Mandibular volumetric increase following distraction osteogenesis.

INTRODUCTION: Mandibular distraction osteogenesis (MDO) for the treatment of Pierre Robin sequence (PRS) enables mandibular lengthening and improves airway and feeding function. It remains unknown how the post-distracted mandibular volume compares to a normal control population. The aim of this study was to analyze mandibular volume and symmetry following bilateral MDO and compare post-distraction measurements to a non-distracted, normal age- and sex-matched control cohort.

METHODS: Demographic information and three dimensional-computed tomographic (CT) images were obtained from normal control and distracted PRS patients. Mandibular volume and symmetry indices were calculated and results statistically analyzed. P values ≤0.05 were considered statistically significant.

RESULTS: 24 CT scans and 48 hemimandibles were analyzed (8 control patients: mean age = 5.6 months, 3 females; 8 distracted patients: mean age pre-distraction = 1.8 months, mean age post-distraction = 5.3 months, 3 females). No complications were encountered in the distracted group. The mean pre- and post-distraction volume in the MDO group measured 7238.1 mm(3) and 15,360.6 mm(3), respectively (P = 0.0003) and the mean percent increase in mandibular volume following distraction was 113.3%. The mean symmetry index increased after distraction from 0.91 to 0.95 (P = 0.31). Matched normal control mandibles measured 13,488.6 mm(3) versus post-distraction mandibles at 15,360.6 mm(3) (P = 0.40). Normal control and post-distraction symmetry indices were 0.99 and 0.95, respectively (P = 0.68).

CONCLUSION: Distraction resulted in a significantly increased mandibular volume and an observed preservation in mandibular symmetry. Post-distraction volume was increased compared to normal controls but remained less symmetrical.