Morphological diversity of peroneus tertius: a cadaveric study

Objective: The objective of this study was to demonstrate morphological anatomical variations of the peroneus tertius muscle which may have important clinical and surgical implications.

Materials and methods: Fifty four specimens of anterior compartment of the leg which were dissected routinely according to the undergraduate course were examined for variations of the above muscles and the anatomy was further defined using appropriate dissection methods.

Results: A wide variation was found with regard to the morphology of peroneus tertius and the extensor digitorum longus muscles with considerable differences between the legs of the same cadaver.

When considering important variations deviating considerably from the normal structure, a variation of the distal attachment of peroneus tertius muscle in two specimens revealed that in addition to the normal attachment to the shaft of the fifth metatarsal, an additional slip inserted to the extensor expansion of the fifth toe. It apparently replaced the fourth tendon of extensor digitorum longus, which only had three divisions in these specimens.  

Seventeen of the specimens had a single muscle belly giving rise to 5 tendons which had the usual distal attachments of the peroneus tertius and the extensor digitorum longus muscle as stated below. Absence of peroneus tertius was noted in one specimen.

Conclusion: The anatomical structure of the peroneus tertius vary substantially from individual to individual, inclusive of differences existing between the left and the right lower limbs of the same cadaver.