Mandibular reconstruction with microvascular re-anastomosed fibular free flaps – Two complementary methods of postoperative transplant monitoring

Abstract

Purpose: Evaluation of two complementary methods, i.e. luminescence ratiometric oxygen imaging (LROI) and contrast-enhanced ultrasound (CEUS) for postoperative evaluation of the perfusion of osseocutaneous fibular free flaps used for mandibular reconstructions. Patients and methods: 15 patients with microvascular re-anastomosed osseocutaneous fibular flaps were included in this trial. Perfusion of the cutaneous part of the flap was determined by measuring a fluorescent oxygen sensor foil covering the flap's skin surface with a handheld fluorescence-microscope. The sensor contains a reservoir of oxygen that is consumed by the tissue, which corresponds to the perfusion status of a flap. Measurements were done before explantation, after successful anastomosis and 1 day after surgery. Additionally, flap perfusion was qualitatively evaluated by contrast-enhanced ultrasound (CEUS) in 13 out of 15 patients. Ultrasound examinations were carried out with a high resolution linear probe after an intravenous bolus injection of 2.4 ml SonoVue^® within the first 14 days after surgery. Results: Out of the 15 harvested and transplanted flaps, 3 showed microcirculatory problems on the first postoperative day. All complications were detected by LROI prior to clinical signs. For LROI, we were able to confirm the threshold slope value of 0.3 for differentiating between well perfused and compromised flaps as suggested in our previous study. CEUS showed qualitatively detectable bone perfusion in the 13 measured flaps. 2 flaps that were lost on the second and third postoperative day were also lost for CEUS control. The flap survival rate was 87%, and the complication rate was 33%. Conclusion: LROI has been proven to deliver reproducible objective results for monitoring cutaneous flaps. In addition, CEUS is a promising method for evaluating the microcirculation of the deeper parts (such as bone) of osseocutaneous flaps. Both methods supplement each other, thus allowing the monitoring of all levels of osseocutaneous flaps.