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Optimization of the artificial urinary sphincter: modelling and experimental validation

Florian Marti, Thomas Leippold, Hubert John, Nadine Blunschi and Bert Müller
Physics in Medicine and Biology
Vol. 51, pp. 1361-1375, February 2006

Abstract

The artificial urinary sphincter should be long enough to prevent strangulation effects of the urethral tissue and short enough to avoid the improper dissection of surrounding tissue. To optimize the sphincter length, the empirical 3-parameter urethra compression model is proposed based on the mechanical properties of the urethra: wall pressure, tissue response rim force, and sphincter periphery length. In vitro studies using explanted animal or human urethras and different artificial sphincters demonstrate its applicability. The pressure of the sphincter to close the urethra is shown to be a linear function of the bladder pressure. The force to close the urethra depends on the sphincter length linearly. Human urethras display the same dependencies as the urethras of pig, dog, sheep, and calf. Quantitatively, however, sow urethras resemble best the human ones. For the human urethras, the mean wall pressure corresponds to (-12.6±0.9) cmH2O and (-8.7±1.1) cmH2O, the rim length to (3.0±0.3) mm and (5.1±0.3) mm, and the rim force to (60±20) mN and (100±20) mN for urethra opening and closing, respectively. Assuming an intravesical pressure of 40 cmH2O, and an external pressure on the urethra of 60 cmH2O, the model leads to the optimized sphincter length of (17.3±3.8) mm.


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@Article{eth_biwi_00440,
  author = {Florian Marti and Thomas Leippold and Hubert John and Nadine Blunschi and Bert M\"uller},
  title = {Optimization of the artificial urinary sphincter: modelling and experimental validation},
  journal = {Physics in Medicine and Biology},
  year = {2006},
  month = {February},
  pages = {1361-1375},
  volume = {51},
  number = {},
  keywords = {}
}