Chaput tubercle fracture

Case contributed by Vladimir Kiselev
Diagnosis certain

Presentation

Presented to the ED after being involved in a low-speed motorbike accident, complaining of pain and swelling in the left ankle and difficulty bearing weight.

Patient Data

Age: 60 years
Gender: Male
x-ray

Initial plain radiographs demonstrated soft tissue swelling over the lateral malleolus and anteriorly over the ankle joint.  An ankle effusion is present.  The frontal view shows an unusual drop-like density projected over the distal fibula.  This is due to the lucent Chaput fracture line.

ct

Bone and joint: Intra-articular fracture of the anterolateral distal tibia (Chaput tubercle) with minor anterolateral displacement. A small 2-3 mm flake fracture fragment lies immediately adjacent to the main fracture site. There is an ankle and subtalar joint effusion.

x-ray

Internal fixation of the Chaput tubercle fracture.

Case Discussion

Initial radiographic evaluation demonstrates a Chaput fracture which was not appreciated at the time. Apparent soft tissue swelling, particularly anteriorly to tibiotalar joint on the lateral radiograph, in combination with clinical findings (inability to bear weight) required further evaluation of the injury. 

The subsequent CT of the ankle demonstrated an avulsion fracture of the anterior aspect of the lateral distal tibial epiphysis (Chaput tubercle).

 

Chaput fractures may be difficult to diagnose on plain radiographs for several reasons, including but not limited to:

  • the avulsed fragment is displaced laterally, and tibiofibular overlap may appear normal (>6mm on AP view and >1mm on oblique view);
  • if there is no significant displacement, the tibiofibular clear space will remain normal measuring <6mm on both AP and mortise views;
  • however, the fragment may present as a drop-like density projecting over the distal fibula as in this case.

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