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Anatomic and technical considerations for optimizing recovery of sexual function during robotic-assisted radical prostatectomy

Carter, Stacey; Le, Jesse D.; Hu, Jim C.

doi: 10.1097/MOU.0b013e32835b6602
ROBOTICS: Edited by Jim Hu
Free

Purpose of review Although cure of prostate cancer is the primary goal of radical prostatectomy, preserving erectile function is also tantamount, given the indolent clinical course of most prostate cancers, particularly low-risk disease. In order to optimize postprostatectomy erectile function during a robotic-assisted radical prostatectomy, there must be a detailed understanding of pelvic anatomy to recognize the optimal nerve-sparing plane and technical finesse to minimize stretch injury to the neurovascular bundle.

Recent findings The magnified, well illuminated robotic-operative field coupled with less blood loss has paralleled greater understanding of the periprostatic ‘fascial’ planes, leading to differentiation of intrafascial versus interfascial nerve-sparing approaches. However, refinement of tissue handling during nerve-sparing to minimize lateral displacement of the neurovascular bundle and attenuate neurapraxia enables earlier and better recovery of erectile function.

Summary The critical maneuvers to preserving erectile function are atraumatic dissection of the prostate away from the optimal nerve-sparing plane to maximally preserve nerve fibers while minimizing neurapraxia. Therefore, attaining these principles involves a conceptual paradigm shift from ‘radical’ prostatectomy to neurosurgery of the prostate.

Department of Urology, David Geffen School of Medicine at University of California, Los Angeles, California, USA

Correspondence to Jim C. Hu MD MPH, 924 Westwood Blvd, Ste. 1000, Los Angeles, CA 90095, USA. Tel: +1 310 825 1172; e-mail: JCHu@mednet.ucla.edu

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INTRODUCTION

For men diagnosed with localized prostate cancer, radical surgical resection of the prostate versus watchful waiting improves disease-specific survival [1]. However, due to the morbidity of the procedure in terms of a high likelihood of blood transfusion, incontinence and erectile dysfunction, radiotherapy was the preferred treatment prior to Walsh's anatomic discoveries and technical refinement toward anatomic radical prostatectomy [2]. The use of robotic assistance has transformed the surgical treatment of prostate cancer. In effect, surgeons have a wider margin for error in terms of pelvic venous blood loss, as both the median and range of blood loss have decreased in the transition from open to robotic-assisted radical prostatectomy [3▪]. Moreover, patient perception of new technology coupled with smaller incisions and less blood loss may increase the appeal of radical prostatectomy as compared to radiation therapy options and the potential anxiety of active surveillance.

Although cancer control is the primary goal of this operation, unintended side-effects associated with surgical resection, such as urinary incontinence and erectile dysfunction, present a technical challenge for urologic surgeons. Likewise for patients, postoperative health-related quality of life (HRQOL) is of important consideration when selecting a course of treatment for prostate cancer [4▪,5]. Among postoperative HRQOL outcomes, decreased potency following radical prostatectomy is commonly reported and is associated with poor postoperative quality of life [5,6]. Surgical technique has evolved in recent decades to improve postoperative potency without sacrificing oncologic control. Recent data suggest that the prevalence of postprostatectomy erectile dysfunction ranges from 64 to 80%, when the operation is performed using a nerve-sparing technique [7]. However, the ability to accurately quantify postprostatectomy erectile function remains challenging despite the use of validated HRQOL instruments, such as the University of California, Los Angeles Prostate Cancer Index, Expanded Prostate Cancer Index, and the Sexual Health Inventory for Men [8–11] Difficulties in administering such instruments to ensure patient versus physician reporting and the use of continuous scores in the instruments to measure what many perceive to be a dichotomous outcome of potent versus impotent remain barriers to the widespread adoption of standardized measurement of sexual function. Therefore, variation in methodology and outcomes from published series confound cross-study interpretation [12]. Despite difficulty in accurately assessing postprostatectomy erectile function, there have been continued efforts to refine surgical approaches and develop operative techniques in an effort to improve functional outcomes after radical prostatectomy. The evolution in the understanding of prostate anatomy with advances in surgical technique in the context of robotic surgery is evaluated in this review.

