A Stepwise Preclinical Microvascular Training Model Based on the Superficial Inferior Epigastric Vessel Flap in the...

Background and Objectives: Transitioning from non-living simulation to clinical free-tissue transfer remains challenging. This pilot study aimed to develop and evaluate a staged in vivo microsurgical training protocol based on the rat superficial inferior epigastric (SIE) flap, in which the anatomical substrate is held constant and only technical demand varies between stages. Materials and Methods: Twenty male Wistar rats were used in five stages of increasing difficulty, progressing from orthotopic replantation and contralateral inguinal transfer to cervical transfer with end-to-end and end-to-side anastomoses using different donor vessel preparations. Outcomes were immediate patency, patency at 10 min, anastomotic leakage, procedural success (immediate patency without moderate-to-severe leakage) and anastomosis time. Proportions are reported with Wilson 95% confidence intervals; groups were compared with Fisher's exact test, trends across stages with the Cochran-Armitage test, and individual anastomosis times with separate arterial and venous linear regressions on stage number, using HC3 confidence intervals unadjusted for within-animal clustering. Results: Fifty-six anastomoses were performed (30 arterial, 26 venous). Immediate patency was 83.3% (25/30) for arterial and 61.5% (16/26) for venous anastomoses, patency at 10 min 70.0% and 46.2%, and procedural success 80.0% and 57.7% (p = 0.087). The arterial-venous difference was of similar magnitude at every endpoint (21.8, 23.8 and 22.3 percentage points) and was already established at declamping: among initially patent anastomoses, attrition by 10 min was 16.0% for arteries and 25.0% for veins (p = 0.69). No significant trend across stages was detected for success (arterial p = 0.38; venous p = 0.94) or patency. Individual anastomosis time increased with stage, with slopes of 2.08 min per stage for arteries (95% HC3 CI 1.46-2.71; R² = 0.703) and 2.69 min per stage for veins (95% HC3 CI 2.18-3.19; R² = 0.821). Mean venous time was higher at every stage. Conclusions: Even considering the limitations of the present study, the staged SIE flap model provides a graded, quantifiable, and standardised framework for preclinical free flap training within a single anatomical substrate.