Comprehensive 3D upper airway analysis in OSA patients after bilateral internal ramus distraction osteogenesis of the mandible (BIRD)

Bilateral internal ramus mandibular distraction (BIRD) has recently been proposed as an effective surgical alternative for the treatment of obstructive sleep apnoea (OSA) in adults. This study analysed post-operative changes in the upper airway and key polysomnographic (PSG) indexes of 32 patients with moderate to severe OSA and aimed to determine if any morphological parameters could predict clinical improvement. All patients were evaluated by cone-beam computed tomography (CBCT) scans and PSG at three time points: pre-surgery (T1), post-BIRD (T2), and post-maxillary advancement (T3). Pairwise comparisons (Wilcoxon test, p<0.05) showed a reduction in the apnoea-hypopnoea index (AHI) from T1 (47.9 ± 23.1) to T2 (14.4 ± 14.3) and T3 (4.7 ± 5.6), with a final cure rate of 81.2% (defined as final AHI <5). All measured airway variables increased after T2 and T3, but only the changes after BIRD were statistically significant. Regression analysis revealed that counterclockwise rotation of the occlusal plane after BIRD correlated with all measured changes in airway parameters. The amount of sagittal advancement of the soft pogonion predicted success: for each mm of advancement, the AHI was reduced by 9.8%. Accurate pre-operative evaluation of soft pogonion advancement is essential for OSA patients considering BIRD. Further research is needed to confirm the findings' significance.