Joost Peerbooms

40 Chapter 3 dressings (question 2) are multiplied by the type of wound dressing (question 1: x 1 or x 2). Questions 3 and 4 are indicators of the wound leakage, questions 5 and 7 are indicators of the type of leakage, and question 6 addresses wound infection parameters. The wound scores were measured by a trained orthopaedic resident (medical ward), who did not know whether PG had been used. Statistics There is little information if the effect of the application of a platelet concentrate could improve repair of wounds after TKA. The purpose of this study was to investigate whether the application of a platelet concentrate could reduce 25% of the wound leakage. Wound leakage was defined as a binary result (leakage or no leakage). With a bilateral alpha of 0.05 and a power of 80%, the intention to treat was 43 patients in each group to show a significant difference (α = 0.05, β = 0.8, 2n = 86). This difference is based on a study of Gardener et al. 12 Wound scores and function scores were measured on days 3 to 5, and at the regular control every 2 weeks. The function scores were also measured at 6- and 12-weeks post-surgery. For purpose of analysis the wound scores were dichotomized according to either “wound closure” (score of 0; no leakage or signs or infection) or “wound leakage” (scores > 0). Absolute difference in rate of wound closure with corresponding confidence intervals were computed according to Altman. 2 Wound closure was analysed with Chi-square between the two groups for each day. Haemoglobin values were measured pre- and postoperatively. The haemoglobin drop was analysed using unpaired Student’s t-test. VAS (Visual Analogue Scale) for pain at rest and pain during walking was measured at intake and 6 weeks and 12 weeks post-operative. The analogue scores 0-10 mm (negligible), 10-30 mm (mild), 30-50 mm (painful), 50-80 mm (moderate), and 80-100 (severe) were regarded as ordinal categories. Analysis was focused on the changes between measurement points in time, using Mann-Whitney U tests. Postoperative frequency use of analgesics was scored on a 5-point scale (never - always) pre-operative, 6 weeks and 3 months post-operative. Changes between measurement points in time were analysed using Mann-Whitney tests. The range of motion of the operated knee was analysed on the second day, third day, fourth day, 2 weeks, 6 weeks, and 3 months post-operative and was analysed using ANOVA for repeated measurements. WOMAC function scores were measured pre- operative, 6- and 12-weeks post-operative. Analysis focused on changes between measurement points in time, using Mann-Whitney U tests. A trained medical person, who was blinded to treatment group, measured all scores.