How does a penile prosthesis actually work?
An inflatable penile prosthesis works by moving fluid from a reservoir into two cylinders inside the penis when a pump in the scrotum is pressed, and a release mechanism empties them afterwards. A semi-rigid prosthesis has no fluid and is bent into position by hand. Satisfaction with implant surgery reaches 92% to 100% when patients are properly counselled.
How does a three-piece inflatable implant produce an erection?
A three-piece implant has a fluid reservoir placed low in the abdomen, a pump in the scrotum and two cylinders inside the erectile tissue of the penis. Pressing the pump moves fluid into the cylinders, which makes the shaft firm. A release mechanism sends the fluid back to the reservoir so that the penis becomes soft again.
"For inflatable models, the steps in operation should be thoroughly reviewed and demonstrated so that the man and his partner are confident regarding the technique." Source 2, p. 32
Once the pump has been used, the erection lasts as long as the man wants and can be produced as often as he wants. Patients may prefer a three-piece design because the erection it produces is more natural.
How is a two-piece implant different?
A two-piece inflatable implant works the same way but has no separate reservoir in the abdomen. It is easier to operate than a three-piece model and may suit a man with poor manual dexterity who still wants a hydraulic device.
The two-piece design is also an option when placing a reservoir carries a higher risk, for example after previous abdominal surgery, extensive scarring or a kidney transplant. Injuries to nearby pelvic structures such as the bladder, bowel and blood vessels have been described with reservoir placement, which is one reason the choice depends on the man's medical history.
How is a semi-rigid implant used?
A semi-rigid implant keeps the penis firm at all times. It is bent upward for intercourse and bent to lie flat against the groin at other times, and it cannot be deflated. The operation is simpler than for an inflatable device and the implant is easy to use.
The drawbacks are a penis that stays permanently firm and is harder to conceal. Satisfaction is generally higher with inflatable devices, but a semi-rigid implant can be more appropriate for men with limited hand dexterity or when cost is a concern. Mechanical failure mostly affects inflatable models and usually comes from a leak in the connecting tubing, and a semi-rigid implant contains no fluid that could leak.
What does a penile prosthesis do and not do?
Both types make the shaft rigid, but the glans does not usually become rigid. Sex drive is not directly affected, and orgasm and ejaculation are not enhanced. Men with scarring of the erectile tissue are told that an implant is unlikely to restore the size they had before the scarring.
No head-to-head studies have shown one implant type to be superior, and no difference in efficacy or safety has been demonstrated among the implants available. Satisfaction with implant surgery is among the highest of any treatment for erectile dysfunction, at 92% to 100% in patients and 91% to 95% in partners, with appropriate counselling.