Classifications of the extensor hallucis longus tendon variations: Updated and comprehensive narrative review

The extensor hallucis longus muscle originates from the anterior surface of the fibula and on the interosseous membrane medial to the origin of the extensor digitorum longus. Its distal attachment is typically located on the dorsal aspect of the distal phalanx of the hallux. However, EHL tendon variations have been reported in anatomical studies based on adults and fetuses. The most common variation is an additional tendinous slip in the region of the distal attachment. Additional tendinous slips can have specific names depending on where they insert. This wide range of morphological variations among the additional tendons has necessitated appropriate classification system to rank all types that could be used by clinicians. The main goal of this review is to summarize information from the available literature about the extensor hallucis longus muscle and to compare classification systems and the results of previous studies. Another aim is to create a new classification system.