36. Cephalometric Imaging Sheds Light on the Effects of Mandibular Distraction on Infants with Robin Sequence

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PURPOSE: Upper airway obstruction (UAO) in infants with Robin Sequence (RS) is secondary to micrognathia and resultant posterior displacement of the tongue. Mandibular distraction osteogenesis (MDO) is a safe and effective treatment for significant UAO, but there is a paucity of data examining associated cephalometric changes. This study carefully examines mandibular cephalometric changes of infants with RS who underwent MDO using internal devices to more deeply understand both immediate and longer-term effects of distraction on mandibular shape. METHODS: Consecutive infant MDO cases (n=53) performed by the same surgeon were analyzed using preoperative and postoperative lateral cephalograms and CT scans of the mandible. Population averages for preoperative and postoperative time points were assessed using a two-sample t-test with equal variance. RESULTS: Significant post-operative morphologic changes were seen in 19 of 21 cephalometric parameters. Length, height, width, and airway parameters improved on average by 20.3 mm (60.7%), 9.8 mm (49.7%), 12.6 mm (36.1%), and 211%, respectively. The majority of cephalometric measurements displayed substantial percent change from the preoperative timepoint to device removal and a much less dramatic percent change from device removal to 6-12 months postoperatively. In fact, none of the parameters measuring mandibular length and angular cephalometrics were significant from device removal to 6-12 months after MDO. CONCLUSION: Cephalometric measurement is a powerful tool that provides a concrete metric to understand how MDO affects not just the immediate but also long-term growth of the mandible. Understanding the more quantifiable effects of mandibular distraction will allow for fine-tuning of surgical practice and optimization of outcomes.