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WALSH ANATOMIC RETROPUBIC RADICAL PROSTATECTOMY

In 1982, Walsh published his technique for an anatomic approach to radical prostatectomy, taking into careful consideration the blood supply and periprostatic anatomy in an effort to reduce blood loss and overall morbidity. Through his study of cadaveric models he identified the pelvic plexus as the autonomic innervation of the corpora cavernosum and the basis for neurophysiologic control of erectile function. He noted that the neurovascular bundle (NVB) coursed in a dorsolateral fashion to the prostate between the rectum and the urethra, proposing that injury to this structure is correlated with decreased postprostatectomy potency. His technique to avoid injury to these nerves involved incising the lateral pelvic fascia anterior to the NVB and dividing the lateral pedicle close to the prostate, avoiding injury to the branches of the pelvic plexus and the surrounding capsular vessels [13]. This served as the basis for the ‘nerve-sparing’ radical prostatectomy in which the neurovascular bundles are preserved, resulting in improved postprostatectomy potency [14]. Further review revealed that potency may be preserved when sparing either bilateral or unilateral NVBs [14–16]. Importantly, no significant difference in positive surgical margins was noted for nerve-sparing procedures in men with organ-confined disease or with extracapsular extension, suggesting that the nerve-sparing operation provides oncologic control while preserving functional outcomes [17▪,18,19].

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EXPANSION OF ANATOMIC PRINCIPLES

The introduction of the nerve-sparing prostatectomy paved the way for further detailed study of the periprostatic neuroanatomy. In 2004, Costello et al.[20] expanded upon Walsh's initial efforts, again using cadaveric models to further detail the precise anatomy of the neurovascular bundles as they relate to the prostate and seminal vesicles. They identified three functional components of the neurovascular bundle. The posterior and posterolateral component runs within Denonvillier's and pararectal fascia and innervates the rectum. A second component in the lateral NVB supplies the levator ani, and finally the cavernosal nerves and prostatic neurovascular supply originally described by Walsh and Donker [13] lie along the posterolateral surface. At the base of the prostate and at the seminal vesicles, the organization of these nerve bundles is rather chaotic, further detailing the complexity of the NVBs and the challenges of performing a technically sound nerve-sparing procedure [20]. In 2006, Eichelberg et al. further illustrated the great variability in the distribution of nerves, using postoperative specimens to demonstrate that while the majority of the periprostatic nerves were found in the posterolateral location as initially described, approximately one-third were located on the anterior surface. They suggest using a higher incision along the ventral surface of the prostate during nerve-sparing to account for this variability [21]. Takenaka, et al.[22] confirmed this finding and described the nerves to be on the lateral and anterolateral surface of the prostate distributed as multiple fine fibers. Other authors have proposed performing a more anterior incision of the lateral pelvic fascia [23]. Taking into account these recent findings regarding the anterior distribution of the nerves, Walsh recently refined his technique, describing a ‘high-anterior release’ of the apical NVB to avoid injury via excessive traction or electrocautery [24].

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EVOLUTION OF NERVE-SPARING WITH ROBOTIC SURGERY

Efforts to detail precise periprostatic anatomy were spurred with the introduction of the robotic-assisted laparoscopic radical prostatectomy (RALP) in 2001 [25]. Robotic surgery offered a new perspective on prostatic anatomy, allowing for a 12-fold magnified three-dimensional view and articulating robotic arms providing wristed, seven-degree motion. Furthermore, the pneumoperitoneum assists in providing a bloodless field for improved visualization of precise anatomic structures [26]. In 2003, Tewari et al.[27] detailed the prostatic anatomy from the perspective of this laparoscopic approach and identified webs of several smaller nerves with a more variable course than previously thought. This was further described as a ‘hammock-like’ distribution, suggesting that the nerves are dispersed along the lateral surface and do not form a single distinct structure.

