Morphological Variability and Clinical Significance of the Fibularis Tertius Muscle: An Extensive Literature Review

Background: The muscles and their tendons exhibit considerable morphological variations. While the anterior leg compartment may seem uniform, several well-documented variants of the tibialis anterior, extensor hallucis longus (EHL) and extensor digitorum longus (EDL) exist. In contrast, little is known about the fibularis tertius muscle (FT). This literature review aims to compile existing data on the FT and its variations and assess this structure's clinical significance. Material and Methods: This comprehensive literature review is based on scientific articles obtained from PubMed. All relevant papers were included, and citation tracking was conducted to ensure a thorough examination of the topic. Results: This detailed literature review synthesizes the latest scientific findings regarding the FT, exploring its variable morphology, functional anatomy, evolutionary significance and clinical relevance. A high morphological variability of the FT is described including its origin, insertion and accessory form. Nevertheless, the FT has been described in cadaveric studies between adults and fetuses, while few classification systems have been proposed. Conclusions: The FT is an intriguing structure that has garnered interest from researchers across various fields, including medicine, clinical practice and biological sciences. There are few clinical implications of the muscle such as FT syndrome or tendon tear. Adequate knowledge of its anatomy is of paramount importance for clinicians.