Types of Penile Prosthesis Penile implants are currently available in a variety of

forms, which can be categorized into two major types: semi-rigid, or inflatable, with a silicon or

Penile Prosthetic Surgery Michael Sohn and Antonio Martín-Morales

Surgical Treatment of Erectile Dysfunction 137

polyurethane jacket. Details of the available length end of each cylinder into each cylinder shaft. The and diameters can be found on the websites of the

newly developed Mentor two-piece penile prosthe- two manufacturing companies: American Medical

sis is called the Excel Resist® device. It consists of a Systems at www.visitams.com; and the Mentor

pair of inflatable cylinders, which are implanted into Corporation at www.mentorcorp.com. When im-

the corpora cavernosa, and a resi-pump that is planted into the corpora cavernosa, they can be

implanted into the scrotum. The cylinders and resi- manipulated by the patient to fit his needs. The Jonas

pump are preconnected and filled with sterile saline implant, produced in Germany, has a silver core and

during the manufacturing process. The volume of

a silicone covering [12]. A soft silicone implant was fluid in the reservoirs of both two-piece inflatable introduced by Subrini. Currently these devices are

penile prostheses is less than in the reservoir of the manufactured in France and sold under the names

three-piece prostheses. The lesser volume of the “SSDA” and “Virilis” in many countries [15]. These

two-piece reservoirs diminishes the difference implants may be indicated in the presence of residual

between rigidity and flaccidity of these systems, spongy erectile tissue, which permits tumescence

compared to the three-piece systems. and complimentary girth expansion around the

Three-piece inflatable implants are composed of central silicone support.

two cylinders, a scrotal pump and a reservoir, which The only “mechanical” prosthesis on the market is

is typically positioned either in the retrovesical space the Dura II, which has articulating segments of poly-

or within the peritoneal cavity. Three-piece implants ethylene held together by a central spring. These

manufactured by AMS are the 700 CX, 700 CXR and articulating segments are covered by a polytetrafluo-

Ultrex devices. The CXR cylinders have a narrow roethylene sleeve surrounded by a silicone jacket.

base and come in shorter lengths than the CX cylin- The Dura II prosthesis is a product of the American

ders. CX and CXR cylinders have a three-layer design Medical Systems (AMS). A similar device, called

consisting of an inner layer of elastic silicone, a “Genesis”, with a hydrophilic coating is planned by

middle layer of woven Dacron–Lycra and an outer the Mentor Corporation. This design provides posi-

layer of silicone. The inner layer fills with fluid to tional memory, allowing the prosthesis to remain

provide rigidity, the outer layer allows for capsule concealed when not in use, yet rigid during inter-

formation around, but not into, the prosthesis, and course [25]. These semi-rigid implants are cheaper

the middle layer permits controlled expansion of the than inflatable prostheses and easier to implant

cylinders. The recently introduced parylene coating because there is no pump or reservoir to place. Semi-

of the cylinders diminishes the risk of aneurysmal rigid prostheses may be implanted through a

dilatation of cylinders. In the CX and CXR cylinders, subcoronal, infrapubic or scrotal incision. Local

the middle layer is woven unidirectionally, permit- anesthesia may be used if the corpora cavernosa are

ting girth expansion but not length expansion. It is not too fibrotic and their dilatation is expected to be

commonly agreed that although very satisfactory easy.

results may be obtained in all subsets of patients, the Inflatable implants are available in two-piece or

CX implant is particularly useful for patients with three-piece models. Two-piece implants are made

Peyronie’s disease or any form of severe organic ED. by AMS and by the Mentor Corporation. The AMS

