Penile Prosthesis 

Several different types of penile prostheses are currently available. Broadly, they may be classified as inflatable or noninflatable (semirigid). There are 2 different types of inflatable prostheses: (1) a 3-piece inflatable consisting of a pump, a reservoir, and 2 cylinders that are placed into the corpora cavernosa (1 in each corpus) and (2) a 2-piece inflatable consisting of a pump and 2 cylinders. The noninflatable prosthesis is a semirigid device that is bendable.

Category

Prosthesis, penile

Device details

Penile prostheses are available from American Medical Systems (AMS) and from Coloplast (formerly Mentor).

American Medical Systems

The AMS 700 Series 3 is a 3-piece inflatable penile implant. It includes an inner layer of silicone, which is coated on both sides with Parylene; a middle woven layer to control expansion of the cylinder; and an outer layer of silicone, which is coated internally with Parylene. The inner silicone layer is reinforced. The middle woven layer is either a unidirectional Dacron-Lycra weave, which allows expansion only in girth (CX and CXR), or a bidirectional weave, which allows expansion in both length and girth (LGX).

The following are the available versions:

• AMS 700 LGX Preconnect
• AMS 700 CX Preconnect
• AMS 700 LGX
• AMS 700 CX
• AMS 700 CXR (requires only a 65 mL reservoir)

The AMS 700 series is also available with InhibiZone, an antibiotic impregnation of rifampin (rifampicin) and minocycline. InhibiZone is not available on the rear tip extenders.

Three types of pumps are available, the standard pump, the Tactile Pump, and the Momentary Squeeze. The prostheses are available preconnected or with separate connections. The preconnected models must be ordered as either infrapubic or scrotal. The Momentary Squeeze pump is available only with preconnected prostheses.

Rear tip extenders are available in lengths of 0.5, 1.0, 1.5, 2.0, 3.0, 3.0, 5.0, and 6.0 cm. The CXR requires narrow rear tip extenders, which are available in sizes ranging from 0.5 to 3.0 cm in 0.5-cm increments. The reservoirs are either 65 mL or 100 mL and have Parylene.

The AMS Ambicor is a 2–piece inflatable penile implant. It is not available with Parylene or InhibiZone. The cylinders are available in lengths of 14-22 cm in 2-cm increments and in 3 different cylinder diameters (12.5, 14, and 15.5 mm).

The AMS Spectra is a semirigid penile implant.

Coloplast

Coloplast makes inflatable penile prostheses in which the pump is made of medical-grade silicone but the inflatable cylinders and the fluid reservoir are made of Bioflex. The Coloplast Titan is a 3-piece penile implant; the Titan Narrow is also available.

The Titan is available in infrapubic and scrotal versions, depending on the method of implantation. The scrotal version has a shorter length of tubing between the cylinders and the pump. The Titan cylinders are available in lengths of 14-22 cm in 2-cm increments and have 1.0-, 2.0-, and 3.0-cm rear tip extenders. Both the Titan and the Titan Narrow expand in girth but not length. The Titan Narrow requires narrower rear tip extenders (9 mm, compared with 12.8 mm for the Titan). Three reservoirs are available: 60, 75, and 100 mL.

The Titan hydrophilic prosthesis allows the surgeon to coat the device with 1 or more antibiotics, which are eluted over time. It was introduced in 2002.

The Coloplast Titan One-Touch Release (OTR) is a 3-piece penile implant with a 1-touch release pad that allows easier deflation of the prosthesis. The Titan OTR is magnetic resonance imaging (MRI)-conditional and latex-free.

The Coloplast Excel is a 2–piece inflatable prosthesis that is not available in the United States. The Coloplast Genesis is a malleable noninflatable penile implant.

3-piece penile implants

The 3-piece penile implants consist of a scrotal pump, 2 cylinders that are placed in the 2 corpora cavernosa (1 in each corpus), and a reservoir that is placed in the abdomen. The pump is used to transfer fluid from the reservoir into the cylinders. Distention of the cylinders produces penile rigidity.

