PFC group (n=38) CKS group (n=39) p-value 1 1 -0.8 (4.1; -20–5) 108 (15; 80–135) 108 (17; 65–135) 88 (12; 59–100) 65 (27; -20–100) 153 (30; 71–200) 20 (16; 0–57) 83 (20; 0–100) 17 (24; 0–80) 2 6 8 -3.3 (6.9; -20–10) 104 (17; 65–140) 100 (21; 45–140] 80 (19; 35–100 55 (30; -10–100 135 (43; 40–200) 24 (22; 0–79) 71 (27; 0–100) 24 (26; 0–70) 3 688 Table 2. Clinical results Revisions (no.) Reoperations (no.) ROM (deg) Extension Flexion Total ROM KSS (points) Knee Function Total WOMAC score (points) VAS satisfaction VAS pain Radiolucency (no.) a Fisher exact test and b Student t-test. secondary resurfacing of the patella. During the removal of the prostheses, it appeared that all femoral components of the failed CKS group were easy to remove, leaving an intact cement layer on the bones—indicating inadequate fixation between prosthesis and cement. Cultures were positive in 2 of the CKS revisions. 8-year survival analysis with revision for any reason as endpoint showed 97% (95% CI: 92–100) sur- vival for the PFC group and 84% (72–96) survival for the CKS group (p = 0.05) (Figure 3A). The survival values for aseptic revision were 97% (92–100) and 89% (78–99) respectively (p = 0.2) (Figure 3B). 2 other patients in the CKS group were reoperated. 1 patient developed postoperative arthrofibrosis and was manipulated under anesthesia, but the knee remained stiff with 20° fixed flexion deformity and 70° of flexion. 1 patient was treated Acta Orthopaedica 2011; 82 (6): 685–691 0.1 a 0.03 a 0.05 b 0.2 b 0.09 b 0.04 b 0.1 b 0.04 b 0.3 b 0.03 b 0.3 b 1 a with open debridement followed by antibiotics for 6 months because of a culture-proven deep infection. 4 years later, there were no signs of infection and the knee functioned well. 2 patients (1 in each group) developed a hematoma, both of which were treated conservatively. There were no thromboembolic com- plications. The 8-year survival analysis with any reoperation as endpoint showed a difference between the PFC group and the CKS group (97% (92–100) for PFC and 79% (CI: 66–92) for CKS; p = 0.02) (Figure 4A). The survival values for aseptic reoperation were 97% (92–100) and 85% (73–97) respectively (p = 0.08) (Figure 4B). Analysis of the radiographs at final follow-up showed a radiolucency smaller than 2 mm in one zone under the tibial component in 2 cases in the PFC group and in 3 cases in the CKS group. These radiolucent lines were already present in the direct postoperative radiographs and no radiolucent line was pro- gressive; none of these 5 cases were classified as radiographic loosening. The skyline patellar radiographs did not show (sub) luxation of the patella in the PFC group or in the CKS group. Discussion Our hypothesis that there would be no difference in clinical outcome between the PFC prosthesis and the CKS prosthe- sis was rejected. With total KSS as primary endpoint, and for survival with any reoperation as endpoint, the CKS group showed a worse result. With our standard prosthesis, the PFC, we found an excellent survival rate of 97% for any revision after 8 years. Other authors have recently reported similar A B Figure 3. Kaplan-Meier survival plots. A. With revision for any reason as endpoint, the PFC group had a survival of 97% (95% CI: 92–100) after 8 years and the CKS group had a survival of 84% (72–96) (p = 0.05). B. With aseptic revision as endpoint, the PFC group had a survival of 97% (92–100) after 8 years and the CKS group had a survival of 89% (78–99) (p = 0.2).