Acta Orthopaedica 2011; 82 (6): 685–691 Table 1. Patient demographics and baseline clinical status PFC group (n = 38) CKS group (n = 39) Sex (female/male) Age, years Height, cm Weight, kg BMI Diagnosis (OA/RA) ROM, degrees Extension Flexion Total ROM KSS, points Knee Function Total WOMAC score, points VAS pain 26/12 65 (10; 45–81) 169 (9; 154–187) 85 (18; 61–130) 30 (5; 21–45) 33/5 –4 (6; -20 to 0) 109 (14; 75–135) 104 (16; 65–125) 53 (17; 9–95) 37 (20; -5–70) 89 (32; 4–150) 54 (13; 25–75) 62 (17; 26–90) 24/15 69 (11; 48–88) 170 (11; 148–190) 82 (15; 60–120) 28 (4; 21–39) 37/2 –5 (6; -20 to 5) 111 (19; 70–140) 106 (20; 70–140) 51 (17; 15–91) 42 (20; -10–90) 92 (29; 40–177) 52 (14; 25–95) 55 (17; 20–91) 687 Statistics A sample size estimation showed that 37 knees per group would be required to detect a clinically relevant difference of 10 points with a standard deviation of 15 points in the total KSS, with an alpha of 0.05 and a power of 80%. Intergroup dif- ferences were determined using Student’s t-test for continuous variables and the Pearson chi-square test or Fisher’s exact test for categorical variables. Survival analyses were performed using the Kaplan-Meier method and compared using log-rank tests. Survival estimates are presented with 95% confidence intervals (CIs). For all data sets, differences were considered statistically significant at p-values < 0.05. Results p u - w o l l o F s i s y l a n A t n e m l l o r n E n o i t a c o l l A After randomization, 5 patients were excluded because a pos- terior-stabilized design was needed after routinely sacrificing the PCL in cases with a flexion contracture of 25 degrees or dence for the primary objective included results on the KSS more (1 in the CKS group and 4 in the PFC group). Because subscores, the Western Ontario and McMaster Universities bilateral involvement might cause bias, 8 other knees were Osteoarthritis Index (WOMAC) score (Bellamy et al. 1988), excluded (5 in the CKS group and 3 in the PFC group). No range of motion, survival, and patient satisfaction and pain, patients were lost to follow-up, but 12 relatively elderly both of which were assessed using a visual analog scale (VAS; patients died of unrelated causes. These patients were analyzed 0 = total dissatisfaction or no pain and 100 = complete sat- according to the latest available follow-up. Consequently, we isfaction or intolerable pain). A reoperation was defined as analyzed 39 knees with a CKS prosthesis and 38 knees with any operative procedure at the involved knee. A revision was a PFC prosthesis (Table 1 and Figure 2), with a mean follow- defined as any removal, exchange, or addition of one or more up of 5.6 (1.2–7.7) years (i.e. 5.4 (1.5–7.7) years for the CKS of the prosthetic components. group and 5.7 (1.2–7.7) years PFC group). With total KSS as primary endpoint, there was a difference between groups in favor of the PFC group at final follow-up (p Assessed for eligibility (87 patients) = 0.04) (Table 2). Evaluation of the postoperative KSS sub- Excluded (5 patients) scores, WOMAC score, range – not meeting inclusion criteria (3) – declined to participate (2) of motion, VAS for patient sat- isfaction, and VAS for pain all Randomized (n = 90) tended to be superior for the 82 patients / 90 knees PFC group (Table 2). At final follow-up, there were differ- ences in KSS knee subscore Allocated to PFC group (n = 45) Allocated to CKS group (n = 45) (p = 0.04) and VAS satisfaction – recieved allocated intervention (n = 41) – recieved allocated intervention (n = 44) – did not recieve allocated intervention – did not recieve allocated intervention (p = 0.04) in favor of the PFC (PS design) (n = 4) (PS design) (n = 1) system. There was 1 revision in the Lost to follow-up (n = 0) Lost to follow-up (n = 0) PFC group; a thicker polyethyl- Discontinued intervention (died; analyzed Discontinued intervention (died; analyzed ene insert was placed for insta- with latest FU) (n = 5) with latest FU) (n = 7) bility. In contrast, there were 6 revisions in the CKS group: in Excluded from analysis (bilateral cases) (n = 3) Excluded from analysis (bilateral cases) (n = 5) 5 patients, the CKS prosthesis Analyzed (n = 38) Analyzed (n = 39) was removed because of poor function and pain and 1 patient was treated with arthrolysis and Figure 2. Flow diagram according to the CONSORT guidelines.