Affiliations: [a] Biomaterials Science Center, University of Basel, Basel, Switzerland | [b] Department of Urology, University Hospital Basel, Basel, Switzerland
Correspondence:
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Address for correspondence: Prof. Bert Müller, Thomas Straumann Chair for Materials Science in Medicine, Biomaterials Science Center, c/o University Hospital Basel, CH-4031 Basel, Switzerland. Tel.: +41 61 265 9660; Fax: +41 61 265 96 99; E-mail: [email protected].
Abstract: The study demonstrates that the minipig urethra is an appropriate animal model for in vitro experiments and therefore promising for long-term animal tests of artificial urinary sphincter systems in vivo. Freshly explanted porcine and minipig urethras were connected to a fluid reservoir that simulated the bladder pressure. This bladder pressure was adjusted by changing the water level (hydrostatic pressure). Specially designed aluminum sphincters loaded with a fluid-filled container were used to close/open the urethras. Results from minipigs and domestic pigs were compared to data published for human urethras. We measured the leak-point pressures (LPP) by adjusting the bladder pressure at a constant sphincter length and by changing the sphincter length at a constant bladder pressure. Because the urethral tissue shows visco-elastic behavior, LPPs for both opening and closing were measured. By fitting the in vitro data, we evaluated the three characteristic parameters from the empirical urethra compression model, i.e. wall pressure (pW), rim force (FR), and rim length (LR). From the experimental data we found agreement of mean values between (male) human urethras: ⟨pW⟩opening=−(12.9±0.9) cmH2O, ⟨pW⟩closing=(8.6±1.1) cmH2O, ⟨FR⟩opening=(0.06±0.02) N, ⟨FR⟩closing=(0.10±0.02) N, ⟨LR⟩opening=(3.0±0.3) mm, ⟨LR⟩closing=(5.1±0.3) mm, and (male) minipig urethras: ⟨pW⟩opening=−(13.4±0.3) cmH2O, ⟨pW⟩closing=−(8.6±0.4) cmH2O, ⟨FR⟩opening=(0.19±0.01) N, ⟨FR⟩closing=(0.21±0.02) N, ⟨LR⟩opening=(2.4±0.1) mm, ⟨LR⟩closing=(3.3±1.0) mm. These in vitro tests quantified by means of the urethra compression model demonstrate that the minipig (especially the male one) represents a suitable animal model for testing artificial urinary sphincters.
Keywords: In vitro testing, animal model, artificial urinary sphincter, minipig urethra, urinary incontinence, urethra compression model
