Posterior Malleolus Fractures

Common Component of Many Ankle Fractures

ankle fracture
Ankle fractures may be complex injuries involving multiple bones. Image © Jonathan Cluett, M.D.

The ankle joint is a complex junction of three bones, the fibula, the tibia, and the talus.  When most people describe an ankle fracture, they are describing injuries to the tibia and/or the fibula bones.  There are many variations of ankle fractures that have different implications for treatment.

One particular type of ankle fracture is called a trimalleolar ankle fracture.  This is a particularly severe type of ankle fracture that involves injury to both the tibia and the fibula.

  At the level of the ankle joint, the bumps on the inner and outer side of the ankle are called the malleoli.  On the inner side of the ankle, the medial malleolus is the tip of the tibia (shin) bone.  On the outer side of the ankle, the tip of the fibula is referred to as the lateral malleolus.  When both of these bones are broken, the injury is called a bimalleolar ankle fracture.

There is also a projection of the tibia back behind the ankle, called the posterior malleolus.  This projection is not as prominent (you can't feel it very easily), and is less commonly injured, but it is an important part of the ankle joint.  When the medial malleolus, the lateral malleolus, and the posterior malleolus, are all broken, the injury is called a trimalleolar ankle fracture.

Posterior Malleolus Fractures

Posterior malleolus fractures are relatively common when the medial and lateral malleolus are fractured.

  In fact, they may occur in up to half of all of these injuries.  The significance of the posterior malleolar fracture, and whether it requires additional treatment is a subject of debate.

Isolated posterior malleolar fractures, meaning without other fractures to the ankle joint, are rare, but can occur.

  In general, these injuries are described as tibial plafond fractures, but a smaller fracture just involving the posterior malleolus can also occur.

Surgery for Posterior Fractures

There is controversy about when surgery is needed for a posterior malleolus fracture.  Traditionally, surgeons recommended that when the fragment of bone involved more than 25% of the end of the tibia bone, that surgery should be performed to stabilize the fracture.  Most surgeons now agree that the size of the fragment is not the critical factor, and rather it is more important to determine if the posterior malleolus fracture causes any instability of the ankle joint.  If it does, it should be surgically stabilized, regardless of the size.

The best way to reposition the fragment of bone is through a separate incision in the back of the ankle.  This allows your surgeon to reposition the posterior malleolus and secure it with a plate and screws.  In some cases where the bone does not need to be repositioned, the fragment can be secured indirectly without making additional incisions.

Rehab After Surgery

Rehabilitation is similar to the rehab for other ankle fractures. Typically, surgeons will immobilize the ankle and allow the incisions to heal before initiating any therapy.  The first phase of rehab is focused on restoring mobility to the ankle joint, followed by resuming weight bearing once the fracture has started healing.  Total time for recovery often takes 4-6 months with the most severe injuries as swelling and mobility take a long time to completely improve.  In some cases, people may need surgical hardware removed at some point down the road.

Sources:

Irwin TA, Lien J, and Kadakia AR. "Posterior Malleolus Fracture" J Am Acad Orthop Surg January 2013 ; 21:32-40.; doi:10.5435/JAAOS-21-01-32.

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