Introduction

The anatomical technique for nerve-sparing radical retropubic prostatectomy and post-operative effect on erectile function were first described by Lepor and Walsh in 1983 [1]. Nearly two decades later technology introduced the possibility of a relatively bloodless surgical field and dramatically improved visualization via laparoscopic radical prostatectomy popularized by Guilloneau, Vallencien, and Abbou and subsequently robotic-assisted radical prostatectomy (RARP) popularized by Menon and indeed many of the authors of this book [2, 3]. While early emphasis was placed on proper anatomic dissection of the neurovascular bundle (NVB), more recently, the avoidance of “trauma” to the NVB has surfaced as an important factor. Evidence suggests that trauma to the NVB is as problematic as preservation [4, 5]. Some degree of injury to the NVB occurs in essentially all cases requiring weeks to months to years for recovery. The delay happens as a consequence of surgeon skill and patient resistance/recovery to injury due to baseline health status and age. In this chapter we will examine anatomic principles of cavernous nerve preservation, pathophysiology of nerve injury, athermal and minimal traction techniques for nerve preservation during RARP, and potency outcomes.

Cavernous Neuroanatomy

Walsh and Donker [6] described the tortuous path of the parasympathetic nerves that run from the pelvic plexus past the seminal vesicles and then along the posterolateral aspect of the prostate between the true capsule and the lateral prostatic fascia (the supra-levator pathway); the nerves continue on just posterior and lateral to the urethra where they pierce the urogenital diaphragm and continue on below the pubic bone (the so-called “infra-levator” pathway) where there are delicate neural interconnections at the penile hilum between the cavernous and dorsal nerves (Fig. 20.1) [7, 8].

Fig. 20.1
figure 1

Supralevator and infra-levator neural pathways of the cavernous nerves. This figure was published in Campbell-Walsh Urology, 9th ed., Walsh PC, Partin AW, Anatomic radical retropubic prostatectomy, Copyright Elsevier 2007

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Recently, attention has been given to the network of ganglia and pre and post-ganglionic nerves coursing along with the CN surrounding the rectum, prostate and seminal vesicles.

If one considers the typical course of recovery of erectile function following RP, the two years typically required for recovery is consistent with long established neuroanatomical teachings. The parasympathetic nervous system and specifically the parasympathetic cavernous nerve is characterized by a long pre-ganglionic nerve that is always myelinated and leaves the spinal cord (S2–S4) and travels to the penis where it enters a 2nd ganglion in the wall of corporal bodies and then short (2–3 mms in length) post ganglionic nerves that complete the innervation (Fig. 20.2) [9]. Hence, if during the dissection of the NVB along the edge of the prostate a recoverable injury such as traction or stretch occurs, the nerve should undergo Wallerian degeneration and then regeneration and recovery. Recently some findings have suggested a link to recovery of sexual function to the number of ganglion along the wall of the rectum or SVs in opposition to classical neuroanatomic and physiologic teachings [10,11,12].

Fig. 20.2
figure 2

Anatomical differences between parasympathetic and sympathetic divisions. This figure was published in Campbell-Walsh Urology, 9th ed., Walsh PC, Partin AW, Anatomic radical retropubic prostatectomy, Copyright Elsevier 2007

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Along classical teachings, in 2005, Costello and associates reported a detailed description of the plexus of nerves running within the NVB based upon a series of elegant micro-dissections in human cadavers [13]. They found multiple nerve branches (6–16 in number) that emanated from the pelvic plexus and spread significantly, with up to 3 cm separating the anterior and posterior nerve fibers, much like the findings of Takenaka and colleagues [14]. Importantly, they found in all 24 dissections, the NVB ran 0.5–2 cm inferior to the tip of the seminal vesicle. Similar to Menon, Costello noted that the NVB courses along the posterolateral border of the prostate within the bounds of lateral pelvic fascia, the pararectal fascia, and Denonvilliers’ fascia (Fig. 20.3) [13]. However, in distinction to Menon and associates, they feel that the nerves located within the Veil of Aphrodite innervate the prostate only. They also noted branches to the levator ani and anterior rectum. Similar to Takenaka, Costello found that the nerves converge at the midprostate, forming a more condensed bundle, and then diverge again when approaching the prostatic apex, where they divide into numerous small branches that descend along the posterolateral aspect of the membranous urethra before penetrating the corpora cavernosa. Figure 20.4 demonstrates the functional organization of the NVB according to their findings. Menon contends that additional nerves important for sexual function may exist within the periprostatic fascia that covers the lateral and anterior surface of the prostate (aptly named the Veil of Aphrodite; see Section 20.9) [15]. The authors acknowledge they have not traced these nerves to the corpora cavernosa. They also hypothesize that because the plane of dissection is away from the cavernosal nerves, other factors such as decreased traction, avoidance of thermal injury, and preservation of extra blood supply may also play a role in preservation of nerve function.

