Yttrium-90 radiochemical synovectomy in chronic knee synovitis: a one year retrospective review of 133 treatment interventions.

Objective. To determine treatment success rates and factors predicting successful outcome using yttrium-90 intraarticular injections for chronic knee synovitis refractory to other treatments. Methods. A retrospective one year review of 133 treatment interventions with yttrium-90 (Y-90) with response recorded at 3, 6, 9, and 12 mo after injection. Results. An excellent, good, or fair response (a treatment benefit) as evaluated by objective (degree of joint effusion, joint tenderness, range of motion) and subjective (visual analog scale, degree of pain) assessments occurred in 81, 82, 80, and 75% of joints at 3, 6, 9, and 12 mo, respectively. When only excellent and good responses were considered successful treatment then 49, 48, 57, and 46% had successful treatment at 3, 6, 9, and 12 mo, respectively. 8 of 15 joints (53%) reinjected after primary treatment failure or relapse showed a beneficial response. Patients treated successfully were more likely to have a normal radiographic appearance rather than one showing destructive changes (78 vs 54% treatment success; p < 0.05); to have localized disease or systemic disease in remission, rather than active systemic disease (66 vs 30% treatment success; p < 0.001); and shorter duration of joint disease (6.9 vs 10.2 years; p < 0.05). Conclusion. Y-90 synovectomy successfully treats patients with chronic knee synovitis refractory to other therapies. Primary treatment failures or relapses may be successfully treated by reinjection. Patients with less destructive radiographic changes, shorter duration of joint disease, and localized disease tend to respond more favorably.