Risk Factors and Prediction of Medial Canthal Angle Regression after Modified V-Shaped Concealed Flap Canthoplasty

Abstract

This study aimed to define a reproducible intraoperative measurement protocol for modified V-shaped concealed flap canthoplasty and to evaluate whether quantitative folding parameters of the anterior MCT limb can support prediction of postoperative medial canthal angle regression. In this prospective cohort, 331 consecutive patients undergoing the procedure were enrolled. Intraoperative folding length (L), folding angle (theta), fold-point position (P), fixation plane, and suture tension grade were recorded using a standardized protocol. Medial canthal angle regression at 6 months was assessed from standardized photographs relative to the 1-week postoperative baseline. Multivariable logistic regression identified independent predictors, and the model was internally validated with bootstrap resampling. The 6-month incidence of medial canthal angle regression was 24.6%. Greater L, theta, and P were protective, whereas tendon/soft-tissue fixation, low suture tension, greater epicanthal fold severity, thick soft tissue, larger preoperative medial canthal angle, and longer operative time were associated with increased risk. The apparent AUC was 0.85 (95% CI, 0.81-0.89), and the optimism-corrected AUC was 0.81 (95% CI, 0.77-0.85). These findings support the feasibility of intraoperative quantitative assessment but should be interpreted as internally validated, single-center evidence that requires external validation before routine decision-tool implementation.