Hydroxyapatite (HA) crystal calcifications in or around the joint can induce acute flares with severe pain. A previous pilot study suggested that the interleukin-1β (IL-1β) inhibitor anakinra was effective. The goal of this observational study was to confirm these results in a larger set of patients and to report on the long-term follow-up.
Flare was defined as acute pain for<10 days. Calcification in or around a joint (rotator cuff: 15/23 patients) was confirmed by conventional radiography and/or ultrasonography (US). Anakinra 100mg daily was administered subcutaneously for 1 to 3 consecutive days. Clinical data collected before the injection and on days 3 and 21 included pain score on a visual analog scale (VAS, 0-10cm) and C-reactive protein (CRP) level. When available, US baseline and follow-up findings were compared. Long-term follow-up data were collected from patient charts and/or after a phone call.
23 patients (15 males, mean [SD] age 58 [11] years) were included. Baseline mean (SD) VAS pain was 7.7 (1) cm and CRP level was elevated in half of the patients. After therapy, mean (SD) VAS pain score decreased rapidly in the first 3 days to 1.6 (1.4) cm (P<0.001) and remained stable for 3 weeks at 1.8 (2.1) cm. US assessment revealed decreased Doppler intensity but no significant change in size of calcifications. No significant side effects were noted. After long-term follow-up (median duration 24 months), half of the patients still had some chronic pain, but only 4 experienced acute relapse.
This study suggests that IL-1β inhibition may be an efficient therapeutic approach for acute HA flare, with a good safety profile.