Recurring synovitis as a possible reason for aseptic loosening of knee endoprostheses in patients with rheumatoid arthritis

We evaluated histologically samples of synovial tissue from the knees of 50 patients with rheumatoid arthritis (RA). The samples were taken during rev ision for aseptic loosening. The findings were compared with those in 64 kn ees with osteoarthritis (OA) and aseptic loosening and in 18 knees with RA without loosening, The last group had been revised because of failure of th e inlay or the coupling system of a constrained prosthesis. All the patient s had had a total ventral synovectomy before implantation of the primary pr osthesis. In all three groups a foreign-body reaction and lymphocellular in filtration were seen in more than 80% of the tissue samples. Deposits of fi brin were observed in about one-third to one-half of the knees in all group s. Typical signs of the reactivation of RA such as rheumatoid necrosis and/ or proliferation of synovial stromal cells were found in 26% of knees with RA and loosening, but not in those with OA and loosening and in those with RA without loosening. Our findings show that reactivation of rheumatoid syn ovitis occurs after total knee replacement and may be a cofactor in aseptic loosening in patients with RA.