Robin Sequence and Mandibular Distraction Osteogenesis: Variations in Craniofacial Morphology and Tooth Development

Thesis (Master's)--University of Washington, 2021Mandibular distraction osteogenesis (MDO) is a treatment option for infants with Robin Sequence (RS) who have severe upper airway obstruction. While this procedure is successful in eliminating airway distress, it can cause changes in craniofacial morphology and tooth development in the growing patient. This study examines the effect of mandibular distraction osteogenesis on craniofacial morphology and tooth development in patients with RS at pre-operative, intra-operative, and mixed dentition timepoints as compared to patients without craniofacial conditions and to patients with RS not treated with MDO. Fourteen infant patients with RS undergoing MDO from Seattle Children’s Hospital met the study inclusion criteria. Pre-operatively at T1, the MDO treatment group was compared to 37 infants without craniofacial conditions. Following MDO at T2, intra-operative and post-operative data was collected from the MDO treatment group. At the mixed dentition follow-up (T3), the MDO treatment group (13 patients) was compared to 19 patients with RS who did not undergo MDO. Data from both groups of patients with RS was compared to norms established by the Michigan Growth Sample. Selected cephalometric linear and angular measurements were assessed at each timepoint and tooth development was evaluated from a panoramic radiograph using a tooth assessment grading scale. Before surgery, the patients with RS planned for MDO had significantly more obtuse gonial angles and shorter mandibular body lengths. Changes occurring secondary to MDO in patients with RS were increased mandibular body length, a less obtuse gonial angle, and forward rotation of the mandible. At the mixed dentition timepoint, patients with RS who had MDO had a significantly more obtuse gonial angles (152.5º, p= 0.006) and steeper mandibular plane angles (51.9º, p= 0.0033) than patients with RS who did not have MDO. The RS-affected groups more similarly resembled one another as compared to the normal control, and they demonstrated significant measures of vertical growth. In the mixed dentition, 30% of RS with MDO patients had one or more teeth with abnormal development as compared to no tooth abnormalities in patients with RS without MDO (p= 0.020). There was no difference in frequency of missing teeth between the groups. There was a low rate of complications associated with MDO in this study, and all patients completed the prescribed course of distraction. No patient with RS required tracheostomy between birth and the time of evaluation in the mixed dentition