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.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
11
Patients 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.
Time frame: Intraoperative (during the surgical procedure)
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)
Time frame: Baseline (preoperative), 1 month, 3 months, and 6 months postoperatively
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
Time frame: Intraoperative (during the surgical procedure)
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
Time frame: Intraoperative (during the surgical procedure)
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
Time frame: Postoperative Day 7 (within the first week postoperatively)
Skeletal Stability and Surgical Movement Outcome
Cephalometric analysis comparing preoperative and postoperative lateral cephalograms to evaluate the gained orthognathic movement and skeletal treatment outcome.
Time frame: 3 months postoperatively
Change from Baseline in SNB Angle via Lateral Cephalometry
Radiographic assessment of horizontal mandibular repositioning and skeletal outcome by measuring the change in the SNB angle on lateral cephalometric radiographs. Unit of Measure: Degrees
Time frame: Baseline (preoperative) and 3 months postoperatively
Change from Baseline in Inferior Alveolar Nerve (IAN) Peak Amplitude via TSSEP
Objective electrophysiological assessment of IAN signal amplitude measured using Trigeminal Somatosensory Evoked Potentials (TSSEP). Unit of Measure: Microvolts
Time frame: Baseline (preoperative), 1 month, 3 months, and 6 months postoperatively
Change from Baseline in Linear Pogonion Advancement (Pog-NB Distance) via Lateral Cephalometry
Radiographic assessment of skeletal advancement and stability measured as the linear distance from Pogonion (Pog) to the NB perpendicular line on lateral cephalometric radiographs. Unit of Measure: Millimeters ($\\text{mm}$)
Time frame: Baseline (preoperative) and 3 months postoperatively.
Frequency of Complete Bony Bridging at the Osteotomy Site via 3D CT Scan
Radiographic assessment of bone healing across the low sagittal medial ramus osteotomy site evaluated on 3D facial Computed Tomography (CT) scans. Categorized as Complete Healing (continuous cortical/cancellous bone bridging across the osteotomy line) vs. Incomplete Healing (persistent radiolucent gap or non-union). Unit of Measure: Number of participants
Time frame: 6 months postoperatively.
Presence of Condylar Bony Alterations via 3D CT Scan
Radiographic evaluation of temporomandibular joint (TMJ) condylar head integrity assessed on 3D facial CT scans. Categorized as Normal (intact condylar surface) vs. Altered (presence of bony remodeling, erosion, or resorption). Unit of Measure: Number of participants
Time frame: 6 months postoperatively
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