Fig. 20.3
figure 3

Position of the NVB and its relationship to the prostate (P), rectum (R), and fascial layers. The widening Denonvilliers’ fascia (DF) laterally fuses with the lateral pelvic fascia (LPF) and pararectal fascia (PF). The posterior and lateral divisions of the NVB run within these fibrous leaves. Reprinted from Costello AJ, Brooks M, Cole OJ. Anatomical studies of the neurovascular bundle and cavernosal nerves. BJU Int 2004;94:1071. With permission from John Wiley and Sons

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Fig. 20.4
figure 4

Functional organization of the NVB: RNV, neurovascular supply to the rectum; DF, Denonvilliers’ fascia; PF, pararectal fascia; LPF, lateral pelvic fascia; LANV, neurovascular supply to levator ani; PNV, neurovascular supply to the prostate; CN, cavernosal nerves. Reprinted from Costello AJ, Brooks M, Cole OJ. Anatomical studies of the neurovascular bundle and cavernosal nerves. BJU Int 2004;94:1071. With permission from John Wiley and Sons

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Pathophysiology and Classification of Cavernosal Nerve Injury

Peripheral nerve injuries (as opposed to central or spinal cord injuries) were initially classified by Sir Herbert Seddon in 1943 (Fig. 20.5) [16]. In this classification, three categories of injury occur: (1) Neurapraxia: a mild compression, blunt impact, or stretch injury to the nerve with no structural damage. A concussion-like state results in a transient conduction block from which full recovery is likely to occur; recuperation may take hours to weeks; (2) Axonotmesis: a moderately severe injury, which results in axonal disruption and Wallerian degeneration; the nerve can regenerate or regrow from the point of injury to the end organ at approximately 2.54 cm/month—recovery takes 8–24 months; (3) Neurotmesis: occurs after severe injury or laceration that transects the nerve completely with no capacity for regrowth. Further, a neuroma or scar may form resulting in a permanent injury with a potential for only partial recovery. During radical prostatectomy, injury to the pelvic nerves and neurovascular bundles occurs along this spectrum of nerve injury. The application of Seddon’s principles to the injury and recovery of function of the cavernosal nerves (CN) was only introduced in 2008 [4]. Basic neurosurgical concepts such as “dissecting the organ off of the nerve as opposed to dissecting the nerve off of the organ” originated from Seddon’s works and are now applied to RARP.

Fig. 20.5
figure 5

Classification of nerve injury according to Seddon [16]. (Illustration by Douglas Skarecky)

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Thermal Injury

The use of “typical” thermal energy on the prostatic pedicle where bipolar cautery is applied to seal arteries promotes desiccation and augments thermal dissemination leading to CN injury. An increase in temperature from just 39 °C–41 °C can produce neural injury [17,18,19]. At 45–55 °C, coagulation occurs [20]. As temperatures continue to rise beyond that point, cell death occurs, with denaturation occurring at 57–60 °C and protein coagulation at 65 °C [21]. Donzelli and associates have shown that both monopolar and bipolar cautery cause thermal injury to nearby neural tissue [22].

Early in our experience, we reported the adoption of an athermal technique to control the prostatic vascular pedicle (PVP) using temporary occlusion of the PVP with bulldog clamps followed by suture ligation [23]. By simply avoiding cautery, potency at 3 months increased from 8 to 38% [23, 24]. However, in the Cautery group, remarkably about 70% of patients had steady recovery of potency [25]. The best explanation for this delay was that although injury to the NVB occurred, the injury was not permanent and the CN could regenerate.

