Penile Prosthesis Implantation

Anatomy and Physiology

A comprehensive grasp of penile anatomy and physiology is imperative for successful penile prosthesis implantation. The penis contains 3 main erectile compartments: the corpus spongiosum, which surrounds the urethra, and the paired corpora cavernosa, which constitute the primary erectile bodies. These compartments are interconnected by a shared midline septum, facilitating fluid communication.

The corporal bodies are enveloped by several layers of fascia crucial for erection. The outermost layer comprises the penile skin, surrounding the superficial (Dartos) fascia. Beneath this lies the deep (Buck) fascia, dividing to encase the corpus spongiosum ventrally and the corpus cavernosum dorsally. A dense, tough layer of inelastic connective tissue, the tunica albuginea, covers the cavernosal bodies. During an erection, blood filling the corporal bodies stretches the tunica albuginea fibers, inducing penile rigidity.

The blood supply to the erectile tissues is multifaceted. Superficially, the external pudendal arteries supply the penile skin. The internal pudendal artery maintains the deep blood supply with 3 main branches to the penis.[4] The bulbourethral artery and the circumflex arteries supply the urethra and glans, which comprise the corpora spongiosa. Finally, the cavernosal arteries branch once more to form the helicine arteries, which dilate with neural parasympathetic stimulation to produce an erection.[5] There are multiple anastomotic connections between these vessels.[6] The venous drainage of the erectile bodies is unpredictable. Most often, the cavernosa and spongiosum drain into emissary veins, which collect into the dorsal vein of the penis.[7] The periprostatic plexus serves as the drainage endpoint for these erectile tissues.[7] 

Penile neural supply and innervation are variable; however, the pathways responsible for erection are well documented. The dorsal nerves stem from the pudendal nerve, providing the sensory and motor nerve supply to the penis.[6] The pelvic plexus provides autonomic innervation. Sympathetic efferents arise from spinal levels T11-L2 and parasympathetic branches from S2-S4.[8] With parasympathetic stimulation, several neurotransmitters allow intracorporal smooth muscle relaxation, arterial dilation, venous occlusion, and subsequent erection.

Indications

Currently, penile prosthesis placement remains a third-line therapy for ED.[9] American Urological Association and the European Urological Association guidelines suggest that a penile prosthesis may be placed for ED that is unresponsive to more conservative therapy, such as phosphodiesterase inhibitors, vacuum erection devices, alprostadil urethral suppositories, and intracavernosal injections.[9] Other indications for placement include Peyronie disease with concomitant ED, penile corporal fibrosis, postpriapism spongiofibrosis, prolonged priapism >24 hours, and severe psychogenic impotence unresponsive to psychotherapy or other measures.[10]

More recently, prosthesis placement has been found helpful as an addition to gender-affirming surgery.[11] However, placing a penile prosthesis after phalloplasty can be surgically challenging, with a high complication rate.[12] As there is no tough, protective tunica to contain the cylinders, hypermobility of the prosthesis with migration, device extrusions, and erosions are common.[12] Anchoring the base of the prosthesis to bone is required. While such surgery can be successful in significantly improving quality of life scores, there is a greater likelihood of such complications and the need for revision surgery compared to standard penile prosthesis placements.[12] 

Contraindications

Penile prosthesis placement is contraindicated in patients who are suffering from any of the following:

• Active infection anywhere in the body, particularly the urinary tract or genital infection
• Unresolved urination problems, including an elevated postvoid residual urine volume secondary to a neurogenic bladder or bladder outlet obstruction
• Patients who are not willing to undergo device revision surgery if necessary
• Patients with serious comorbidities, usually cardiovascular, where engaging in sexual activity could be dangerous

Equipment

Penile prosthesis implantation offers multiple options approved by the United States Food and Drug Administration, including malleable and inflatable devices. Surgeon experience and preference, patient factors, and anatomical considerations guide implant type selection. Malleable devices feature 2 solid intracavernosal implants, bent upward for erection simulation or downward when not in use. Advantages include simplified surgical implantation, patient ease of use, and lower failure rates. However, erosion rates may be higher, with less patient satisfaction than inflatable devices.[13][14] 

The current gold standard for penile prostheses is the 3-piece inflatable model, accounting for 90% of new implants.[9] These devices consist of 2 cylinders in the corporal bodies, a fluid reservoir placed submuscularly or within the space of Retzius, and a scrotal pump for inflation control, allowing for rigid erections and flaccidity when desired.[13]. Alternatively, the 2-piece inflatable prosthesis with a scrotal pump and smaller reservoirs is most useful in patients with prior pelvic surgery or a history of pelvic radiation, as no dissection is required within the abdomen or pelvis.[15] Patient satisfaction rates exceed 80% with 3-piece devices and over 70% with 2-piece models.[16][17] Satisfaction rates with malleable prostheses are similar.