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INTRAFASCIAL AND INTERFASCIAL NERVE-SPARING

By taking into account the previously described anatomic principles and implications of delicate and athermal nerve dissection, several techniques have been proposed to optimize recovery of sexual function using a robot-assisted laparoscopic approach. The intraoperative magnification offered by the robot and wristed surgical instruments enables identification and preservation of periprostatic fascial planes housing the nerve fibers [26]. A thorough understanding of these planes is crucial for performing an anatomic dissection while avoiding mechanical and thermal injury to the NVBs [28]. The endopelvic fascia comprises multilayered connective tissue that encases the prostate and bladder and supports these structures by inserting onto the pubic bone as the puboprostatic ligaments. The layer of fascia that directly covers the prostate is the prostatic fascia, forming an intrafascial plane between this and the capsule. Just exterior to this laterally is the levator fascia, part of the parietal fascial layer, which serves as the boundary for an interfascial plane. Posteriorly, this same interfascial plane is bound by Denonvilliers fascia. Dissection along these avascular planes allows preservation of the neurovascular bundles, as the majority of the NVB is thought to run between the anterior extension of Denonvilliers fascia and the levator fascia. Dissection external to this – in the extrafascial plane – risks direct injury to the NVB and is shown to have significantly poorer sexual function outcomes [29–31]. Many authors advocate an interfascial dissection as a method of performing a nerve-sparing procedure without compromising oncologic control in appropriately selected patients [32]. Some caution against performing an intrafascial nerve-sparing operation at the risk of positive surgical margins, particularly in those patients with T3 disease. Other studies have supported its use in that it offers improved potency with similar oncologic outcomes [33–35].

The ‘Veil of Aphrodite’ was first described by Menon and Hemal in 2004 [36,37] and refers to a plane of cavernosal nerves extending from the posterolateral to anterolateral surface of the prostate in a curtain-like distribution. Just as open surgeons utilize a high anterior release of the lateral pelvic fascia to preserve the anterior nerves, robotic prostatectomists propose this similar technique. An avascular interfascial plane is entered between the prostatic fascia and the lateral pelvic fascia. The ideal site of entry into this plane is debatable, as some authors propose incising the fascia laterally at the base and developing a plane towards the apex, whereas others suggest improved visibility using a posterior approach through Denonvilliers fascia [37,38]. Regardless of the initial entry point, the goal is to dissect within the interfascial plane to dissect the prostate medially while preserving the NVB laterally, creating a ‘veil’ of spared neurovascular tissue that is suspended from the pubourethral ligaments. Subsequent data have confirmed that this technique does not increase positive surgical margins and offer improved potency outcomes as compared to a conventional nerve-sparing procedure [37,39,40]. Menon et al.[41] report that in 85 patients in whom the ‘Veil of Aphrodite’ technique was used, 94% had erections sufficient for penetration at a median follow-up of 18 months when using phosphodiesterase-5 inhibitors. However, Ganzer et al.[42▪] used immunohistochemical staining to map the distribution of the parasympathetic proerectile nerve fibers to largely course posterior to the horizontal axis of the prostate, calling into question whether high-release ‘Veil of Aphrodite’ dissections result in greater periprostatic tissue bulk scaffolding along the neurovascular bundle to attenuate nerurapraxia and improve erectile function rather than leaving more nerve fibers behind.

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ATHERMAL HEMOSTASIS

As the understanding of the anatomic distribution of the nerves continued to evolve, methods for tissue dissection were also examined. Ong et al.[43] used canine models to demonstrate that the use of electrocautery for hemostasis during dissection of the NVB results in significant decreased erectile response and recommend avoiding its use during nerve-sparing procedures. Further support of athermal dissection for preservation of erectile function is illustrated by Ahlering et al. in a case series demonstrating better erectile function for nerve-sparing without the use of cautery [44]. A recent systematic review showed significant improvement in 12-month potency rates using a cautery-free technique [45▪]. Additionally, while some advocate using the harmonic scalpel during prostate pedicle ligation and nerve-sparing due to less nerve injury relative to electrocautery, the heated tip of the harmonic scalpel may easily damage unmyelinated nerve fibers that comprise the neurovascular bundle [46].

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MINIMIZING NEUROVASCULAR BUNDLE DISPLACEMENT DURING NERVE-SPARING AND NEURAPRAXIA

Although many studies have focused on achieving the optimal fascial plane of dissection, other authors have investigated the effect of intraoperative traction to the NVB on surgical outcomes. The mechanical stretch neuropathy has been demonstrated in vivo animal models [47]. Mulhall et al.[48] suggested that in addition to nerve dissection, neurogenic erectile dysfunction may also develop transiently due to mechanical traction. Rassweiler et al.[49,50] minimize traction to the NVB during seminal vesicle dissection, asserting the cavernous nerves are at especially high risk of traction injury during this step because the NVB runs in such close proximity. Kaul et al.[50] believe delayed dorsal vein complex ligation and endopelvic fascia sparing reduces traction on the NVB and cavernous nerves during dissection of the prostatic fascia. Tewari et al.[51] exclusively employ sharp dissection and avoid excessive traction during NVB release.

