Consideraciones de prótesis de pene - Nature 16

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REVIEWS A practical overview of considerations for penile prosthesis placement Landon Trost, Philip Wanzek and George Bailey

Abstract | Penile prostheses have remained the gold-standard therapy for medically refractory erectile dysfunction (ED) since their popularization. Advances in device design and surgical techniques have yielded improved rates of infection, satisfaction, and mechanical survival of devices. Operative techniques in penile prosthesis surgery include the use of adjunctive procedures (such as ventral phalloplasty and release of the suspensory ligament), management of penile fibrosis, and manoeuvres to correct Peyronie’s-disease-related curvature. Complications include urethral and corporal perforation, crossover, infection, impending erosion, and/or supersonic transporter deformity. Long-term data regarding mechanical, overall, and infection-free survival demonstrate excellent results, and, given the consistently high satisfaction rates and limited alternatives for medically refractory ED, penile prostheses are likely to remain a relevant and important treatment strategy for the foreseeable future.

Department of Urology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA. Correspondence to L.T. ([email protected]) doi:10.1038/nrurol.2015.270 Published online 1 Dec 2015

The desire to enhance or restore erectile and sexual function has likely been a long-standing objective of mankind, with early reports dating to the 16th century 1. Given age-related and comorbidity-related declines in erectile function, the ability to restore penile rigidity has become the sexual medicine equivalent of the fountain of youth. Mechanical devices to restore function emerged as viable treatment options. The first known examples of penile prostheses were reported in the 1500s, with initial designs probably used to assist in urinary function over sexual performance1. By 1936, rib cartilage was being placed in the penis to restore rigidity, then synthetic materials such as acrylic, polyethylene, and silicone were used in the 1950–1960s2–7. Arguably, one of the greatest historical advances occurred in 1973, when Brantley Scott reported outcomes of patients undergoing placement of inflatable penile prostheses (IPP)7. Since that time, ongoing device enhancements and improved surgical techniques have made penile prostheses the gold-standard therapy for medically refractory erectile dysfunction (ED). Given the importance of penile prostheses in contemporary practice, the objective of this Review is to provide an overview of clinical evaluation, indications for placement, device characteristics, notable improvements, surgical techniques, management of complications, long‑term outcomes, and future perspectives on treatment.

Contemporary devices Penile prostheses have undergone numerous modifications to augment mechanical reliability, infection rates, and overall patient satisfaction6. Arguably, some of the

more considerable device enhancements include the introduction of silicone in 1964 (more biocompatible and flexible than previously used polyethylene and acrylic materials), Bioflex™ (Mentor; now Colopolast, Denmark) in 1983 (a polyurethane implant with enhanced strength over silicone), inclusion of a woven fabric layer and threeply system (American Medical Systems (AMS), USA) in 1987 (which enhanced the strength of silicone devices), Parylene® (Specialty Coating Systems, Inc., USA) coating (AMS) in 2000 (which provided enhanced strength), kink-resistant and nylon-reinforced tubing between 1986 and 1987 (which reduced postoperative sequestration of fluid), lock-out valves (which reduced autoinflation), and preconnected cylinders (which reduced tubing-related complications)7,8. Additional noteworthy modifications included the use of InhibiZone™ by AMS (which incorporated antibiotics into the prosthetic lining) in 2001, and hydrophilic coatings by Coloplast (which reduced bacterial adherence and enabled antibiotic absorption) in 2002, both of which improved outcomes by reducing infection rates9,10. Currently, several classes of penile prostheses are available for implantation including malleable or semirigid, two-piece, and three-piece devices (TABLE 1). The most commonly used penile prostheses are manufactured by AMS and Coloplast. Three-piece penile prostheses include the AMS 700™ series (including the CX, CXR, and LGX devices) and the Coloplast Titan™ and Titan NB™. Several notable features characterize each of the devices. The CXR and NB devices have reduced diameters (10 mm compared with the standard 12 mm),

