Anatomy and Vascularization of the Flexor Hallucis Longus Muscle and Its Implication in Free Fibula Flap Transfer: an Anatomical Study

Contracture as well as weakness of the flexor hallucis longus (FHL) are possible complications following free fibula flap harvest. Possible causes have been related to fibrotic change of the muscle either due to devascularization or compartment-like syndrome after a tight wound closure. This study elucidates the vascularization and nerve supply of the FHL muscle after fibula flap harvest in a fresh cadaver model.A fibula bone flap was harvested through a lateral approach in 20 fresh limbs. The popliteal artery was isolated and injected with a silicone compound, the muscle isolated, and its neurovascular supply visualized.The distal third and fourth portion of the FHL muscle was always found to be located in a more compressed and deeper compartment. The peroneal artery was entirely filled by the silicone compound in 17 fresh cadaver limbs with at least one branch supplying the distal fourth of the FHL. The posterior tibialis artery was filled in all limbs and an average of 2 branches was found to supply the muscle. In all dissections, the nerve supplying the FHL originated from the tibialis nerve with an average of three branches perforating the muscle.Following fibula harvest, the FHL muscle will maintain vascular supply through the distal portion of the peroneal artery and the posterior tibialis artery. Nerve injury to the FHL muscle is unlikely during flap harvest.