Mattei et al.[52] hypothesized that excessive traction on the NVB and the resultant neuropraxia have negative effects both on continence and erectile function, detailing their technique for a tensionless, energy-free approach. They also describe vascular control in an athermal manner, using only microclips, and additionally advocate preservation of the bladder neck, early release of the NVB, dissection of the seminal vesicles only after complete lateral dissection of the NVB, and the use of the fourth robotic arm for constant tension-free exposure. However, media from some of these studies demonstrate assistant surgeon suction counter-traction of the neurovascular bundle to facilitate nerve-sparing. In contrast, Kowalczyk et al.[53▪] demonstrated an earlier return of sexual function and potency after a technical modification specifically avoiding assistant countertraction on the NVB during dissection (Fig. 1). They found clinically significant higher sexual function scores at 5-months postoperatively in a retrospective series of patients undergoing RALP, after adjusting for preoperative variables and nerve-sparing status, whereas no difference was found at 12-months, which the authors attribute to temporary neuropraxia. Additionally, after eliminating continuous assistant counter-traction of the neurovascular bundle, Alemozaffar et al.[54▪] minimized lateral displacement of the neurovascular bundle inherent in the use of blunt dissection to peel the neurovascular bundle away from the prostate (Fig. 2), demonstrating improved 5 and 12-month recovery of sexual function (Fig. 3).

FIGURE 1

FIGURE 1

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

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SURGICAL LEARNING CURVE

Several high-volume surgeons with large series have reported on sequential surgical, oncologic, and functional outcomes, lending insight into the effect of a learning curve on RALP. Secin et al.[34] have also reported a large international, multicenter study on the effect of the learning curve on positive surgical margin outcomes. However, less is known regarding a learning curve effect on sexual function. Zorn et al.[55] reported improvement in operative time, blood loss, positive margins, and urinary continence, but no significant differences were demonstrated in sexual function at 12 months in a 700 patient series, despite increased surgeon experience. Conversely, Alemozaffar et al., through video review, demonstrated a learning curve for preservation of erectile function during robotic-assisted radical prostatectomy that comprised 413 cases to consistently achieve the nerve-sparing dissection plane, 268 cases to become independent of continuous countertraction to facilitate nerve-sparing dissection, and 400 cases to attenuate transient lateral displacement of the neurovascular bundle. Additionally, trainee involvement at the surgeon console during the nerve-sparing step was associated with worse erectile function recovery, emphasizing the existence of a significant learning curve for maximizing erectile function outcomes [54▪]. Moreover, this finding highlights the need for procedure-specific robotic simulators to overcome the nerve-sparing learning curve for neophyte robotic surgeons.

Gumus et al.[56] also defined a learning curve in reporting improved potency rates in a smaller series of 120 men. Although cross-comparisons are made difficult by varying definitions of potency in the literature, the authors suggest that a surgeon without previous experience may be able to achieve similar functional results as some high-volume centers after 80 cases. However, there was no mention of specific technical modifications that improved potency outcomes.

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CONCLUSION

From Walsh's initial description of an anatomic approach to radical prostatectomy to the advent of robotic prostate surgery, advances in the understanding of the neurovascular supply of the prostate have been met with continued evolution in surgical technique. Further understanding of prostatic fascial planes, the adoption of athermal, cautery-free technique and efforts to minimize traction during nerve dissection has enabled continued advances in optimizing recovery of sexual function.

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Acknowledgements

None.

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Conflicts of interest

There are no conflicts of interest.

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REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

  • ▪ of special interest
  • ▪▪ of outstanding interest

Additional references related to this topic can also be found in the Current World Literature section in this issue (pp. 102–103).

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REFERENCES

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42▪. Ganzer R, Stolzenburg JU, Wieland WF, Brundl J. Anatomic study of periprostatic nerve distribution: immunohistochemical differentiation of parasympathetic and sympathetic nerve fibres. Eur Urol 2012; 62:1150–1156.

