Background: Reliable detection of any circulatory issue threatening flap viability after free flap surgery is essential for prompt flap salvage. Currently, the gold standard of flap monitoring is clinical monitoring. However, this method presents logistical challenges to insufficient trained personnel. Auxiliary methods are becoming increasingly vital.
Materials and methods: Twelve swine pedicle myocutaneous flaps were harvested and monitored using infrared cameras to investigate the developed monitoring parameters and vascular thrombosis in the free flap model.
Results: The mean flap surface temperature after vein or artery occlusion decreased significantly, but the differences were relatively small. As a result, the difference between recorded (flap surface temperature [Ts]) and predicted (estimated surface temperature [Tes]) flap surface temperature (ΔT = Ts- Tes) was used as the parameter for pedicle thrombosis. A ΔT of <0.86°C was used as a vascular occlusion criterion; the sensitivity and specificity of this parameter were 90% and 81%, respectively. The standard deviation of the surface temperature (SDT) was another indicator of vascular occlusion; the estimated sensitivity and specificity for vessel occlusion of SDT < 0.48°C were 84% and 73%, respectively.
Conclusions: Infrared thermal imaging has the advantages of being noninvasive, contact-free, continuous, and able to detect the whole flap surface area. Two indicators, ΔT and SDT, can be used with high sensitivity and specificity for early prediction of flap pedicle thrombosis. Further human studies are necessary to validate clinical application of infrared thermal imaging.
Keywords: Free flap; Infrared thermal imaging; Pedicle thrombosis.
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