Inflatable penile prosthesis in the radical prostatectomy patient: a review

Erectile dysfunction (ED) rates after radical prostatectomy (RP)

Penile erection is the culmination of complex series of highly integrated phenomena involving the central nervous system, peripheral nervous system, endocrine system and the vascular system. These systems must be working in concert and at a high level in order for full erection to occur. ED may occur when there is an impairment or derangement to any of these systems. ED has been defined as the inability of a man to achieve or maintain an erection sufficient for satisfactory penetrative sexual intercourse¹.

Post-RP ED may be neurogenic, venogenic, arteriogenic or a combination of these etiologies. In all cases, injury of the cavernous nerves occurs during dissection of the prostate. The injury, whether caused by contact, traction, electro-cautery or transection, initiates a cascade of events that culminates in ED. Microscopically, cavernous nerve-fiber injury initiates Wallerian degeneration that will incapacitate the axon back to the cell body, typically at the level of the spinal cord. The lack of nervous input at the end-organ (cavernous muscle) is a major contributor to cavernosal tissue degeneration and atrophy^2,3. Venous leakage is another underlying mechanism responsible for ED after prostatectomy. Bilateral cavernosal nerve injury has been shown to induce cavernosal smooth muscle death which will lead to veno-occlusive dysfunction³. Chronic hypoxia, denervation, and activation of the TGF-β cascade are believed to initiate the apoptosis process, and increase the deposition of collagen-laden scar tissue^4–7.

The initiating factor in the development of arteriogenic ED as a result of radical pelvic surgery is transection of the accessory pudendal arteries. These arteries arise from the peri-prostatic vasculature and course toward the penis and providing a significant portion of the arterial inflow required for normal erectile function^8,9.

The incidence of post-prostatectomy ED has been reported to be between 29-88%^10–16. This wide range of values can largely be attributed to failure to control various confounding factors including age, degree of nerve sparing, different definition of potency and preoperative ED. The CaPSURE study revealed that only 20% of patients returned to their preoperative baseline potency levels 1 year after RP¹². In the Prostate Cancer Outcome Study (PCOS), 59.9% of men self-reported having ED following RP¹⁴. Similar results were found by the Memorial Sloan-Kettering Cancer Center group^17–19. According to The Scandinavian Prostate Cancer Group, men who chose watchful waiting had a 45% incidence of ED. Those that selected RP as a treatment option experienced an incidence of ED at 80%²⁰.

Inflatable penile prosthesis (IPP) utilization after RP

Phosphodiesterase-5 inhibitors (PDE5Is) initially were the first-line treatment for ED secondary to RP. However, they are not uniformly effective. In a subset of patients who initially respond, the response deteriorates over time as progressive cavernosal tissue damage occurs and subsequent venous leak develops^18,21,22. Penile implant surgery is a viable treatment option in patients in whom nonsurgical ED treatments are unsatisfactory or are associated with adverse effects²³. The utilization rate of penile implants after RP varies from 0.8 to 1.9%^24,25. These reported rates have been obtained from analysis of the Surveillance Epidemiology and End Results (SEER) cancer registry database. The higher rate of 1.9% in a study by Stephenson et al.²⁵ is probably due to a younger cohort, as 45% of subjects were younger than 65 years. There are numerous reasons that could be postulated for low utilization of penile implants. Firstly, prostate cancer treatment modalities have improved, thereby decreasing the incidence of ED that is unresponsive to nonsurgical intervention. Secondly, effective nonsurgical treatment modalities have been developed as alternatives to surgical treatment, predominantly PDE5Is. Meta-analysis of contemporary publications by Tal et al. revealed an overall erectile function recovery rate of 58% among men younger than 60 years after RP²⁶. The study acknowledged that the definitions of ED were different in each member study and some men used of PDE5i’s for erectile rigidity²⁶. Nevertheless, Stanley et al. found that there was no significant change in total number of penile implant procedures over a 10-year period before and after the introduction of sildenafil citrate²⁷.

Surgical considerations

Reservoir placement

The reservoir is normally placed in space of Retzius. This is done to reduce the creation of inguinal floor weakness and to reduce the potential risk of visceral injury. After ensuring complete bladder drainage, the index finger is placed through the IPP incision and advanced to the medial aspect of the external inguinal ring. Using firm pressure, the finger is advanced in a posterior direction, piercing transversalis fascia. If finger pressure is inadequate, the fascia can be perforated with the tip of an instrument (scissors or clamp). This action will create a rent large enough to insinuate an index finger into the space of Retzius. Alternatively, a long-bladed nasal speculum is useful in expanding the retroperitoneal space.

