Comparing long term pedicule independency results of free fasciocutaneus flap and free muscular flap

Use of free flaps to cover congenital or acquired extensive tissue defects, or for functional reconstruction is common in plastic surgery. Transfer of free flap is done by the anastomosis between well defined vasculature of the flap and the suitable vessels of the recipient site. While at first, these tissues depend on the vascular pedicule for blood supply, they eventually form new vessels with wound bed and adjacent tissues by neovascularisation, consequently become independent from the vascular pedicule for blood supply. This pedicule independency process, which allows the transfered free flaps to be nourished by the wound bed, is yet to be elucidated. And the difference of this process according the flap types draws attention. Nowadays, indocyanine green spy angiography imaging is widely used for simultaneous imaging of the perfusion in flap surgery. We also use it in our clinic to protect the pedicule in secondary procedures like, flap thinning after flap surgery, scar revisions, further advancement of the flap. The aim of this study is to compare the pedicule independency processes of free fasciocutaneous flaps and free muscular flaps according to flaps' tissue content, the recipient site, patient morbidity and demographic characters of the patients, by using indocyanine green spy angiography imaging. ICG angiography images of 22 patient who consult to our clinic, between 2018 and 2020 had analyzed. Out of these 22 patiens, 13 had free fasciocutaneous flap reconstruction and the other 9 patients had free muscular flap reconstruction. Of these 22 patients, 17 were male and 5 were female. Patients' ages differ between 12 and 69 years. 13 patients (10 male, 3 female) had free anterolateral thigh (ALT) flap reconstruction, 8 patients (6 male, 2 female) had free latissimus dorsi flap reconstruction and 1 patient (male) had free vastus lateralis muscle flap reconstruction. After minimum of 3 months follow up period, during their secondary procedures we also recorded the ICG angiography imaging videos of the flaps before and after the pedicule occlusion. In the analyzing program of the SPY imaging system, the adjacent tissue to the patient's free flap tissue is considered as the reference point as nourised by %100. And the perfusion patterns of the flaps analyzed according to 4 regions; proximal, distal, central and peripheral. The time when ICG first introduced to the flap and the time when ICG peaks had noted, and total time between these points divided by 4, and the mean values of flap regions have evaluated according to these 4 points of time. As a result of the evaluation between the free fasciocutaneous and free muscle flap groups, in the early phases of the perfusion period after pedicle occlusion, decreased perfusion is observed in the proximal and central regions of the flap, while an increased perfusion in peripheral and distal region is observed. In the phase 2 of the free ALT flap group, it was concluded that the perfusion median value, was 33.3 before the occlusion in central region, is 28 after the occlusion and this perfusion loss was significant (p=0.03). When the Phase 3 was examined, it was concluded that the median perfusion value was 19.7 before the occlusion and the distal region's median value increased to 23.8 after the occlusion and this perfusion increase was significant (p=0.007). Data obtained from the beginning of flap perfusion and full flap perfusion times were analyzed, no significant difference was found at ALT flaps' reference skin (p=0.068). In the muscle flap group, it was found that after occlusion, perfusion always started later than the reference skin and was statistically significant (p=0.012). In the ALT flap group, the mean perfusion time before occlusion was 31.5 seconds, while the perfusion time after occlusion increased to 66.7 seconds (p=0.003). In the muscle flap group, the perfusion time before occlusion was 23.6 seconds, while the perfusion time after occlusion increased to 95.4 seconds (p=0.008). Complete perfusion time increased 2 times in the ALT flap group, and nearly 4 times in the muscle flap group. This is the first study that clearly demonstrate the blood flow from the peripheral region to the flap in fasciocutaneous and muscle flaps by using ICG angiography. In our study, it was concluded that revascularization occurred clinically in both flap types when sufficient time was waited. After pedicle occlusion, we can observe that the perfusion pattern in muscle flaps show more changes than fasciocutaneous flaps. The tolerance of both flap types to pedicle damage cannot be predicted but, after pedicle occlusion, the prolongation of the perfusion time and even after minutes the low perfusion rate in some areas of the muscle flaps, making this type of flap more unreliable in pedicule independency than fasciocutaneous flaps. Key Words: Pedicule independency, free flap, indocyanine green