Bilaterally Variant Accessory Fibularis Muscle: Its Phylogenetic, Molecular and Clinical Perspective

Accessory fibularis muscle is prevalent in 2.9-21.8% of the world population. Incidentally during routine dissection of a 75-year-old male cadaver, bilaterally accessory fibularis muscle was observed. On both the sides, proximal site of attachment was same but muscle displayed different distal sites of insertion in the foot. Appearance of accessory muscle in the leg is indicative towards the ongoing phylogenetic evolution operating at the molecular level. Bio-mechanical advantage of this variant muscle is the additional support provided to the subtalar joint. Also it acts as synergist to fibularis longus and brevis during eversion of the foot. Clinically this muscle may predispose to chronic ankle pain, dislocation of peroneal tendons from retromalleolar groove and post fracture dislocation in foot. Wide range of accessory fibularis muscle has been previously reported with different nomenclature, however, existence of two different variants in same cadaver has been rarely reported. The current observation is significant for clinicians to acknowledge when evaluating and operating patients with foot disorders.