79 - Fibularis Unicus: A Novel Discovery of a Singular Muscle in the Lateral Leg Compartment

Poster Board Number: 79
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Co-authors:

Alexys Bolden, B.Sc. - Medical Student, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine; H. Wayne Lambert, Ph.D. - Professor and Vice Chair, Pathology, Anatomy, and Laboratory Medicine (PALM), West Virginia University School of Medicine

Abstract Body : A single muscle was discovered in the lateral compartment of the right leg during routine cadaveric dissection of a 76-year old female whole-body donor. This muscular variation is unique in that a minimum of two muscles (fibularis longus and brevis) normally reside in the lateral leg compartment. This singular variant muscle did branch distally to insert into several locations within the foot to mirror the typical distal insertion of normal or supernumerary fibular muscles. These insertions included inserting into the: 1) base of the 1^st metatarsal and medial cuneiform bones, like the fibularis longus muscle; 2) base of the 5^th metatarsal, like fibularis brevis; and 3) retrotrochlear eminence of the calcaneus, like the fibulocalcaneus (peroneocalcaneus) externum, a variant of the supernumerary fibularis quartus muscle. Additional distal insertions of this singular fibular muscle included the lateral malleolus of the fibula. Due to this fibular muscle being unique and the only muscle within the lateral leg compartment, the “fibularis unicus” is the name proposed for this novel and exceedingly rare leg muscle variant.