90Y-Yttrium Citrate as a colloidal suspension is used for therapeutic radiosynovectomy of large joints (knees). The equivalent 90Y-Yttrium Silicate has been withdrawn from the market.
90Y-Yttrium Citrate is used for therapeutic irradiation of synovial hypertrophy of knee joints mainly for mono- or oligo-articular arthritis of chronic inflammatory rheumatism particularly rheumatoid polyarthritis. Results are similar to surgical synovectomy, but the risk of morbidity and the side-effects are much lower. The suspension is injected in each painful joint which is then kept in the same position for a few hours or days to avoid the escape of the radioactive substance from the injected joints. The reduction of extra-articular escape is the major issue in this modality but is now well controlled.
The maximum tissue penetration for 90Y in radiosynoviorthesis applications is estimated at 11 mm.