AMS 700 series

In the American Medical Systems (AMS) 700 LGX, the cylinders are designed to allow elongation by as much as 15-20%, depending on the patient’s anatomy. This is the only implant that provides controlled length and girth expansion. The device also includes the Momentary Squeeze pump with a lockout valve and a deflation button, InhibiZone, and a Parylene-coded reservoir designed to mitigate cylinder fatigue and improve reservoir durability. Devices in the AMS 700 product line should be filled with sterile, normal saline.

In 2004, AMS updated the 700 series by introducing the Tactile Pump, which provided the ability to transfer a slightly larger volume of fluid with each squeeze. The exterior surface of the pump was modified to allow easier inflation. In addition, the deflation component of the pump was also increased in size, and sharper edges were added to permit easier localization of the deflation valve and thus facilitate deflation.

In 2006, the AMS 700MS was introduced with the Momentary Squeeze pump to allow easier deflation. To deflate the device fully, the patient had only to press the button and then squeeze the cylinders. The size of the pump was decreased to improve comfort, and the device had a lockout valve to prevent autoinflation.

When InhibiZone is used, the following recommendations are appropriate:

• If a hypersensitivity reaction develops to a device coated with InhibiZone, the penile prosthesis should be removed and the patient treated appropriately
• Devices with InhibiZone should not come into contact with ethyl alcohol, isopropyl alcohol or other alcohols, acetone, or other nonpolar solvents; these solvents may remove the antibiotics from the device
• InhibiZone components should not be soaked in saline or other solutions before implantation; however, they may be briefly rinsed or dipped in a sterile solution immediately before implantation
• Use of products with InhibiZone should be carefully considered in patients with hepatic or renal disease because use of rifampin and minocycline can place additional stress on the hepatic and renal systems
• Patients who receive a device with InhibiZone and are also taking methoxyflurane should be carefully monitored for signs of renal toxicity
• Patients who receive a device with InhibiZone and are also taking warfarin should have their prothrombin time (PT) monitored because tetracyclines have been reported to affect coagulation
• Use of products with InhibiZone should be carefully considered in patients receiving thionamides, isoniazid, and halothane because of the potential hepatic side effects that have been reported in patients receiving these drugs and higher doses of rifampin

AMS Quick Connect Sutureless Window Connectors should not be used in revision procedures involving previously implanted component tubing: they may be less effective in this setting.

CXR rear tip extenders are not compatible with CX or LGX cylinders.

Coloplast Titan

In 2002, Mentor introduced a more anatomic distal cylinder tip to its Alpha 1 cylinders. The revised tip permitted a better fit and a more natural aesthetic result. The narrow-base cylinder design yields less pronounced folds upon deflation, and when the device is inflated, it expands to a girth of 19 mm, which is the same as that of the AMS 700 series. In 2000, a lockout reservoir had been introduced to prevent autoinflation of the penile cylinders. Coloplast bought Mentor's urology business in 2006.

In 2002, the Titan hydrophilic-coated prosthesis was introduced. The coating is covalently bonded and designed for long-term attachment to the device to help inhibit bacterial adherence. The hydrophilic surface allows physicians to use their current antibiotic device preparation. When the prosthesis is soaked in an antibiotic solution before implantation, it will be coated with the drug, which is then eluted over time. In addition, the surface of the cylinders becomes lubricious, which makes it easier to implant.

In vitro studies indicate that the hydrophilic coating decreases the ability of bacteria to attach to the device.^[1] In a study comparing infection rates for Coloplast Titan penile implants coated with vancomycin and gentamicin or rifampin and gentamicin with rates for InhibiZone-impregnated AMS penile implants, the investigators reported lower infection rates with the rifampin-gentamicin Titan prosthesis and the InhibiZone-impregnated AMS prosthesis than with the vancomycin-gentamicin Titan prosthesis.^[2]

