomy

BACKGROUND: Intraoral vertical ramus osteotomy (IVRO) requires placement of the osteotomy posterior to the mandibular lingula (ML) to avoid injuring the inferior alveolar neurovascular bundle (IANB), yet limited visualization of the ML makes it a "blind" procedure. Common lateral landmarks, including the antilingula (AL), midwaist point (MWP), and midpoint of the coronoid-gonion line (MCG), are used to guide osteotomy placement, but their reliability remains uncertain. This study evaluated their application in a Kenyan population. METHODS: A retrospective cross-sectional analysis of cone-beam computed tomography (CBCT) scans of 304 rami was conducted. The ML and the lateral landmarks were identified using 3-dimensional reconstruction. Spatial relationships were assessed using polar plots to evaluate their correspondence with the ML. RESULTS: The AL was present in 90.1% of cases but showed wide variability, with minimal overlap with the ML. The ML was posterior to the AL in 92.0% of cases, with an observed safe zone extending up to 15 mm posterior to the AL. The MWP and MCG demonstrated greater consistency but retained variability, with the ML located posterior to these landmarks in 92.1% and 96.4% of cases, and the observed safe zone extending up to 14 and 11 mm posterior to the MWP and MCG, respectively. CONCLUSION: Lateral mandibular landmarks are unreliable as sole guides for IVRO, and conventional safety margins of 2 to 5 mm may underestimate posterior ML variability in this population. The safe zone appears to lie further posterior, supporting the use of customized cutting guides to improve surgical safety.