Continuing Education Activity

Penile prosthesis implantation is performed for erectile dysfunction refractory to conservative therapy. Inflatable and malleable devices are available options for patients. Multiple implantation approaches can be used successfully depending on patient anatomy and preference. This activity reviews the best practices for implantation of penile prosthesis in patients who have failed more conservative measures. Further, this activity reviews the technique for penile prosthesis placement and highlights the role of the interprofessional team in evaluating and treating patients requiring a prosthesis.

Objectives:

• Identify the contraindications of penile prosthesis implantation.
• Describe the technique employed for penile prosthesis implantation.
• Review the appropriate evaluation of the potential complications with penile prosthesis implantation.
• Summarize interprofessional team strategies for improving care coordination and communication to advance penile prosthesis implantation and improve outcomes.

Introduction

Penile prosthesis (PP) has been an option for males with erectile dysfunction since first introduced in 1973.[1] Since that time, various devices have been implanted with the goal of improving sexual function in men affected by erectile dysfunction (ED). As the worldwide prevalence of ED is expected to increase to over 322 million by 2025, the demand for implantable PP should continue to rise.[2] Associated factors include the aging population as well as a sustained increase in conditions such as obesity, diabetes, and cardiovascular disease that may lead to diminished erectile function.[3]

Anatomy and Physiology

A detailed understanding of the anatomy and physiology of the penis is required for penile prosthesis implantation. The erectile tissues of the penis are separated grossly into three compartments. These include the corpus spongiosum, which encompasses the urethra, and paired cylindrical corpus cavernosum, which form the main erectile bodies. These corporal bodies connect via a midline septum, allowing for free communication between the erectile tissues.

The aforementioned compartments are encased by several fascial layers that are relevant to the erection. The outermost layer, the penile skin, surrounds the superficial (Dartos) fascia. Underneath this layer is the deep (Buck) fascia. Buck fascia splits to surround the corpus spongiosum ventrally and the corpus cavernosum dorsally. The cavernosal bodies are enveloped by a layer of dense connective tissue, tunica albuginea. The tunica albuginea fibers are stretched during erection, which allows for rigidity. 

The blood supply to the erectile tissues is multifaceted. Superficially, the external pudendal arteries, via the femoral artery, supply the penile skin. The deep blood supply is maintained by the internal pudendal artery with three main branches to the penis.[4] The bulbourethral artery supplies the urethra and glans. The dorsal artery branches into circumflex arteries, which supply the spongiosum and urethra. Finally, the cavernosal arteries branch once more to form the helicine arteries, which dilate with neural stimulation to produce an erection.[5] There are multiple anastomotic connections between these vessels.[6] 

The venous drainage of the erectile bodies is less predictable. Most often, the cavernosum 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 the 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, supply sensory, and motor supply to the penis.[6] Autonomic innervation is provided by the pelvic plexus. Sympathetic efferents arise from spinal levels T11-L2 and parasympathetic branches from S2-S4.[8] With parasympathetic stimulation, several neurotransmitters allow for smooth muscle relaxation, arterial dilation, venous occlusion, and subsequent erection.

Indications

Currently, penile prosthesis placement remains a third-line therapy for erectile dysfunction.[9] Urologic guidelines suggest PP is placed for ED that is unresponsive to more conservative therapy, such as phosphodiesterase inhibitors and intracavernosal injections.[9] Other indications for placement include Peyronie disease with concomitant ED, penile fibrosis, post-priapism spongiofibrosis, and psychological impotence. More recently, prosthesis placement has been found useful as an addition to gender-affirming surgery.[10]

Contraindications

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

• Active infection anywhere in the body, particularly urinary tract or genital infection
• Unresolved problems of urination such as elevated residual urine volume secondary to the neurogenic bladder or bladder outlet obstruction
• Patients not willing to go for device revision surgery

Equipment

Multiple options are currently FDA approved for penile prosthesis implantation. These include malleable devices and inflatable devices. Proper selection of implant type depends on surgeon experience/preference, patient factors, and, finally, anatomical considerations. Malleable devices consist of two solid intracavernosal implants which can either be bent upward to stimulate erection or down when not in use. Benefits include ease of implantation, ease of use for the patient, and low failure rates. However, rates of erosion may be higher, and patient satisfaction rates may be slightly lower.[11][12] 

