Ultrasonographic evaluation of enthesitis in patients with ankylosing spondylitis

Abstract

The aim of this study was to assess sensitivity and responsiveness of power Doppler ultrasound (PDUS) in detecting enthesitis for ankylosing spondylitis (AS) patients compared to clinical examinations. Twenty AS patients initiating etanerceptunderwent clinical and PDUS examinations of six bilateral entheseal sites at baseline and after 1, 2 and 3 months of treatment. Clinical and PDUS examinations identified at least one entheseal lesion in nine (45%) and 19 (95%) patients, respectively. Furthermore, of 240 entheseal sites examined in these 20 patients, PDUS detected 123 entheseal lesions (51.3% of sites), compared with only 47 entheseal lesions (19.6%) detected by clinical examination (P<0.05). The entheseal lesions found on PDUS were most commonly identified by calcification (33.3%), tendon edema (29.2%), abnormal blood flow (25.8%), a thickened tendon (22.1%), cortical irregularity (12.9%), bony erosions (9.6%) and bursitis at the tendon insertion to the bone cortex (7.1%). Improvements in clinical symptoms and laboratory parameters, and significant decreases in PDUS scores were observed following treatment with etanercept. Improvements in PDUS scores continued during follow-up in patients who entered remission following treatment. In conclusion, PDUS improves detection of structural and inflammatory abnormalities of the enthesis in AS compared to physical examination. In addition, PDUS may be useful inascertaining medications.

Fig.1

Pathological ultrasonographic appearances of Achilles tendon. In a patient with ankylosing spondylitis, the pathological Achilles tendon is thickened and hypoechoic (↓). The fluid within the bursa mucosa exceeds normal ranges and can be accompanied by bursal hyperplasia (i.e., bursitis→). Bone irregularities are seen at the tendon enthesis insertion into the bone cortex (↑) (A). A blood-flow signal can be detected at the tendon insertion into the exposed bone cortex (B).

Fig.2

Ultrasonographic appearances of Achilles tendon before and after treatment in a patient with AS. The Achilles tendon is not clear and hypoechoic (A, arrow), with a blood flow signal (B) before treatment. After three months of etanercept treatment, the ultrasonographic appearances reveals improvements in tendon structure (C) and blood flow (D).