more recently , tewari et al reported this structure as the retrotrigonal layer and emphasized that this tissue may serve as a key surgical anatomical landmark to orient the location of the vasa and seminal vesicles , which are located just beneath this layer   ( fig . , we have used this structure to identify the vas deferens and seminal vesicles in the midline at the posterior aspect of the prostato - vesical junction . however , aside from the presence and position of the layer , it seems that there have been no reports about the natural function of the layer . the aim of our study , therefore , was to discover a possible role of this structure . considering this layer 's positioning around the bn , we postulated that it might have some role in the control of urinary continence . to verify this , we assessed whether there was difference in the recovery of postprostatectomy incontinence ( ppi ) according to whether the retrotrigonal layer ( which was incised during posterior dissection of ralp ) was reconstructed or not . from may 2007 to september 2010 , a total of 181 consecutive patients underwent ralp by a single surgeon ( bhc ) at our institution . all of the preoperative , perioperative , and postoperative data were collected through a retrospective review of the patients ' charts . all men were continent for urine before surgery ( no involuntary urine loss of any kind ) and had neither undergone transurethral resection of the prostate nor had a history of neurological disease . to control the learning curve , we divided our patients into two groups depending on whether a retrotrigonal layer backup stitch ( rtbs , as described below ) was performed . these stitches were not used in group 1 ( cases 31 to 124 ) but were used for the patients in group 2 ( cases 125 to 181 ) . all cases were carried out by use of the transperitoneal , six - port technique . after the endopelvic fascia was opened and the dorsal vein complex ( dvc ) ligated , the anterior bn was divided . the posterior bn was then divided at the midline of the prostate - vesical junction . at this stage , after division of the retrotrigonal layer , both the vasa and seminal vesicles were found just beneath the retrotrigonal layer ( fig . the seminal vesicles were then completely dissected as the transected distal ends of the vasa were pulled anteriorly by using the fourth robotic arm . subsequently , posterior dissection was continued as far distally as possible , and the posterior aspect of the prostate was nearly freed from the rectum . then the nerve sparing ( interfascial ) was performed from the apex to the base , if deemed indicated according to the patient 's preoperative potency and tumor characteristics ( table 2 ) . after the prostatic pedicles were ligated , apical dissection and urethral transection were performed . posterior anastomosis was performed in a clockwise direction starting at the 5 o'clock position and ending at the 10 o'clock position . anterior anastomosis was performed with the second arm of the suture in a counterclockwise direction , and both sutures were tied together . here , the only technical difference between our two groups was an incorporation of the retrotrigonal layer into the posterior aspect of the vesicourethral anastomosis in group 2 . in group 2 , when we made conventional , continuous running sutures on the posterior bladder wall , this stitch was performed at a minimum of four points on the posterior bladder wall . after completing the anastomosis , routine postoperative care was administered , and the urethral catheter was removed 5 to 7 days after surgery . follow - up for all patients was conducted at 1 week , 1 month , 3 months , and then every 3 months for up to 2 years . continence recovery was determined by direct interview with the patients at each visit to our outpatient clinic . the two groups were statistically compared for patient age , body mass index ( bmi ) , prostate volume , pre - ralp prostate - specific antigen ( psa ) level and international prostate symptom score ( ipss ) , length of membranous urethra , number of nerve - sparing procedures , pathologic gleason score , pathologic stage , margin - positive rates , biochemical recurrence , rates of adjuvant radiation therapy , overall operative time , robotic console time , and postoperative continence rate . the student 's t - test or the mann - whitney test was used to analyze numerical variables , and the chi - square test or the fisher 's exact test was used to analyze categorical variables . to compare the interval before the return of urinary continence between the two groups , we used the kaplan - meier method with the log - rank test to analyze the differences between the curves . to minimize and control for selection bias there were no significant differences between the groups with respect to patient age , bmi , prostate volume , preoperative psa level , or preoperative obstructive and irritative ipss ( p>0.05 ) ( table 1 ) . there were also no significant differences between the groups in the number of nerve - sparing procedures , pathologic gleason score , pathologic stage , positive surgical margin , biochemical recurrence , or rates of adjuvant radiation therapy ( p>0.05 ) ( table 2 ) . for overall operative time and robotic console time , times were considerably shorter in group 2 ( cases 125 to 181 ) than in group 1 ( p<0.0001 ) ( table 2 ) . according to our definition , group 1 showed continence rates of 40.4% , 70.2% , and 90.4% at 3 , 6 , and 12 months , respectively ; in group 2 , the continence rates were 42.1% , 70.1% , and 89.7% , respectively . the median ( 95% confidence interval ) time to continence recovery was four months ( range , 1 to 12 months ) in group 1 and four months ( range , 1 to 9 months ) in group 2 . kaplan - meier curves showed no significant difference in the recovery of continence between the two groups ( log rank test , p=0.629 ) ( fig . prostate volume , serum psa , preoperative total ipss , pathologic gleason score , length of membranous urethra , and rtbs technique were not significant risk factors for the recovery of continence after ralp ( p>0.05 ) ( table 3 ) . in patients with no preoperative erectile dysfunction ( international index of erectile function-5 score > 21 ) , intercourse was reported in 72.5% and 76.2% of the patients undergoing bilateral nerve - sparing surgery at 12 and 24 months of follow - up , respectively . various intraoperative techniques for improving ppi have been introduced for use in open radical prostatectomy [ 6 - 14 ] , lrp , and ralp series [ 16 - 18 ] . although many of these techniques showed continence outcomes that were superior to those of procedures performed without the techniques , some controversies regarding the