Objective: The purpose of this article is to evaluate prospectively the utility of sonographic measurements of the common extensor tendon for diagnosing lateral epicondylitis.
Subjects and methods: Forty-eight patients with documented lateral epicondylitis and 63 healthy volunteers were enrolled and underwent ultrasound of the elbow joint. The common extensor tendon overlying the bony landmark was scanned transversely, and the cross-section area and the maximum thickness were measured. Clinical examination was used as the reference standard in the diagnosis of lateral epicondylitis. Data from the patient and control groups were compared with established optimal diagnostic criteria for lateral epicondylitis using receiver operating characteristic curves. Qualitative evaluation with grayscale ultrasound was also performed on patients and healthy volunteers.
Results: The common extensor tendon was significantly thicker in patients with lateral epicondylitis than in control subjects (p < 0.01). Tendon thickness greater than 4.2 mm (sensitivity, 78.4%; specificity, 95.2%; accuracy, 87.7%) and area larger than or equal to 32 mm(2) (sensitivity, 86.3%; specificity, 82.5%; accuracy, 84.2%) were highly predictive of lateral epicondylitis. For qualitative evaluation with gray-scale ultrasound, overall sensitivity, specificity, and accuracy values in the diagnosis of lateral epicondylitis were 76.5%, 76.2%, and 76.3%, respectively.
Conclusion: The quantitative sonographic measurements had an excellent diagnostic performance for lateral epicondylitis, as well as good or excellent interreader agreement. A common extensor tendon cross-section area greater than or equal to 32 mm(2) and a thickness of 4.2 mm correlated well with the presence of lateral epicondylitis. However, further prospective study is necessary to determine whether quantitative ultrasound with these cutoff values can improve the accuracy of the diagnosis of lateral epicondylitis.