Patients who have significant scarring of the corpora Ambicor prosthesis consists of a pair of inflatable

cavernosa, e.g. after priapism or with extensive Pey- cylinders, which are implanted into the corpora cav-

ronie’s disease, or having a re-implant after previous ernosa, and a pump, which is implanted into the

removal of an infected prosthesis, may benefit from scrotum. The cylinders and pump are preconnected

an inflatable implant with narrow cylinders such as during the manufacturing process and the system is

the CXR, which requires dilation of the corpora cav- prefilled with sterile saline. To achieve an erection,

ernosa to only 10 mm. The only penile prosthesis the scrotal pump is squeezed and released several

that can lengthen with inflation is the AMS Ultrex times. This inflates the cylinders by transferring

prosthesis. This prosthesis also has three layers, but saline solution from a small reservoir located at the

the middle layer of Dacron–Lycra has a bi-directional

138 Chapter 12 weave that permits both length and girth expansion

Table 12.3 Implant rates of all manufacturers. (Personal of the cylinders. However, the Ultrex prosthesis is

data with permission of AMS, Germany [22].) not appropriate for patients with Peyronie’s disease

because these patients need greater stiffness than is

Year

Overall

USA Europe

provided by the Ultrex prosthesis.

Three-piece inflatable implants manufactured by 3.880

the Mentor Corporation share a similar design to the 3.960

previously described models. The main difference is

that the Mentor implants are made based of an inert

aromatic polyurethane polymer called Bioflex TM .

Compared to silicone, Bioflex TM has increased abra-

sion resistance and higher tensile strength. An addi-

tional feature of the current Mentor “Titan” or

three-piece inflatable prostheses, is a lockout valve that reduces the common phenomenon of auto- inflation of the prosthesis [16]. The lockout valve is

ments and in clinical use, is composed of 2 g of gen- also used in the two-piece Excel Resist® device. The

tamycin and 100 000 units of bacitracin in 1000 ml of Titan prostheses are also available in a narrow-base

saline [17,21].

version, which is best used in patients with severe Reduced infection rates have been reported fibrosis of the corpora cavernosa, as described above

recently for the AMS InhibiZone TM and the Mentor for the AMS CXR prosthesis.

Resist TM products [18,19,20]. The three-piece As infection is the most feared complication

implants of AMS and Mentor can be seen with their of penile prosthetic surgery, two- and three-piece

coatings in Figure 12.2. The two-piece device of implants specifically modified to reduce this risk

Mentor is also available with hydrophilic coating, have been recently introduced into clinical practice.

while the AMS two-piece Ambicor device is not. The InhibiZone TM prostheses by AMS are coated

Notably, to avoid elution of the coating prior to with a combination of rifampicin and minocycline to

implantation, the various components should not be inhibit bacterial growth. In these prostheses, the sur-

soaked in saline or other solutions for a prolonged faces of the prostheses, which come into contact with

period. However, conventional parenteral prophy- the adjacent tissue, are impregnated with quantifi-

lactic antibiotic protocols should be maintained. able doses of these antibiotics that elute into the area

Penile prosthesis implantation is a frequent opera- surrounding the prosthesis after surgery. Both

tion performed worldwide. The implant statistics drugs elute initially at high rates, with a significant

over the last years are summarized in Table 12.3. decrease in rifampicin after one and minocycline

The introduction of PDE5 inhibitors into the after seven days. The inhibitory effect of the Inhibi-

market in 1998 initially caused a significant drop in Zone TM treatment is greatest for Staphylococcus epider-

implant rates worldwide, but in more recent years a midis and Staphylococcus aureus [17,8].

constant increase of implants has been noted. Mentor has also developed a method to reduce

Seventy-five percent of penile implant sales are in penile prosthetic infection. This method uses an

the United States, where 90% of implants are three- intensely hydrophilic coating called Resist TM that

piece and two-piece devices. Outside the United is applied to the Titan and Excel prostheses. Its

States 40% of all implants are non-hydraulic devices increased lubrication has been shown to decrease

bacterial adherence in vitro. Furthermore this coating absorbs antibiotics that can elute into surrounding tissues over 24 to 72 hours to further

Patient and Implant Selection

decrease infection. An antibiotic-soaking solution, It is of critical importance to offer this treatment only which has been tested both in laboratory experi-

to properly selected patients, and furthermore to

Surgical Treatment of Erectile Dysfunction 139

Fig. 12.2 (a) AMS 700CX InhibiZone TM . (b) Mentor-Alpha 1. (c) Mentor Titan with Resist TM -Coating (here, colour- enhanced with methylene-blue).

