Introduction: Substitution treatment and radiosynoviorthesis has a leading role in preventing irreversible hemophilic arthropaties. Aim: The aim of the study is to evaluate the effects of radiosynovectomy on the length of intervals between subsequent bleedings in patients with hemophilic synovitis.

Materials and Methods: 33 joints were treated with radiosynovectomy in 28 patients with bleeding disorders. 90Y colloid was used in knees and 186Re colloid for elbow, shoulder and ankle. 20 patients were on prophylaxis. X-rays of treated joints were evaluated on Peterson scale between 0 (normal) and 13 (severe joint destruction). In observation period (range 6 – 44 months) bleeding episodes were recorded and data statistically analyzed.

Results: Before RS, the average interval between haemorrhages was 16.4 days. Immediately after RS, the average interval between haemorrhages more than tripled. Namely, the average length of the first non-bleeding interval after RS was almost 60 days. In the period covering the first five bleeding episodes after RS, the average non-bleeding interval increased to 47.1 days. Therapeutic effects of RS considerably depend on location (joint) of bleeding, damage of the joint and of the patient. But controlling for location and damage of the joint and age of the patient, after RS every sub sequent non-bleeding interval was 11% shorter (p=0.05) than previous non-bleeding interval. After more than 10 bleeding episodes had occurred since RS, the non-bleeding intervals were no longer significantly shorter than before RS (at p=0.05). Therapeutic response to RS could be, therefore, observed in the period of more than 430 days after the procedure.

Conclusion: Radiosynovectomy significantly reduces hemorrhages in target joints for the average period of 14 months. It is more efficient in patients with less affected joints and less efficient in younger patients. The therapeutic effect of RS diminished with the elapse of time.