Radiation Synovectomy: Results in Rheumatoid Knee Effusions Treated with Radioactive Yttrium

48 rheumatoid knee joints were treated with intra-articular 90Y resin colloid injections. The dose was 6 mCi, as a rule. The length of the follow-up period was from 1 to 3 years. The percentage of excellent and good improvements was 60 at 12 months, 49 at 18 months and 36 at 24 months. There were 8 primary failures (17%). The failure rate increased in the following cases: (1) in joints with signs of radiological damage, (2) in patients with a generally progressive disease, (3) in joints with long-term effusions, (4) in seropositive cases. Eight knee joints in which isotope therapy had failed were later operated on. The most serious findings were proliferative synovitis, erosions and degenerated menisci. Nearly half the patients had a slight flare-up of the synovitis shortly after 00Y injection. Acute crystal-induced synovitis was observed in one case 1 month after the isotope injection. No other side-effects were noticed. Osmic acid was injected simultaneously with 90Y in 7 patients with symmetrically affected knee joints. In this series of patients the effect of 90Y lasted longer than that of osmic acid.