US diagnosis of UCL tears of the thumb and Stener lesions: technique, pattern-based approach, and differential diagnosis.

The thumb is a central component supporting the intricate movements of the hand. Patients with acute thumb pain, particularly after trauma, require prompt evaluation of structural integrity, thus avoiding long-term morbidity such as instability, chronic pain, and osteoarthritis. Injury to the ulnar collateral ligament (UCL) of the thumb requires imaging for diagnosis of surgically important entities such as the Stener lesion. Historically, routine radiography including stress views does not allow such diagnosis and is potentially detrimental to patient care. Both magnetic resonance imaging and ultrasonography (US) are currently used for direct evaluation of the UCL of the thumb and are safe and accurate. US is more dynamic and less time-consuming and may be easier to perform. Furthermore, other disorders such as tenosynovitis, tendon tears, and articular pathologic conditions can involve the thumb and thenar region and may also be diagnosed with US. In this context, US is an underused tool because it is potentially an adjunct to the clinical examination in the appropriate setting. A sound knowledge of the regional anatomy and basic training in the principles of US should equip the imager with the skills necessary to evaluate the UCL of the thumb and its surrounding structures.