Three-piece inflatable prostheses are the current gold standard as they allow for rigid erection and flaccidity when desired.[11] These devices consist of two cylinders placed in the corporal bodies and filled with saline to produce rigidity. A fluid reservoir which may be placed either sub muscularly beneath the rectus or within the space of Retzius is included, as well as a scrotal pump to control the device. Alternatively, a two-piece inflatable prosthesis, which includes a scrotal pump as well as cylinders equipped with smaller reservoirs, remains a viable option. Two-piece devices may be useful in patients with a history of pelvic surgery or radiation, as no dissection is required within the abdomen or pelvis.[13]

Preparation

A thorough history and physical should be performed prior to surgical planning of penile prosthesis placement. While a full discussion of the clinical evaluation of erectile dysfunction is beyond the scope of this article, several considerations should be made prior to proceeding with implantation. It is vital to obtain some baseline understanding of the patient’s symptoms. Specific questionnaires, such as the International Index of Erectile Function (IIEF-5), can be used to determine the patient’s degree of erectile function.[14] Further, a detailed discussion of prior therapies should be undertaken, with specific regard to long term use of erectogenic injections, as these may cause corporal fibrosis.[15] 

It is equally important to obtain a detailed assessment of the patient’s prior surgical history. Any major pelvic surgery, including radical prostatectomy, radical cystectomy, colorectal surgery, and renal transplantation, should be noted, as incision site and reservoir placement may need to be adjusted. If the patient has a history of ischemic priapism or advanced Peyronie disease, it is useful to obtain a timeline of these conditions. Further, ED can act as a harbinger for many other conditions, including advanced cardiovascular disease.[16] Therefore, past medical history and medications must be carefully reviewed by the clinician. In many cases, cardiac risk stratification and/or medical clearance will need to be obtained before surgery. Once a thorough history is obtained, it is necessary to perform a physical exam. Physical exam should include evaluation of the abdomen, observing for any surgical incisions which may affect tissue planes within the pelvis. Additionally, radiation tattoos can often clarify the specific modality of treatment in those patients with a history of prostate cancer.

Finally, careful examination of the genitalia is warranted. The stretched length and girth of the penis should be evaluated. Any curvature or palpable plaques should be carefully documented. This may also be an appropriate time to discuss the goals of implant surgery. The surgeon should clearly discuss that the stretched penile length will be a realistic goal for erectile length after the implant is placed.[17] 

It should be noted that this procedure will not lengthen the penis, and a small but not insignificant penile shortening may occur. Once a thorough history and physical exam are performed, patient counseling on the risks and benefits of the procedure is warranted. The surgeon should stress that this procedure is intended to be a permanent treatment for ED. Additionally, the risk of implant infection, erosion, and the possibility for revision in the future should be discussed. Injury to the bladder and urethra are unlikely, but additional possible complications of the procedure. As with all implant surgery, infection control remains paramount. Therefore, certain modifiable factors should be addressed prior to surgery. First, patients with diabetes should be counseled on the importance of blood glucose control, as hemoglobin A1C greater than 8.5% has been shown to increase postoperative surgical site infections with regard to PP.[18] Smoking cessation should be discussed well before surgery to facilitate optimal wound healing. Meta-analyses have confirmed a link between postoperative surgical site infections and tobacco use.[19]

Technique or Treatment

Infection control is an important consideration when discussing penile prosthesis implantation. While antibiotics are not routinely given weeks or days prior to surgery, preoperative parenteral antibiotics must be given. The most recent guideline from the American Urological Association guidelines advocates for the use of an aminoglycoside plus cephalosporin or vancomycin as first-line prophylaxis.[20] 

