Abstract
Background: Current descriptions of the unilateral cleft lip and nasal deformity (uCLND) are based upon limited sample sets and subjective observations. While those descriptions are inconsistent and contradictory, theoretical models, including Hogan's “tilted tripod” and Fisher's “nasal arch forms”, have never been tested. Given that favorable outcomes of treatment remain elusive, detailed study of the deformity is critical in devising better treatments. The purpose of this study was to develop a data-driven three-dimensional (3D) model of uCLND that spans the spectrum of presentation and involves a pervasive underlying mechanism. Methods: We studied 3D images of 100 infants with unrepaired cleft lip at 6 months of age. Objective assessment included the landmark positions, anthropometric dimensions, and shape-based measures. Cleft severity was stratified by the lateral displacement of subnasale, so that a model could be developed using linear regression. Results: With progressive deviation of subnasale, the non-cleft alar base moved lateral, the cleft alar base was left posterior, and the nasal dorsum followed the caudal septum (deviating towards the non-cleft side). The “twist” resulted in opposing cleft alar dome collapse, non-cleft alar ring constriction (the non-cleft nasal sill narrowed, lateral genu rose, and alar-cheek junction became more acute), and displacement of the philtrum from midline. Conclusions: Our study not only supports theoretical models of uCLND but also clarifies vectors of change and reveals significant non-cleft side alterations. On the basis of our findings, the objectives of treatment should involve centralization of the columella and philtrum and rebalancing the nose by untwisting the orthogonal displacement of the alar bases. © 2021 Elsevier Ltd