Simple and generalizable formula for predicting deep inferior epigastric artery perforator flap weight in breast reconstruction.

Abstract

Prediction of flap weight is valuable for surgical planning when using a deep inferior epigastric artery perforator (DIEP) flap for breast reconstruction and may reduce donor site morbidity and perfusion-related problems. The aim of this research was to develop a simple and generalizable formula for predicting DIEP flap weight. We retrospectively reviewed 100 patients who underwent breast reconstruction with a DIEP flap at our institution between November 2018 and July 2025. We developed the following formula: predicted flap weight = α × W × H × T, where W and H denote flap width and height, T denotes subcutaneous thickness, and α is a coefficient specific to each flap design. The relationship between the WHT value and actual flap weight was assessed using the Pearson correlation coefficient. Prediction accuracy was evaluated by K-fold cross-validation. The number of folds was varied to examine the relationship between the number of training cases and prediction accuracy. Multivariate analysis was performed to identify factors associated with estimation error. The Pearson correlation coefficient was 0.964. The mean absolute percentage error was 12.7% when using 5 cases to estimate the coefficient, 12.3% when using 10 cases, and 12.2% when using 20 cases. Multivariate analysis revealed that thinner subcutaneous tissue significantly increased the estimation error (P = 0.01). This formula demonstrated excellent accuracy, requiring only a simple measurement in a small sample. This approach is practical and generalizable for preoperative planning of breast reconstruction using a DIEP flap and is broadly applicable across institutions and flap designs.