Surgical prep should be performed with alcohol-based skin prep. Though iodine-based prep has historically been used for genitourinary surgery, recent data suggest improved post-prep skin cultures with chlorhexidine-based products for implant surgery.[21] Double gloving should be considered, as “clean” under gloves may be used while the implant is placed into the proper position after the rest of the dissection is completed. Furthermore, device manufacturers now offer implants impregnated with rifampin/minocycline. Alternatively, hydrophilic implants that can absorb various antibiotic/antifungal solutions are also available.[22] One large systematic review did confirm lower rates of infection in coated devices when compared to non-coated devices.[23] 

Once the room and patient have been prepared for surgery, general anesthesia is administered. Next, the patient is prepped from the umbilicus down to the mid-thigh, and sterile draping is applied. A foley catheter is placed on the sterile field, and the bladder is drained. This serves both to help avoid injury to the bladder and also to more clearly identify the urethra. An Iodoform drape can be applied over the skin if preferred and cut to expose only the penis and scrotum in order to minimize skin contact. Using this so-called “no-touch” technique may allow for a decreased rate of infection.[24] 

Three-piece, inflatable devices can be placed via an infrapubic or penoscrotal incision depending on surgeon preference and patient anatomy. Infrapubic placement allows for reservoir placement under direct visualization; however, the penoscrotal or high scrotal approach has been preferred historically. A skin incision is made, and subcutaneous tissue is dissected. Dissection can be aided by the use of a self-retaining retractor with blunt tissue hooks. Dissection is carried down through the Dartos and then Buck fascia to the tunica albuginea on each side of the urethra. It may be helpful to place stay sutures in the corporal bodies on either side of the urethra prior to making a corporotomy incision. Doing so can both aid in ease of incision as well as closure once a cylinder has been placed. Corporotomy is then performed using Bovie cautery. Once the corporotomy is made, the corporal bodies may be initially dilated with blunt tip scissors. Sequential Hegar dilators can then be used to dilate down to the crus proximally and distally to the mid glans. Careful attention should be paid to ensure distal dilation occurs in a craniolateral direction to avoid corporal crossover or urethral injury. After both sides are appropriately dilated, the surgeon should evaluate for corporal crossover by placing a dilator in both corpora and looking for asymmetry. If crossover has occurred, the surgeon can elect to abort the remainder of the procedure. Alternatively, a distal perforation can be repaired in 2-layers using an absorbable suture. Proximal perforations can be managed by placing a non-absorbable suture through the solid base of the cylinder, in the fashion of a “sling stitch."[25] 

If a urethral injury has occurred, as noted by irrigation flowing around the catheter and out of the meatus, the procedure should be aborted and a catheter should be left in place for several days.[26] Next, the reservoir is placed within the space of Retzius. This is accomplished by following the spermatic cord upward through the external inguinal ring. The pubic ramus is then palpated, and space is developed using blunt-tipped scissors. Additionally, dilation of the space may be achieved using a foley catheter balloon inflated to 60-100cc.[27] The bladder must be fully decompressed before reservoir placement, as bladder injury is an avoidable complication associated with this step. The empty reservoir can then be guided over a finger into the tract that was created, either with a nasal speculum or a clean Yankauer suction tip. The reservoir should then be test filled to confirm the proper position. Alternatively, in patients who have undergone prior pelvic surgery or complicated hernia repair, a submuscular location can be selected for reservoir placement.[28] 

Once the reservoir has been placed, cylinder measurements should be performed. The measurements should be confirmed verbally by the surgeon, surgical technician, as well as the medical device provider if present. Only after confirmation should the device be opened and prepared for implantation. The proper cylinder size is an important part of implant function and durability. A suture with a Keith needle is attached to the distal end of the cylinder and loaded through a furlough device, then placed through the glans. This procedure is then repeated on the contralateral side. Once both cylinders are in place, 60 ml of saline is used to inflate to evaluate size and positioning. Rear tip extenders can be used to more accurately size the corporal bodies. The corporotomy is then closed by tying the corporal stay sutures together. If necessary, an additional interrupted suture may be placed, with caution not to puncture the cylinder. Next, the scrotal pump is placed by developing a subdartos plane. This is performed using a combination of blunt and sharp dissection. A nasal speculum may be used to form a pocket within the scrotal sac. The dartos tissue can then be re-approximated over the pump. The tubing for the pump, reservoir, and cylinders are then connected. It is essential to confirm that no air is introduced to the system during connection.

