Kazue Hayakawa, Hideki Date, Sho Nojiri and Harumoto Yamada
Objective: We report a rare case of revision total knee arthroplasty for monoarthritis of the knee due to rheumatoid arthritis (RA). Case: The patient was a 72-year-old woman, who underwent revision surgery at 8 years and 7 months after left unicompartmental knee arthroplasty. Bacteriological examination of the synovial fluid was negative, and no crystals were found by microscopic examination. When the Knee Society score was determined, the knee score was 43 points and the function score was 45 points. No periprosthetic radiolucent lines were observed and there was no loosening. Erosion of the lateral femoral and tibial condyles was observed. CRP 3.6 mg/dL, erythrocyte sedimentation rate 129 mm/h, RF 101 U/mL, MMP3 732.2 ng/mL, anti-CCP antibody 190.3 U/mL. Revision TKA was done with a NexGen CR Flex (Zimmer Corp.) RA was diagnosed by histopathological examination of the synovium. Detailed investigation with bone scintigraphy and gallium scintigraphy did not identify inflammation of any other joints. However, pain and swelling of the right knee joint appeared 5 months after revision surgery, and right TKA was performed. Histopathological examination of the synovium resected from the right knee also revealed findings typical of RA. Discussion: Revision TKA is likely to increase in the future because of more patients undergoing UKA and an increase in the age of onset of RA. If knee pain occurs in patients after unicompartmental knee arthroplasty, monoarthritis due to RA should be considered as a possibility. Accordingly, we should follow patients after UKA while keeping the possibility of RA in mind.