Maxillomandibular Development after Mandibular Distraction Osteogenesis in Isolated Pierre Robin Sequence Patients

Abstract

Mandibular distraction osteogenesis (MDO) is a favored surgical technique for addressing the airway difficulties that result in patients with Pierre Robin sequence. Devices are placed to distract the micrognathic mandible forward and generate bone at bilateral mandibular osteotomies.1 Though it is generally accepted that these patients will continue to develop with disproportionate maxillomandibular growth after distraction2, the timeline for relapse back to a skeletal class II relationship, as well as differences between male and female development post-distraction, is not well-described.The purpose of this study is to characterize a timeline of maxillomandibular growth for patients with isolated Pierre Robin sequence (iPRS) after MDO during infancy based on Steiner's analysis and clinical impressions, as well as to identify differences in post-distraction growth between males and females. The researchers hypothesized that these patients would demonstrate disproportionate growth after distraction and that females would relapse at a faster rate than males. By improved understanding of this timeline, clinicians may better educate parents with expectations for their child's craniofacial development after distraction.Department records were retrospectively reviewed to identify patients with iPRS who underwent MDO during infancy from 2004 through 2016. Patients with post-distraction imaging from which cephalometric data could be traced (i.e., lateral cephalograms or cone beam computerized tomography [CBCT] scans) were included. These were traced by 2 independent reviewers for SNA, SNB, and ANB angles, according to Steiner's analysis to determine skeletal classification. Patients with pre- and post-distraction lateral profile photos were assessed by 1 reviewer for skeletal classification based on clinical appearance. Patient age at distraction, sex, time from initial distraction to imaging study, and prior maxillomandibular surgeries were abstracted. Descriptive statistics and significance testing were performed; 38 patients with iPRS who underwent MDO were identified. Of these, 15 (39.5%) had at least 1 postoperative lateral cephalogram. Average time from surgery to initial lateral cephalogram (TAS) was 67.81 months for all patients (range 25.53 to 129.93 months). The majority of patients (n = 12) had an ANB > 2° at the time of lateral cephalogram. One patient (TAS 25.53 months) had an ANB of 1.3°, whereas 2 patients (both with prior cleft palate repair) had an ANB < 0° (TAS 32.67 and 97.17 months). Nine (60%) of all patients with lateral cephalogram data fell within 1 standard deviation of average TAS (39.52 to 96.1 months), with corresponding average SNA, SNB, and ANB angles of 80.97, 73.99, and 7.03, respectively; 33% of these patients (n = 3) had prior palatal surgery. Of the 38 patients, 37 had pre- and post-distraction lateral photographs; 13 of 15 (86.7%) females, and 12 of 22 (54.5%) males relapsed to a skeletal class II relationship by the last follow-up appointment (P = .04). The mean postoperative follow-up months for females (69.3 months) and males (79.9 months) was similar (P = .50). Based on post-distraction cephalometric tracing, 80% of patients reverted back to a skeletal class II relationship by an average of 68 months. Based on post-distraction clinical appearance, 68% of patients reverted to a class II relationship by an average of 76 months. Furthermore, a more significant percentage of females relapsed to a skeletal class II relationship compared to males at similar follow-up points. These findings may help clinicians and parents better understand and prepare for the maxillomandibular developmental timeline of these patients post-distraction.