Radiosynoviorthesis of acromioclavicular joint using 169Er-citrate: prospective evaluation of efficacy.

Background: There is a clinical need for therapeutic alternative in patients with persisting painful arthritis of AC-joint and failure of previous treatments. However, no radiopharmaceutical is currently explicitly approved for radiosynoviorthesis of acromioclavicular joint. The aim of our study was to prospectively assess the efficacy and safety of radiosynoviorthesis of acromioclavicular joint using erbium-169 citrate.

Material And Methods: Radiosynoviorthesis of acromioclavicular joint was performed in 51 consecutive patients (18 males, 33 females) mean age 64.3 (range 43.8-82.6, median 63.6) years with clinically confirmed arthritis of 85 acromioclavicular joints. The efficacy of RSO was reported by patients according to 10-step visual analogue scale of pain (VAS) (0 = no pain, 10 = most severe pain) at 6 months after radiosynoviorthesis and by ranking the global therapeutic effect of RSO in 4 categories (1 = the best effect, 4 = no change). To assess the variation of blood perfusion in treated joints, the efficacy of RSO was also evaluated by variation of target (acromioclavicular joint)/non-target (soft tissue) uptake ratio (T/NTR) of metylendiphosphonate (99mTc) measured as number of counts over region of interest on blood pool phase of two-phase bone scintigraphy performed before and 6 months after RSO.

Results: Radiosynoviorthesis was followed by significant decrease in VAS, mean - 3.1 (-47%). Excellent, good, moderate and bad response was observed in 57 (67%), 25 (29%), 1 (1%) and in 2 (2%) of acromioclavicular joints respectively. A significant correlation between decrease of T/NTR and variation of VAS in % (ρ = 0.532, p < 0.0001) and between T/NTR and subjective evaluation of therapeutic effect in scale 1-4 (ρ = 0.388, p = 0.0002) was observed. However, it was not possible to identify the cut-off value of relative decrease in T/NTR showing sufficient sensitivity and specificity to detect the therapeutic response.

Conclusion: Results of this prospective study permit to conclude a good efficacy and safety of radiosynoviorthesis using erbium-169 citrate in a series of patients with arthritis of acromioclavicular joint in whom previous line(s) of treatment did not lead to satisfactory pain relief.