If the space of Retzius is obliterated due to previous pelvic surgery, ectopic placement of the reservoir should be considered^40,41. The reservoir may be placed in the deep to the abdominal musculature superior or posterior to transversalis fascia⁴². A Foerster or Debakey clamp may be used to advance the deflated reservoir to its ectopic position. Stember et al reported the outcomes of 2687 men who underwent ectopic reservoir placement⁴². In total, 83%, of men had reservoirs placed posterior to the transversalis fascia. The remainder had reservoirs placed in the anterior transversalis space. No injuries to the bowel or major blood vessels occurred with initial insertion of the reservoir, however two patients experienced bladder injury. Eight patients required reservoir revision secondary to herniation⁴².

Satisfaction rates after penile prosthesis implantation

Serial reports regarding of penile prosthesis surgery outcomes demonstrate excellent long-term mechanical reliability of contemporary prosthesis models; satisfaction is superior when compared to PDE5Is and injections. Carson et al. performed a retrospective long-term multicenter study on 372 patients who underwent penile prosthesis implant and focused on the longevity, morbidity and patient satisfaction⁴⁷. More than 80% of patients were satisfied with the function of the device, the ease of inflation, and level of rigidity. Steege et al. reported that patient satisfaction with semi-rigid prostheses was higher than 90%, however, inflatable devices enjoy a slightly higher satisfaction⁴⁸. Holloway and Farah reported that the AMS 700 Ultrex prosthesis had a 86% patient and 76% partner satisfaction at a mean postoperative follow-up of 42 months⁴⁹. In a study by Rajpurkar et al., the investigators demonstrated significantly enhanced erectile function and sexual satisfaction when compared to those receiving sildenafil and intracavernosal prostaglandin⁵⁰.

The psychosexual adaptation to penile implant may take up to 6 months. The patients experience a marked enhancement in erectile function with elevation of libido. Apprehension regarding the maintenance of an erection during intercourse is markedly assuaged. In addition to an upsurge in the regularity of sexual activity, a decrease in feeling of sadness, depression, anxiety and an improvement in sexual satisfaction has also been noted⁵¹.

Two major factors contributing to high level of satisfaction are rapid generation of erection and consistently excellent rigidity. Other factors, such as degree of postoperative pain and swelling, postoperative complications, ease of concealment, cosmetic outcome, device function, ease of use and partner acceptance, are critical in determining the patient satisfaction. Potential predictors of patient dissatisfaction with penile prosthesis include Peyronie’s disease, a body mass index >30, or previous RP⁵².

Predictors of requiring a penile prosthesis

The natural recovery time of erectile function may be up to 24 months after radical pelvic surgery; however, resultant penile rigidity may be maximized by early treatment with intracorporal injection therapy^53–55. Various different symptomatic treatments are available for patients who fail to regain a natural erection. Sildenafil becomes effective in the late recovery phase as the nerves recover from intraoperative injury⁵⁴. At 2 or more years from surgery, the recovery of natural function and improved response from other therapies is unlikely and implantation of penile prosthesis is warranted⁵⁴. A study by Tal et al. found that men who had surgery as an initial treatment (versus radiotherapy), were of a younger age, were of African/American/Hispanic race, were unmarried, and were living in a geographic region other than the North-east were more likely to utilize penile implants²⁵. Similarly, in a retrospective analysis of claims data from Medicare & Commercial databases of 3928 men undergoing penile prosthesis, Segal and Burnett elucidated the factors with the greatest predictive strength of penile prosthesis implantation, which included a diagnosis of prostate cancer, a diagnosis of diabetes mellitus and previous treatment with first-line ED therapy⁵⁶.

Conclusion

In the population of patients with prostate cancer, the concept of survivorship has become a central tenet of patient care. To that end, quality of sexual life, and especially erectile function has become a significant issue. Penile prosthesis surgery remains an excellent option for restoring erectile function to those who fail more conservative measures. IPP implantation enjoys high satisfaction rates for patients and their partners. Intraoperative complications can be distressing, but with prompt recognition, most of these complications can be navigated with excellent postoperative results.

Data availability

No data are associated with this article.