Penile Prosthesis

Indications for Penile Prosthesis (4):

1. Failure or rejection of conservative therapy for ED
   • Irreversible organic etiology of ED
   • Psychological impotence after failure of all other treatment
2. Peyronie disease in which ED and erectile deformity coexist
3. Penile fibrosis
4. Phalloplasty following trauma, radical penile cancer surgery or gender change

Contraindications (8):

1. Situational ED
2. ED resulting from relationship conflict
3. Potentially reversible ED
4. Spinal cord injury
5. Uncontrolled diabetes mellitus
6. Noncompliance with concurrent medication (e.g., for hypertension or diabetes)
7. Inability to follow instructions
8. Hygiene issues and skin cleanliness

Types of Prostheses

Classification

• Semirigid rods
  • Malleable
  • Positional
• Inflatable
  • 2-piece
  • 3-piece
• At the present time in the US, 70% of patients are implanted with 3-piece inflatable devices, 20% are implanted with 2-piece devices, and 10% are implanted with semirigid rods.

Semirigid rods

• Paired, solid cylinders that fill each corpus cavernosum
• Subdivided into malleable vs. positional devices
  • A malleable device has a central core that allows a patient to position the penis upward for sexual intercourse and downward at other times.
  • A positional device incorporates a series of articulating polyethylene discs with a central metal cable support, which make it better able to maintain upward and downward positions

Advantages (4):

1. Relatively inexpensive
2. Easy to implant
3. Easy to use
4. Low mechanical failure rate

Disadvantages (3):

1. Simulates a constant erection, may be difficult to conceal
2. Does not increase penile girth
3. Quality of erection decreases over time (due to loosening of scar capsule around device)

Inflatable

• Designed to approximate normal function more closely by permitting girth and length expansion during erection and penile flaccidity when not in use
• Consist of 2 hollow intracorporeal cylinders, each of which fills a corpus cavernosum; the cylinders are inflated with saline solution to produce penile rigidity during sexual activity and are deflated after intercourse.
• Subdivided into 2-piece vs. 3-piece devices
  • 2-piece device
    • Consists of the two cylinders and a scrotal pump.
      • Reservoirs in the proximal portion of the cylinders are prefilled with saline and preconnected to the pump via silicone tubing.
      • Pressing a valve mechanism in the pump transfers the solution from the reservoirs into the distal, inflatable portion of each cylinder.
      • Bending the cylinders down for several seconds activates a release valve that deflates the device by allowing the fluid to flow back to the reservoirs.
  • 3-piece device
    • Consists of the two hollow cylinders, a scrotal pump, and a saline-filled reservoir.
      • Silicone tubing connects the cylinders to the pump and the pump to the reservoir.
      • Repeatedly squeezing the pump transfers saline from the reservoir to the cylinders until adequate rigidity is achieved
      • Pressing a valve mechanism in the pump causes the fluid to flow back to the reservoir.
  • Both devices are available in several widths and lengths and come with optional rear tip extensions to allow them to be tailored to each patient.
  • Advantages of two-piece compared to three-piece (2):
    1. No need to implant a separate reservoir
       • Facilitates surgery and may be useful with patients in whom placement of the reservoir is extremely difficult because of colostomy, ileostomy, kidney transplant, or extensive pelvic surgery
    2. Reaches full inflation with fewer squeezes of the pump
  • Disadvantages of two-piece compared to three-piece (3):
    1. Pump is very small and hard, making it difficult for patients to manipulate
    2. Implantation requires a larger incision of the tunica albuginea
    3. Feels and acts less like a natural erection

Pre-operative Counselling and Evaluation

• Penile prosthesis is a highly effective treatment for ED but considered an irreversible procedure accompanied by numerous risks; positioning the device permanently results in the loss of any pre-existing erectile capability
• Thorough preoperative assessment and education can help identify the best type of prostheses for any specific circumstance.
  • A patient with limited manual dexterity is recommended to receive a semirigid prosthesis
  • A small, narrow penis should be considered for an AMS LGX.
• Evaluation includes history, physical exam including intracorporeal injection of a vasodilating agent, and penile Doppler ultrasound study after intracorporeal injection of a vasodilating agent
  • The stretched penile length should be measured
  • Patients should know that the preoperative length of the fully stretched flaccid penis is typically the maximal length that can be obtained after prosthetic surgery and that the procedure may result in a degree of penile shortening and glans softening
  • Intracorporeal injection allows assessment for possible concomitant abnormalities such as shortening, hourglass deformity, and curvature
  • Penile doppler can evaluate for severity of ED, vascular flow, tumescence, and penile anatomy
• Patients are often concerned about the size of the incision required to implant the device and should be reassured that only a 1-inch incision is necessary.

