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The Impact Of Neonatal Mandibular Distraction On Long-term Mandibular Growth And Morphology
Justin Beiriger, BSE, Miles Pfaff, MD, Maryanna Owoc, BA, Adi Mittal, BA, Sarah Erpenbeck, BA, Madeleine Bruce, BA, Justine Lee, MD, Joseph Losee, MD, Jesse Goldstein, MD.
University of Pittsburgh, Pittsburgh, PA, USA.

PURPOSE:
Mandibular distraction osteogenesis (MDO) is the gold standard treatment for upper airway obstruction associated with Robin Sequence (RS). Given the relatively recent introduction of MDO, the long-term effects of MDO on mandibular morphology approaching or at skeletal maturity remain unknown. The objective of this study was to morphologically characterize the mandibles of distracted and conservatively managed RS patients compared to unaffected age- and sex-matched controls at or approaching skeletal maturity. METHODS:
This retrospective study included RS patients who underwent neonatal MDO and those conservatively managed (CM). All MDO patients underwent internal distraction and both syndromic and non-syndromic patients were included. Mandibular morphometric analysis was performed on all mandibles via 3D-rendered computed tomographic (CT) images at the latest timepoint. Age- and sex-matched unaffected controls were used for comparison. Mean ± standard deviation was reported, student’s t test was utilized, and a p-value of 0.05 or less was considered statistically significant. RESULTS:
13 RS patients (57.1% female; 21% syndromic) were included: 6 CM and 7 MDO. The age at MDO was 2.9 ± 3.6 months and age at latest CT was 17.6 ± 2.2 years for the CM group and 16.5 ± 2.9 for the MDO group. When compared to controls, CM patient mandibular body length was shorter and the anterior symphyseal angle was more obtuse (p=0.009 and <0.001, respectively). The mandibular volume of CM was smaller than matched controls (p=0.05). When compared to controls, the MDO patient ramus height and body length were shorter (p=0.008 and <0.001, respectively) and the gonial angle and anterior symphyseal angle were more obtuse (p=0.013 and <0.001, respectively). The mandibular volume of MDO was also significantly smaller than matched controls (p=0.043). While CM patients did require mandibular advancement ± maxillary advancement at a higher rate than MDO patients (83.3% vs. 42.9%%), no statistical difference was detected. CONCLUSION:
Neonatal MDO was associated with discrete morphologic changes unique to the RS mandible at or approaching skeletal maturity that included a volumetrically smaller and shorter mandible with a more obtuse gonial and anterior symphyseal angle. This study provides further insight into the long-term effects of MDO on mandibular morphology and the importance of continuing to optimize MDO parameters to limit long-term interventions.


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