Proposal of a cephalometric method in computed tomography to mandibular analysis in infants with Pierre Robin sequence treated by fast and early mandibular osteo-distraction: pilot study

Background: Newborns with Pierre Robin Sequence (PRS) usually show varying degrees of upper airway obstruction and difficulty feeding due to severe micrognatia. Mandibular distraction osteogenesis has become popular as an alternative treatment option when other medical or surgical techniques are unsatisfactory. The aim of this study is to test a three-dimensional (3D) cephalometric method in computed tomography (CT) to measure effective mandibular and midface length, and maxillomandibular ratio (Md/Mx ratio), as a mode of growth normalization expression in PRS patients before and after Fast and Early Mandibular Osteo-distraction (FEMOD), for assessing the diagnostic method and the efficacy of surgical treatment. Methods: In this retrospective pilot study, six PRS patients treated via the FEMOD surgical protocol were included. The measurements of effective maxillary and mandibular length were performed on 3D reconstructions from pre-surgical (T1) and post-surgical CT (T2). The growth disparity between the mandible and the maxilla was verified in T1 and was compared with the measurements obtained from the adaptation of the McNamara Norms; the correction of growth disproportion after FEMOD was assessed. Results: In T1, the PRS patients’ mandibular length and the Md/Mx ratio were smaller than the expected mandibular length (p = 0.029) and the expected Md/Mx ratio (p = 0.028). In T2, the PRS patients’ mandibular length and the Md/Mx ratio did not show significant differences from the expected results (p = 0.461 and p = 0.400). Conclusions: The 3D cephalometric analysis identifies the disproportion in pre-surgical maxillomandibular growth between PRS and reference measurements, and demonstrates that FEMOD allows the achievement of proportionality in the growth of the maxillomandibular complex in PRS patients.