Mapping the Mandibular Lingula in Pierre Robin Sequence: A Guide to the Inverted-L Osteotomy

Background: The inverted-L osteotomy for mandibular distraction in Pierre Robin sequence (PRS) is a useful technique for avoiding injury to the tooth root and inferior alveolar nerve. Identification of the lingula is understudied and may decrease iatrogenic complications. This study aims to map the position of the lingula in the micrognathic mandible and compare the location of the lingula in relative normal mandible. Methods: This is a retrospective cohort study of symptomatic PRS patients. Three-dimensional CT scans were reviewed and the relative lingula position described. Results: The study includes 11 PRS patients and 4 controls. The average measurements were overjet 9.99 (PRS) versus 4.28mm (control) (P=0.001), vertical ramus height 16.05 versus 23.04mm (P=0.003), and width 15.16 versus 20.67mm (P=003); horizontal ramus length 26.58 versus 40.62mm (P=0.001), gonial angle 132.648 versus 123.58 (P=0.018); horizontal lingula position 7.25 versus 10.75mm (P=0.001), vertical position 9.02 versus 11.34mm (P=0.026). The ratio along the x-axis in PRS was 0.44 versus 0.52 in controls (P=0.138); along the y-axis, the ratio was 0.57 versus 0.49 (P=0.078). Conclusions: Compared to normal controls, overjet is greater, vertical ramus height and widths are lesser, horizontal ramus length is lesser, and the gonial angle is greater in PRS patients. When analyzed as proportions along the height and width of the vertical ramus, there is no statistical difference (P>0.05) in the position of the lingula between PRS patients and normal controls.