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REVIEWS Key points • Penile prostheses have high rates of long-term device survival, few complications, and high satisfaction in appropriately selected individuals; no data suggest superiority of any one approach or manufacturer • The indications for the preferential use of three-piece, two-piece, or malleable prosthetics are poorly defined, although three-piece devices are typically preferred over alternatives if clinically indicated • Important considerations for infection control include use of anti-infection-coated devices, perioperative antibiotics, alcohol-based surgical site scrub, and use of a no-touch technique • Penile prosthesis revision and salvage surgery (in both infected and noninfected prostheses) should incorporate washout protocols to reduce infection if a new device is to be placed • Placement of a penile prosthesis in men with corporal fibrosis or with Peyronie’s disease might require adjunctive techniques • Intraoperative complications including proximal corporal perforation and crossover can be managed without aborting the procedure, whereas the optimal management of urethral perforation (particularly distal perforation) remains poorly defined

which enables use in small or scarred corpora where limi­ ted dila­tation is achievable. The LGX penile prosthesis enables expansion in length as well as girth, whereas the Titan™ devices enable unrestricted circumferential expansion. Lock-out valves are located in the pump in the AMS devices and in the reservoir in the Coloplast devices. Cylindrical strength is enhanced in the AMS three-piece devices by the Parylene® coating and woven, three-ply fibre technology, while Coloplast three-piece IPPs use Bioflex® for additional strength. Preconnected cylindrical tubing is of a fixed length with the AMS devices and increases with model size with Coloplast IPPs. Current reservoirs include the AMS 65 ml and 100 ml spherical and 100 ml reduced profile Conceal™. Coloplast produces 75 ml and 125 ml Cloverleaf™ reservoirs and only these reservoirs have received FDA approval for ectopic (­commonly used to infer submuscular) placement. Infrequently used penile prostheses include the twopiece and malleable devices. The only currently available two-piece system is the AMS Ambicor®, which has the reservoir in the rear portion of the prosthetic cylinders to avoid the need for separate reservoir placement. Malleable devices include the AMS Spectra™ and Coloplast Genesis™. The Spectra™ and Ambicor® do not currently include InhibiZone™, whereas the Genesis™ incorporates a hydrophilic coating. Currently, no data exist demonstrating superior protection from infection for either malleable device. All contemporary devices are considered MRI safe, with the notable exception of the Spectra™ which is listed as MRI-conditional11. This device was given this designation owing to a 1.6 °C increase in temperature noted following 15-minute exposure to a 3‑T MRI, therefore, it is of minimal clinical significance.

Clinical evaluation and indications Patient selection Placement of a penile prosthesis results in displacement of cavernosal tissue, therefore, this procedure is considered permanent and irreversible, and is reserved for

men who are either intolerant of, or fail to achieve adequate responses to, more conservative therapies, such as ­phosphodiesterase‑­5 inhibitors, intraurethral suppositories, intracavernosal injections, and vacuum erection devices. Men with combined ED and Peyronie’s disease, in whom surgical correction of Peyronie’s disease is antici­ pated, have traditionally been considered for placement of a penile prosthesis earlier than men with ED alone12–14. However, this treatment paradigm might change now that clostridium collagenase has been introduced as a treatment option for Peyronie’s disease. Other select patients who are often considered for early placement of penile prostheses include those who have had prior phallic reconstruction, spinal cord injury, or those with other contraindications for more conservative therapies. Clinical considerations before surgery include an assessment of hand function to ensure the patient can operate an IPP pump, prior surgeries resulting in obliter­ ation of the space of Retzius (to assess a possible role for ectopic reservoir placement), and determination of potential surgical devices. Preoperative counselling, t­ horough informed consent (consisting of a detailed explanation of risks, benefits, and expectations of surgery), assessment of factors associated with dissatisfaction (such as personality characteristics including compulsive and/or ­obsessive tendencies, unrealistic expectations, revision surgery, surgeon shopping, entitled feeling, denial of current condition, and other psychiatric disorders), and establishment of appropriate postoperative expectations are also an important aspect of clinical evaluation to optimize satis­ faction and overall outcomes15,16. The Sexual Medicine Society of North America has provided a sample template highlighting key discussion points to assist with the informed consent process17.