In 2008, the Coloplast Titan One-Touch Release (OTR) was approved. This device allowed the patient to achieve deflation with a single squeeze and release. In a study comparing the Coloplast Titan OTR with the previous Genesis pump, there was a statistically significant reduction in the number of postoperative teaching sessions patients required to operate the device properly (1.19 for OTR vs 1.87 for Genesis).^[3] The Titan OTR was subjectively just as easy to implant and inflate as the Genesis pump, and it was easier to deflate.^[3]

2-piece inflatable penile implant

The AMS Ambicor consists of a pair of cylinders and a single pump bulb placed in the scrotum. Squeezing the scrotal pump transfers fluid from the rear tip cylinder reservoirs into the central cylinder chambers, which, once full, do not expand. The fluid within the chambers becomes pressurized, resulting in penile rigidity. The device is deflated by holding the penis in the bent position for several seconds.

The advantages of the Ambicor include ease of use, fast and simple 1-step deflation, flaccidity that appears natural in comparison with noninflatable implants, and concealment. Its disadvantages include the requirement for a degree of manual dexterity, the possibility of leakage or malfunction, and flaccidity that is not as natural as that achieved with the 3-piece device.

Noninflatable implants

The AMS Spectra Concealable penile prosthesis is a single-use implant consisting of a pair of cylinders that are surgically inserted into the 2 corpora cavernosa. It is manually placed in the up position for intercourse and the down position for everyday activities. Its advantages include ease of use, concealment within the body and with simple bending, minimal requirement for manual dexterity, and simple surgical insertion. Disadvantages include firmness when not in use and relative unsuitability for individuals requiring repeated cystoscopy.

Coloplast manufactures the Genesis Malleable Penile Prosthesis, which was previously manufactured by Mentor and referred to as the Acuform prosthesis. The Genesis prosthesis has a hydrophilic coating.

Placement of a penile prosthesis is indicated for erectile dysfunction (ED). Typically, the prosthesis is placed after other forms of therapy have failed.

For proper device inflation and deflation, patients must have adequate manual dexterity and strength. Patients must be counseled in advance regarding the long-term implications of a penile prosthesis. They should be aware that the majority of prostheses create an erection by increasing girth, not length; consequently, an erection created by means of a prosthesis may appear shorter than a normal physiologic erection.

Furthermore, patients should be aware that if the device is removed for any reason, other treatment options are unlikely to be successful in providing an erection. In some individuals, but not all, the vacuum device may be successful after removal of a prosthesis.

Proper counseling is crucial to postoperative satisfaction. In a study evaluating the roles that preoperative counseling and patients’ realistic understanding of inflatable penile prosthesis (IPP) surgery play in determining postoperative satisfaction, the authors noted that lower preoperative expectations scores correlated almost linearly with higher satisfaction scores after surgery.^[4]

Placement of a penile prosthesis is contraindicated in patients who have active urogenital infections or active skin infections in the region of the surgery.

Implantation of an InhibiZone-impregnated American Medical Systems (AMS) 700 series prosthesis is contraindicated in patients with known allergy or sensitivity to rifampin or to minocycline or other tetracyclines. It is also contraindicated in patients with systemic lupus erythematosus (SLE), because minocycline has been reported to aggravate SLE.

In a long-term multicenter study of the American Medical Systems (AMS) 700CX inflatable prosthesis that assessed efficacy, safety, and patient satisfaction, 92% of the prostheses were functional after 3 years, and 86% were functional after 5 years.^[5] Moreover, 88% of the patients in this study indicated that they would recommend the procedure to someone else, and 86% stated that they would undergo the procedure again if necessary.

A long-term multi-institutional study of 200 consecutive patients who underwent placement of an AMS 3-piece inflatable implant demonstrated a 92% patient satisfaction rate and a 96% partner satisfaction rate.^[6]

In a study evaluating 3 penile prosthesis pump designs in a blinded survey of practitioners, the Titan One-Touch Response (OTR) model received the highest clinician preference ratings.^[7]

A comparison study by Wang et al, using the Sexual Health Inventory for Men (SHIM) Question 5 for evaluation of general satisfaction, demonstrated a 94% satisfaction rate with the AMS Ambicor.^[8]

Placement of a penile prosthesis is indicated for the treatment of erectile dysfunction (ED). In most cases, this is done in patients with ED refractory to medical therapy. Patients must be extensively counseled regarding the risks and benefits of prosthesis placement, and they must be informed that alternative therapies may not be successful in the treatment of ED should the prosthesis be removed. Some may notice a loss of penile length in the erect state, because most prostheses do not provide expansion in length.

