Anatomical Variations of the Peroneus Tertius and Extensor Digitorum Longus Muscles – Case Presentation

Introduction: The extensor digitorum longus and peroneus tertius muscles have multiple morphological variations. The tendinous slips of these muscles are used as grafts to replace other damaged tendons. Case presentation: We present a unique anatomical variant observed during dissection of a cadaver at the Department of Anatomy and Embryology of the “George Emil Palade” University of Medicine, Pharmacy, Science and Technology of Târgu Mureș, Romania. The peroneus tertius muscle was identified on the left lower extremity as originating from the inferior third of the fibula and interosseus membrane. The posterior belly of this muscle joins the muscular belly of the extensor digitorum longus muscle. The tendons of toes II to V detach from the extensor digitorum longus muscle with an additional tendon. This last tendon gives off an accessory tendinous slip; lateral to this, the peroneus tertius muscle tendon is observed. In case of the right lower limb we also noted the peroneus tertius muscle originating from the distal part of the extensor digitorum longus muscle. Regarding the extensor digitorum longus muscle we describe an accessory tendinous slip. Conclusion: The anatomical variation reported in this study is similar to those reported by previous studies, but displays particular characteristics regarding the VI tendon of extensor digitorum longus and the joining of the peroneus tertius and extensor digitorum longus muscles in the left lower extremity.