Longitudinal and Horizontal Load Testing of Inflatable Penile Implant Cylinders of Two Manufacturers: An Ex Vivo Demonstration of Inflated Rigidity

Abstract

Introduction: Since the inception of the inflatable penile prosthesis, a new era has been ushered in for the management of erectile dysfunction. Despite multiple innovations to improve function and reliability, there are no current data comparing the biomechanical properties of these devices.

Aim: To compare the resistance of the Coloplast Titan (Minneapolis, MN, USA) with that of the AMS 700 LGX (Minnetonka, MN, USA) penile prosthesis cylinders to longitudinal (penetration) and horizontal (gravity) forces.

Methods: We compared two cylinder sizes from each company: the Coloplast Titan (18 and 22 cm) and the AMS 700 LGX (18 and 21 cm). To evaluate axial rigidity, which simulates forces during penetration, we performed a longitudinal load compression test to determine the load required to cause the cylinder to kink. To test horizontal rigidity, which simulates the horizontal forces exerted by gravity, we performed a modified cantilever test and measured the degrees of bend for each device. All devices were tested at 10, 15, and 20 PSI to simulate in vivo pressures.

Main outcome measures: The main outcome measurement for the longitudinal load test (penetration) was the force required for the inflated cylinder to bend, thereby affecting its rigidity. The main outcome for the horizontal rigidity test (gravity) was the angle of displacement, in which a smaller angle represents a more horizontally rigid device.

Results: Longitudinal column testing (penetration) demonstrated that less force was required for the AMS device to kink compared with the Coloplast implant across all three fill pressures tested. The Coloplast Titan also had a smaller angle of displacement at the modified cantilever test (gravity) compared with the AMS implant across all fill pressures.

Conclusion: The Coloplast Titan demonstrated greater resistance to longitudinal (penetration) and horizontal (gravity) forces in this study. The AMS device was very sensitive to fill pressures. In contrast, the Coloplast Titan's ability to resist these forces was less dependent on the device fill pressure.

Keywords: Erectile Dysfunction; Material Properties; Prosthesis.

Figure 1

ADMET eXpert 7600 Single Column Testing Machine load testing of AMS 700 LGX 21(A-B) and Coloplast Titan 22(C-D).

Figure 2

Maximum load of compression achieved at device failure and location of failure at different fill pressures. The lowest column load required to achieve kinking is reported for each cylinder represented by an individual dot.

Figure 3

Load and location of device failure at 10, 15, and 20 PSI.

Figure 4

Unloaded and loaded cantilever testing of the AMS 700 LGX 18cm and Coloplast Titan 18cm.

Figure 5

Angle of displacement of unloaded and loaded AMS and Coloplast devices.