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Magnetic induction of novel shape memory alloy penile prosthesis

McVary, K1; Columbo, A1; Le, B2

1: SIU, United States; 2: University Wis. United States


Objectives: We previously developed a novel shape memory alloy prosthesis using a lasercut Nitinol extruded tube that expands and becomes rigid when activated to simulate an erection. We also described how it is possible to activate it using magnetic induction (MI) in vitro without the use of pumps or reservoirs. To better understand the thermal safety and efficacy of this approach in tissue, we tested MI activation using an in vitro animal tissue model and human cadavers.

Materials and Methods: We used a commercially available magnetic inductor with a power of 1000W and a custom made 2mm copper coil of 3 turns of 4cm diameter. The prosthesis or nitinol tube was inserted down the length of a pork-product sausage or implanted in the corpora cavernosa of a human cadver. Two thermocouples were placed to measure temperature changes: (1) on the exoskeleton, and (2) 2 mm away in the tissue. The miniductor was waved over the embedded prosthesis and activated. Temperature tracings were recorded over time. As a control, the same setup was placed on a laboratory hot plate with temperature set at 43C.

Results: Using magnetic induction to a nitinol tube, the prosthesis temperature rose from 23C to 43C in 20 secs, with only a 2C change in tissue temperature. With the lasercut prosthesis 43C was reached in 36 secs with a 4C rise in surrounding tissue. With the cadaver, it took 46 secs to reach target temperature. With magnetic induction tissue temperature never rose above 5C from baseline. With the hot plate, the tissue and prosthesis gradually rose in temperature together from 23C to 43C over 300 secs with conduction of heat. In all cases, the activated device simulated previously described erection parameters in terms of mechanical rigidity and expansion.

Conclusions: Magnetic induction effectively penetrates animal and human cadaveric tissue and allows for potentially faster heat transfer and activation of a novel shape-memory penile prosthesis. There is no evidence of any thermal damage to local tissues from this process of activation. Further design optimization can enhance the magnetic induction process.


Work supported by industry: yes, by BostonScientific (industry funding only - investigator initiated and executed study). The presenter or any of the authors act as a consultant, employee (part time or full time) or shareholder of an industry.

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