Quantitative evaluation of free anterolateral thigh flap perfusion using indocyanine green angiography: A retrospective analysis of 13 consecutive cases

Advancements in microsurgical techniques have reduced the failure rate of anterolateral thigh flaps (ALTF); however, flap necrosis remains a major concern in some cases. Indocyanine green angiography (ICGA) is a reliable intraoperative method for evaluating flap perfusion, but subjective interpretation of fluorescence intensity by surgeons is inconsistent. This study aims to validate the feasibility and clinical utility of a quantitative analysis approach for ALTF using ICGA-derived fluorescence imaging. A retrospective analysis was performed on ICGA data from 13 ALTF procedures used for soft tissue reconstruction in limbs. Parameters analyzed included relative perfusion value (RPV), signal-background ratio (SBR), maximum fluorescence intensity (Imax), time to peak (Tmax), half-peak perfusion rate (S0-50), peak perfusion rate (S0-100), and half-peak-peak perfusion rate (S50-100). Their associations with flap necrosis were evaluated. Inflow indices showed no significant correlation with flap necrosis. However, RPV and SBR were significantly associated with necrosis, displaying high sensitivity (94.1 and 88.2%) and specificity (82.2 and 91.1%), with cutoff values of 21.5% for RPV and 50.5% for SBR. ICGA facilitated the identification of distinct perfusion patterns in ALTF reconstruction. Quantitative analysis of arterial phase fluorescence parameters, particularly RPV and SBR, demonstrated strong predictive value for flap necrosis, offering an objective tool to guide intraoperative decision-making.