Presentation
Ankle sprain followed by lateral ankle region pain, swelling, and difficulty in weight-bearing.
Patient Data
Soft tissue thickening involving the lateral ankle region. A vertically oriented tiny bone flake on the lateral side of the calcaneum in the frontal view. No bone lesion/ periosteal reaction/ dislocation.
Small effusion in the anterior ankle joint recess. Normal anterior inferior tibiofibularlar ligament. Thicker, hypoechoic anterior talofibular ligament bands with suspicious focal thinning. A calcaneal avulsed bone flake at the calcaneofibular ligament attachment site. Donor site defect is present. Both avulsed fragment and donor site defect are very well seen in two orthogonal planes. The affected ligament is edematous as compared to the asymptomatic side.
Cine-loops are aligned to the long and short axis of the calcaneofibular ligament. The ligament can still be taut on dynamic scanning (ankle varus tilt) favoring a few fibers still attached to the usual location.
Asymptomatic side cine-loops for comparison. It shows normal fibrillar echopattern of the ligament which makes it 'brighter' than the affected edematous 'darker' ligament.
The frontal view with a slight oblique plane better demonstrates the avulsion fragment.
Case Discussion
Ankle and foot radiographs were done for a young patient with a lateral ankle sprain. Lateral ankle region soft tissue thickening was reported but an avulsion fracture was missed (yes by me).
Ultrasound a week later shows calcaneofibular ligament bony avulsion from the calcaneum, anterior talofibular ligament sprain, or partial thickness defect. With 'perfect hindsight', the fracture was visible in the initial x-ray.
A companian case with MRI: https://doi.org/10.53347/rID-62452
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