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Figure. Oblique view radiograph of the right foot.
A 53-year-old man presents with a 5-month history of right ankle pain. He believes the pain started after he twisted his ankle while dancing at a wedding. The pain was sharp in nature, but the patient states he was able to continue dancing. Although the pain has improved, he continues to experience sharp pain in the lateral foot during physical activity. An oblique view radiograph of the foot (Figure) taken at a local emergency department is read as a likely avulsion fracture of the lateral cuboid.
Which treatment is the best choice for this patient?
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The oblique view radiograph of the right foot shows a well-corticated, oval-shaped bone lateral to the calcaneocuboid joint that is consistent with an os peroneum. Accessory ossicles like an os peroneum may be confused with an avulsion fracture. An os peroneum is an accessory ossicle imbedded within the peroneus longus tendon, which courses from the posterior fibula to the lateral calcaneus and cuboid before inserting into the first metatarsal and medial cuneiform. An os peroneum is found in 20% of the population and occurs bilaterally in 60% of cases.1 The ossicle is usually asymptomatic but can become painful following an injury. A painful os peroneum, often called os peroneum syndrome, can be due to a fractured ossicle and tenosynovitis or tearing of the peroneus longus tendon.
The most common physical examination finding associated with os peroneum is pain to palpation over the ossicle. As there are many potential causes of lateral foot pain, magnetic resonance imaging is the best study to evaluate for the broad differential diagnosis.2
Treatment of os peroneum syndrome includes rest, the application of ice, oral nonsteroidal anti-inflammatory drugs, and immobilization with a walking boot or cast. Operative treatment of a painful os peroneum includes excision of the ossicle with primary repair of the peroneus longus tendon.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
References
1. Vora BMK, Wong BSS. Common accessory ossicles of the foot: imaging features, pitfalls and associated pathology. Singapore Med J. 2018;59(4):183-189.
2. Heckman DS, Reddy S, Pedowitz D, Wapner KL, Parekh SG. Operative treatment for peroneal tendon disorders. J Bone Joint Surg Am. 2008;90(2):404-418.
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