Long-Term Cephalometric Skeletal Stability Following Maxillomandibular Advancement for Severe Obstructive Sleep Apnea

Purpose: There is a lack of data on long term cephalometric analysis of skeletal stability following maxillomandibular advancement (MMA) for severe obstructive sleep apnea (OSA). The purpose of this study was to determine the long term skeletal stability of subjects who had undergone MMA for OSA.

Subjects and Methods:This was a retrospective cohort analysis of adult patients treated with MMA for polysomnogram confirmed severe OSA between January 1, 1992 and December 31, 2014. Inclusion criteria included overnight polysomnogram severe OSA (AHI > 35), treatment with MMA of at least 8 mm, adequate pre- and post-operative lateral cephalometric radiographs, and at least 260 weeks (5 years) of post-operative follow-up. Predictor variables were the presence of OSA and treatment by MMA. Outcome variable was skeletal stability based on serial cephalometric tracings for SNA, SNB, and ANB. Using computerized software (Dolphin Imaging 10.0, Carlsbad CA), lateral cephalometric radiographs were digitized and standardized for 3 time points, T0 (pre-operative), T1 (1 week post-operative), T2 (last follow-up of at least 5 years). The Steiner analysis was utilized to determine skeletal stability by analyzing the changes in skeletal landmarks SNA, SNB, and ANB. Incidence of malocclusion was determined through clinical and photographic examination.

Method of Statistical Analysis: A prior sample size analysis to detect a significant difference between means of dependent groups with the two-way paired t-test using an alpha error of 0.05, a power of 95%, and based on data from Faria et al given pre- and post-operative changes in SNA (81.84° +/- 5.69° to 87.53° +/- 4.74°). A total of ten subjects would be required. Statistical significance between groups means was determined using the two-way paired t-test with significance set at the p < .05 level.

Results: Ten subjects who met the inclusion criteria were included. Average follow-up was 450.3 weeks (8.7 years). Average age was 57.9 +/- 9.0 years. Gender distribution was even at 5 each. Pre-operative AHI was 59.8 +/- 17.9. The amount of MMA was 8.75 mm at maxillary central incisor. All subjects received rigid fixation and a period of maxillomandibular fixation ranging from 3 to 5 weeks (average 3.5 weeks). No subjects received orthodontia and there were no incidences of malocclusion. There were statistically significant increases between T0 and T1 for SNA (82.4° +/- 4.0° to 88.3° +/- 5.1°, P = 0.01) and SNB (78.8° +/- 1.9 to 83.2° +/- 3.9°, P = 0.01). There were statistically significant increases between T0 and T2 for SNA (82.4° +/- 4.0° to 87.5° +/- 2.3°, P = 0.01) and SNB (78.8° +/- 1.9 to 82.9° +/- 3.5°, P = 0.03). There were small, but statistically insignificant relapses between T1 and T2 for SNA (D = -1.6 °, P = 0.7), SNB (D = -1.2 °, P = 0.9), and ANB (D = -0.5 °, P = 0.9).

Conclusion:Changes in the SNA, SNB, ANB from T1 to T2 suggest a small statistically insignificant skeletal relapse as the mean differences were small (ranging from -1.6° to -0.5°) without development of malocclusion and may be considered clinically insignificant. Therefore, within the its limitations, this preliminary study revealed that long term (greater than 8 years) skeletal stability is achievable in large (greater than 8 mm) MMA surgery for severe OSA. Further research with increased number of subjects will be required to validate these results.

References:

1. Faria AC, et al. Cephalometric analysis of modifications of the pharynx due to maxillo-mandibular advancement surgery in patients with obstructive sleep apnea. Int J Oral Maxillofac Surg. 42(5):579, 2013.
2. Lee SH, et al. Skeletal stability of patients undergoing maxillomandibular advancement for treatment of obstructive sleep apnea. J Oral Maxillofac Surg. 73(4):694, 2015.