The recommendation to avoid thermal injury during RARP has been well documented. In fact, in 2012 a consensus RARP group recommended that the simplest solution to avoid thermal injury is to not use thermal energy altogether near the NVB [26]. Although complete avoidance of cautery has its stated advantages this method necessitates the use of clips which requires traction. How then does one avoid traction when controlling the PVP? Further investigations into the thermodynamics of cautery by Mandhani, Tewari and colleagues (2008) showed that during RARP both mono and bipolar electrocautery raise temperatures to an equivalent degree but mono-polar cautery appeared to coagulate more efficiently and hence shorter periods of application reduced thermal spread compared to bipolar cautery [27]. Khan, Ahlering and associates demonstrated the thermodynamic impact of heat sink effect by adjacent arteries and veins. They demonstrated in a porcine model that blood flow, though the inferior epigastric vessels, markedly reduced thermal spread [28]. Zorn and colleagues also demonstrated that the pathological findings thermal spread to adjacent tissues can be measurably reduced by using cold irrigation concomitantly with cautery [29]. The use of judicious spot monopolar cautery can control bleeders and minimize traction. When cautery is used we generally use short bursts of intermediate (35 w) monopolar cautery performed in a pinpoint fashion. The addition of cooled saline irrigation may further limit the spread of heat from surgery [29]. We find that point cautery using a single blade of the monopolar scissors is most efficient and precise.

Traction Reduction and Neurovascular Bundle Dissection

As discussed previously, a major mechanism of neuropathic injury is traction. In this regard, there are two primary schools of thought existing with regard to the direction of NVB dissection and minimization of nerve traction. The technique originally described by Walsh is considered retrograde as the prostate is initially freed at the apex and carried back toward the bladder. Walsh notes that if unilateral wide excision is planned, the contralateral NVB should be freed from the prostate at the apex to avoid traction injury [30]. The counter-school favors antegrade dissection of the NVB initially described during laparoscopic RP. Some believe the latter approach has several advantages. First, geometrically speaking, the use of long straight instruments makes the antegrade approach more practical because it is easier to see (especially with a 30° lens). This technique also allows for dissection in an intuitive, straightforward direction toward the penis, as compared to trying to see around the prostate and dissect back toward the bladder. In addition, this dissection may be accomplished with less traction on the NVBs. When contemplating forces associated with traction during the antegrade approach, neurosurgeons dictate there is less risk of traction injury when the prostate is dissected off of the NVB rather than dissecting the NVB off of the prostate.

Patel combines an antegrade and retrograde approach. Before controlling the pedicles with clips, he initiates the separation of the nerve in the mid-prostate and dissects antegrade to the apex and retrograde to the PVP. Patel developed this hybrid technique to more clearly separate the NVB from the PVP. He notes this separation permits precise clipping of the PVP without concern for inadvertent injury to the NVB, which he believes is not necessarily the case with a pure antegrade approach [31].

The principles of “traction and counter-traction” are important in terms of surgical exposure and performing an anatomically correct dissection. On the other hand, these principles are in direct opposition to the neurosurgical premise of “dissecting the tumor off of the nerve”. This basic premise of neurosurgery has been known and taught for decades to avoid undue nerve injuries during procedures across all surgical disciplines. Excessive traction on the neurovascular bundle has profound unintended consequences as the NVB is fragile [5]. Traction injury occurs by direct stretching of the arterio-nervosa causing bleeding in the perinerium leading to secondary inflammation and compression of the axon. When the injury is severe enough to injure the axon, (called axonotmesis) the axon will go through Wallerian degeneration and subsequent regeneration which typically takes 9–15 months. The goal of reducing traction injury is to reduce axonotmesis and hence increase neurapraxia. Neurapraxia is the lowest level of nerve injury similar to a concussion and the nerve regains function within days to weeks. Similar to other specialties in which “dissecting the tumor off of the nerve” is instilled from day 1, we as robotic surgeons must turn our concentration toward minimizing traction during ligation of the PVP and dissection of the NVB especially at the apex. The hallmark of successful reduction in axonotmesis is an obvious increase the percent of men who report erections within the first three months of surgery. This remains a particularly challenging goal for the experienced surgeon and a formidable obstacle for the novice.

Our technique begins with division of the PVP. The transition between the PVP and NVB is reliably identified when after transecting the last vessels in the PVP the prostate typically springs or releases forward. On the right side, we use the fourth arm to gently hold up on the prostate. An inter-fascial dissection is done in antegrade fashion sharply with scissors. As the dissection is carried toward the urethra, the prostate is continually re-grasped with the left hand to “see around the corner” and follow the contour of the prostate. The assistant never uses the suction irrigator to traction the NVB. Bleeders encountered are left alone or sutured. On the left side, the assistant holds the prostate with a grasper just superior-lateral to the seminal vesicle and gently pulls the prostate out of the pelvis toward the camera and medially. The antegrade approach also facilitates the difficult task of separating the NVB at the apex. Near the left apex, a maneuver which can facilitate release of the NVB is to switch the scissors to the left hand for dissection of the left NVB (or to the right for left-handed surgeons). This allows the surgeon to avoid crossing instruments. It is our opinion that inadvertent permanent transection injury occurs most frequently at the left apex due to “crossing” of the hands. Of note transection of the tissues anterior to the urethra (dorsal venous complex and puboprostatic ligaments) has no evident risk of NVB injury.

