In haemophilia, repeated bleeding into a joint (chronic haemarthrosis) leads to chronic synovitis, inflammatory arthritis and progressive arthropathy (joint destruction). The synovium is a thin layer of tissue that lines the joint space. Its inflammation (chronic synovitis) leads to overgrowth and increase in blood vessels, thus predisposing to chronic haemophilic haemarthrosis. Joint destruction and deformity can be prevented if frequent joint bleeding is effectively eliminated before the onset of arthropathy and this requires removal of synovium (synovectomy) The removal of the synovium can be done either through surgical or non-surgical procedures. It has been known for long that if certain substances (chemicals and radioactive agents) are injected into the joint, they decrease the volume and activity of the synovial tissue. As these procedures are minimally invasive, non-surgical synovectomies are of special importance for haemophilic patients who have developed inhibitors to clotting factors.
The procedure is ideally done in a haemophilic patient with frequent joint bleeds (two to three bleeds per month) in a particular joint, who has failed to adequately respond to conservative treatment with clotting factor replacement and physiotherapy, and who has no radiological evidence of joint damage. In reality, most patients seen in haemophilia clinics for chronic haemarthrosis and synovitis already have some degree of articular deterioration. This does not disqualify them as candidates for radiosynovectomy, although patients must clearly understand that articular degeneration already present cannot be improved with the procedure. The aim is to control joint bleeding and prevent further damage.
Radiosynovectomy or radiosynoviorthesis is a local intra-articular (inside the joint) injection of radioactive substances in colloidal form. The proliferative tissue is destroyed, secretion of fluid and accumulation of inflammation causing cellular compounds stops and the joint surfaces become fibrosed, providing long term symptom relief. The radionuclides are injected in colloidal form so that they remain in the synovium and are not transported by lymphatic vessels causing radiation exposure to other organs. The type of radionuclide to be used is determined by the size of the joint to be treated and includes Erbium-169 (for finger joints), Rhenium-186, Phosphorus-32, etc. (for larger joints like wrist, elbow, shoulder, ankle and hip) and P-32, Yttrium-90 etc. for knee & shoulder. In recent years several other radionuclides like Holmium-166, Rhenium-188, Samarium-153, etc. have also been introduced. These isotopes emit beta-emissions, have a shallow depth of penetration and moderate half-life. The risk of chromosomal damage and malignancy has been assessed and found to be minimal with this procedure. The procedure is often done on an out-patient basis though some patients who have inhibitors maybe kept overnight to monitor for possible bleeding. Generally, a dose of clotting factor is given to keep the blood level around 50% of normal (or that dose which is most effective in controlling bleeding in the patient). Following injection, the joint is put through range of motion so that the isotope is evenly dispersed throughout the synovial surface and is then immobilized for 48 hours. No strenuous activity is permitted for about a fortnight.
In comparison with surgical synovectomy, this procedure produces equivalent results, costs less, clotting factor requirement is lower, allows the patient to remain ambulatory, and is repeatable. There is more than 75% reduction in bleeding (slightly less in repeated procedures). In fact, radiosynovectomy is now considered the initial procedure of choice for the treatment of patients with haemarthrosis in haemophilia, the only limitation being its limited availability.