Device selection The decision as to which device and/or reservoir is best in each clinical scenario is debatable and has not been authoritatively defined. Three-piece penile prostheses are often preferred as first-line devices if clinically appropriate, as they have traditionally demonstrated improved satisfaction over the alternatives18–23. Historically, twopiece devices were often used in cases where prior abdominal surgeries precluded the placement of a reservoir in the orthotopic location (most commonly the space of Retzius); however, the availability of lower-profile reservoir designs from AMS and Coloplast has increased the feasibility of using alternative ectopic locations, such as in the abdominal submuscular space (FIG. 1). Malleable devices are commonly used in cases of limited hand function and might have an increasing role during salvage surgery for infection or among men with refractory ischaemic priapism24–26. Surgical approach The optimal surgical approach for placement of a penile prosthesis (which could be infrapubic, transscrotal or circumcision) is debatable, with no study consistently demonstrating the superiority of one technique over another. Limited comparative data exist on surgical approaches, but infection rates and patient reported outcome measures

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REVIEWS Table 1 | Contemporary penile prostheses Device

Cylinder diameter (mm)

Cylinder length (cm)

Unique characteristics

Recommended reservoir fill volumes (ml)

Rear tip sizing (cm)

Antimicrobial feature

0.5, 1.0, 1.5, 2.0, 2.5, 3.0, or 4.0

InhibiZone™

75 or 125 for the Cloverleaf™

1.0, 1.5, 2.0, or 3.0

Polyvinylpyrrolidone — a hydrophilic coating

AMS 3‑piece devices (with silicone material, Parylene® coating, and one-touch release to deflate) 700 CX

12.0–18.0

12, 15, 18, or 21

NA

700 CXR

9.5–14.5

12, 14, 16, or 18

For men with short, narrow corpora

700 LGX

12.0–18.0

12, 15, 18, or 21

Expands length and girth

65 or 100 for spherical reservoirs or 100 for concealed reservoir

Coloplast 3‑piece devices (with Bioflex® material, zero degree tubing, and soft molded distal tip) Titan

13.0–16.0

11, 14, 16, 18, 20, 22, 24, 26, or 28

NA

Titan NB

11.0–12.0

11 or 14

For men with short, narrow corpora

Titan OTR

13.0–16.0

11, 14, 16, 18, 20, 22, 24, 26, or 28

OTR to deflate

Titan OTR NB

11.0–12.0

11 or 14

For men with short, narrow corpora OTR to deflate

AMS 2‑piece devices Ambicor

12.5, 14.0, or 15.5

14 or 16, 16, 18 or 20, or 18, 20 or 22

Fluid reservoir in the proximal end of the cylinders

Cylinders are prefilled

0.5, 1.0, 1.5, 2.0, 2.5, 3.0, or 4.0

None

12, 16, or 20

Alternating polyethylene and titanium segments connected by a central cable

N/A

0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, or 6.0

None

14–23, 16–25, or 18–27

No moving internal parts and trimmable custom sizing

NA

1.0, 1.5, 2.0, or 3.0

Polyvinylpyrrolidone — a hydrophilic coating

AMS malleable devices Spectra

9.5, 12.0, or 14.0

Coloplast malleable devices Genesis

9.5, 11.0, or 13.0

AMS, American Medical Systems; NA, not applicable; OTR, one-touch release.

seem to be similar 27,28. In a study of two surgical residents trained in both infrapubic and transcrotal approaches, the trainees reported super­ior proximal dilation and cylin­ der placement with the infrapubic approach, equivalent facility in positioning the reservoir between techniques, and superior distal cylinder and pump placement with the penoscrotal approach29. The penoscrotal approach is suggested as the preferred method in cases of revision surgery to reduce the likelihood of sensation loss, but no studies have directly compared sensory changes between the infrapubic and transcrotal techniques27–35. Reservoir placement is also an evolving practice. Implanting a reservoir in the orthotopic location refers to placement in the space of Retzius via the inguinal ring or direct placement through the abdominal fascia (FIG. 2). In contrast, ectopic placement refers to any location outside of the standard perivesical space and is most commonly used to describe locations within the anterior abdominal wall (FIG. 1)31. Implantation of ectopic reservoirs has received increasing attention owing to the develop­ ment of low-­profile reservoirs and can be performed via a direct cut-down technique or through the inguinal canal. Indications for selecting reservoir location are not well defined, although ectopic might be preferred in cases where the perivesical space has been compromised to avoid potential inadver­tent intraperitoneal placement or injury to adjacent structures. Two retrospective studies have reported safety and efficacy outcomes of ectopic

reservoir placement 32,33. In the largest series (n = 93) of men undergoing high submuscular placement of an IPP, Chung and colleagues34 reported no bowel, bladder, ureteral, or vascular injuries at a mean follow-up duration of 5.5 months.

