258 Chapter 10 postoperative potency in order to reduce the influence of these factors on the postoperative status of the patients.26–28 The matching factors include the date of the surgery (the learning curve of the surgeon has been shown to influence chances of postoperative potency26), the age of the patient (shown to influence the chances of postoperative potency27,28), body mass index (BMI) of the patient (shown to influence the chances of postoperative potency27,28), and the preoperative intentions of saving the NVBs during surgery (shown to influence the chances of postoperative potency27). All potent patients were manually compared to the impotent patients. Based on the number of variables in which the pairs matched a matching score of 0 to 4 was given to the patients, and each matched variable resulted in a point in the total matching score. The patients were matched in the same manner as in the selection of the continency-group (based on age, difference < 5 years = 1 matching point), BMI (difference < 3 points = 1 matching point), date of the surgery (difference < 3 months = 1 matching point), and preoperative intention of saving the NVBs during surgery on both sides 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 A). If matched pairs with similar matching scores existed, a definitive choice was made based on the variable on which the patients matched (Appendix A). Power analysis Since this is a pilot study, a power analysis was performed based on the measures from one of the methods (GEARS) used during this study. The sample size analysis Figure 1 study design
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