Clinical and ultrasonography assessment of peripheral enthesitis in ankylosing spondylitis

Abstract

Objective: The aim of this study was to compare clinical examination with power Doppler US (PDUS) in the detection of entheseal abnormalities in patients with AS.

Methods: Thirty-six AS patients underwent clinical and PDUS examination of the following bilateral entheseal sites: common extensor tendon at its insertion at the lateral humeral epicondyle; gluteus tendons at their insertion at the greater trochanter; quadriceps tendon at its insertion at the superior pole of the patella; patellar tendon at its proximal insertion at the inferior pole of the patella; patellar tendon at its distal insertion at the tibial tuberosity; Achilles tendon at its insertion at the calcaneus; and plantar aponeuroses at its insertion at the calcaneus.

Results: Clinical and PDUS examination revealed at least one abnormal enthesis in 23 (63.9%) and 35 (97.2%) AS patients, respectively. Furthermore, of 432 entheses examined in our 36 AS patients, 64 (14.8%) were considered abnormal by clinical examination and 192 (44.4%) by PDUS. US abnormalities most commonly found were enthesophytes (31.7%), calcifications (33.7%), thickening (29.8%) and hypoechogenicity (26.6%). We found erosions and PD signals in 9.7 and 6% of examined entheseal sites, respectively. The evidence of entheseal abnormalities by clinical examination has a poor likelihood ratio (LR) for the presence of US abnormalities with vascularization (LR = 1.61), without vascularization (LR = 1.24) or erosions (LR = 1.51) at all sites.

Conclusions: PDUS permits detection of structural and inflammatory abnormalities of the enthesis in AS and may complement the physical examination in order to better evaluate enthesitis.