Does the Rigid External Distraction Device Alter Maxillary Pitch in Cleft Maxillary Distraction?

Abstract

Statement of problemCorrection of cleft maxillary hypoplasia remains a controversial topic. Surgical correction can be accomplished through Le Fort I orthognathic correction, internal distraction osteogenesis, or external distraction osteogenesis.1 Proponents of rigid external distraction (RED) osteogenesis describe the ability of multi-vector directional distraction control as opposed to univector internal distraction. There are currently limited data on the ability of the RED system to alter the maxillary occlusal pitch.The purpose of this study is to address the following clinical question: “Among cleft patients presenting with severe maxillary hypoplasia and treated with rigid external distraction, does the rigid external distraction system result in alteration of the maxillary pitch?”The study hypothesis is: among cleft patients presenting with maxillary hypoplasia treated with RED, the investigators hypothesize that there is no change in maxillary pitch with distraction.The study's specific aims are to design a retrospective cohort study and enroll a sample composed of cleft patients with maxillary hypoplasia treated with RED: 1) identify a cohort of patients with cleft maxillary hypoplasia, 2) quantify the degree of pre-operative maxillary hyperplasia, 3) measure changes in maxillary position achieved through RED. Materials and methodsTo address the research objectives, the investigators designed a retrospective cohort study. The study sample was derived from the population of patients with cleft maxillary hypoplasia who underwent RED by the Department of Oral and Maxillofacial Surgery at the University of Alabama - Birmingham from June 2007 to August 2019. Subjects eligible for study inclusion had cleft maxillary hypoplasia and underwent RED. Subjects were excluded if there were incomplete data collection or their records were not available for review.Demographic and radiographic variables were recorded. Demographics included gender, age at date of surgery, and history of ULCP vs. BLCP. Radiographic variables included standard cephalometric data recorded prior to distraction (T1) and after completion of distraction (T2). Methods of data analysisDescriptive statistics were computed for all study variables. Due to the potential for both positive and negative occlusal pitch change, a paired 2-tailed T-test was used to compare T1 and T2. The level of statistical significance was set at P < .05. ResultsThe study sample was composed of 45 subjects with a mean age at surgery of 12.2+3.4 years. Twenty-two (49%) were BCLP and 27 (60.0%) were male. At T1, mean SNA was 76.35+/-6.4 degrees, and the maxillary occlusal plane to Frankfort horizontal plane was 8.18+/-6.9 degrees. The mean anterior-posterior distraction distance was 11.4+/-5.7 mm. At T2, the mean SNA was 86.0+/-7.5 degrees, and the occlusal plane to FH was 3.78+/-7.3 degrees. The average maxillary occlusal pitch change was -4.4+/-5.8 degrees (P = .005). ConclusionFor cleft lip and palate patients with maxillary hypoplasia, surgical advancement with RED results in counterclockwise rotation of the maxillary occlusal plane.