Condylar Remodeling and Relapse Patterns in Skeletal Class II High-Angle Patients Following Bimaxillary Surgery with Rigid Internal Fixation

Abstract

Background and Objective: Skeletal Class II high-angle patients undergoing bimaxillary orthognathic surgery present a uniquely challenging biomechanical environment characterised by hyperdivergent mandibular growth, steep occlusal plane inclination, and inherent susceptibility to progressive condylar resorption. Rigid internal fixation (RIF) has largely supplanted wire osteosynthesis in contemporary practice; however, its differential influence on condylar remodelling morphology and long-term skeletal relapse in this specific phenotype remains incompletely elucidated. This prospective cohort study evaluated condylar remodelling patterns, three-dimensional skeletal stability, temporomandibular joint (TMJ) outcomes, and patient-reported quality of life over 36 months following bimaxillary surgery with rigid internal fixation versus conventional wire osteosynthesis in skeletal Class II hyperdivergent patients.

Methods: One hundred and eight skeletally mature patients meeting strict inclusion criteria for skeletal Class II malocclusion with Frankfort-Mandibular Plane Angle (FMA) > 30° were prospectively recruited at a quaternary craniofacial unit (Noora Hospital Srinagar) between January 2021 and December 2022. Participants were allocated to RIF (n=56) or wire osteosynthesis control (n=52) groups based on surgeon assessment and patient preference. Cone-beam computed tomography (CBCT) was performed at six standardised time points over 36 months. Three-dimensional condylar morphometric analysis and cephalometric superimposition were conducted using Mimics Innovation Suite v26.0. Primary outcomes included condylar remodelling index (CRI), 3D skeletal relapse vectors, and percentage of planned surgical movement retained. Secondary outcomes included TMJ symptom scores, patient-reported VAS outcomes, and complication rates.

Results: At 36 months, the RIF group demonstrated significantly lower total 3D skeletal relapse (2.1 ± 0.7 mm vs. 4.0 ± 1.3 mm; p < 0.001), superior retention of planned surgical movement (71.8 ± 6.2% vs. 52.6 ± 8.8%; p < 0.001), and substantially lower condylar remodelling index (4.4 ± 1.4 mm² vs. 8.6 ± 2.7 mm²; p < 0.001). Adaptive condylar remodelling was observed in 68.0% of RIF condyles versus 41.0% of control condyles (p < 0.001). Condylar resorption occurred in 22.0% versus 39.0% of condyles (p = 0.021). TMJ pain VAS scores improved significantly in both groups but were markedly better in the RIF cohort at 36 months (1.2 ± 0.6 vs. 2.8 ± 1.1; p = 0.001). Stable occlusal outcomes were achieved in 69.6% of RIF patients versus 44.2% of controls (p = 0.012). Overall complication rates were lower in the RIF group (10.7% vs. 21.2%; p = 0.039).

Conclusion: Rigid internal fixation in bimaxillary surgery for Class II high-angle patients confers significantly superior condylar stability, reduced skeletal relapse, higher rates of adaptive remodelling, and improved patient-reported outcomes at 36 months compared to wire osteosynthesis. Virtual surgical planning with CAD/CAM-fabricated occlusal splints and precise intraoperative condylar positioning are critical determinants of postoperative TMJ health and long-term skeletal stability in this biomechanically high-risk patient cohort.