Extensor carpi ulnaris (ECU) and tibialis posterior (TP) tendons are often involved in RA and the present aim was to examine by ultrasound (US) their frequency of inflammation and sensitivity to change in comparison to joint involvement as well as clinical examinations.
US, clinical and laboratory assessments were performed when starting biologic DMARD (bDMARD) and after 1, 2, 3, 6 and 12 months including bilateral grey-scale (GS) and power Doppler (PD) semi-quantitatively (0-3) scoring of ECU and TP tendons and 18 joints. Changes from baseline to follow-up were explored by Wilcoxon signed rank test, associations by Spearman's rank correlations and responses to treatment by Standardised Response Means (SRMs).
157 patients (mean age/disease duration 52.4/10.2 years) were included. ECU/TP tenosynovitis was frequent (baseline GS/PD pathology in 76/50% of patients) and more prevalent than synovitis of large joints. Tenosynovitis sum scores decreased throughout follow-up (p<0.001) and was correlated with US of joints (0.51-0.62), clinical assessments (swollen joint count (0.29-0.41) and assessor's global (0.35-0.46)) (p<0.001). US tenosynovitis sum scores had SRMs comparable to joint, clinical and laboratory assessments.
Tenosynovitis in ECU/TP tendons were frequent, sensitive to change during bDMARD treatment and were associated to joint and clinical assessments. This supports the argument for tenosynovitis to be included in US scores of RA patients, while further studies should explore which tendons.