title: Does Mandibular Distraction Vector Influence Airway Volumes and Outcome?
abstract: OBJECTIVE
  The goal of mandibular distraction in the Pierre-Robin sequence is to maximally expand the oropharyngeal airway. It has been hypothesized that a steep oblique distraction vector might allow greater airway enlargement compared with horizontal distraction. This study compared vector orientation in relation to airway volume and overall clinical outcome.
  
  
  METHODS
  Micrognathic infants who underwent mandibular distraction with sufficient computed tomographic data were retrospectively reviewed. Demographic, diagnostic, perioperative, and distraction data were recorded. Groups were separated based on distraction vector (group 1, horizontal; group 2, oblique). Airway and mandibular volumes were measured using Mimics (Materialise, Leuven, Belgium). Morphologic and outcomes data were analyzed. Statistics involved 2-tailed t test, Pearson correlation, and analysis of covariance (ANCOVA).
  
  
  RESULTS
  Mean age at distraction was 40 days, with devices maintained for 82 days on average. Fifty percent of patients were girls and 65% had cleft palate. Forty computed tomograms were analyzed. Airway (1,234 vs 3,501 mm3; P < .01) and mandibular (5,457 vs 11,827 mm3; P < .01) volumes, minimal airway area (12.5 vs 63.7 mm2; P < .01), and posterior airway space distance (2.3 vs 9.8 mm; P = .04) were significantly increased after distraction. Patients also had clinically improved sleep studies after distraction (apnea hypopnea index, 51.3 vs 5.5; P < .01). Vector analysis showed an average of 5.3° and 14.0° in groups 1 and 2, respectively (n = 10 each). Intergroup analysis showed a trend toward increased airway volume in horizontal vectors (548 vs 255% of preoperative volume; P = .058), with slightly longer distraction length (20.3 vs 16.6 mm; P = .17). However, ANCOVA regression analysis showed no difference in the relation between vector and length. Other morphologic data and sleep study outcomes (apnea hypopnea index, 7.0 vs 3.9; P = .09) also were not statistically different between groups. Longer lengths of distraction correlated with narrower anterior mandibular angle and longer mandibular body length.
  
  
  CONCLUSIONS
  Substantial airway enlargement occurs after mandibular distraction. Final airway volumes were similar between groups regardless of vector, which was confirmed by multivariate ANCOVA regression. The 2 methods achieved airway stabilization, with clinical outcomes similar between the 2 groups.
authors.affiliation: Craniofacial Fellow, The Hospital for Sick Children (Sick Kids), Toronto, ON, Canada.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Zellner
authors.affiliation: Medical student, Department of Surgery, Section of Plastic Surgery, Pritzker School of Medicine, University of Chicago, Chicago, IL.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Mhlaba
authors.affiliation: Associate Professor of Surgery, Department of Surgery, Section of Plastic Surgery, Pritzker School of Medicine, University of Chicago, Chicago, IL.
authors.forename: Russell R
authors.initials: RR
authors.lastname: Reid
authors.affiliation: Associate Professor of Surgery, Director of Cleft and Craniofacial Program, Department of Surgery, Section of Plastic Surgery, Yale University School of Medicine, New Haven, CT. Electronic address: derek.steinbacher@yale.edu.
authors.forename: Derek M
authors.initials: DM
authors.lastname: Steinbacher
mesh_terms: D000402:Airway Obstruction / Q000000981:diagnostic imaging / Q000209:etiology*; D002972:Cleft Palate / Q000601:surgery; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery*; D008844:Micrognathism / Q000000981:diagnostic imaging / Q000601:surgery*; D019857:Osteogenesis, Distraction / Q000009:adverse effects* / Q000379:methods; D010855:Pierre Robin Syndrome / Q000000981:diagnostic imaging / Q000601:surgery*; D017286:Polysomnography; D012137:Respiratory System / Q000000981:diagnostic imaging / Q000503:physiopathology; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome