Although erectile dysfunction has been described since ancient times, adequate treatment has only been available for the last four decades. The era of implantable devices began with the development of silicone-based prosthetic materials in the late 1960s, as a result of the United States space program (1
). Modern penile prosthetic devices were first developed in the early 1970s, when Small et al. (2
), along with Scott et al. (3
), reported the implantation of penile prosthetic devices into the corpora cavernosa to fill the cavernous space and provide a physiologically functional erection with good cosmetic results. These devices have undergone multiple redesigns and improvements between the early prosthetic devices and the currently available inflatable penile prostheses. Mechanical malfunction rates in these early devices were reported in excess of 60% of cases. Current inflatable prosthetic devices have a far improved mechanical reliability, with 81% to 94%, 68% to 89%, and 57% to 76% at 5, 10, and 15 years, respectively (4
). Design changes over the past several decades have included replacement of stainless steel connectors with plastic connectors, addition of nonkinked tubing, single-design construction,
Teflon cylinder input sleeves, multiple-layer cylinders, and most recently, the technologic advances in infection prevention in implant design.
TABLE 69.1 CURRENTLY AVAILABLE PENILE PROSTHESES
American Medical Systems
Titan with OTR/touch pump, zero degree/narrow base cylinders
LGX, Length and Girth eXpansion; CX, Controlled eXpansion; CXR, Controlled eXpansion Reduced size cylinders; OTR, one-touch release.
The currently available devices can be divided into semirigid, mechanical, and multiple-component inflatable penile prostheses, of which there are two- and three-piece models available (Table 69.1
). The semirigid rod and mechanical prostheses available today are the successors of the earliest devices designed in the 1970s. These devices, although easier to implant, have few advantages over the newer inflatable devices, as infection and mechanical malfunction rates are similar. The Genesis (Coloplast Inc, Minneapolis, Minnesota) is the currently available semirigid rod device that consists of a central metal core and a silicone elastomer rod (Fig. 69.1
). The mechanical Spectra (American Medical Systems, Minnetonka, Minnesota) implant employs a spring and cable design with alternating titanium and polyethylene segments (Fig. 69.2
). The Genesis is the only available malleable device with a hydrophilic coating that allows for the impregnation of antibiotics.
The three-piece inflatable penile prostheses continue to be the most satisfactory prostheses once they are implanted, provided they remain functional. These prosthetic devices produce the most natural-appearing rigidity in girth and length and excellent flaccidity for optimal concealment. The threepiece inflatable penile prostheses vary in construction from three-layer silicon/Dacron/Lycra/silicone in the AMS 700 Series (American Medical Systems, Minnetonka, Minnesota) (Fig. 69.3
) to a single layer of Bioflex, a polyurethane material, in the Coloplast Titan series (Coloplast Inc, Minneapolis, Minnesota) (Fig. 69.4
). The Titan model is coated with polyvinylpyrrolidone, a hydrophilic material that allows absorption of an antibiotic solution of the surgeon’s choice. The preimplantation antibiotic “dip” provides a hydrophilic layer to resist bacterial adherence. The AMS 700 implants are impregnated with InhibiZone, a proprietary combination of rifampin and minocycline that is U.S. Food and Drug Administration (FDA) approved to reduce infections. Options with both available inflatable devices include standard or narrow cylinders and girth expansion and/or length elongation. Numerous trials have shown comparable efficacy, satisfaction rates, mechanical reliability, and infection rates between the two currently available inflatable devices.
FIGURE 69.1 Coloplast Genesis semirigid rod penile prosthesis. (Genesis is a trademark of Coloplast A/S. Copyright © Coloplast Corp. Reprinted with permission. All rights reserved.)
FIGURE 69.2 American Medical Systems Spectra mechanical penile prosthesis. (Spectra is a trademark of Coloplast A/S. Copyright © Coloplast Corp. Reprinted with permission. All rights reserved.)
To improve ease of surgical implantation and avoid the portion of the prosthesis placed within the abdominal region, two-piece devices were designed. Because these two-piece inflatable prostheses remove the separate reservoir, additional fluid is available either by a larger scrotal pump or a combination of proximal cylinder and pump reservoir. Although these devices provide adequate penile stiffness in many patients, the limited reservoir capacity decreases the flaccidity and, in some patients, may diminish rigidity. These prostheses are especially difficult to deflate in patients with small penises and may provide inadequate rigidity in patients with longer penises. Although less optimal than three-piece devices, these two-piece implants are ideal for patients in whom reservoir
placement is absolutely contraindicated. However, ectopic reservoir placement is an option for those that a three-piece device is desired, and previous surgical history precludes the ability to safely place the reservoir in the standard location. The only currently available two-piece inflatable penile prosthesis is the AMS Ambicor (American Medical Systems, Minnetonka, Minnesota) (Fig. 69.5
FIGURE 69.3 American Medical Systems 700 LGX three-piece inflatable penile prosthesis. (Courtesy of American Medical Systems, Inc.)
FIGURE 69.4 Coloplast Titan touch zero-degree three-piece inflatable penile prosthesis. (Courtesy of Coloplast.)
FIGURE 69.5 American Medical Systems Ambicor two-piece inflatable penile prosthesis. (Courtesy of American Medical Systems, Inc.)