Infection control Infection control remains a critical aspect of penile pros­thesis surgery. Although modifications (such as InhibiZone™ and hydrophilic coatings) have greatly reduced infection rates, surgical techniques and practices also contribute considerably to controlling infection. Perioperative considerations Very limited data exist regarding several perioperative aspects of penile prosthesis surgery, including the type and duration of antibiotics, and surgeon hand cleaning prior to surgery. In the absence of definitive data, consensus panels have provided expert opinion statements and recommendations35,36. The AUA currently recommends perioperative use of an aminoglycoside and a first-generation or second-generation cephalosporin or vancomycin, which might be continued for up to 24 h after surgery 35. A panel of prosthetic surgeons modified this recommendation slightly and recommended continued antibiotics for ≥24 h after surgery, with all participating prosthetic surgeons administering antibiotics for 5–14 days after surgery 36.

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REVIEWS Regarding the use of preoperative showers or bathing with antiseptic solutions, a Cochrane systematic review of seven randomized controlled trials (RCTs) concluded that no clear benefit was gained with this practice over placebo37. The optimal agent for operative site skin cleansing remains debatable. A Cochrane systematic review reported outcomes of 13 RCTs and concluded that, with low-quality evidence, alcohol-containing products had the highest probability of being effective38. Results also demonstrated that 0.5% chlorhexidine alcohol-based solutions had lower rates of surgical-site infections in clean cases (those cases without entry into organs related to the gastrointestinal or genitourinary tracts) than alcohol-­based povidone–iodine paint. Comparison of

Figure 1 | Various locations for submuscular ectopic reservoir placement. Nature Reviews | Urology Ectopic refers to any location outside of the traditional perivesical space, although contemporary use of the definition most often indicates submuscular locations in the anterior abdominal wall such as deep to the rectus abdominis muscle and superficial to the transversalis fascia and peritoneum. Alternative locations include lateral to the rectus, either in the cephalad periumbilical region or more caudal (purple dots). In the more lateral position, the reservoir might be located deep to any of the muscular layers including the external oblique, internal oblique, transversus abdominis, or transversalis fascia. Modified from the Mayo Clinic with the permission of Mayo Foundation for Medical Education and Research. All rights reserved.

skin cultures from men undergoing genitourinary prosthetics following treatment with either chlorhexidine or povidone–iodine showed that the chlorhexidine was superior in eradicating skin flora39. Importantly, chlorhexidine did not result in increased genital skin irritation compared with povidone–iodine.

Prosthetic and soaking solutions All three-piece devices and the Coloplast malleable devices provide some degree of antiseptic coating. The AMS-InhibiZone™ devices include a material impregnated with rifampicin and minocycline. Coloplast uses a hydrophilic coating that reduces bacterial adherence and permits uptake of aqueous antibiotic solutions (which are selected based on regional antibiotic resistance). Both additions have resulted in reduced infection rates compared with devices that do not have these coatings40–44. The optimal selection of antibiotics for use with Coloplast devices has not been defined, but Wilson and colleagues45 reported outcomes from five commonly used solutions. Sections of hydrophilic-coated devices were dipped in solutions of trimethoprim–polymixin B, trimethoprim– sulfamethoxazole, bacitracin, rifampin–minocycline, or rifampin–trimethoprim–sulfamethoxazole. Results from in vitro assessments of zones of inhibition demonstrated excellent efficacy for all solutions tested, except for bacitracin. Given the equivalent results, the authors recommended routine use of trimethoprim–sulfamethoxazole as it is inexpensive, easy to handle, and readily available in comparison with the other solutions. Currently, no studies exist that suggest superiority of either AMS or Coloplast regarding ­infection rates since the introduction of antiseptic coatings. No-touch technique Although various strategies have been used to reduce bacterial skin contamination for many years, the ‘no-touch’ technique was formally introduced in the literature in 201146. This technique modified the traditional approach by adding a separate instrument table used only for the initial skin incision. Once the skin is incised and underlying tissues are sufficiently dissected to permit skin exclusion, a new, separate drape is placed over the top of the existing surgical field and secured so that all skin surfaces are covered. Finally, the original instrument table is taken down, and the surgeon’s gloves and gown are changed. Outcomes from a series of 2,215 patients undergoing antibiotic-coated IPP placement before and after introduction of the no-touch methodology showed reductions in infection rates from 2.00% to 0.46%47. As these reports currently represent a s­ ingle-surgeon series, additional validation is required. Revision cases Revision surgery is often required in cases of device malfunction, impending erosion, malpositioning, or other device defects. Only limited (and some contradictory) data are available on outcomes, but the majority of series report infection rates of 8–13% among men undergoing revision surgery before the introduction of antibiotic-coated devices and 2–10% following their

