Extra heads of Adductor Hallucis muscle and an atypical attachment of several fibers: a case report

Abstract

Purpose: The presence of supernumerary heads in the Adductor Hallucis (AddH) muscle represents a rare variant of plantar muscle variation that may exhibit divergent clinical manifestations in affected individuals. Clinical presentations may include progressive foot or heel pain, paresthesias, foot discomfort, limited range of motion in the mid/hindfoot regions, hallux vagus/varus deformity, and articular abnormalities. Methods: In this case, a unique variation of the AddH was presented in a female cadaver, along with a literature review. The variation was characterized by the atypical attachment of several fibers to the intermuscular septum, and it was found that the cadaver had two-headed AddH muscles on both sides, with medial and lateral heads. Results: The present case showed that the medial part of the Oblique Head (OH) blended with the tendon of the Flexor Hallucis Brevis (FHB), while the lateral part met with the tendon of the Transverse Head (TH). The origin of OH different than the previous types, while the origin site of TH was classified as type B. In contrast to previous reports, the medial and lateral heads of OH were recorded on both sides. Conclusion: The varied organization of both heads and the location of AddH muscles may be attributed to various combinations of primordial muscles or anomalies during embryological development. Therefore, the variations and types of AddH should be taken into account during foot surgery. © 2023 Elsevier B.V., All rights reserved.