INDICATIONS FOR SURGERY
Although there are a variety of penile prosthesis designs currently available for implantation, not all patients with erectile dysfunction are candidates for penile prosthesis implantation. Penile prostheses are generally the procedure of last resort for those men failing more conservative measures such as oral phosphodiesterase type 5 (PDE5) inhibitors, vacuum erection device, urethral alprostadil, and intracavernosal injection therapy. For those men in whom penile prostheses are suggested, careful counseling before penile implant procedures will limit many of the problems with postoperative dissatisfaction. Once the discussion and demonstration of penile implant varieties has been carried out, patients can be counseled about the most appropriate penile prosthesis for their individual use. Patients may choose a specific prosthetic type based on their needs and preferences (1
). Younger patients with normal manual dexterity and patients who wear form-fitting clothing, or who shower in public at athletic facilities, often choose a three-piece inflatable penile prosthesis, as the penile appearance in the flaccid position is better than other designs. For these patients, implantation of a semirigid rod penile prosthesis requires a significant lifestyle change; hence, they are better served with an inflatable device. Similarly, patients with Peyronie’s disease, secondary implantation, or significant peripheral neuropathy, such as that occurring in severe diabetes, are best served with an inflatable penile prosthesis, as
intracavernosal pressures are decreased between uses, and the possibility of extrusion is diminished.
For patients in whom the convenience of inflation and deflation are not important, the risks and mechanical malfunctions may outweigh the disadvantages of a malleable penile prosthesis. Such patients as paraplegics who require external urinary collection device, those with inadequate manual dexterity, or those with significant obesity may be better served with a malleable penile prosthesis.
Surgical implantation of penile prostheses can be carried out using several surgical approaches and incisions. Semirigid and mechanical malleable prostheses can be implanted through a distal penile approach. Multiple-piece prostheses can be implanted by either the infrapubic or penoscrotal approach. Although individual surgeons have a variety of rationales for each of these approaches, there does not appear to be any clear advantage in patient satisfaction or outcome of the two approaches. Patient anatomy may dictate appropriate choice. Patients with previous abdominal surgical procedures where reservoir placement is difficult may be better served with an infrapubic approach, whereas patients with morbid obesity may be better approached through a penoscrotal incision. Two-piece devices, because there is no separate reservoir, are best implanted through a penoscrotal incision.
Infection prevention is of utmost importance during placement of a penile implant. Perioperative antibiotic treatment is critical in diminishing incidence of infection and prosthetic removal. Importantly, the recently introduced InhibiZone impregnated coating on the AMS 700 series implants and the lubricious hydrophilic coating of the Coloplast Titan series implants have reduced infection risk by threefold. Contemporary series report an infection rate of approximately 1% to 3% (5
). Eid et al. (6
) have described a “no-touch” technique, which takes meticulous care in preventing the device from touching the skin during implantation and has decreased the overall infection rate of virgin and revision cases to 0.46%. Other studies have shown the risk for infection in revision penile prosthesis cases to vary from 6.7% to 18.8% (5
). A perioperative dosage of an intravenous antibiotic agent is recommended by the American Urological Association and should be administered within 1 to 2 hours of the incision and continued for 24 hours postoperatively. Recommended agents include an aminoglycoside plus a first-generation cephalosporin, second-generation cephalosporin, or vancomycin for prophylaxis of the most common pathogenic skin flora (5
). Patients may be discharged with a continued course of oral antibiotic therapy at the surgeon’s discretion. The use of antibiotic-coated penile implants, while reducing the incidence of postoperative infection, does not preclude the need for systemic, perioperative antibiotics.
Three-piece inflatable penile prostheses, as well as semirigid and two-piece prostheses, can be implanted by a transverse or vertical penoscrotal incision. This approach has distinct advantages in obese patients and is the most common approach for routine penile prosthesis implantation. The scrotum is carefully clipped, and the lower abdomen, genitals, and upper thighs are prepped. Various methods of skin prepping have been described including prolonged preoperative scrubs and most recently alcohol-based solution; however, these are surgeon-dependent. Because the penoscrotal approach requires differentiation of corpora cavernosa from the corpus spongiosum during dissection, initial placement of a Foley catheter may facilitate exposure. Prior to making the incision, a local anesthetic dorsal penile block with plain bupivacaine to decrease postoperative pain may be used (7
). A penile ventral ring block is not performed, as it may distort the tissue planes of the initial dissection. The incision is placed in the upper portion of the scrotum and is usually transverse horizontal, one fingerbreadth below the penoscrotal junction. The Scott/Lone Star retractor (Lone Star Medical Products; Stafford, Texas) facilitates exposure with this incision (Fig. 69.6
). Once the skin incision has been carried out, a blunt Henry sweep maneuver with an opposite spreading motion of two hooked
index fingers aids the dissection, as it is carried down to the corpora cavernosa bilaterally (8
). Buck’s fascia is opened at the penoscrotal junction over each corpus. The corpus spongiosum is exposed. The midline spongiosal attachments of the scrotal septum may be taken down sharply for better proximal corporal exposure, and rake hooks are gently used with the Lone Star retractor to secure the bilateral testicles inferiorly, and six blunt hooks are useful to retract the lateral and superior aspects of the skin incision (Fig. 69.7
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