Inflammatory Damage

Following primary injury either mechanical (dissection, traction) and/or thermal to the NVB there is undoubtedly a secondary wave of inflammatory damage that ensues possibly leading to additional delays in recovery. The inflammatory cascade includes activation of coagulation factors, pro-inflammatory cytokine formation, hypoxia, microcirculatory impairment from endothelial damage, acidosis, free radical production, and apoptosis [32]. Neutrophil and macrophage infiltration with subsequent release of proteolytic enzymes further contribute to tissue destruction [33, 34].

Hypothermia and Reduction of Inflammation

Theoretically, this inflammatory cascade might be blocked or mitigated with the use of local tissue hypothermia. Application of hypothermia pre-emptively (before dissection starts) should prepare tissues for imminent damage by lowering their metabolic rate and oxygen demands. With sufficient temperature reduction, the cell enters into a quiescent state of low energy utilization. When injury ensues, energy reserves are available for repair without going into anaerobic metabolism. As a result, less lactate formation occurs, protein synthesis is preserved, and most importantly, the inflammatory cascade is blunted. With less pro-inflammatory molecules and free radical species generated, the risk of apoptotic cell death is reduced. Tissue damage from leukocyte infiltration is further reduced because cooling also blocks adhesion molecule transcription and inhibits neutrophil adherence [35].

The use of local tissue hypothermia for injury is well established. Everyone is familiar with applying an ice pack to an injured extremity. Icing is well known to greatly reduce pain and edema after closed soft tissue injury [36, 37]. There is objective proof of this therapeutic effect; Schaser and coworkers quantified this effect by assessing microvascular permeability after controlled striated muscle injury in rats with or without superficial cold therapy for 20 min [38]. The cold-therapy group was found to have significantly decreased interstitial fluorescent-labeled albumin levels compared to sham animals. In addition, cold therapy was found to preserve microcapillary density and reduce leukocyte adhesion, chemotaxis, and myonecrosis. Kelly and colleagues showed that regional hypothermia to 4 °C protected against ischemic peripheral nerve injury after prolonged application of a tourniquet to the hind limb in rats [39].

We previously implemented a strategy for local hypothermia using a cooling balloon in the rectum designed to cool the NVBs and urethra. The basic hypothesis was that the most important factor for improving outcomes in experienced surgeons centered on reducing patient related inflammation as opposed to surgeon skill/technique. Our preliminary findings suggested we were able to reduce inflammation and improve continence [40]. However, our recently completed randomized control trial (RCT) failed to show clinical improvement in continence or sexual function in five high-volume surgeons [41]. In the RCT high volume surgeons (500–3500 case experiences) were selected in order to minimize differences in surgeon experience and skill. In the end, it appears that surgeon skill/technique, but not necessarily experience, far outweighed patient related inflammation issues. Recently evidence for alternative anti-inflammatory approaches to reduce the time of nerve recovery has been advocated by Patel et al. [42] and Lee et al. [43] using tissue biografts and an anti-adhesion shield, respectively. Although both approaches have been promising in single surgeon experiences, multi-centered RCTs are necessary to weigh the impact of multiple surgeons and their skill versus patient related inflammatory injury factors.

Preoperative Assessment and Planning and Potency Outcomes

The most important step in counseling patients regarding recovery of sexual function is baseline documentation of their potency. We recommend a minimum of obtaining a International Index of Erectile Function (IIEF-5) also known as SHIM (Sexual Health Inventory for Men), age, medical issues such as hypertension, diabetes, cardiac disease and testosterone levels (free and total). To this end, rigorous data collection and reviewing of personal and expert video recordings facilitates a firm understanding of one’s own experience and outcomes.

A preoperative IIEF-5 score of 22–25 is highly predictive of recovering normal sexual function [44]. However, defining sexual recovery still remains a challenge. We suggest utilizing both a quantitative (EPIC, yes/yes) and qualitative assessment (IIEF-5 score) to clarify sexual function outcomes. The two most important questions in this regard are from the EPIC questionnaire: 1) are your erections adequate for intercourse and 2) are your erections satisfactory [45]? A subjective patient self-assessment comparing erectile firmness as a percentage of pre-operative firmness is also useful in assessing recovery at three months postoperatively [46]. In our experience, we have not had a single recovery following radical prostatectomy in patients with a baseline IIEF-5 below 14. Further, in patients already taking a PDE-5 inhibitor, we recommend subtracting 7 from their baseline IIEF-5 score to obtain a truer assessment of preoperative sexual function.

