Objective: Combining ceramic with polyethylene reduces the wear rate of arthroplasty prostheses. Nagoya City University (NCU) -type alumina ceramic total knee arthroplasty (TKA) was first applied clinically in July 1989, and there are now two types of NCU device : (1) NCU 1, comprised solely of alumina ceramic components, and (2) NCU 2, comprising an almina ceramic femoral component and a titanium tibial component. We investigated the outcomes of NCU 1 and NCU 2 in rheumatoid arthritis (RA) .
Methods: From July 1989 to August 1994, NCU TKA was performed in 43 knees of 30 patients with RA (3 males and 27 females) . The mean age at the operation was 58.4 years, and the mean follow-up period was 122 months. NCU 1 and NCU 2 were applied to 30 and 13 knees respectively. Clincal evaluation was based on the Japanese Orthopaedic Association RA knee score (JOA score), and we also assessed the range of motion and radiographic results.
Results: The mean JOA score improved from 39.7 to 70.8 for NCU 1 and from 39.8 to 77.5 for NCU 2. However, the mean flexion range decreased from 108.7° to 105.8° for NCU 1 and from 111.2° to 96.9° for NCU 2, although the mean extension ranges improved from -12.7° to -3.7° and from -18.8° to -4.8°, respectively. Radiographically, there were 15 knees with a radiolucent line and 14 knees with sinking. The rates of these phenomena tended to be higher in cementless cases. One case required reoperation due to aseptic loosening of the femoral component.
Conclusions: No polyethylene wear was evident in this study, indicating the advantage of combining ceramic with polyethylene in TKA. To prevent radiographic changes, each component of NCU TKA in RA should be fixed with cement. Also, the NCU needs to be redesigned to improve the range of motion.