select the model that best fits the patient’s needs and surement of the length of the penis. The length after anatomy. Patients who are eligible for a penile

prosthetic implantation is usually similar to the implant should be assessed with a detailed systemic

length of a completely stretched flaccid penis. It is medical and sexologic history [14]. Candidates for

worthwhile to spend time with the patient illustrat- penile prosthesis implantation should fulfill the

ing this concept because, commonly, patients have following criteria:

unrealistic expectations of penile length that cannot • Good general health

be met by any form of therapy. The physical exami- • Failure of medical therapy for ED or,

nation may also allow the detection of areas of signif- • Contra-indication to medical therapy of ED

icant scarring within the corpora cavernosa. Patients • Psychologic stability

with Peyronie’s disease may not report a penile bend • Patient and partner fully informed

even though they may have extensive corporal • Informed consent for surgery

fibrosis, which can ultimately limit the intraopera- • Unsuccessful trial of vacuum devices or at least

tive dilatation of the penis. In such cases, the final consideration of these devices [14,55]

penile length and girth may be unsatisfactory to the The complete medical assessment may include the

patient [55]. Preoperative identification of corporal following elements if they are available:

fibrosis and other factors that impact on postopera- • The international index of erectile function (IIEF)

tive results, plays a very important role in reducing or other validated questionnaires to objectively

or eliminating patients’ disappointment with post- assess severity of ED and subsequent postoperative

operative length and girth. During the physical outcome

examination, the manual dexterity of the patient • Penile colour Doppler sonography with intracor-

should be assessed, as it must be sufficient when an poral pharmacologic injection

inflatable prosthesis is used. Obesity may be a factor • Nocturnal penile tumescence test, especially

making the use of any prosthesis more difficult; this when the initial medical evaluation suggests the

is a physical feature that must be addressed [14]. possibility that the patient’s ED is predominantly

In patients with poorly-controlled or treated psychogenic

diabetes mellitus, it is wise to obtain a preliminary • In cases with medico–legal questions, a compre-

diabetologic consultation to normalize their glucose hensive diagnostic work up should be done [14]

metabolism. There is controversy as to whether

A thorough physical examination is very important. abnormally high serum glycosylated hemoglobin is a This should include an assessment or actual mea-

marker for higher risk of postoperative infection.

140 Chapter 12 Several investigators suggest that patients with

uncompensated diabetes mellitus may have an implant placed safely [23,55,57].

A critical point in the evaluation of the candidate for an implant is to identify active infections at the time of surgery. A urine culture is mandatory in all patients. Patients who have infectious lesions in the genital area or other local infections, and patients who have active systemic infections, should defer surgery until the infection has resolved. It has been suggested that patients should scrub their genitalia with an antiseptic solution during the five days prior to hospital admission, and should take an oral quinolone during the same period [14].

When an AMS three-piece implant is planned for

a patient with long penile length, the CX device should be used because CX devices provide better rigidity than Ultrex devices at longer penile length [56]. Patients with limited dexterity should be of- fered malleable devices. If the limited dexterity is due to a neurologic condition in which there is reduced penile sensation, there is an increased risk of urethral or cutaneous erosion of the implant. In such cases, the surgeon should consider implanting somewhat shorter cylinders, to reduce the risk of erosion. In patients with severely scarred corpora, CXR or Mentor narrow-based devices should be used. If patients are disappointed postoperatively with their penile length, they can be advised that daily inflation of the prosthesis may produce corporal dilatation, and that surgical replacement with longer cylinders may be possible at a later time [24]. In patients undergoing secondary or repeat prosthesis implantation, the Ultrex device may be considered if preoperative physical examination re- veals a 2 cm or more difference between the non- stretched and stretched penile length. However, Ultrex cylinders should not be used in patients with Peyronie’s disease.

In patients who have had retropubic prostatec- tomy, cystectomy or other causes of perivesical scarring, two-piece implants offer the advantage of not requiring retropubic placement of an implant reservoir. However, the difference in rigidity and girth between the inflated and deflated states of two-piece penile prostheses is limited compared to three-piece implants. Alternatively, intra-

abdominal, rather than retropubic, placement of the reservoir of a three-piece device can be chosen for the patient with retropubic fibrosis [25].

Types of Penile Prosthesis Penile implants are currently available in a variety of