What is a Stener lesion?
The major associated complication of UCL tear is the Stener lesion, in which the torn UCL is proximally retracted, and lies in a location superficial to the adductor pollicis aponeurosis. In this location, the UCL cannot heal and reattach to the proximal phalanx.
The retracted UCL appears on MRI as a curled up, low signal intensity ball. The subjacent adductor aponeurosis appears as a low signal intensity linear focus. The combination of a low signal intensity ball and low signal intensity linear structure has been referred to as a “yo-yo on a string.” In this author’s experience, the low signal intensity ball is generally seen and the low signal intensity linear focus less so.