Biomechanical Studies of the Inflatable Penile Prosthesis: A Review

The penile prosthesis remains the primary surgical treatment for refractory erectile dysfunction. Over the decades, inflatable penile prostheses’ mechanical reliability, patient satisfaction, safety, and functional erectile restoration have greatly improved. During this time, many studies of biomechanical properties of the prosthesis have been conducted to better understand their biomimicry to the erect human phallus. To review all current literature on the biomechanical properties of the penile prosthesis, including prosthesis biomechanical function, and variability in model-related performance. A Medline PubMed search was used to identify all articles of interest related to subjects involving the penile prosthesis and its related biomechanical properties. The following were included in the search for articles of interest: “biomechanics,” “mechanics,” “mechanical properties,” “axial rigidity,” “penile implant,” and “penile prosthesis.” Articles were further screened for content and English language. Here we perform a literature review of the bio-mechenical function, performance, and patient satisfaction of penile implants. Axial rigidity helps determine the ability of an erect penis to complete vaginal intromission and pelvic thrusting without buckling. Recent cadaveric data show that at maximum inflation, Coloplast and American Medical Systems (AMS) implants had comparable performance. Variability was seen at various lower fill pressures, where more severe buckling was observed. Coloplast Titan showed a tendency toward better resistance to longitudinal and horizontal forces. The AMS CX device showed similar performance to the Titan, and the AMS LGX device was shown to be most sensitive to fill pressure variation. Additionally, rear tip extenders (RTEs) appear to negatively affect axial loading, especially in settings of larger implants. Current research suggests that circumferentially expanding devices, such as AMS CX and Coloplast Titan, show better resistance to longitudinal (penetration) and horizontal (gravity) forces and, unlike the AMS LGX device, are less sensitive to device fill pressure. Additionally, RTEs have been shown to negatively impact axial loading, especially in larger cylinder inflatable penile prostheses >20 cm in length. Madiraju SK, Wallen JJ, Rydelek SP, et al. Biomechanical Studies of the Inflatable Penile Prosthesis: A Review. Sex Med Rev 2019;7:369–375.