Comparison of sonography and MRI for diagnosing epicondylitis

The aim of this prospective study was to compare the sensitivity and specificity of sonography with those of MRI in evaluating epicondylitis.

The affected elbows of 11 patients with suspected epicondylitis were examined sonographically, and the contralateral (normal) elbow was also examined for comparison. In 10 of these patients, the affected elbow was also examined with MRI. In addition, both elbows of 6 volunteers without epicondylitis were examined sonographically; 1 elbow of each volunteer was designated as the "test" elbow and was examined with MRI. The sonograms of the patients' affected elbows and the volunteers' test elbows were paired with the sonograms of the contralateral elbows for comparison and were randomly shown twice to 2 readers. These readers, working independently and without knowledge of the findings of MRI, were instructed to state whether each elbow was normal or affected by epicondylitis. The MRI scans were then shown to the readers for similar review.

Sonographic features of epicondylitis included outward bowing of the common tendon, presence of hypoechoic fluid subadjacent to the common tendon, thickening, decreased echogenicity, and ill-defined margins of the common tendon. Sensitivity for detecting epicondylitis ranged from 64% to 82% for sonography and from 90% to 100% for MRI. Specificity ranged from 67% to 100% for sonography and from 83% to 100% for MRI.

Sonography is as specific but not as sensitive as MRI for evaluating epicondylitis. Used as an initial imaging tool, sonography might be adequate for diagnosing this condition in many patients, thus allowing MRI to be reserved for patients with symptoms whose sonographic findings are normal.