ED pitfalls: Posterior malleolar fractures

Scott Orman, ED Specialist, and Jacob Munro, Orthopaedic Surgeon

Posterior malleolar fracture - image from wikiradiography.com

Posterior malleolar fracture – image from wikiradiography.com

The x-ray above shows what could be interpreted as a relatively innocuous injury – an apparent isolated undisplaced fracture of the posterior malleolus of the ankle.

Suitable for conservative management, discharge from ED, and follow-up in fracture clinic?

Probably not!

The posterior malleolus is typically fractured by rotational injury an/or axial loading. Posterior malleolar fracture WITHOUT other injuries to the ankle or lower leg is uncommon – only 4% in one case series examining all ankle fractures. More commonly, posterior malleolar fractures occur in combination with proximal fibular fractures (Maison-Neuve), syndesmosis injury, posterior tibiofibular ligament injury, and/or spiral tibial diaphyseal fracture. These injuries commonly require surgical intervention, and the presence of a posterior malleolus fracture with them worsens prognosis.

Syndesmotic injury: a potential association with posterior malleolus fracture - image from drchiodo.com

Syndesmotic injury: a potential association with posterior malleolus fracture – image from drchiodo.com

Even if another injury is NOT present with a posterior malleolar fracture, criteria for surgical intervention are complex and highly surgeon-dependent.

THE BOTTOM LINE

Upon discovery of a posterior malleolar fracture in the ED – maintain a high index of suspicion for associated injuries.  There is a high chance that other structures are injured also and that surgical intervention is required for an unstable ankle. Careful clinical examination is required, (including the proximal lower leg), and the threshold for further imaging (especially CT) should be low.

In accordance with this, the orthopaedic department at Auckland Hospital have requested that we refer all posterior malleolus fractures to them acutely for review, even if no associated injuries are immediately apparent.

References:

Rockwood and Green – Fractures in Adults: 6th Edition

 Diagnosis of an isolated posterior malleolar fracture in a young female military cadet: Int J Sports Phys Ther. 2012 Apr 7(2): 167-172

 Posterior malleolus fracture: J Am Acad Orthop 2013 Jan 21(1) 32-40

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