The decision regarding the type of prosthesis to be placed depends on the patient's wants and needs, the surgeon's preference, and the patient's anatomy and history.

For example, patients with ED and a history of Peyronie disease and penile curvature are best treated with prostheses that expand in girth but not length, such as the Coloplast Titan and the AMS 700CX.^[9] In patients with extensive intracorporal fibrosis, a narrow cylinder (Coloplast Narrow Base or AMS 700 CXR) may be best. Generally, 3-piece prostheses achieve better results than 2-piece prostheses in men with larger phalluses.

Patients who have previously undergone extensive abdominal or pelvic surgery or irradiation, hernia repair with mesh, colostomy, or renal transplantation may be better candidates for 2-piece prostheses, which do not involve intra-abdominal reservoir placement. Alternatively, a 3-piece prosthesis can be implanted and the reservoir placed ectopically into a nonoperated or nonirradiated area of the abdomen in an extraperitoneal location. In patients who have radical prostatectomy ED, the reservoir can be safely placed transinguinally.^[10]

Neurologically impaired patients may do better with a multiple-component prosthesis, which has a lower rate of erosion than semirigid prostheses do.^[11]

A variety of precautions may be taken to help minimize the risk of infection, including the following^[9] :

• Administering preoperative and postoperative oral or parenteral antibiotics
• Ensuring that the urine is sterile
• Eliminating any other sources of infection
• Minimizing traffic in the operating room
• Scrubbing and shaving at the time of surgery
• Providing copious intraoperative irrigation with an antibiotic solution

Short-term follow-up is necessary to ensure that the device has been properly placed, that no signs or symptoms of infection exist, that the patient has been properly instructed in the use of the prosthesis and is comfortable with it, and that no technical complications exist, such as cylinder crossover or perforation.

Patients should be counseled regarding long-term complications, including infection and malfunction. They should be instructed to follow up if pain, swelling, redness, discharge, or fixation of the pump or tubing occurs. Similarly, follow-up is needed if the device malfunctions. Visible tips indicate an erosion.

The most significant complications related to placement of a penile prosthesis are infection and malfunction (in multiple-component prostheses).

Infection

Infection rates for initial implantation range from 1% to 3%, whereas rates for penile prosthesis revisions are reported to range from 7% to 18%.^{[12, 9, 5]} Removal of the entire device, copious irrigation with a multiple-antibiotic solution and an aseptic solution, and placement of an antibiotic-coated inflatable penile prosthesis may decrease these rates.^{[13, 14]}

Malfunction

Inflatable penile prostheses have been modified over the years in efforts to reduce the risk of malfunction. In 2007, Wilson et al, using the Kaplan-Mer product limit method to estimate the long-term survival of 2384 initial implants involving 4 different inflatable penile prostheses, found that the estimated 10-year mechanical survival rates for the American Medical Systems (AMS) 700CX, AMS 700 Ultrex, and Mentor Alpha 1 devices were 67.7%, 61.5%, and 82.15%, respectively.^[15]

The reinforcement of Mentor’s pump tubing, which was introduced in 1992, increased the Alpha 1’s estimated mechanical survival rate from 65.1% to 88.75%. Furthermore, the application of the Parylene coating to the AMS 700 CX cylinders increased the 3-year estimated mechanical survival rate from 88.4% to 99.9%.

Other complications

Other, less frequent complications of penile prosthesis implantation include cylinder erosion through the skin or the urethra, cylinders that are too short and do not support the glans, cylinder crossover, corporal perforation, pump migration, redundant tubing in the scrotum, reservoir compression of pelvic veins, reservoir hernia, and reservoir erosion into adjacent organs.^[15]