Surgical Technique

• Position: supine
• Step by step
  • Incision and dissection down to corpora
    • The three-piece device can be inserted through a scrotal or infrapubic incision.
    • Narrower inflatable and semirigid devices should be available for all cases in the event that implanting a three-piece device becomes difficult.
  • Cylinder placement
    • The tunica albuginea of each corpus cavernosum is identified on either side of the urethra
    • An incision is made in the tunica albuginea taking care to avoid the underlying cavernosal muscle
    • Blunt scissors are used to develop a space between the tunica albuginea and cavernosal muscle
    • Sequential dilation of the corpora is done using Hegar dilators.
      • The use of force is unnecessary and should be avoided to prevent perforation of the tunica albuginea and damage to the urethra at the meatus or the crus, which can occur during either distal or proximal dilation.
    • The corporeal lengths should be measured distally and proximally to select an optimally sized cylinder
    • The device is opened on the surgical field and prepared for implantation
    • The cylinders are implanted
    • A watertight closure of the corporotomy can be achieved with a running 3-0 PDS using a hemostatic stitch or by approximating the previously placed tagging 3-0 PDS
    • Poor support of the glans penis by cylinder or rod tips leads to a drooping appearance of the glans, in which it appears to "flop" over the prosthesis.
      • This deformity may result from inadequate distal dilation, too short cylinders, or in the case of minor deformity, variations in anatomy where the corpora cavernosum does not extend completely under the glans.
      • For a severe deformity, definitive correction involves removing both cylinders, perforating the distal corpora with scissors, resizing, and then inserting longer cylinders or the same cylinders with longer rear tip extenders.
      • For mild defects, dorsal plication of the glans back onto the shaft of the penis (glansplasty) is preferable when there are minor but otherwise bothersome degrees of poor glanular support.
  • Pump placement
  • Reservoir placement
    • Before reservoir placement, it is important to ensure the bladder is empty to avoid bladder perforation.
    • The reservoir is typically placed in the space of Retzius.
      • Submuscular reservoir placement with a flat reservoir or a separate incision should always be performed in all patients after previous surgery involving the space of Retzius (robotic prostatectomy, radical cystectomy, and abdominoperineal resection and in patients with history of pelvic fracture with bladder rupture and pelvic surgery)
  • Closure
    • A closed-suction drain should be used if the surgeon is not satisfied with hemostasis

Postoperative care

• The efficacy of postoperative prophylactic antibiotics has not been demonstrated in prospective studies and remains controversial; most surgeons prescribe 7 days of quinolones
• During the first week, the patient should avoid sitting on the scrotum (this can push the pump upward) and lifting more than 15 pounds or any other activities that could cause displacement of the reservoir into the inguinal canal.
• Brief-style underwear should be worn for the first month, with the penis placed on the lower abdomen and oriented toward the umbilicus until the device is first inflated. Such positioning promotes capsule formation around the cylinders and will orient the erection in an upward direction.
• The reservoir should be maintained full (i.e. implant completely deflated) during the postoperative period to allow capsule formation over a full reservoir to prevent auto-inflation.
  • If the capsule forms around a partially filled reservoir, the capsule will restrict future expansion of the reservoir, prohibit complete cylinder emptying, and potentially cause auto-inflation, resulting in a need for surgical revision
• At ≈4 weeks after surgery, the patient is taught how to operate the device

Complications

Intraoperative

• Organ injury/perforation, cylinder crossover, and damage to the device during implantation
  • Corpora cavernosa perforation
    • To prevent distal or proximal crossover into the contralateral corpus during initial dilation, constant traction should be applied to the shaft of the penis by pulling on the glans, and the curvature of the scissors should be maintained away from the midline of the penis, with the tips next to the tunica albuginea.
    • If crossover occurs, it is usually preferable to recognize it and correct it when recognized, rather than after further dilation or insertion of the cylinders.
    • Most likely location for perforation is at the septum
    • Distal perforation
      • Evaluated by exposing the damaged corpus apex through a transverse incision of the skin and tunica albuginea near the glans
      • Management
        • A small hole can usually be located distally on the medial aspect of the cavernosal cavity and repaired using separate PDS stitches. The distal apex of the corpora needs to be closed with a second running suture, and a slightly shorter prosthetic cylinder is selected for the perforated side; this is necessary to prevent the distal tip of the cylinder from resting on the urethral suture repair.
        • A more conservative approach would be to terminate the procedure and bring the patient back for implantation 3 months later.
          • The disadvantage of this strategy is that the length of the shaft is foreshortened, and dilation of the scarred corpora is much more difficult.
        • If the perforation occurs after both corpora are dilated, a semimalleable cylinder can be placed in the nonperforated side to preserve penile length.
    • Proximal perforation
      • Evaluated by placing a dilator in each crura, and their heights can be compared to confirm that one has penetrated too deeply inside the perineum.
      • Management
        • Repair by anchoring the cylinders to the surrounding corpora tissue by placing stitches above and below the input tubing, which prevents the cylinder from proximal migration and allows the perforation to heal.
  • Urethral perforation
    • Management
      • Abandon the procedure and divert the urine with a urethral catheter until deferred repair.
        • Urethral repair would be difficult and is unnecessary.
        • If the contralateral malleable cylinder has already been placed and there is no septal perforation, then it may be left in place.
        • If this occurs with an inflatable prosthesis, the entire device should be removed and the urethra allowed to heal.

