This prospective clinical trial aims to evaluate the clinical and radiographic outcomes of the low sagittal medial ramus osteotomy-a technical modification of the conventional sagittal split osteotomy (SSO)-for treating patients with skeletal Class II and Class III malocclusions.
Standard sagittal split osteotomies carry risks of complications, including unfavorable osteotomy propagation (bad splits) toward the condyle, ramus fragmentation, lingual interference of the distal segment, and inferior alveolar nerve (IAN) injury. To minimize these risks, this study utilizes a modified medial cut positioned low (below the lingula in an area with adequate marrow space) and short (terminating anterior to the lingula). This design aims to prevent osteotomy extension into the condylar region and eliminate lingual interference during segment repositioning.
Patients with skeletal Class II or Class III malocclusion requiring mandibular orthognathic surgery.
Age range from 18 to 45 years old.
Systematically healthy patients classified as ASA physical status I or II (American Society of Anesthesiologists)
Patients with a pre-existing history of inferior alveolar nerve (IAN) sensory impairment.
Patients with active or severe degenerative joint disease (DJD).
Patients with a prior history of orthognathic surgical procedures.
Patients presenting with systemic diseases or conditions known to compromise normal bone healing.
Single group
Low Sagittal Medial Ramus Osteotomy
Procedure/SurgeryPatients undergoing orthognathic surgery using the low sagittal medial ramus osteotomy modification. The medial osteotomy cut is initiated slightly above the mandibular occlusal plane, positioned low (below the lingula in an area with adequate marrow space) and short (terminating anterior to the lingula and retrolingual fossa) to achieve 3D mandibular repositioning guided by CAD/CAM virtual surgical planning.
Number of Participants with Unfavorable Osteotomy Split ("Bad Split")
Intraoperative evaluation of the occurrence of unfavorable osteotomy propagation (e.g., condylar neck fracture, ramus fragmentation, or buccal/lingual plate fracture) during the sagittal split procedure, assessed via direct visualization and manual palpation.
Change from Baseline in Inferior Alveolar Nerve (IAN) Conduction Latency via TSSEP
Objective electrophysiological assessment of IAN neurosensory function measured using Trigeminal Somatosensory Evoked Potentials (TSSEP). Unit of Measure: Milliseconds (ms)
Number of Participants with IAN Entrapment in the Proximal Segment
Direct intraoperative visual assessment to report the frequency of the inferior alveolar nerve being contained within the proximal segment versus the distal segment immediately following sagittal splitting
Incidence of Distal Segment Lingual Bony Interference
intraoperative assessment of lingual bony interference during distal segment positioning into the planned occlusal alignment. Evaluated as a categorical outcome: Presence (bony contact requiring additional osteotomy modification or recontouring to achieve passive seating) vs. Absence (passive seating achieved without bony contact). Unit of Measure: Number of participants
Condylar Position within the Glenoid Fossa via Panoramic Radiography
Postoperative radiographic assessment using panoramic radiographs to confirm anatomical centering and placement of the condyle within the glenoid fossa. Evaluated as Adequate Position vs. Displaced Position
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