Tumor control, urinary continence and sexual potency make up the Trifecta of RP. Post-surgery incontinence is one of the most functionally devastating complications, which could make patients too depressed to maintain social relationship and can even lead to suicide. Albkri A et al[5] figured out that 28.1% patients regretted for RP decision because of complications. Unfortunately, there is so far no universal definition of continence up to now, which makes the morbidity of continence post-RP vary[6]. As literatures reported, ImC varied from 18%[7] to 63.5%[8], while continence at 3 months from 45%[9] to 82%[10], and continence at 12months from 79.8%[2] to 91%[11]. In consideration of urinary consequences on record, morbidity of incontinence after RP in real world could probably be higher than reported[12]. Grivas N et al[13] pointed out that continence at 12months post-surgery was only 49.2% with strict definition.
The debate between cancer free and continence still lacks conclusion. Routinely, the more tissue near the tumor incised, the better tumor control. But it also means more potential functional structures to be cut, and incontinence is more likely to happen. Therefore, the discovery of landmark structure for urinary continence is needed. There are many hypotheses, such as membrane urethra length, urethral sphincter complex, detrusor apron of bladder neck, pelvic floor musculature, DVC, and NVB[3], etc. Asimakopoulos AD et al[14] preferred complete periprostatic anatomy preservation to protect maximal functional structure and got 100% continence (≤ 1pad per day) just at the time of catheter removal. However, this procedure may not be suitable for patients with higher tumor stage. Here we suppose DF to be the answer, particularly for the early-term and mid-term urinary control after RP.
DF has been demonstrated to be a multiple-layer structure both in cadaveric studies[15, 16] and histologic studies[17, 18] on specimen of RP. At the central-post direction of prostate and proximal of urethra, DF’s fascicles tend to fuse and adhere with PC to form a dorsal raphe (DR)[16, 18]. The tendinous DR, which extends distally to prostate apex and ends at perineal tendon, may act as a fulcrum to support prostate and proximal urethra[19]. At the lateral-post direction of prostate, DF disperses to connect with LAF (Figure-2). Dalpiaz O et al[19] described DF as part of musculofascial suspension system, stabilizing prostate apex and proximal urethra. Interestingly, there was similar view on stress urinary incontinence (SUI) of females. DeLancey[20] delineated endopelvic fascia and anterior vaginal wall as the hammock-like supportive layer of urethra, which could stabilize and help to close urethra during cough. Sling, placing a supportive material behind urethra, had been a staple procedure for SUI and withstood the test of time[21]. Back to continence after RP, we hypothesized “hammock theory” still work on and preferred DF to be the critical structure (Figure-1, 2 and Figure-4), which could uplift vesicourethral anastomosis. Meanwhile, DR just acted as the fulcrum beneath urethra and contributed to closure of it when abdomen pressure increased. Hence, together with DR (also part of DF), DF was supposed to be the critical landmark for continence post RP. Our research also proved that DFS could significantly improve ImC (OR = 26.418, P < 0.001). However, because of individual difference, DF or DR could not be kept intact in every operation. So, we proposed a grading system for DFS procedure and our study showed that different grades can indicate different continence prognosis after RP (Figure-4).
Considering that the scattering neurovascular plexus, which innervates corpora cavernosa and sphincter complex, is embedded in the multiple-layers of DF[3, 22], there was a minority of nerve fibers located in front of DF which would be dissected inevitably[23], while most of them are located in post-lateral and post regions of prostate[3] (Figure-1). Tewari et al[24] proposed a nerve-sparing (NS) grading system based on “landmark vein (LV)” lateral to prostate. An intra-fascial dissection was defined as grade 1, while an extra-fascial dissection was defined as grade 4. Srivastava et al[25] demonstrated that grade 1 achieved more early continence than grade 4(71.8% vs 43.5%), which may account for incomplete continence situation with intact DF.
DF-sparing technique doesn’t equal to complete periprostatic anatomy preservation or intra-fascial dissection. DFS procedure emphasizes dissecting before anterior layer of DF to protect the whole DF fascicles and the majority of neurovascular fibers, which is a procedure with a specific target to be spared, making the incision area selective but thorough. Whereas complete peri-prostate sparing technique aims to preserve functional structure as much as possible[14]. However, good functional recovery may sacrifice safety of tumor control. DF-targeted sparing procedure provides a compromised solution to the dilemma of urinary- or tumor-control. In our research, Group DFS achieved 83.3% ImC, 90.3% continence in 3 months, 91.7% in 6 months, 93.1% in 12 months, better than Group Control at every time point with no difference in PSM (20.8% vs 20.7%, P = 0.988), especially no difference of PSM in post-lateral direction of prostate (4.2% vs 2.4%, P = 0.665).
Another key point to protect neurovascular plexus is the limited usage of energy devices, such as ultrasonic or electronic scalpels, bipolar coagulator, especially during prostate apex anatomy[26], in which nerve fibers penetrate DF or periprostatic tissue to innervate urethral sphincter. The electrical and thermal conduction may cause extra damage to neurovascular fibers nearby. Thereby, “blunt”, or “cold” dissection for prostate apex with finger, forceps, or scissors is preferred. The NS grading system proposed by Patel et al[27] proved the idea. In Patel’s system, grade 5 NS was performed between “landmark artery (LA)” lateral to prostate and PC with neither sharp dissection nor energy devices, which resulted in complete nerve sparing (> 95%). Grade 4 NS (75%) was also performed between LA and PC with sharp dissection but without energy devices.
Last but not least, we preferred to pay more attention to ImC post RP. Temml C et al[28] testified that QoL wasn’t related to duration of incontinence but frequency and degree of incontinence, need for pads, etc. Coyne KS et al[29] pointed out remarkable prevalence of 19.1% anxiety and 6.6% depression in patients with urinary incontinence (UI). Anxiety may trigger and aggravate UI in return. So better ImC may guarantee not only “extra” better continence in the future but also positive mental health.
Indeed, there are limitations in present research including small sample size, retrospective, and lack of randomization. Therefore, a prospective randomized controlled study with larger sample size should be organized for further verification.