Indocyanine green angiography and the old question of vascular autonomy - Long term changes of microcirculation in microsurgically transplanted free flaps

BACKGROUND: Free tissue transfer has become a routine procedure with low failure. In case of a compromised vascular pedicle, flap survival is time dependantly possible due to flap autonomization. However it remains unknown at what time and to which degree different factors influence flap autonomization. METHODS: We investigated 16 patients after free flap reconstruction at different anatomic locations who eventually presented for other medical reasons. To assess the perfusion pattern we performed Indocyanine Green angiography. RESULTS: The mean follow-up after free flap reconstruction was 58,1 month. A total of 16 flaps were examined at different anatomic locations. In 2 cases digital subtraction angiography demonstrated an occlusion of the anastomosis after arteriovenous loop despite vital flaps. Indocyanine Green angiography showed no signs of mal-perfusion or non-perfusion in the transplanted flaps and capillaries across the flap borders in 9 cases. CONCLUSION: Flap autonomization is possible even in patients with problem wounds and poorly vascularized wound beds independent from the anatomic localization. Multiple factors exist, that influence the autonomization process over time. Indocyanine Green angiography seems to be a promising tool to visualize and study the skin perfusion pattern of free flaps over longer periods.