Extensor carpi ulnaris tendinopathy
Insidious onset ulnar sided wrist and distal forearm pain, no history of trauma.
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Complete short segment longitudinal tear of the distal (extensor carpi ulnaris) ECU tendon , which appears undisplaced in the ulnar bony groove under the overlying extensor retinaculum. The tendon sheath and subsheath appear fragmented and edematous with fluid surrounding the tendon . There is evidence of soft tissue edema at ulnar side of wrist with minimal edema at outer fibres of ulnomeniscal homologue. No obvious subluxation of tendon within its sheath or in relation to the ulnar bony groove.
These constellation of findings are consistent with longitudinal tear of ECU with chronic tendinosis in concert with mild tenosynovitis
The extensor carpi ulnaris tendon (ECU) originates as two heads which attach to the lateral epicondyle and the middle third of the posterior ulna. It has a single distal insertion upon the posterior aspect of the base of the fifth metacarpal. The ECU functions to extend and adduct the hand, and is important in the ability to ulnar deviate the hand.
A unique anatomical characteristic of the ECU is the fibro-osseous tunnel which stabilizes the tendon at the level of the distal ulna. This fibro-osseous tunnel is formed by the distal ulna and a 1.5 to 2cm in length band of connective tissue referred to as the ECU subsheath. The subsheath lies deep to the extensor retinaculum, which itself does not attach to or stabilize the ECU tendon. The ECU, its subsheath, and the extensor retinaculum are readily seen using MRI .
Tenosynovitis and tendinosis of the ECU are not uncommon, with these abnormalities being a frequent early finding in patients with rheumatoid arthritis. In athletes, the ECU is the second most common site of wrist tendinopathy, typically associated with rowing, racquet sports, and golf. In such patients, chronic stress upon the tendon results in inflammation of its synovial lining, causing tenosynovitis.Over time, stress may also lead to tendon degeneration and altered collagen content, resulting in tendinosis with or without partial tears.