This is a peer-reviewed journal article in which the authors characterize the distribution of periprostatic nerves using immunohistochemical analysis to identify proerectile parasympathetic nerves from sypathetic nerves on whole-mount sections of prostates following nonnerve-sparing laparoscpic radical prostatectomy The purpose was to identify the quality of nerves in the ventrolateral position of the prostate to enhance surgical planning for improved potency results. They found that only a minority of the ventrolateral periprostatic nerves were of parasympathetic proerectile quality, and thus a high incision of the prostate during nerve-sparing operations may help to preserve more parasympathetic nerves at the base and middle, but is of little help at the apex.

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45▪. Ficarra V, Novara G, Ahlering TE, et al. Systematic review and meta-analysis of studies reporting potency rates after robot-assisted radical prostatectomy. Eur Urol 2012.

This is a systematic review and meta-analysis designed to evaluate the prevalence and risk factors of erectile dysfunction after robotic-assisted radical prostatectomy and to identify surgical techniques that may improve the rate of potency recovery. The purpose was to compare Robot-assissted radical prostatectomy to open radical prostatectomy had laparoscopic radical prostatectomy in terms of postoperative potency rates. The authors are the first to conclude that there is a significant advantage of RALP compared with the open radical retropubic prostatectomy approach in terms of 12-month potency rates and that the use of a cautery-free technique improves the incidence of potency recovery.

46. Chen C, Kallakuri S, Vedpathak A, et al. The effects of ultrasonic and electrosurgery devices on nerve physiology. Br J Neurosurg 2012. [Epub ahead of print]
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50. Kaul S, Savera A, Badani K, et al. Functional outcomes and oncological efficacy of Vattikuti Institute prostatectomy with Veil of Aphrodite nerve-sparing: an analysis of 154 consecutive patients. BJU Int 2006; 97:467–472.
51. Tewari AA, Takenaka AA, Mtui EE, et al. The proximal neurovascular plate and the tri-zonal neural architecture around the prostate gland: importance in the athermal robotic technique of nerve-sparing prostatectomy. BJU Int 2006; 98:314–323.
52. Mattei A, Naspro R, Annino F, et al. Tension and energy-free robotic-assisted laparoscopic radical prostatectomy with interfascial dissection of the neurovascular bundles. Eur Urol 2007; 52:687–695.
53▪. Kowalczyk KJ, Huang AC, Hevelone ND, et al. Stepwise Approach for Nerve Sparing Without Countertraction During Robot-Assisted Radical Prostatectomy: Technique and Outcomes. Eur Urol 2011; 60:536–547.

This is a retrospective study in which the authors compare potency outcomes following nerve-sparing robot-assisted radical prostatectomy when performed with and without countertraction on the neurovascular bundle. They demonstrate that use of countertraction results in neuropraxia and delayed recovery of sexual function and potency. The authors describe a stepwise surgical technique to perform nerve-sparing without countertraction.

54▪. Alemozaffar M, Duclos A, Hevelone ND, et al. Technical refinement and learning curve for attenuating neurapraxia during robotic-assisted radical prostatectomy to improve sexual function. Eur Urol 2012; 61:1222–1228.

This is a retrospective study of 400 consecutive nerve-sparing robot-assisted radical prostatectomy in which the authors demonstrate and quantify the learning curve for improving sexual function outcomes. The specific technical modifications that were made over the course of the 400 surgeries that contributed to the improvement in outcomes are included in the article.. The authors conclude that improved postoperative sexual function was associated with greater surgeon experience, younger patient age, and better preoperative sexual function. The authors find that attentuating lateral displacement of the neurvascular bundle decreases neuropraxia, thus improving postoperative sexual function.

55. Zorn KC, Wille MA, Thong AE, et al. Continued improvement of perioperative, pathological and continence outcomes during 700 robot-assisted radical prostatectomies. Can J Urol 2009; 16:4742–4749.
56. Gumus E, Boylu U, Turan T, Onol FF. The learning curve of robot-assisted radical prostatectomy. J Endourol 2011; 25:1633–1637.
Keywords:

prostate anatomy; robotic-assisted radical prostatectomy; sexual function; surgical technique

© 2013 Lippincott Williams & Wilkins, Inc.