Controversy exists over how long a free flap is dependent on its pedicle and if neovascularization is different between flap types, recipient sites, and irradiated and nonirradiated patients. An understanding of the timing of this process should optimize the safety of secondary procedures involving the flap. In a prospective clinical study, hemoglobin oxygenation and capillary flow were measured in 50 flaps (25 forearm flaps, 15 osteocutaneous fibula flaps, and 10 anterolateral thigh flaps) 4 and 12 weeks postoperatively. The flaps were located at the floor of the mouth, cheek, or tongue (n = 39) or at the hard or soft palate (n = 11). Measurements were carried out using the O2C monitoring system under temporary digital occlusion of the pedicle. After 4 weeks, 17 free flaps were found to be autonomized indicated by the O2C measurements comparing both values before and after digital compression of the vascular pedicle. After 12 weeks, 41 patients had completion of free flap autonomization, as indicated by the HbO(2) and CF before and after pedicle compression. The location of free flap in the lower jaw (P < 0.0001 after 4 weeks, P = 0.013 after 12 weeks), fasciocutaneous radial forearm flaps after 4 weeks (P < 0.0001), and not irradiated recipient site after 4 weeks (P = 0.014) were found to be positive factors significantly influencing autonomization. In conclusion, free flap autonomization depends on several variables which should be considered before further surgery after free flap reconstruction as the transferred tissue can be still dependent on its pedicle.
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