Peroneus quartus: prevalance and clinical importance.

INTRODUCTION: The most common variant muscle of the ankle, peroneus quartus muscle, is located in the lateral leg compartment. In literature there is ambiguous nomenclature of this muscle because of its different origin and insertion sides. It is related to many pathologic conditions in the lateral ankle compartment but also it can be used as a tendon graft for reconstructive procedures.

MATERIAL AND METHOD: We dissected 115 cadaver legs and investigated prevalence of peroneus quartus. We also present 2 year result of a patient who had torn superior peroneal retinaculum reconstructed with peroneus quartus tendon.

RESULTS: The peroneus quartus muscle, with a number of different attachments, was present in 5.2 % (6/115) of the legs. It most commonly arose from the peroneus brevis muscle and inserted into the retrotrochlear eminence of the calcaneus. Associated pathologies are longitudinal degeneration and tear in the tendon of peroneus brevis. There is no any association between the prevalence of peroneus quartus and the height of retrotrochlear eminence or presence of peroneal tubercule (p > 0.05). But there is strong relationship between peroneus brevis degeneration and peroneus quartus existence (p: 0.03). We also defined a new type of peroneus quartus with a bifurcated insertion around the peroneus brevis. In literature our case report is unique because we present a patient who has torn superior peroneal retinaculum which is reconstructed with peroneus quartus tendon with 2 year follow up.

CONCLUSION: Peroneus quartus may lead to some pathologic conditions (pain, snapping, tear, synovitis, etc.) in the lateral ankle compartment but it may be used to reconstruct some pathologic conditions. Orthopaedics, anatomists and radiologists should be aware of this accessory tendon structure because of its clinical importance.