Preparation

A comprehensive history and physical examination are essential before planning penile prosthesis placement; this includes assessing the patient's symptoms and using tools like the International Index of Erectile Function (IIEF)-5 to gauge erectile function.[18] Additionally, discussions about prior therapies such as erectogenic injections and any history of priapism are crucial to identifying potential complications like corporal fibrosis.[19] While a detailed clinical evaluation of ED is extensive, these considerations are fundamental before implantation.

In addition to evaluating the patient's symptoms and prior therapies, a detailed assessment of their surgical history is crucial before planning penile prosthesis placement. Major pelvic surgeries like radical prostatectomy, radical cystectomy, colorectal surgery, and renal transplantation may necessitate adjustments to the incision site and reservoir placement. Understanding the patient's history of conditions like ischemic priapism or Peyronie disease helps anticipate potential complications. Furthermore, since ED can be linked to various underlying conditions, including advanced cardiovascular disease, a thorough review of past medical history and medications is essential.[20] Cardiac risk stratification and medical clearance may be necessary in many cases before proceeding with surgery.

After obtaining a comprehensive history, a thorough physical examination is crucial before proceeding with penile prosthesis placement. The abdomen should be evaluated for any surgical incisions that may impact pelvic tissue planes, and radiation tattoos can help identify prior radiotherapy for prostate cancer. The genital examination includes assessing stretched penile length and girth, noting any curvature or palpable plaques. 

Following a comprehensive history and physical examination, thorough patient counseling on penile prosthesis placement is essential. Surgeons must emphasize that the procedure aims to provide a permanent solution for ED. Patients should be informed about potential risks, including implant infection, erosion, dissatisfaction with results, and the likelihood of future surgical revisions. While injuries to the bladder and urethra are rare, they are possible complications. Surgeons should also discuss surgical goals and potential complications, emphasizing that the procedure won't lengthen the penis and may result in slight shortening and that the stretched penile length will be an optimal realistic goal for erectile length after the implant is placed.[21] Clear communication ensures informed decision-making by patients considering penile prosthesis placement. Thorough and complete preoperative counseling and setting realistic patient/partner expectations will contribute significantly to postoperative satisfaction with the prosthesis.[22]

Infection control is critical in implant surgery, necessitating preoperative management of modifiable factors. Patients with diabetes should aim for optimal blood glucose control, as elevated hemoglobin A1c levels (>8.5%) correlate with increased postoperative infections in penile prosthesis placement.[23] Smoking cessation should be addressed early to enhance wound healing, as tobacco use is associated with higher rates of surgical site infections.[24] Preoperatively addressing these factors improves outcomes and reduces the risk of complications in penile prosthesis surgery.

Technique or Treatment

Infection Prevention

Infection control is of utmost importance in penile prosthesis implantation. While antibiotics are not routinely given weeks or days before surgery, targeted, weight-based dosing for preoperative parenteral antibiotics is recommended to help prevent penile prosthesis infection.[25] The most recent guideline from the American Urological Association (AUA) advocates using an aminoglycoside plus a cephalosporin or vancomycin as first-line prophylaxis.[26] Recently, the standard AUA-recommended vancomycin plus gentamicin prophylactic antibiotics for penile prosthesis placement has been questioned as it was associated with a higher risk of infection.[27] The same review suggested that antifungal prophylaxis helped reduce infection risk.[27] Further research is necessary to identify optimal antibiotic prophylaxis for penile prosthesis placement, but for now, it may be prudent to add an antifungal agent to the usual prophylactic regimen.[27]

For surgical preparation in penile prosthesis implantation, chlorhexidine-based skin prep is recommended over iodine-based solutions, as recent data suggests improved post-prep skin cultures with chlorhexidine-based products for implant surgery.[28] Double gloving during the procedure, with clean under gloves for handling the implant, is advisable. Additionally, implants impregnated with rifampin/minocycline or hydrophilic implants absorbing antibiotic/antifungal solutions benefit infection prevention.[29] Evidence from systematic reviews supports lower infection rates with coated implants than noncoated ones, emphasizing the importance of employing these infection control measures during surgery.[30]