efficacy or limitations of these techniques persist [ 19 - 24 ] . besides , we had found that our initial experiences with ralp ( cases 1 to 124 ) showed acceptable continence outcomes without the use of such techniques . for these reasons , we did not fully trust the efficacy of the current and past intraoperative techniques for improving ppi until now . for techniques focusing on the bn , which is regarded as an internal sphincter a bn preservation technique was introduced to theoretically improve ppi on the basis of the idea that sparing as much bn as possible during rp might result in a sphincter mechanism more closely resembling that of the preoperative state . however , srougi et al found that the technique did not improve ppi and in fact might compromise cancer control because of the marginal positivity of the bn . intussusception of the bn , a technique introduced by walsh and marschke , was another modification intended to result in earlier return of urinary control . concerning the anatomy around the bn , there are some newly visited aspects ( especially posterior to the bn ) in addition to the well - known anatomy that was described by myers . such trends have resulted from the evolution of rp from an open technique to lrp or ralp . that is to say , the anatomy around the posterior bn has been examined under the enhanced and magnified vision of laparoscopic surgery and , more importantly , as a result of the different ( antegrade ) dissection of lrp / ralp . for example , in 2001 and 2002 , myers described the extension of the longitudinal detrusor muscle of the bladder anteriorly , in front of the anterior commissure of the prostate . he termed this the detrusor apron and explained that this structure had generally been unappreciated during rp by many urologists . in another example , in 2006 , secin et al described some longitudinal muscle fibers extending from the bn to the base of the prostate during the dissection of the posterior bn in lrp . they proposed that these fibers actually correspond to the posterior longitudinal fascia of the detrusor muscle . an earlier report regarding this structure could be found . when describing the ' montsouri ' technique of lrp , guillonneau and vallancien described the presence of a fascial structure with cephalocaudal striations that needed to be incised horizontally during the posterior bn dissection . however , this terminology was challenged by several authors , because , according to our current anatomical knowledge , the dnf does not extend anterior to the seminal vesicle . instead , the term posterior layer of the detrusor apron was suggested , in view of the similarity between this structure and the detrusor apron that myers had described . more recently , tewari et al used cadaveric dissections and real - time videos from ralps to describe a tissue layer posterior to the bn that extended from the posterior aspect of the trigone to the base of the prostate , which is consistently encountered after division of the posterior bn . , they emphasized that this tissue may serve as a key surgical anatomical landmark to locate the vasa and seminal vesicles , which are located just beneath this layer . aside from its presence or accurate termination , however , it seems that the natural role or function of the layer is not clearly known . therefore , we postulated that this layer might have some role in the control of urinary continence , considering its position around the bn . to verify this , we analyzed the outcomes in continence recovery after dividing our ralp cases into two groups ( with or without rtbs ) . accordingly , we started to perform rtbs techniques from the 125th case of our ralp series . we compared the data of the patients with rtbs ( cases 125 to 181 ) with those of our initial ralp cases ( without rtbs , cases 31 to 124 ) , in which the retrotrigonal layer had been used only as a landmark for posterior dissection of the bn . our ralp technique in all 151 cases did not include any of the current or past techniques for improving ppi , including puboprostatic ligament ( ppl ) preservation , additional anterior support of the ppl / dvc , bn preservation , membranous urethral lengthening , or posterior reconstruction of denonvilliers ' musculofascial plate ( such as the rocco stitch ) . moreover , there was no significant difference in the number of nerve - sparing procedures between our two groups . accordingly , we think that our comparison of the two groups was quite reliable in terms of both surgical   aspects and baseline patient characteristics . during posterior dissection of the bn , the retrotrigonal layer was clearly identified in all but four of our patients , although the thickness varied from one case to another . from our experience , we fully agree with tewari et al that this tissue may be a key landmark for use in the dissection of the posterior bn . although some authors have reported the use of an " ultradissection technique " or modified ultradissecction ( in asians with relatively small body sizes ) during bn dissection , we felt that the approach via the retrotrigonal layer was easier . also , incorporating the retrotrigonal layer into the posterior aspect of the vesicourethral anastomosis presented no difficulty . however , upon analysis of our results , our rtbs technique did not show any role in the improvement of ppi . we think that this conclusion is bolstered by the fact that the surgeries in group 2 ( with rtbs ) were performed when our procedures for ralp were far more stabilized in every other step that might affect the continence outcome ( e.g. , nerve sparing , etc ) , and yet there was no significant difference in continence recovery between the two groups . the finding of significant differences in operative time and console time between the groups ( table 2 ) also supports this conclusion . our study would have more power if verified knowledge existed of the innate , accurate point at which the retrotrigonal layer has its distal insertion . such knowledge will be essential to put our conclusions in context , because the residual retrotrigonal layer was sutured to the membranous urethra ( fig . the limitations of the present study include the retrospective comparison with a historical cohort and the lack of randomization . as such , the results should be considered exploratory or observational , not definitive . to address this concern , we are planning a prospective randomized trial with validated continence measures to more rigorously assess the effectiveness of rtbs . . a verified description of the innate , accurate point at which the retrotrigonal layer has its distal insertion and prospective randomized studies with larger numbers of patients will be essential to confirm our results .