234 Chapter 9 These results show it is possible to detect a difference in sample means of 2.65 on the total GEARS score. For this study we assume the GEARS score in the incontinent patients is similar to that of a fellow and the GEARS score in the continent patients is similar to that of an expert. Based on a power calculation using .05 as Alpha, a Power of .80, and an effect size of 2.65 a sample size of 6 patients per subgroup would be sufficient for the main objective of this study. Selection and Matching The patients were selected based on the patients’ pre-operative and post-operative urinary continence as measured using the International Consultation Incontinence Modular Questionnaire-short form (ICIQ-SF-score). The ICIQ-SF is a Patient-reported outcome measures (PROMS) questionnaire which registers the patient’s urinary incontinence on three domains, the frequency of urine leakage (0-5 points), the amount of leakage according to the patient (0-6 points), and the interference of the urine leakage with everyday life (0-10 points). An additional question which asks in which situation the urine leaks gives more insight into the type of incontinence. The cumulative scores of the three question (0-21 points) represent the patient’s experience of urinary incontinence. In this study an ICIQ-SF score of 0 at 6 and 12 months postoperative was defined as continent, whilst and ICIQ-SF of >10 at 6 and 12 months postoperative was defined as incontinent. Exclusion criteria were urinary incontinence prior to surgery, and surgical procedures where no or incomplete video material was available. The patients in the continency group were matched according to the date of the surgery, the age of the patient, BMI of the patient and the preoperative intentions of saving the neurovascular bundles during surgery. All incontinent patients were manually compared to the continent patients by the researcher (AB). Based on the number of variables in which the pairs matched a matching score of zero to four was given to the patients, each matched variable resulted in a point in the total matching score. The patients were matched based on age (difference of <5 years = 1 matching point), BMI (difference <3 points = 1 matching point), date of the surgery (difference <3 months = 1 matching point), and preoperative intentions of saving the neurovascular bundles during surgery on both sides (NVB sparing the same in both patients = 1 matching point). A matching score of 4 was the best possible match. Based on the matching scores the best matched patient pairs were selected for analysis, since almost no perfect matches existed (Appendix 1a). If matched pairs with similar matching scores existed a definitive choice was made based on the variable on which the patients matched (appendix 1a).
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