Penile Prosthesis Implantation

Once general anesthesia is induced, the patient is prepped from the umbilicus to the midthigh, and sterile draping is applied. A Foley catheter is inserted to drain the bladder, reducing the risk of injury and facilitating urethral identification. Optionally, an Iodoform drape may be applied to expose only the penis and scrotum, minimizing skin contact and potentially lowering infection rates—an approach known as the "no-touch" technique.[31] 

In a 3-piece inflatable penile prosthesis placement, the surgeon may opt for an infrapubic or penoscrotal approach based on preference and patient anatomy. With the infrapubic approach, reservoir placement is done using direct visualization. Alternatively, the penoscrotal or high scrotal approach is historically preferred. The procedure involves a skin incision followed by dissection through the subcutaneous tissue, Dartos, and Buck fascia to reach the tunica albuginea. Dissection can be aided by using a self-retaining retractor with blunt tissue hooks. Stay sutures may be placed in the corporal bodies to facilitate corporotomy incision and closure. Corporotomy is then performed using Bovie cautery.

Once the corporotomy is made, blunt-tip scissors may dilate the corporal bodies, followed by sequential Hegar or Brooks dilators to extend the dilation to the crus proximally and distally to the midglans. Care must be taken to ensure distal dilation occurs in a craniolateral direction to prevent corporal crossover or urethral injury. Sequential Uramix or Mooreville dilators can be used in corporal fibrosis where dilation is difficult.[32] These instruments include a cutting surface at the tip of the dilator, which is passed with a twisting motion to activate the cutting action. While this is effective in drilling and cutting through dense fibrotic tissue, it is also associated with a higher rate of corporal perforations.[33] After dilation, the surgeon assesses for corporal crossover by placing a dilator in both corpora and observing for asymmetry with crossover, potentially prompting termination of the procedure.

Suppose a urethral injury is noted to have occurred during the dilation, indicated by irrigation flowing around the catheter and out of the meatus. In that case, the surgery should be stopped, and a Foley catheter should be left in place for several days.[32] Long-term catheterization is typically not recommended to avoid stricture formation.[32] Smaller urethral perforations usually heal without primary closure, while larger ones may require closure in 2 layers using absorbable sutures. Proximal injuries can be addressed via a transscrotal approach.[13] Additionally, a nonabsorbable suture through the solid base of the cylinder, resembling a "sling stitch," can aid in closure.[34]

After corporal body dilation, the reservoir is positioned within the space of Retzius. This is accomplished by tracing the spermatic cord upward through the external inguinal ring, palpating the pubic ramus, and creating space using blunt-tipped scissors. Further dilation may be performed using a Foley catheter balloon inflated from 60 to 100 mL.[35] The bladder must be fully decompressed before reservoir placement to prevent bladder injury. The empty reservoir is then guided into the created tract using a nasal speculum or Yankauer suction tip, followed by a test fill to confirm positioning. Alternatively, a submuscular location can be selected for reservoir placement in patients who have undergone prior pelvic surgery or complicated hernia repair.[36]

Once the reservoir is in position, measurements for the cylinders are taken, with verbal confirmation by the surgeon, surgical technician, and, if present, the medical device provider. After confirmation, the device is opened and prepared for implantation. Proper cylinder size is crucial for function and durability. A Keith needle suture is attached to each cylinder's distal end, loaded through a Furlow device, and passed through the glans. This process is repeated on the opposite side. After placing both cylinders, 60 mL of saline is used for balloon inflation to assess size and positioning, with rear tip extenders aiding in accurate corporal body sizing. The corporotomy is then closed by tying the corporal stay sutures together, followed by additional interrupted or continuous sutures, being cautious not to puncture the cylinder.

Next, the scrotal pump is positioned by creating a subdartos plane through blunt and sharp dissection, often using a nasal speculum to form a pocket within the scrotal sac. The Dartos tissue is then reapproximated over the pump, and tubing for the pump, reservoir, and cylinders is connected, ensuring no air is introduced into the system. Once all components are connected and positioned, the skin is closed in 2 layers, possibly with a drain if overnight hospitalization is planned. The drain and Foley catheter are typically removed on postoperative day 1, and the penis is gently wrapped in sterile gauze with a compression dressing, then positioned upwards on the lower abdomen to prevent downward curvature postoperatively.