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REVIEWS

Figure 2 | Traditional orthotopic reservoir placement. Orthotopic refers to the Nature Reviews | Urology perivesical, preperitoneal location and is achieved through either indirect placement via the inguinal canal or direct placement through the abdominal wall fascia. Modified from the Mayo Clinic with the permission of Mayo Foundation for Medical Education and Research. All rights reserved.

introduction10,41,47–49. However, the use of washout protocols and antibiotic-impregnated devices occurred simultaneously in many practices, therefore, determining which factor led to greater reductions in infections is difficult. Wilson and colleagues41 specifically compared the efficacy of washout protocols among men under­going revision surgery with antibiotic-coated devices. Their results demonstrated that the use of antibiotic-coated devices in revision cases did not result in reduced numbers of infections compared with historical comparisons, whereas the use of a washout protocol significantly decreased infections from 10% to 3% (P = 0.01). Cultures obtained from penile prostheses at the time of revision surgery in non-clinically infected individuals have demonstrated growth of bacteria in 10–80% of cases, with some authors suggesting that nearly all prostheses exhibit the presence of biofilms9,50–52. Given this high rate of bacterial colonization, washout procedures are frequently employed to thoroughly irrigate all spaces prior to reintroduction of the new prosthesis. The original Mulcahy washout technique was performed in men with clinically infected prostheses, but subsequent reports have suggested using similar washout protocols in uninfected revision cases also has benefit10,53–55. Results from series comparing outcomes of uninfected penile prosthesis revision surgeries demonstrated reductions in

infection rates from 10–25% without washout to 3–4% with washout 10,41,53. The presence of bacteria on penile prosthesis’ capsule tissues was reduced from 43% to 25% using washout 51. By contrast, other limited series have demonstrated no significant differences in infection rates between revision cases performed with mini-washout (0%) and no washout (2.3%, P = 1.00)56. Given the limited availability of high-level evidence, contradictory findings, varied protocols, and heterogeneous populations, the role of and optimal regimen for washouts is poorly defined. Management of select components of the implant during revision surgery is also debatable. Options at the time of revision include exchanging one or more items (including the pump, cylinders, and/or reservoir), performing a complete device removal and replacement, or placing a new device while leaving the prior defunctionalized reservoir in situ (termed ‘drain and retain’). Results from the largest series of men undergoing revision IPP surgery (n = 214) demonstrated higher infection and erosion rates in patients undergoing selective rather than complete device exchange (9.1% versus 5%)10. Evidence for the drain and retain concept was gained from a series of 55 patients — 39 underwent artificial urinary sphincter surgery and 22 received an IPP (of whom 18 had revision IPP) — who were left with a reser­ voir in situ at the time of revision or explant surgery 57. Retrospective outcomes from chart review demonstrated an overall infection rate of 1.8% in the drain and retain group compared with 1.5% in a comparable cohort, which was not significantly different (P = 0.88). No erosions or obstructions to adjacent organs were noted at a mean follow-up duration of 24 months. However, given the lack of prospective data and limited number of IPP revision cases included, additional studies and external validation of this technique are required.

Adjunctive techniques Several adjunctive techniques have been described to improve perceived outcomes of penile prosthesis surgery. Historically, one of the leading causes of patient dissatisfaction with penile prostheses was the perceived reduction in penile length postoperatively. Currently, whether any length is actually lost is not clear. Some experts think that the perception of length loss might be caused by patients not having erections for many years, and hence they are not aware of their true existing length. Others feel that the glans penis no longer fills with blood. No references exist for any of these theories though, and existing studies fail to demonstrate objective correlations with the subjective reports58. Osterberg and colleagues59 reported results from 20 men who underwent placement of a penile prosthesis and compared preoperative stretched penile length and pharmacologically induced erections with postoperative lengths. Results demonstrated statistically significant reductions in median penile length from 15.0 cm (stretched length) preoperatively to 13.5 cm after implantation (P = 0.01), with 70% of patients experiencing a median loss of 0.5 cm. These findings are consistent with other data, which have also noted slight (mean 0.74 cm loss at 1 year, P