Clinical Evaluation of Fibularis Tertius Muscle Prevalence

Abstract

The fibularis tertius muscle (FTM) in man has been developed over time to acquire subsequent bipedal gait. The FTM functions as a crucial contributor in dorsiflexion and eversion, postulated over the years as a stabilizer of the talocrural joint, avoiding forced investment and protecting the anterior talofibular ligament. The literature describes that FTM is absent in 10% of cases, with no data on Chilean population. A study of surface anatomy in 168 young subjects, 60% female and 40% male students at the Universidad de Talca, Chile, with a mean age of 20.6 ± 1.68 years, was conducted. The presence of FTM was identified following the implementation of a clinical assessment protocol that determines the presence of muscle on the basis of a progression called F1, F2, and F3. The FTM was present in 49.11% of cases. On the right side, 20% (n = 37) of the subjects presented the FTM in F2 and 30% (n = 50) in F3. On the left side, 1% (n = 2) showed the muscle in F1, 21% (n = 35) in F2, and 26% (n = 44) in F3. Our results contrast with the high prevalence of FTM in the literature and suggest studies of association with lesions of the talocrural region.