The Fibularis (Peroneus) Tertius Muscle in Humans: A Meta-Analysis of Anatomical Studies with Clinical and Evolutionary Implications

Abstract

Being considered an exclusive human structure for a long time, fibularis tertius (FT) is believed to have a secondary function of foot dorsiflexion and eversion. This study is an attempt to approach the issue from an anatomical perspective. A systematic literature search identified 35 studies (7601 legs) which met the inclusion criteria. The weighted results of FT presence were as follows: an “adult cadaveric” frequency of 93.2% and a clinical frequency of 80%. The most common FT origin and insertion sites were the distal half of fibula and the base of the 5th metatarsal, respectively. In 95% of cases, an accessory fibular muscle was detected when FT was lacking. We demonstrated that the discrepancy found between the adult cadaveric and clinical frequency values would point out a probable bias in interpreting previous kinesiological results. On an evolutionary level, comparative anatomy demonstrated a very low FT prevalence among monkeys while reaching a frequency of 30% in gorillas, the only non-human apes having an almost exclusive terrestrial locomotion. The consistent prevalence among humans and the presence of similar functional muscles when it is missing would support an essential role of FT during the phylogenetic development of the erect bipedal posture and probably during gait.

Fibularis Tertius: Anatomical Study and Review of the Literature

“…It is very rare among the great apes though it is found in about 29.6% of gorillas (terrestrial apes). Its overwhelming presence in both humans and gorillas, and its absence or rarity among other apes, indicate an evolutionary acquisition related to bipedalism (Yammine and Erić, ). Hence, from an evolutionary point of view, the FTM is most likely to serve an important function during walking.…”

“…Studies in recent years have elucidated the clinical relevance of the FTM; the muscle serves as a reference landmark for the anterolateral aspect/portal during ankle arthroscopy (Yammine and Erić, ). The insertion of the fibularis brevis and FTT at the fifth metatarsal suggest that their actions can impose torsional stresses on the areas of the bone in which Jones fractures and stress fractures occur (Vertullo et al, ).…”

Peroneus Tertius Syndrome: A Rare Cause of Anterolateral Ankle and Rearfoot Pain

“…The peroneus tertius is a variably present muscle that has been shown to differ in size, origin, and tendon configuration between individuals (2,5,11). Numerous studies have documented the variable insertion of the peroneus tertius, the most common being an accessory tendon slip to the base of the fourth metatarsal (12).…”

“…Phylogenetically, the peroneus tertius is thought to have played an evolutionary role in the development of human bipedal locomotion (6,7,11). The peroneus tertius is considered a weak ankle joint dorsiflexor, and its primary function is to evert the foot (4).…”

Advanced Ankle and Foot Sonoanatomy: Imaging Beyond the Basics

“…The PT muscle originates from the distal one-third of the fibula shaft and the interosseous membrane [45]. After leaving the undersurface of the SER and IER, the PT tendon courses just lateral to the extensor digitorum longus tendons, and it has a broad insertion on the superior aspect of the fifth metatarsal base ( Figure 19A).…”