Background Inflammation of the entheses (enthesitis) is a characteristic finding of ankylosing spondylitis (AS). Despite the growing interest in rheumatology for musculoskeletal ultrasound (US), there are not many studies evaluating the entheses in AS through the US.

Objectives

1. To compare US findings of entheses between AS patients and healthy subjects;

2. To assess entheses by US and correlate with clinical, functional and inflammatory aspects in patients with AS

Methods We conducted a cross sectional study of 50 patients with AS and 30 healthy volunteer subjects matched for age and sex. Were evaluated by US the following entheses: brachial triceps, femoris quadriceps, proximal patellar tendon, distal patellar tendon, calcaneal tendon, and plantar fascia. The clinical evaluation of patients included a global health scale, visual analogue scale (VAS) for pain and swollen, calculation of BASDAI, BASFI, BASMI, HAQ-S, ASDAS-VHS and enthesitis index SPARCC (Spondyloarthritis Research Consortium of Canada Enthesitis Index). The US exam was performed at right and left entheses of samples by a radiologist expert in musculoskeletal “blind” to clinical findings and based on MASEI index (Madrid Sonographic Enthesis Index) and the analysis of its sub items (bursistis, calcification, erosion, power doppler, thicknening of tendon, structural change). For evaluation was used the Esaote MyLab60 machine equipped with a linear transducer with a frequency of 6-18 MHz.

Results Were evaluated by US 960 entheses of total sample of 63 men (78,75%) and 17 women (21,25%). The patients had mean age of 43,44 (± 9,91) years and healthy subjects 38,7 (±8,52) years. The mean disease duration was 11,11 (± 6,77) years. The comparison of average MASEI total score between patient and control groups (16,32 + 11,11 / 10,70 + 5,27) was not statistically different (p = 0,519). There was a statistical difference between groups for the detection of erosion (17 patients/0 healthy; p= 0,00) and power Doppler (PD) in calcaneal entheses (6 patients/0 healthy; p= 0,053) and for erosion (7/0; p=0,037) and thickening of the plantar fascia (38/9 p = 0,002). The latter showed an odds ratio of 3,47 (p = 0,03) of belonging to AS group, according to logistic regression. There was no difference between groups for ultrasound evaluation of other entheses. Correlation of entheses US findings and clinical, functional, inflammatory aspects was weak. However, the PD of the calcaneal entheses was correlated with VAS pain (0,344 p= 0,00) and VAS swollen (0,486 p = 0,00). The VAS pain and VAS for swollen of the calcaneal entheses correlated statistically (0,653 p = 0,00).

Conclusions At ultrasound, the entheses of the feet were the only ones able to differentiate AS patients from healthy subjects. This difference was mainly due to bone erosion in both the calcaneal tendon, as in plantar fascia. The PD on the calcaneal entheses was the only parameter on US that correlates with clinical variables.

References E de Miguel, T Cobo, S Muñoz-Fernández et al. Validity of enthesis ultrasound assessment in spondyloarthropathies. Ann Rheum Dis 2009;68;169-174

Disclosure of Interest None Declared