Postoperative Detection of Free Flap Congestion in a Fitzpatrick Skin Type VI Patient using the Flir Thermal Imaging Camera: A Case Report and Literature Review

Abstract

BACKGROUND: Free flaps are routinely used in complex tissue reconstruction due to their functionality and reliability. Postoperative monitoring remains a challenge despite the current available modalities. Clinical examination remains the gold standard, with color being the most sensitive marker of flap compromise. Assessment of flap color is more challenging in Fitzpatrick V-VI skin types, masking visual signs of ischemia or congestion. A Forward-Looking Infrared (FLIR) ONE smartphone based thermal imaging camera can be used to detect differences in flap temperature from the surrounding native tissue and could be used to identify early flap compromise. This simple technology used with a smartphone may be a useful method to assess postoperative flap perfusion. METHODS: Institutional review board approval was obtained for postoperative flap monitoring using FLIR technology for patients undergoing complex reconstruction with a free anterolateral thigh (ALT) flap. The FLIR camera is a simple attachment that plugs into iPhone models 7–12 and takes thermal pictures with temperature readings by a spot pyrometer using their App. Preoperatively the FLIR camera spot pyrometer measured baseline temperature by ALT flap location. Temperature recordings of the flap and the surrounding native tissue were taken immediately postoperatively and then at regular intervals in addition to our standard free flap monitoring protocol. This protocol was utilized for one patient in this report who underwent a free ALT flap to scalp after sarcoma resection and Fitzpatrick skin type VI. RESULTS: FLIR thermography measured the preoperative central flap temperature at 32.6°C. Immediately postoperatively the flap temperature was 33.9°C, and the surrounding native skin was 35.8°C. Sixteen hours postoperatively the central portion of the flap was found to be 28.0°C, 8.4°C cooler than the surrounding native skin, suggesting flap ischemia. Clinical examination of the flap showed edema and return of dark blood on scratch test but no frank discoloration. Handheld Doppler signal showed arterial signal but no venous signal. The patient was taken immediately for operative exploration, which showed a 30 cm3 hematoma compressing the vascular pedicle. Following evacuation, the central flap’s temperature was 35.6°C. The patient was discharged on POD 7 and still has a complete reconstruction. CONCLUSIONS: FLIR ONE was helpful in detecting flap congestion and ultimately flap salvage. Prompt operative evacuation of the hematoma prevented flap loss and associated morbidity to the patient. This patient case highlights the inherent challenges in evaluating skin paddles of Fitzpatrick V–VI skin types and depicts the utility of a low-cost thermography camera that can aid in identifying a threatened flap. The user-friendly, non-contact nature of FLIR ONE adds a useful and objective datapoint in postoperative free flap monitoring that can improve patient outcomes when combined with conventional monitoring techniques in all patients, particularly those with difficult flaps to monitor. Our team hopes to continue studying thermal camera temperature differences in postoperative free flap monitoring to service our patients and provide insight into this technology’s utility for reconstructive plastic surgery.