A Prospective Registry Analysis on Soft-to-Hard Tissue Ratios in Profile View; Midline Changes in the Lip Region after Mono- and Bimaxillary Repositioning Surgery

Abstract

Introduction We aimed to determine the ratios of the lower and upper lip landmarks in the sagittal and vertical direction for maxillary osteotomies and mandibular lengthening surgeries, in a prospective way. Methods This prospective cohort study is the second part of the OSRES (Orthognathic/orthofacial Surgery RESearch group); patients that underwent mandibular and/or Le Fort I surgery without genioplasty were included. Pearson correlation determined significant patient and surgical variables. The relationship between hard and soft tissue changes was determined by correlation analysis. Results An average ratio of 103% was found for sB:B for mandibular advancement surgery without genioplasty and 83% for sB:Pg with genioplasty. Lower jaw surgery yielded a ratio of 68% for Li:Ili in the horizontal direction and 69% with a genioplasty. Displacement of the upper jaw gave a ratio of 83% for Ls:Iui anteriorly for all surgery groups combined. Horizontal displacement of the upper jaw yielded a strong correlation with a ratio of 88% for sA:A. Conclusions The equations presented in this study for landmark sB, sA, labrale inferius, and labrale superius can aid preoperative planning of lip position. No accurate way was found to predict stomion inferius and stomion superius. Highlights We prospectively arranged for computerized measurements of sB:B, Li:Ili, Ls: Iui, Stoi:Ili, Stos: Iui, and sA:A ratios on lateral cephalograms using FaceWizz. The influences of direction and the type of surgery were studied. Moderate to strong correlations were found for horizontal ratios of sB:B, Li:Lli, Ls:Iui, and sA:A. Weak correlations were found for vertical movement of Stos:Iui and Stoi:Ili.