Ultrasound evaluation of the acromioclavicular joint.

OBJECTIVE: To evaluate the value of ultrasonography in assessing arthritic acromioclavicular (AC) joints. METHODS: One hundred twenty-six AC joints of 63 healthy subjects (2 groups) were prospectively examined by ultrasound to determine the-normal limits of capsular distention and the width of the joint space. Thirty-three AC joints of 32 patients with chronic arthritis were evaluated by ultrasound and, for comparison, by radiography, computed tomography (CT), and magnetic resonance imaging (MRI). RESULTS: The mean ultrasonographic distance of the joint capsule from the bone rim was 2.2 mm +/- standard deviation (SD) 0.5 mm in 21-32-year-old control subjects and 2.9 +/- 0.7 mm in 37-81-year-old control subjects. The mean width of the joint space was 4.1 +/- 0.9 mm and 3.5 +/- 0.9 mm in the same control groups, respectively. In detecting soft tissue changes in arthritic AC joints MRI was better than ultrasound. In revealing bony surface changes, CT was the best method and radiography was least sensitive but quite specific. Our most prominent finding was that ultrasound is able to exclude joint inflammation; when the ultrasonographic distance of the joint capsule from the bone rim was < 3 mm, there was no synovial hypertrophy or effusion on MRI scans. CONCLUSION: Ultrasound can detect AC joint changes reliably. It is able to exclude joint inflammation. Effusion in the AC joint may reflect inflammation, but may also be a sign of degeneration.