Postoperative

Infections

• Epidemiology
  • Overall infection rates following initial penile prosthesis insertion range from 1-3%
    • Rate is significantly higher (7-18%) for revision surgery
• Risk factors
  • Most infections are caused by bacteria on the skin at the time of surgery that attach to the device and are then introduced into the patient
  • Patient risk factors
    1. Poor patient hygiene
    2. Spinal cord injury
    3. Urinary tract infection
    4. Distant sites of infection
    5. Revision surgery performed for previous device infection
       1. unclear if diabetes or immunosuppression are associated with risk of infection
  • Intraoperative risk factors
    1. Inadequate skin preparation with alcohol/chlorhexidine
    2. Prolonged surgical time (i.e., >2 hours)
    3. Prolonged and repeated exposure of components of the prosthesis to patient’s skin
    4. Frequent repositioning and resizing of the cylinder, pump, or reservoir
    5. Scrotal hematoma (particularly if liquefied)
    6. Not changing gloves before handling the device
  • Post-operative risk factor
    • Prolonged hospitalization
  • Most important factors to minimize the risk of device infection include (2)
    1. Procedures that decrease inoculating bacteria into the surgical wound (4)
       1. Alcohol skin preparation
       2. Reducing surgical time
       3. No touch surgical technique
       4. Perioperative antibiotic use
    2. Use of antibiotic-coated prostheses
       • Specially coated three-piece devices have been developed to inhibit bacterial adhesion and proliferation. These coatings have decreased the incidence of infection by 50-70%
• Microbiology
  • Typically involves organisms that colonize the skin, such as (3):
    • Staphylococcus epidermidis
    • Staphylococcus aureus
    • Candida albicans
• Diagnosis and Evaluation
  • History and Physical Exam
    • History
      • Clinical deterioration with persistence of pain and tethering at 3-4 weeks after surgery suggests an infection
        • Pain that does not seem to improve and is persistent or increased at 2-weeks after surgery should not prompt the use of antibiotics
          • If the device is not infected, the patient should experience clinical improvement within the next 7-14 days.
          • If the device is infected, antibiotics are useless at this point and may delay diagnosis.
      • Fever, erythema, swelling, elevated white blood cell count, and incision drainage are late signs and symptoms of infection and are usually not observed at the initial postoperative visit.
      • The sooner an infection is diagnosed, the better the chance for successful salvage and aggressive early salvage should be considered before systemic symptom such as fever, elevated white blood count, erythema, and abscess formation of scrotum occur
  • Imaging
    • Studies such as scrotal sonography, computed tomography scan, and magnetic resonance imaging are not helpful in making an early diagnosis.
• Management
  • Infection necessitates the removal of all device components as well as any permanent sutures or graft material used during corporeal reconstruction
    • The use of systemic antibiotics to treat symptomatic patients is typically insufficient because of the biofilm and attempts to remove only part of an infected device typically results in persistent infection
  • A “salvage” procedure involving removal of the infected prosthesis, wound washout, and immediate device replacement can help facilitate reimplantation and preserve penile length.
    • Contraindications to salvage prosthesis:
      • Patients presenting with enterococcus, tissue necrosis, sepsis, diabetic ketoacidosis, or cylinder erosion into the urethra

Device malfunction

• The most common types of malfunction in a three-piece prosthetic device include cracks in the silicone tubing, leaks, and pump disruption
• Management
  • If malfunction occurs
    • Within a few months after implantation: consider replacing only the defective component, especially if this avoids a repeat corporeal incision
    • After the device has been in place for >2 years: complete replacement is indicated

Other complications

• Postoperative complications occurring less frequently than infection and device malfunction include erosion, S-shaped penile deformity, poor glans support (see above), and scrotal hematoma.
  • Erosion
    • Typically occurs months or years after implantation
    • Can manifest in several different locations.
    • Management
      • Complete removal of all the components of the device, regardless of the location and possible salvage replacement.
        • If only one of the cylinder tips has eroded through the meatus, the entire device needs to be removed, including the pump and reservoir, and a malleable cylinder is placed in the noneroded side only, to prevent shortening of the penis.
        • The perforation must be allowed to heal for 8 to 12 weeks before reimplantation is attempted
• Pain only when the device is inflated during intercourse
  • May indicate that the cylinders are too large and are buckling, causing pain.
  • MRI scan with the prosthesis inflated is the best imaging modality to prove the possible size discrepancy and buckling is the next step.
  • If the diagnosis is confirmed, revision of the penile prosthesis with placement of smaller cylinders will usually resolve the problem

Special Scenarios

Repeat implant

• Infection rates are significantly higher after repeat prosthesis insertion; risk of mechanical failure, erosion, penile pain, and hemorrhage are not higher after repeat prosthesis insertion.
• Delayed reimplantation may result in loss of penile size; early replacement has been advocated for patients considering replacement.

References

• Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 30