Measuring the Position of the Mandibular Foramen in Relation to the Dentoalveolar Plane in Pierre Robin Patients: Establishing Safety of the Horizontal Osteotomy

Abstract

Background: Mandibular distraction with horizontal osteotomy of the ramus and vertical distraction vector has successfully treated airway obstruction in young Pierre Robin patients. Placing the osteotomy just above the dentoalveolar plane can minimize damage to the inferior alveolar nerve. This study maps the position of the mandibular foramen relative to the height of the dentoalveolar plane to demonstrate the safety of this technique in Pierre Robin neonates. Methods: Retrospective review of 3D CT scans of Pierre Robin patients was performed with inclusion criteria: ≤1 year of age, bilateral micrognathia requiring surgical intervention for airway (ie, tracheostomy versus mandibular distraction), no prior mandible surgery, and pre-operative 3D CT study. Demographic information collected included: age at CT scan, age at surgery, and genetic diagnosis. Using the 3D study of each patient's right mandible, a line at the level of the mandibular dentoalveolar plane was drawn across the lingual surface of the ramus and the distance to the mandibular foramen at a length perpendicular to the dentoalveolar plane line was then measured. Results: Fifteen patients were included in the study (at least 9 Pierre Robin). Average age at time of CT scan was 71.4 days old. The mandibular foramen was below the level of the dentoalveolar plane in all cases at an average distance of 4.7 mm. Average ramus height 46.2±13.4 Conclusions: The dentoalveolar plane was consistently above the mandibular foramen in all patients. Thus, the horizontal corticotomy at a level just above the mandibular dentoalveolar plane spares the inferior alveolar nerve in neonatal Pierre Robin patients undergoing vertical vector mandibular distraction.

Evaluating Sensory Nerve Outcomes After Horizontal Osteotomy for Mandibular Distraction in Infant Robin Sequence Patients

“…These discrepancies highlight the need for specific anatomic data given the edentulous, smaller, and micrognathic mandible in the very young Pierre Robin patient. The first part of our study identified the mandibular foramen as existing an average of 4.7 mm below the dentoalveolar plane 37 . An osteotomy above this intraorally visible and palpable landmark would, therefore, avoid nerve transection.…”

“…The first part of our study identified the mandibular foramen as existing an average of 4.7 mm below the dentoalveolar plane. 37 An osteotomy above this intraorally visible and palpable landmark would, therefore, avoid nerve transection. It should be noted that the included study population in the CT component was small given that availability of both the requisite CT data and software package to allow for fine measurement was not available at the Children's Hospital Wisconsin until after 2011.…”

Safety of Mandibular Osteotomies in Infants with Pierre Robin Sequence: Computer-Aided Modeling to Characterize the Risks of Various Techniques

“…3,26,27 To evaluate safety with the mandibular osteotomies, small series have examined neonatal mandibular anatomy in patients with Pierre Robin sequence. 28,29 Virtual surgical planning has also become a useful tool for some to allow the design of custom osteotomy patterns to avoid collateral damage. 6,30 We identified seven osteotomy techniques that have been described for use in mandibular distraction osteogenesis.…”