[Quantitative Analysis of Power Doppler Images in Lateral Humeral Enthesopathy]

PURPOSE OF THE STUDY The evaluation of efficiency of power Doppler sonography in the diagnosis of lateral humeral enthesopathy, role of correct assessment of Doppler sonographic images with the method of quantitative analysis, assessment of statistical differences between a group of patients with lateral humeral enthesopathy and a control group of healthy subjects and assessment of the diagnostic power of this test. In addition, consideration of the relevance of each area of the lateral compartment for assessment and diagnosis making in lateral humeral enthesopathy. MATERIAL AND METHODS A total of 41 subjects, aged 18 to 60 years, entered the study. Thirteen patients were diagnosed with lateral humeral enthesopathy on the basis of clinical tests and a positive reaction of the lateral humeral epicondylus to administration of local anaesthetic. The control group consisted of 28 subjects without clinical signs of lateral humeral enthesopathy and subjective complaints. Power Doppler activity was evaluated in the whole region studied and in sub-regions involving the enthesis of the common extensor tendon and the periosteum of the lateral epicondyle with the area distal to it. The evaluation was based on calculating the overall surface with power Doppler activity using the method of quantitative image analysis. Each patient was measured on three occasions and the median of values obtained was used in calculation. To assess the diagnostic power of this test, all values obtained from the whole power Doppler region measured were used. The optimal dividing criterion at which the method had a maximum of sensitivity and specificity was determined. RESULTS The most evident, statistically significant difference between the patient and the control group was recorded in the whole "Range of Interest" (ROI) region (p=1.34x10-6). A significant difference was also found in sub-regions corresponding chiefly to the tendon of the extensor carpi radialis brevis muscle and to the periosteum of the lateral epicondyle (p=0.0043). On the other hand, no significant difference was recorded in the sub-region of the proximal common extensor tendon (p=0.066). A Receiver Operating Characteristic (ROC) was performed to evaluate the sensitivity and specificity for a colour representation of each power Doppler image (a cut-off level). Calculation of the diagnostic power of the test gave a value of 0.915 (p=0.05) below the ROC curve. The optimal marginal value, at which both sensitivity and specificity were highest, was determined to be 455 pixels (sensitivity, 80.5%; specificity, 93.8%). DISCUSSION Power Doppler sonography has already been investigated in view of its potential for the diagnosis of lateral humeral enthesopathy. The results, however, have so far been assessed chiefly categorially, based on the examining physician's opinion. The problematic step in the whole procedure is the technique of power Doppler examination. It is necessary to maintain a constant setting and an examination technique eliminating artefacts. When these conditions are met, the method has both high sensitivity and specificity. In addition, because of being non-invasive, the method is convenient for routine use. CONCLUSIONS Power Doppler sonography is a method convenient to confirm or exclude the diagnosis of lateral humeral enthesopathy. Our results showed its statistical significance and diagnostic power (sensitivity and specificity). In the future, the quantitative image analysis could become a valuable adjunct method of evaluation not only for power Doppler images. Key words: Doppler sonography, quantitative image analysis, lateral humeral enthesopathy.