Lastly, an oncological plan is of utmost importance when counseling the patient. The decision to perform bilateral, unilateral, or wide excision nerve sparing is based on T stage, Gleason score, site and percent involvement of biopsy cores. Some surgeons also assess for extra prostatic extension on magnetic resonance imaging to further guide operative planning [47, 48]. We recommend ipsilateral wide excision with obvious abnormal digital rectal findings and/or higher volume disease (i.e., multiple cores with 50–75%) or high-grade disease (Gleason 4 + 3 or higher).

High Anterior Release and the Veil of Aphrodite

Menon’s technique emphasizes the presence of accessory nerves located in the anterior prostatic fascia which may be important for potency. In this approach, the lateral prostatic fascia is incised anteriorly – the so-called high anterior release (HAR) or Veil of Aphrodite. In 2005, Kaul et al. reported on outcomes with this technique. A total of 154 consecutive men underwent RARP with antegrade NVB preservation and Veil of Aphrodite modification [49]. The dissection for the Veil of Aphrodite begins by entering the intrafascial plane between the prostatic fascia and the capsule, starting infero-laterally near the PVP and carried up to the apex. The authors note that at the conclusion of the dissection, an intact “Veil” of periprostatic tissue should extend from the pubo-urethral ligament to the bladder neck. Among men with an average age of 57.4 and preoperative SHIM of >21, at 12 months 96% were having intercourse (defined as an answer of ≥3 to question 2 of the SHIM), 69% had “normal erections,” and 20.6% achieved a median post-operative SHIM of 22. Of note, oncologic efficacy was not compromised with this technique—positive surgical margin rates among patients with pT2 disease was 5%, mostly at the apex, but none within the region of the Veil of Aphrodite.

Walsh’s group has also described a modification to their interfascial NVB dissection technique which includes a release of the levator fascia much higher on the prostate (more medial and anterior at the apex) than they previously did [50]. In this report, the authors compared outcomes of 93 pre-potent men (IIEF-5 22–25) who underwent bilateral nerve sparing with HAR and 74 patients who underwent standard nerve-sparing radical prostatectomy. Post-operative potency was defined, with or without PDE5 inhibitors, as a IIEF-5 of ≥16 and/or a response of “most times or almost always” to the question “In the last 4 weeks, when you attempted sexual intercourse, how often was it satisfactory to you?” Return to baseline was defined as an IIEF-5 of ≥22. Of note, overall median age was 53 (range 49–57). Patients who underwent unilateral or bilateral nerve sparing with HAR achieved a 90.9% potency rate compared with 76.8% for patients who did not (p = 0.03); 69.7% of men in this HAR group returned to baseline potency status, compared with 54% (p = 0.07). The authors suggest that improved potency with this technique occurs due to decreased traction injury as there was no apparent improvement in outcomes when the HAR was unilateral or bilateral.

Anatomically, there is little evidence to support the notion that HAR release preserves more autonomic nerve fibers important for erections. Using intraoperative electrical stimulation nerve mapping during radical prostatectomy, Takenaka and colleagues found that stimulation at the base of the putative NVB (where the more anterior fibers would be running) increased intraurethral pressures rather than intracavernous pressures [42]. Nerve stimulation at the rectal wall 1 cm posterolateral to the putative NVB resulted in increased intracavernous pressure. This finding was substantiated clinically by the previously described study by Kaul et al. who found improved continence rates with the Veil of Aphrodite technique (97% required no pads at 12 months) [49].

Effect of Unilateral Wide Excision on Potency

Excision of one of the NVBs may be necessary in efforts to control cancer. Walsh et al. [51] and Kundu et al. [52] both reported their experience with unilateral nerve-sparing (UNS) surgery. In 1987, Walsh et al. reported that 69% of men potent before RP who had unilateral wide excision were potent after RP, compared to 85% who had bilateral NS (BNS). Kundu et al. reported a similar trend in overall potency rates at 18 months, of 53 and 76% after UNS and BNS RP, respectively. A unifying theme among these reports is that reducing the volume of nerve tissue by 50% only reduced potency rates only by about 15–20%. In 2009 we similarly reported the impact on potency and time to recovery of potency in men undergoing either unilateral versus bilateral nerve preservation [53]. We defined wide excision as all tissue from the midline of the rectum from the bladder neck to the urogenital diaphragm. We analyzed a highly select group aged ≤65 years with normal IIEF-5 scores (22–25) to insulate the analysis from confounding patient-related variables.

