What Is a Penile Prosthesis (Happiness Rod)? How Does It Work?

In modern inflatable penile implants, cylinders, connecting tubes, pumps, and reservoir systems have undergone significant improvements over the years. More kink-resistant tubing, lockout systems designed to prevent unintended inflation, easier-to-use pumps, and pre-connected systems that reduce the number of connection points are among these developments. The aim is both to reduce the risk of mechanical failure and to make the implant easier for patients to use.

In the future, the use of more durable and flexible materials is expected to further extend the lifespan of penile implants. Since these devices are designed to remain inside the body for many years, advances in material technology are likely to play an important role in the future of penile implants.

With inflatable penile implants, the patient needs to manually operate a pump located inside the scrotum. This may be difficult, particularly for patients with reduced hand strength or dexterity.

For this reason, one of the new technologies currently being investigated involves implants that can be activated externally without the need for manual pumping. The aim of developing remotely controlled systems is to make the implant easier to use while potentially reducing mechanical problems associated with pumps and hydraulic connections.

A more advanced approach involves implants made from shape-memory materials. Researchers are investigating heat-sensitive materials capable of changing their rigidity. In an experimental model, an implant made from a nickel-titanium alloy was activated within approximately 45 seconds using externally applied magnetic energy.

Such a system could potentially reduce the need for pumps, reservoirs, and hydraulic connections in the future. However, important questions regarding long-term safety, achievable rigidity, ease of use, and the possibility of unintended activation by magnetic fields still need to be clarified. Therefore, these technologies are not currently alternatives to standard penile implants in routine clinical practice.

One of the main concerns among patients considering penile implant surgery is penile length. Therefore, one emerging approach is to prepare the penile tissue before surgery as much as possible and preserve the existing length.

For this purpose, the use of vacuum and penile traction devices before surgery has been investigated. In a small randomized study, patients who used a vacuum device for 10–15 minutes per day for at least one month before surgery experienced an average 0.8 cm increase in stretched penile length, compared with an average change of 0.2 cm in patients who did not use the device. Surgeons also reported that corporal dilation during surgery was easier in patients who had used vacuum therapy.

In another small study, patients who underwent traction therapy for two hours per day for 2–4 months before surgery demonstrated an average increase of 1.5 cm in length measured during surgery. However, 60% of patients reported difficulty using the device, while 40% reported pain. Therefore, although these approaches appear promising, the gains may be limited and require a high level of patient compliance.

Another area of interest in newer approaches is how patients perceive their penile length after penile implant surgery.

This is different from the concept of the implant itself increasing penile length. In some patients, correcting the skin attachment between the penis and scrotum may help increase the visible portion of the penis. In a study evaluating this approach, known as “ventral phalloplasty,” 36 of 43 patients who underwent the procedure together with penile implant surgery reported that they perceived an increase in penile length.

Various techniques involving tissues in the pubic region have also been investigated to increase visible penile length. However, these additional procedures are not part of standard penile implant surgery. Because additional surgical procedures may also introduce additional risks of complications, they should be considered in selected patients and performed by experienced surgeons.

The reservoir of a three-piece inflatable penile implant is traditionally placed in a specific anatomical space within the pelvis. However, particularly in patients who have previously undergone prostate surgery or other pelvic/retroperitoneal procedures, the anatomy of this area may have changed.

For this reason, new reservoir designs and alternative placement locations have been investigated. Flatter or cloverleaf-shaped reservoirs have made it easier to place the reservoir in alternative anatomical locations outside the traditional space.

The aim of these alternative approaches is particularly to reduce the risk of rare but serious complications such as injury to the bladder, bowel, or major blood vessels. However, reservoirs positioned closer to the surface may create different problems, such as being palpable or becoming displaced, particularly in thin patients. Therefore, reservoir placement should be planned according to the patient's anatomy and previous surgical history.

One of the most important issues in the development of penile implant technology is infection. Today, the use of antibiotic-coated or hydrophilic-coated implants plays an important role in reducing the risk of infection.

However, new research is focusing not only on killing bacteria but also on preventing biofilm formation on the surface of the implant.

Biofilm is a protective layer formed when microorganisms attach to the surface of an implant. Once this structure develops, bacteria may be better protected from both the immune system and antibiotics. Because bacterial colonies may begin to form in as little as 16 hours, infection-prevention measures around the time of surgery are particularly important.

More experimental studies are investigating ways to disrupt established biofilms. For example, ultrasound-targeted microbubbles used in combination with antibiotics and the effects of certain antimicrobial peptides against biofilms have been investigated. However, these methods are not yet standard treatments for penile implant infections, and further research is required.

Alongside technological advances, important changes have also been made to surgical techniques. One of these is the “no-touch” technique.

With this approach, contact between the implant and the skin of the genital area is minimized as much as possible. When the implant placement stage begins, previously used gloves and certain surgical materials are replaced. Infection rates as low as approximately 0.35% have been reported with this approach in patients receiving their first penile implant.

In addition, treating urinary tract infections before surgery, controlling blood glucose levels in patients with diabetes, stopping smoking at least four weeks before surgery, appropriate antibiotic prophylaxis, and the use of antibiotic-coated implants are all components of strategies aimed at reducing the risk of infection.

New approaches continue beyond the completion of surgery. Particular attention is being given to improving postoperative pain control and reducing the need for strong pain medications.

Multimodal pain management approaches, including local anesthetic blocks applied to the penis or pudendal nerve, long-acting local anesthetics, and the combined use of paracetamol or anti-inflammatory medications in appropriate patients, have been reported to reduce the need for strong pain medication after surgery.