Postoperative Care

Traditionally, patients have stayed in the hospital overnight after prosthesis placement for proper postoperative instruction and Foley catheter removal. Following catheter removal and confirmation of bladder emptying, patients historically received prophylactic antibiotics at discharge, although recent data suggest no significant difference in infectious complications compared to those without antibiotics.[37] In recent studies, ambulatory same-day surgery has emerged as an equivalent and cost-effective alternative.[38] Patients may receive a short course of narcotic pain medication and are advised to avoid heavy lifting until the follow-up visit in 7 to 14 days. Scrotal support or tight underwear can be used after removing the sterile dressing, and showering is typically permitted 24 hours after surgery. The patient is also instructed to pull the scrotal pump caudally or inferiorly several times daily to prevent proximal pump migration.

Complications

As advancements in technology and surgical techniques progress, complications following penile prosthesis implantation have decreased. However, they remain a significant challenge for the prosthetic urologist. Infection represents the most concerning complication of penile prosthesis surgery. Patients may exhibit acute symptoms such as fevers, constitutional symptoms, incision site drainage, or more subtle signs that can emerge months or even years later. Treatment often involves broad-spectrum antibiotics and complete removal of all prosthesis components. However, studies suggest a new implant can be placed immediately after removal, provided thorough washout procedures are followed.[39] 

Improper cylinder sizing is another prevalent complication of penile implant surgery. If the cylinders are too short, patients may experience supersonic transport deformity and "floppy glans syndrome," resulting in a poor cosmetic appearance and difficulties with vaginal penetration.[40] Conversely, oversized cylinders can elevate the risk of chronic pain and erosion, necessitating device removal (explantation) in cases of significant erosion.[34]

Cranial migration of the scrotal pump presents another challenging complication following prosthesis placement, impacting device functionality and affecting the appearance and sensation of the penis and scrotum. Preventive measures include ensuring proper pump placement and tubing beneath the Dartos fascial layer during closure and advising patients to regularly pull the pump down into the scrotum to mitigate this issue.

Postoperative urinary retention is a common complication, affecting up to 27% of patients after penile prosthesis placement.[41] Management typically involves Foley catheterization or clean intermittent self-catheterization. Patients with preexisting prostate enlargement symptoms treated with alpha-blockers and 5-alpha reductase inhibitors are at higher risk for this complication.[41]

Patients may develop penile shortening due to the penile prosthesis procedure, or it may be preexisting from trauma, scarring, postpriapism corporal fibrosis, radiation, or surgery. Penile lengthening procedures have been described with good long-term results.[42] One involves cutting the suspensory ligament and implanting a soft, conforming silicone spacer between the corpora cavernosa and the pubic symphysis. This technique adds approximately 2 cm to penile length with good long-term results and patient satisfaction.[42] Device malfunction is a rare complication after penile prosthesis placement due to advancements in implant technology and reliability. In the rare event of a malfunction, a single component replacement may be considered a solution.[43]

Clinical Significance

Penile prosthesis implantation has emerged as a safe and effective solution for managing ED, offering patients sustained improved quality of life.[44] With the prevalence of ED steadily rising, the popularity of penile prostheses is expected to increase. Over the past 5 decades, substantial advancements in technology have enhanced the outcomes of this procedure, resulting in better functionality, reliability, durability, and cosmetic outcomes for patients. These developments underscore the importance of continued research and innovation in the field to refine further and optimize penile prosthesis implantation techniques.

Enhancing Healthcare Team Outcomes

Penile prosthesis implantation requires a comprehensive and coordinated approach from a multidisciplinary healthcare team to ensure patient-centered care, optimal outcomes, patient safety, and effective team performance. Physicians, particularly urologists and surgeons, must possess advanced surgical skills and expertise in evaluating patients for candidacy, selecting the appropriate implant type, and performing the procedure safely and effectively. Advanced practitioners, such as physician assistants and nurse practitioners, play a vital role in assisting with patient evaluation, preoperative preparation, and postoperative care, contributing to efficient workflow and comprehensive patient management. Nurses are essential in patient education, perioperative care, and postoperative monitoring, ensuring that patients are well-informed, comfortable, and supported throughout their surgical journey. Pharmacists contribute by managing medications, including prophylactic antibiotics and pain management, to prevent complications and optimize patient outcomes.

Effective interprofessional communication and care coordination among team members are critical elements in ensuring the success of penile prosthesis implantation procedures. Clear communication facilitates seamless transitions of care, early identification of potential issues, and prompt intervention when needed. By working cohesively, healthcare professionals can enhance patient satisfaction, improve clinical outcomes, promote patient safety, and optimize team performance in penile prosthesis implantation.