Rare Anatomic Variant of Septocutaneous Perforator of Fibula Osteocutaneous Flap Running Dorsally to Flexor Hallucis Longus.

We report a rare anatomical variant of a septocutaneous perforator (SCP) arising from the peroneal artery (PA) and running dorsally around the flexor hallucis longus (FHL) muscle, identified during fibular osteocutaneous flap harvesting for maxillary reconstruction. Typically, SCPs from the PA run ventrally to the FHL, whereas musculocutaneous perforators (MCPs) penetrate the muscle. SCPs running dorsally around the FHL, particularly those arising from the PA, have not yet been reported. A 53-year-old male patient underwent total hard palatectomy, followed by maxillary reconstruction with a fibular osteocutaneous flap. Preoperative computed tomography angiography revealed a perforator from the PA, initially thought to be an MCP due to its mediodorsal course. Intraoperatively, the perforator was identified as the SCP running dorsally around the FHL. This perforator was accidentally ligated during flap harvesting, necessitating perforator-to-perforator anastomosis to restore blood flow. The flap was successfully transplanted into the maxilla, highlighting the importance of preoperative imaging in perforator mapping. If the course of the perforator was correctly identified preoperatively as an SCP arising from the PA and running dorsally around the FHL, the flap could have been harvested without additional microvascular anastomoses. Magnetic resonance angiography, which offers superior differentiation between SCPs and MCPs, may prevent this complication when computed tomography angiography does not provide a definitive assessment of the perforators' course.