Pump-Free Penile Prosthesis Can Work, Early Study Shows

Pam Harrison

June 01, 2015

A pump-free and touchless method of activating a nonhydraulic penile prosthesis seems to perform as well as any hydraulic inflatable prosthesis, and would be much easier for the patient to use and for urologists to implant, an ex vivo study suggests.

"Mechanical devices can malfunction and require revision, which is a negative event for patients," said Kevin McVary, MD, from the Southern Illinois School of Medicine in Springfield.

"Our plan is to prevent such malfunctions," he told Medscape Medical News. And the new device "would make one of the more complex procedures that urologists do one of the easiest, so it could actually be transformative."

In their study, Dr McVary and his colleagues demonstrated that they could repeatedly activate the penile prostheses without pumps or reservoirs.

He presented the results at the American Urological Association 2015 Annual Meeting in New Orleans.

The team used a nonhydraulic shape-memory alloy 22 cm (8.6 inch)-penile prosthesis made out of nitinol, a metal alloy of nickel and titanium commonly used in medical devices. A 1000 W Mini-Ductor II (Induction Innovations, Inc.) and a coil 2.5 cm (1 inch) in diameter was used to activate the prosthesis.

The perpendicular force required to induce the prosthesis to transition from the flaccid to erect configuration was 0.3 kgf, which is comparable to the force required for an inflatable prostheses, Dr McVary reported.

The fully activated device resisted buckling forces of 2.66 kgf, meaning that on penetration, the prosthesis will not buckle or bend and should remain as rigid as current inflatable devices, he explained.

The final temperature reached by the prosthesis at maximum force was 42 °C (108 °F).

"Using a handheld magnetic inductor, we were able to successfully activate the shape-memory alloy penile prosthesis with no direct contract," the investigators report. "The time needed to reach a straight, erect configuration using this 1000 watt magnetic inductor was approximately 120 seconds."

"We have to do some animal studies testing the same technology," said Dr McVary. "We're in the midst of getting that arranged."

"But we found that the operating-force parameters are consistent with current market devices, and future use of a variable power generator could improve response times," he added.

It's long been known that 40% to 50% of men do not respond to any of the PD-5 inhibitors, suggesting that alternative options are needed to improve the treatment of erectile dysfunction.

We know that there's a large population of men who are good candidates for an implant, yet it's a big step.

The number of men who could benefit from a penile implant is much greater than the number who end up undergoing the procedure, said session comoderator Natan Chaim Bar-Chama, MD, from the Icahn School of Medicine at Mount Sinai in New York City.

"We know that there's a large population of men who are good candidates for an implant, yet it's a big step," he told Medscape Medical News.

Having said that, the satisfaction rate for all other therapies use to treat erectile dysfunction is relatively low, at about 50% to 60%. However, if you survey men who've had implants, 80% to 90% say they would do it again, Dr Bar-Chama reported.

Currently, any form of hydraulic prosthesis involves the implantation of several different pieces, along with tubing connecting those pieces.

"Once you increase the number of pieces you put in, you have the potential for malfunction over time and, because of that, there is hesitancy on the part of urologists to proceed with implantation," said Dr Bar-Chama.

Even if malfunction rates with the hydraulic implants are quite low, "the data from this abstract show that when rigidity is achieved, the level of hardness that this implant provides is as good as or better than what we currently have," he said.

"My hope is that because it's a simple unit, it will be embraced by many urologists who are using the multicomponent implants now," he explained. If it is, "more patients who are good candidates for this procedure would be able to benefit from an easy-to-use cosmetically appealing prosthesis that would enhance their quality of life dramatically."

This study was funded by American Medical Systems and by a grant from the National Collegiate Inventors and Innovators Alliance. Dr McVary and Dr Bar-Chama have disclosed no relevant financial relationships.

American Urological Association (AUA) 2015 Annual Meeting: Abstract PD26-03 Presented May 17, 2015.


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