Polyethylene wear of the PCA unicompartmental knee. Prospective 5 (4-8) year study of 120 arthrosis knees.

In Lund, 120 arthrosis knees had the PCA unicompartmental endoprosthesis during 1983-1987 and were followed prospectively for 5 (4-8) years. 17 knees were excluded from the final clinical follow-up because of the development of rheumatoid arthritis (2), severe neurologic disease (3), or death (12). Subjectively, 68 knees were much improved, 26 improved and 9 had failed. First-steps problems were only present in the uncemented group of 49 knees. Of the 9 failures (7 cemented and 2 uncemented) 6 were revised. The main reason for revision was loosening of the femoral component (2), tibial component (2), or both components (1), and polyethylene wear (1). However, all revised tibial components showed polyethylene wear, in 4 quite pronounced. Weight-bearing radiographs (61 knees) revealed major polyethylene wear in an additional 14 knees; not only in thin tibial components. There may be an increasing clinical problem due to polyethylene wear. With the presented findings the PCA unicompartmental knee endoprosthesis cannot be recommended.