Anterior talofibular ligament injury with an avulsed bone fragment from talus

Case contributed by Charlie Chia-Tsong Hsu
Diagnosis certain

Presentation

Inversion injury to left ankle. There is focal tenderness and swelling over lateral malleolus. Patient reports history of recurrent left ankle sprain and instability.

Patient Data

Age: 30 years
Gender: Female

Anteriorposterior ankle radiograph demonstrates a subtle lucent region in the lateral facet of talus (red arrow). An unequivocal wedge radiodensity is present in the adjacent soft tissue (blue arrow). There is soft tissue swelling adjacent to the lateral malleolus. Patient was referred for CT study for further characterization. 

Coronal CT images demonstrate bone avulsion from the lateral facet of the talus. 

Case Discussion

The prevalence of bone avulsion from anterior talofibular ligament (ATFL) injury may be higher than previously thought because the avulsed bone fragment may only be faintly visible or not visible at all on ankle radiographs. Operative findings of acute sprained ankles found that 12% of ATFL injury had avulsed bone fragment 1. Haraguchi et al in an anatomical study suggest two new radiographic projection for evaluating suspected avulsion fractures of the lateral malleolus 2. The management of subtle avulsion fracture from ATFL injury is unlikely to be different to an isolated ATFL ligamentous injury.   

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