The 2-year potency (yes/yes) outcomes in men undergoing BNS was 92% and in men undergoing wide excision of one nerve was 80%. About a 15% reduction in potency outcomes after a 50% reduction in nerve volume speaks to significant redundancy. Further qualitatively speaking the average IIEF-5 in men undergoing successful BNS versus successful UNS was 22.0 (20.2–23.8) versus 21.0 (19.8–22.1), respectively (P = 0.37). Another qualitative assessment, patient-reported “fullness of erections”, showed similar findings to the IIEF-5 scores. Hence the redundancy is remarkable as the quality of erections was similar in men with one versus two nerves spared. The time-line to recovery with UNS and BNS were parallel suggesting crossover rather than compensation as accounting for the mechanism of redundancy. Similar findings with open and laparoscopic techniques have been reported by others; with ratios of 1.1–1.43 [53,54,55,56]. This information implies that there is significant nerve redundancy and questions the logic of intra-fascial nerve sparing and the risk of a positive surgical margin.

Testosterone and Recovery

Symptoms of hypogonadism include erectile dysfunction, low libido, fatigue, mood changes, decreased bone mineral density, increased body fat and associated co-morbid conditions such as cardiovascular disease, neurovascular disease, diabetes and metabolic syndrome [57]. Hypogonadism is defined in males by the combination of specific symptoms and testosterone levels below 350 ng/dl or 230 ng/dl [58]. In the setting of prostate cancer, calculated free testosterone (FT) appears to be more clinically significant [59]. The FT level has two implications: higher free testosterone levels appear to favorably predict low grade Gleason score and faster recovery of sexual function. Thus, it is important to obtain both pre-and postoperative testosterone and free testosterone levels. Further, in patients who are hypogonadal post-surgery, it is reasonable to consider testosterone replacement therapy in carefully selected men who are compliant with follow-up. Evidence shows that testosterone therapy can be safe in the post-prostatectomy setting. While PSA levels may rise in association with testosterone therapy, prostate cancer recurrence rates are not effected [60].

Postoperative Prophylaxis for Erectile Dysfunction

Radical prostatectomy has significant effects on the vasculature to the corpora cavernosum. Approximately half of patients experience venous insufficiency and 50% of patients experience arterial insufficiency, leading to fibrosis and loss of smooth muscle [61]. Rat models have shown endothelial cell apoptosis, decreased nitric oxide levels, and hypoxia contribute to fibrosis [62].

Several studies have explored methods to prevent fibrotic changes and promote sexual recovery. Montorsi and associates reported that 6 months following surgery spontaneous erection occurred in 67% of patients who performed self injection with PGE-1 compared to 20% in patients that did not use injection therapy. Moreover, only 17% of patients who injected PGE-1 developed venous leak by doppler ultrasound criteria versus 53% of patients who did not [63]. Studies examining vacuum erection devices (VED) have shown similar results [64]. Finally, Padma-Nathan et al. showed that nightly sildenafil following radical retropubic prostatectomy resulted in higher rates of recovery of full potency (27% vs. 4%) in a randomized trial [65, 66]. Schwartz and colleagues performed a histological study to examine the effects of sildenafil, finding that higher doses (100 mg vs. 50 mg every other night) results in greater volume of cavernosal smooth muscle fibers in post-operative biopsies [67]. In a 2014 randomized trial, Montorsi and colleagues that showed tadalafil hastened recovery [68].

Still existing studies are limited and lack sufficient numbers. As a result, at this time, there is no clear consensus. Our current regimen is 5 mg of tadalafil nightly starting on postoperative day 1. For those patients who are highly motivated, PGE-1 self-injection three times per week is also offered. Alternatively, adding an VED to a daily tadalafil can be initiated to prevent issues with penile girth and length in motivated patients; we recommend 10 min a day without a constriction band [69].

Conclusion

With increased understanding of the neuroanatomy of the male pelvis efforts to preserve the cavernosal nerves during radical prostatectomy have been met with increased success. Extraordinary care should be taken to avoid electrocautery, excessive heat application, and traction in the vicinity of the cavernous nerves. Our results using a cautery-free minimal traction technique seem to promote the return of erectile function. These efforts can be enhanced with prophylactic medications.