Once all components are connected and in position, the skin is closed in two layers. A drain may be placed if the patient is scheduled to stay in the hospital overnight. The drain may be removed on postoperative day number one at the same time as foley catheter removal. The penis is then wrapped in sterile gauze and a gentle compression dressing. The penis should then be placed upward on the lower abdomen, to limit any downward curvature of this penis postoperatively. Most patients will stay in the hospital overnight following prosthesis placement. This allows for proper guidance on post-operative instructions, as well as the ability to remove the foley catheter without an additional visit to the outpatient clinic. The foley catheter is removed, and adequate bladder emptying is confirmed. Historically, prophylactic antibiotics have been prescribed on discharge; however, recent data suggest no significant difference in infectious complications when compared to the antibiotic-free group.[29] 

A short course of narcotic pain medication may be warranted. The patient is instructed to avoid any heavy lifting until the follow-up visit in 7-14 days. Scrotal support or tight mesh underwear may be used after the sterile dressing is removed. Showering is generally acceptable 24 hours after surgery. Finally, the patient is instructed to pull the pump caudally several times per day upon discharge to prevent migration.

Complications

As technology has improved and surgical approaches have continued to develop, complications following penile prosthesis implantation have been reduced. However, complications still remain a significant challenge for the prosthetic urologist. Infection is the most worrisome complication of prosthesis surgery. Patients may present acutely ill with fevers, constitutional symptoms, and drainage from the incision site. Alternatively, more indolent infections may not be picked up for months or even years after prosthesis placement. In either scenario, treatment typically involves the initiation of broad-spectrum antibiotics and removal of all prosthesis components. Notably, the literature does suggest that a new implant can be placed immediately following removal as long as an appropriate washout has been performed.[30] 

Another common complication of penile implant surgery is improper cylinder sizing. If the cylinders are too short, the patient may have a supersonic transporter (SST) deformity and potential for “floppy glans syndrome.”[31] This can lead to a poor cosmetic appearance and make vaginal penetration difficult. Alternatively, oversized cylinders may increase the risk of chronic pain and erosion.[25] 

If significant erosion is present, the device must be explanted. Cranial migration of the scrotal pump is another complication of prosthesis placement that is difficult to manage. Migration can make the pump difficult to use and can cause an abnormal appearance and feel to the penis and scrotum. This complication can be avoided by incorporating the pump and tubing underneath the closure of the Dartos fascial layer. Finally, device malfunction is a rare complication following prosthesis placement as implant technology has continued to evolve. This may present one uncommon scenario in which a single component replacement may be considered.[32]

Clinical Significance

Penile prosthesis implantation remains a safe and effective surgical management for ED with sustained quality of life improvements.[33] Given the steady increase in ED, it is likely that PP implantation will continue to grow in popularity. Over the last 50 years, significant developments in technology have allowed for improved outcomes, functionality, and cosmesis. Future research into optimal materials and surgical approaches should provide continued benefit for penile prosthesis patients.

Enhancing Healthcare Team Outcomes

Penile prosthesis implantation is a procedure that can have a profound impact on a patient's quality of life. However, serious complications such as implant infection, erosion, or injury to surrounding anatomic structures can occur. Therefore it is important to identify risk factors preoperatively. Additionally, a thorough multidisciplinary approach is needed to limit complications and improve outcomes. Before proceeding with surgery, the patient should have the primary evaluation by a urologist. Further, a medical and cardiac evaluation may be necessary in select cases. The anesthesiologist will need to evaluate the patient on the day of surgery, as many patients will have COPD, obstructive sleep apnea, or other conditions that require careful anesthesia planning. Further, pharmacist contribution is essential for proper parenteral antibiotic dosing. Targeted, weight-based dosing for parenteral antibiotics are recommended to help prevent penile prosthesis infection (Level 2 evidence).[34] 

Postoperative nursing care is also important, specifically concerning catheter and drain management while in the hospital setting. Overall, a team approach helps ensure all risk factors are minimized. By providing a multidisciplinary approach, patients can be given the opportunity for the safest outcomes with the highest satisfaction.