Monitoring Achilles enthesitis in ankylosing spondylitis during TNF-α antagonist therapy: an ultrasound study

Objective. Enthesitis is considered as the primary anatomical lesion in ankylosing spondylitis (AS). Therapeutic effects of TNF-alpha antagonist treatments for enthesitis on imaging changes are still limited to case reports or small sample-sized trials. We aimed to investigate the potential of ultrasonography (US) to detect early changes after TNF-alpha antagonist therapy of Achilles enthesis of AS patients. Methods. Forty-three AS patients with active disease, requiring TNF-alpha antagonist therapy, were included. Physical examination was performed to detect Achilles enthesitis and/or retrocalcaneal bursitis. US of the Achilles tendon was performed bilaterally. Grey-scale (GS) and power Doppler (PD) scores on a 0-2 semi-quantitative scale and total additive scores (TS) were calculated. Follow-up US examinations were performed 2 months after the initiation of therapy. Results. At baseline, 11 patients (26.2%) were symptomatic in physical examination for either Achilles enthesitis or retrocalcaneal bursitis, whereas 36 (83%) had GS US pathological findings and 10 (23.3%) had PD signal. GS score and TS decreased significantly [3.6 (3.0) vs 2.3 (2.2), P < 0.001 and 4.7 (4.9) vs 2.7 (3.3), P < 0.001, respectively], whereas the decrease in PD score was not significant after 2 months of follow-up. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), ESR and CRP levels also showed significant improvements. Conclusions. Subclinical Achilles enthesitis, detected only with GS US, is present in a subset of AS patients and a significant improvement can be demonstrated after 2 months of TNF-alpha antagonist therapy. In addition to standard outcome measures, US might be an additional useful tool to monitor therapy in SpA patients with Achilles enthesitis.