Variant fibulocalcaneus muscles of the ankle: Photographic evidence and clinical significance

Abstract

Anomalous fibulocalcaneus muscles have gained recent attention in the clinical literature. During 207 cadaveric leg dissections, novel variants of three fibulocalcaneus muscles associated with the ankle joint were identified: 1) fibularis quartus, 2) fibulocalcaneus internus, and 3) anterior fibulocalcaneus. Approximately 20% of dissected limbs contained a fibularis quartus, including several rare muscle variants, including a fibulocuboideus and a novel fibulocalcaneocuboideus. One fibulocalcaneus internus was identified, which led to the first gross anatomical case report since 1914 and the first photograph of this rare muscle. Seven examples of the anterior fibulocalcaneus, a novel muscle first reported in 2010, were identified with bilateral presentation in three cadavers. Photographic evidence of these variant fibulocalcaneus muscles will be presented, and the clinical significance of these variant muscles will be discussed. Biometric and radiologic studies of these muscles are ongoing. Radiologists and clinicians should be aware of these muscles when embarking in diagnosis and imaging interpretation, especially when chronic ankle pain is involved.