Presentation
Trauma 6 months ago. Progressive pain in the right ankle and difficulty bearing weight.
Patient Data
Abnormal configuration of the peroneus brevis tendon being C-shaped enveloping adjacent peroneus longus tendon (boomerang appearance in axial) associated with distention of the tendon sheath with fluid signal. Picture consistent with longitudinal peroneus brevis tendon split tear with tenosynovitis.
Intact Achilles tendon and other tendons around the ankle.
No evidence of ligamentous injury.
No soft tissue mass lesions.
Lateral malleolar subchondral pseudo-cystic changes.
Minimal ankle joint effusion.
Annotated image of our study showing the peroneus brevis hemitendons (red arrows) surrounding the grossly intact peroneus longus tendon (yellow arrow).
The axial image depicts the boomerang sign.
Case Discussion
The peroneus brevis (PB) tendon is more likely to get injured than the peroneus longus (PL) due to its crowded location at the level of the retromalleolar groove. A longitudinal split tear is the most frequent type. When this tear occurs the anterior subluxation of the PL tendon impedes the healing of the torn PB. PB tendon frequently have irregular contours and may show increased signal intensity on MR images.
US may depict the tear clearly but MRI is usually needed to assess for any associated cause of crowding that predisposed the injury like a peroneus quartus muscle (an accessory muscle) or a hypertrophied PL or a nearby torn ligament. The management is usually surgical where the PB tendon is repaired and sometimes a peroneus quartus is excised.
The lateral malleolar subchondral pseudocystic changes are a result of an element of osteoarthritis.
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