Defining mandibular morphology in Robin sequence: A matched case-control study

Robin Sequence (RS) is classically defined as the triad of micrognathia, glossoptosis, and airway obstruction. While there remains significant debate over diagnostic criteria for severity, there is consensus regarding micrognathia as a defining feature of the condition. The purpose of this study was to compare mandibular morphology among infants and children with RS to infants and children without RS using maxillofacial computed tomography. Our hypothesis was that there are discrete morphologic differences between RS and non-RS mandibles. Our goal was to determine if there are defined and measureable differences in RS mandible shape that can be used in defining the sequence. We identified 20 cases with RS and 20 age- and sex-matched controls without RS. Linear, angular, and composite measurements were obtained for each patient. Cases had shorter mandibular sagittal lengths (-27%, p = 0.001), shorter inferior border arc lengths (-11.5%, p = 0.002), steeper gonial angles (+10.5%, p < 0.001), and narrower symphyseal angles (-11.5%, p < 0.001). Mandibular shape in RS was more rounded/elliptical (p < 0.001) and infants with RS had a significantly smaller submental cross-sectional area (-29.4%, p < 0.001). These shape differences anterior to the gonial angle of the mandible appear to be a defining morphologic feature in RS.