Abstract Objective This study aims to evaluate postoperative craniocervical changes after bilateral sagittal split ramus osteotomy (BSSRO), to test mandibular translation and rotation as predictors, and to explore their coupling with tongue and hyoid adaptations. Materials and methods A total of 210 patients (88 males, 122 females; 18–58 years) were equally divided into skeletal Classes I–III. Cephalograms in natural head posture were obtained pre- and postoperatively. Craniocervical change (ΔNSL/OPT) was the primary outcome. Mandibular translation (ΔGo–Me) and rotation (ΔFH–MP) served as predictors, with tongue and hyoid variables as secondary outcomes. Reliability was assessed using intraclass correlation coefficients (ICCs). Statistical analyses included analysis of variance (ANOVA), correlation, and multivariable regression. Results Measurement reproducibility was excellent (ICC 0.92). Mandibular advancement (Class II) and setback (Class III) produced class-specific changes in ΔGo–Me and ΔFH–MP. Postoperatively, Class II showed cervical flexion (−3.09° ± 7.12°) whereas Class III showed cervical extension (+2.92° ± 5.48°, P .001). ΔNSL/OPT correlated with ΔFH–MP (r = 0.25, P = .002) and ΔGo–Me (r = 0.17, P = .017), though only ΔFH–MP remained significant in regression (β ≈ 0.47° per 1° rotation). ΔNSL/OPT was most strongly correlated with ΔSNH (r = 0.62, P .001), indicating coordinated craniocervical–hyoid adaptation. Tongue showed modest lengthening, flattening, and anterior shift across both advancement and setback groups. Conclusions Cervical extension after BSSRO is primarily driven by mandibular rotation rather than translation, underscoring the clinical importance of incorporating rotational vectors into surgical planning. Coupled tongue–hyoid adaptations reflect early neuromuscular compensation, with potential implications for long-term stability and functional outcomes.
Kaboosaya et al. (Tue,) studied this question.