Subluxation of the extensor carpi ulnaris (ECU) tendon is regarded as a relatively uncommon injury. It typically results from forced supination, volar flexion, and ulnar deviation of the wrist, which disrupts the ECU subsheath and subluxes the ECU tendon out of its groove in the distal ulna. These injuries are most common in athletes, especially golf and tennis players, which is due to the swing and stroke mechanics involved in these sports. Owing to its fairly generic presentation of ulnar-sided wrist pain, many ECU subluxations are missed on initial evaluation, which often leads to poor long-term outcomes. When properly diagnosed, conservative treatment is usually recommended for most acute injuries, while surgery is reserved for chronic cases and those that fail to improve after a conservative regimen.1-4
Pathophysiology
Related Anatomy
Inoue and Tamura created a classification system that grouped ECU subluxation and dislocation into the following 3 types:
Incidence and Related Conditions
Differential Diagnosis
Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208
A typical patient is a 20-year-old, left-handed, collegiate female tennis player. During a regional NCAA tournament, she forcefully hit a 2-handed backhand shot with exaggerated topspin on the ball. As she struck the ball, her wrist went from an exaggerated supination position into pronation during the follow-through phase of the stroke. This transition placed excessive strain on the ECU tendon of her left wrist and led to ECU subluxation and subsequent ulnar-sided pain and clicking in her wrist when she rotated her forearm.
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