Beta-particle dosimetry of various radionuclides used in the treatment of rheumatoid arthritis was estimated using Monte Carlo radiation transport simulation coupled with experiments using reactor-produced radionuclides and radiachromic film dosimeters inserted into joint phantoms and the knees of cadavers. Results are presented as absorbed dose factors (cGy-cm2/MBq-s) versus depth in a mathematical model of the rheumatoid joint which includes regions of bone, articular cartilage, joint capsule, and tissue (synovium) found in all synovial joints. The factors can be used to estimate absorbed dose and dose rate distributions in treated joints. In particular, guidance is provided for those interested in (a) a given radionuclide's therapeutic range, (b) the amount of radioactivity to administer on a case-by-case basis, (c) the expected therapeutic dose to synovium, and (d) the radiation dose imparted to other, nontarget components in the joint, including bone and articular cartilage.
Ten cases are described of catastrophic failure of the polyethylene liner of three different designs of uncemented acetabular component. Failure occurred as a result of either 'wearthrough' to the metal backing, liner fracture or a combination of both, at a mean of 4.6 years after implantation (2 to 7.6). At revision there was metallosis in all hips and osteolysis of the femur or the pelvis in six. Catastrophic failure was seen only in cups with a minimum polyethylene thickness of less than 5 mm.
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