The idea of penile implant (prosthesis) surgery goes back a very long time, but the root of the “modern” penile implants can be traced back to the 1970s when Drs. Scott, Timm, and Bradley’s described the use of inflatable silicone cylinders to be placed inside the erectile chambers of the penis (i.e. corpora cavernosa). Around the same time, Dr. MD Small published his experience with the implantation of the Small-Carrion implant. Improvements and modifications over the ensuing 40 years have resulted in devices that provide excellent functional and cosmetic results closely mimicking the natural appearance of penis in the flaccid and erect states.
Penile implants may be used for the treatment of organic erectile dysfunction (i.e. not psychologoical) due to a variety of causes. A trial of more conservative measures such as oral pills, VED, or intracavernosal injection therapy before moving onto prosthesis surgery is advocated by most experienced implant surgeons. It has been shown that penile prosthesis surgery can be safely and effectively performed after radical surgery or radiation therapy for prostate cancer with minimal intraoperative and postoperative adverse events. Patients who fail to respond to other treatments may effectively regain their ability to engage in satisfactory sexual intercourse after penile implant surgery. With proper patient selection, satisfaction rates are extremely high (greater than 90%) in both the patient and their partner.
SEMIRIGID / ROD PROSTHESES
These prostheses are constructed of two solid prostheses that are independently placed inside the erectile chambers of the penis. They are ideal for patients who are not particularly interested in the cosmetic advantages of the inflatable implants and prefer the practicality and ease of use of these devices. In certain cases, non-inflatable implants can be used for patients with spinal cord injury or renal transplant recipients.
Semirigid implants may be placed through an infrapubic (just above the penis) or scrotal incision and have a very good safety record.
The multicomponent inflatable devices are made by the AMS and Coloplast corporations. The majority of the inflatable implants used in the United States are “3-piece” units composed of a pump, a reservoir and two cylinders. The AMS corporation also manufactures a “two-piece” inflatable implant. The physician will review the risks and benefits of each type of prosthesis with the patient.
The general structural design of the AMS and Coloplast three-piece prostheses is similar: a reservoir to be placed in the space around the bladder (the perivesical space), a pair of cylinders for placement in the erectile chambers of the penis, a pump that is placed in the scrotum to inflate and deflate the device, and the associated tubing for the connections between these units.
The latest versions of inflatable implants available in the United States are designed to minimize chances of adverse events and infections in particular. Specifically, the AMS implants are coated with antibiotics (Inhibizone coating) and the Coloplast implants have a special (“hyrdrophilic”) coating that is designed to adhere to antibiotic molecules when soaked in the appropriate solution.
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As in most procedures, the overall success of the operation is dependent on adherence to protocols before, during, and after the operation including strict infection control. The patients receive antibiotics 1-2 hours prior to surgery and then for a limited period after the operation based on the surgeon’s recommendations. The most common organisms responsible for implant infections are staphylococcus epidermidis and escherichia coli. Fortunately, with the advent of the newer generation implants, the incidence of infections in “virgin” (i.e. first time) implants is very low (lower than 2% in most centers).
Whether the surgery is performed as an inpatient operation with overnight stay or in an outpatient or inpatient setting is governed by the surgeon and patient preference and economic considerations based on the patient’s insurance coverage. Peer reviewed publications have shown that implants can be safely placed in an outpatient setting, but many surgeons prefer to keep the patients overnight, a choice that may be practical and reassuring for some patients. Oral antibiotics (cephalosporins or fluoroquinolones) are typically prescribed for 7-10 days after the surgery and the patient is asked to avoid heavy lifting. Most physicians will teach the patient to use the implant 3-4 weeks after surgery and advise the patient to start using the implant 4-6 weeks after implantation (depending on the type of implant or surgical approach). In order to minimize the chances of accidental inflation of the implant (auto-inflation), the patient is asked to keep the cylinders fully deflated (and therefore the reservoir full) between weeks 4 and 8 after surgery when the body is “healing” around the reservoir. This will allow maximum space development around the reservoir and decrease the chances of auto-inflation.
More than 80% of the modern inflatable implants remain functional 5 years after implantation and some studies have reported rates as high as 93 during this period.
Some studies have reported that three-piece prostheses are more mechanically reliable than the two-piece implants. Dr. Goldstein and his peers conducted a multi-institutional retrospective study to assess safety and efficacy outcome pertaining to the Mentor (now Coloplast) Alpha-1 implant and found that with 2 years of follow-up, there were no morbidities of any type in approximately 90% of implant recipients.
Major intra-operative complications related to implant surgery are extremely rare. Other adverse events associated with prosthesis surgery include erosion into the urethra or adjacent organs, reservoir herniation into the scrotum (i.e. the reservoir is found outside the desired location near the bladder), and glans bowing or SST deformity (the tip of the penis has a downward bend). These complications are rare and typically amenable to corrective measures in experienced hands.
Despite the aforementioned improvements in implant coating and technology in general, penile implant infections have not been fully eradicated. This complication was reported to occur in approximately 2-3% of first-time implants in most series, but the reported range is widely variable. The current reported infection rates with the antibiotic enhanced versions is even lower at 1-2%. Factors that can contribute to implant infections include a depressed immune system, inadequate peri-operative prophylaxis and lax sterile protocol, prolonged hospitalization, prolonged operative time, and repeat implantations. The combination of any other procedure with penile prosthesis surgery has also been associated with higher infection rates.