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

This study aimed to define a reproducible intraoperative measurement protocol for modified V-shaped concealed flap canthoplasty and to characterize the association between quantitative folding parameters of the anterior limb of the medial canthal tendon (MCT) and postoperative medial canthal angle regression. In this prospective cohort, 331 consecutive patients undergoing the procedure were enrolled. Intraoperative folding length (L), folding angle (θ), 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 was used to explore associations between intraoperative measurements and postoperative regression, and the resulting model was internally validated with bootstrap resampling. The 6-month incidence of medial canthal angle regression was 24.6%. Greater L, θ, 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 area under the receiver operating characteristic (ROC) curve (AUC) of the internally validated model was 0.85 (95% confidence interval [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 requiring external validation before broader clinical application.