292 Chapter 11 Discussion In this study we investigated whether intraoperative urethral stump measurements can be performed using the Kinovea software from pre-recorded RARP videos and if these measurements could be used as predictors of postoperative urinary incontinence. Our results the Kinovea software can be used to measure urethral dimensions in pre-recorded RARP videos. The results showed a weak positive correlation between the SUL measured using Kinovea and the MUL measured with MRI, the correlation between SUL and the VUL showed no significant results. The lack of correlation between the VUL and SUL could be due to the fact that during dissection of the prostatic apex the urethra is deformed due to the traction of the prostate during this step of the surgery this method could be further improved using a video frame where no tractions are applied on the prostate and on the perineum of the patient i.e. during vesico-urethral anastomosis. There was a correlation between the urethral width measured with Kinovea software (SUW) and MRI (MUW) The width of SUW using Kinovea showed no correlation with the VUW measured on an MRI. This could possibly be the result of the traction on the prostate during dissection, as the diameter becomes smaller with traction and therefore the urethral tissue thinner. Another reason could be the thinning of the urethra during the apical dissection of the prostate. In this case, the selection of the video frame could have an impact on the quality of measurements of the urethral stump. The fact that the urethral stump measurements taken with Kinovea (SUL and SUW) were correlated with the MRI measurements (MUL and MUW) validate the Kinovea software as an accurate tool for the measurement of the urethral stump length and width. The performance of the measurements using Kinovea took on average 5 minutes per patient. In this study in both MRI measurements (MUL and VUL) and the SUL, a significantly longer median urethral length in the continent group compared to the extremely incontinent group. Although the median difference in SUL (2.44 mm) is shorter than the median difference in MUL (3.31 mm) and the median difference in VUL (4.27mm) the preoperative measurements show it is possible to find a measurable difference. The influence of the urethral length on continence has been proven with different modalities11,12 including MRI measurements. In a recent study, Kohjimoto et al. demonstrated that the length of resected MUL specimen was an independent predictor of urinary incontinence after RARP.11 Moreover, in another recent paper Song showed that a longer preoperative and postoperative length of membranous urethra was
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