# Evaluating the potential of quantitative assessment of intraoperative fasciocutaneous flap perfusion using microscope-integrated indocyanine green fluorescence angiography

## TL;DR

This study shows that quantitative ICG-FA can detect perfusion issues in surgical flaps more accurately than traditional methods.

## Contribution

The study demonstrates the potential of quantitative ICG-FA for objective perfusion assessment in fasciocutaneous flaps.

## Key findings

- Quantitative ICG-FA parameters like Ttp and inflow/outflow slopes effectively identified compromised flaps.
- Perfusion-related complications were associated with delayed fluorescence peaks and reduced washout in distal flap regions.
- Conventional assessments failed to detect all compromised flaps, highlighting the need for quantitative methods.

## Abstract

Perfusion-related complications are a leading cause of morbidity and flap loss in reconstructive surgery. While indocyanine green fluorescence angiography (ICG-FA) is commonly used, its subjective interpretation may miss early signs of perfusion disturbances. Quantitative ICG-FA (Q-ICG-FA) offers a more objective method, but its potential in fasciocutaneous flaps remains insufficiently studied.

This retrospective study analyzed intraoperative ICG-FA data from patients undergoing fasciocutaneous flap reconstruction. Fluorescence-time curves (FTCs) were generated from three regions of interest (ROIs): reference tissue (ROI1), proximal flap (ROI2), and distal flap (ROI3). FTCs and derived quantitative parameters, including time-to-peak (Ttp) and normalized inflow/outflow slopes, were compared between patients with (PRC) and without (No PRC) perfusion-related complications.

Twenty patients were included. Seven patients experienced a perfusion-related complication, most commonly venous congestion (n = 5). FTCs of compromised flaps showed delayed fluorescence peaks and reduced washout, most pronounced in ROI3. Quantitatively, the PRC group showed prolonged Ttp in ROI2 (105 vs. 36 s, p = 0.013) and ROI3 (209 vs. 48 s, p = 0.001), lower normalized mean inflow slopes in ROI2 (2.4 vs 0.9%/s, p = 0.029) and ROI3 (4.2 vs. 1.6%/s, p = 0.002), and reduced mean outflow slopes in ROI3 (0.1 vs. 0.2, p = 0.021). Conventional clinical assessments failed to identify all compromised flaps.

Q-ICG-FA objectively distinguished flaps with and without perfusion-related complications. Dynamic parameters, particularly Ttp and inflow/outflow slopes, were most associated with perfusion compromise. Larger studies are needed to validate these findings.