Distal intersection syndrome progressing to extensor pollicis longus tendon rupture: a case report with sonographic findings.

The purpose of this case report is to describe the value of musculoskeletal ultrasound (US) in diagnosing both distal intersection syndrome (DIS) and rupture of the extensor pollicis longus (EPL) tendon in the same patient. A 38-year-old female presented for evaluation of a painful bump of unknown etiology on the dorsolateral aspect of her non-dominant wrist. US demonstrated tenosynovitis distal to Lister's tubercle of the EPL and extensor carpi radialis tendon sheaths, consistent with DIS. Immobilization therapy was employed, during which time the patient suffered rupture of the EPL tendon. Follow-up US examination confirmed this additional diagnosis. Characteristic US findings of DIS and EPL tendon rupture were observed. Surgical intervention was required and the patient recovered without complication. Although EPL rupture is relatively common in the literature, DIS is rare. This is the first known case of imaging-proven DIS progressing to EPL tendon rupture. This case underscores the value of US as a widely available, cost effective, and dynamic imaging modality for evaluation of wrist complaints.