How does a penile prosthesis work?

How Penile Prostheses Work

Penile prostheses are mechanical devices implanted within the corpora cavernosa of the penis that provide rigidity for sexual intercourse in men with erectile dysfunction who have failed or cannot use less invasive treatments. 1

Types of Penile Prostheses

There are two general categories of penile prostheses:

• Malleable (non-inflatable) prostheses: Also called semirigid rod prostheses, these devices maintain a constant rigidity but can be bent into different positions. They offer advantages of lower cost, better mechanical reliability, and ease of use without requiring patient training on inflation/deflation techniques. 1

• Inflatable prostheses: These devices provide a more natural appearance in both flaccid and erect states. They consist of:

  • Two-piece inflatable prostheses: Include cylinders and a pump mechanism
  • Three-piece inflatable prostheses: Include cylinders, a scrotal pump, and a fluid reservoir placed in the abdomen 1, 2

Mechanism of Action

Malleable/Semirigid Prostheses

• Consist of paired rods implanted into the corpora cavernosa
• Always maintain some degree of firmness but can be positioned in different orientations
• Simpler design with fewer mechanical parts means higher reliability and lower risk of mechanical failure 1, 3

Inflatable Prostheses

• Three-piece design (most common):

  • Paired cylinders implanted in the corpora cavernosa
  • A pump placed in the scrotum
  • A fluid reservoir positioned in the abdomen
  • When activated, the scrotal pump transfers fluid from the reservoir to the cylinders, creating rigidity
  • A deflation mechanism returns fluid to the reservoir, restoring flaccidity 1, 2

• Design improvements have reduced mechanical failure rates to 6-16% at 5 years, with modern devices featuring:

  • Lockout valves to prevent auto-inflation
  • Antibiotic or hydrophilic coatings to reduce infection risk (1-2% infection rates with coated models) 1, 4

Advantages and Considerations

• Advantages:

  • Provides reliable rigidity for intercourse when other treatments fail
  • Inflatable devices offer a more natural appearance in both flaccid and erect states
  • High satisfaction rates among patients and partners 5, 6

• Considerations:

  • Surgical implantation is essentially irreversible
  • May result in penile shortening compared to natural erections
  • Potential for mechanical failure requiring reoperation
  • Risk of infection (though reduced with modern coated devices)
  • May reduce effectiveness of other therapies if the device is subsequently removed 1, 4

Patient Selection and Counseling

• Penile prosthesis implantation should be considered for men with erectile dysfunction who:

  • Have failed or cannot use less invasive treatments
  • Have no active infections (systemic, cutaneous, or urinary tract) 1

• Thorough counseling should include:

  • Types of prostheses available
  • Possibility of complications (infection, erosion, mechanical failure)
  • Differences from natural erections, including potential penile shortening
  • Potential reduction in effectiveness of other therapies if device removal is needed 1, 4

Modern Innovations

• Current devices are MRI-compatible at 1.5 Tesla field strength 1, 4
• Infection-inhibiting coatings have significantly reduced infection rates 1, 4
• Mechanical reliability has improved with design modifications such as lockout valves to prevent auto-inflation 1, 2

Penile prosthesis implantation remains an important and effective treatment option for erectile dysfunction, with continuous improvements in device design enhancing reliability, safety, and patient satisfaction. 5, 6, 2