title: Experimental investigation of the structural behavior of equine urethra.
abstract: OBJECTIVE
  An integrated experimental and computational investigation was developed aiming to provide a methodology for characterizing the structural response of the urethral duct. The investigation provides information that are suitable for the actual comprehension of lower urinary tract mechanical functionality and the optimal design of prosthetic devices.
  
  
  METHODS
  Experimental activity entailed the execution of inflation tests performed on segments of horse penile urethras from both proximal and distal regions. Inflation tests were developed imposing different volumes. Each test was performed according to a two-step procedure. The tubular segment was inflated almost instantaneously during the first step, while volume was held constant for about 300s to allow the development of relaxation processes during the second step. Tests performed on the same specimen were interspersed by 600s of rest to allow the recovery of the specimen mechanical condition. Results from experimental activities were statistically analyzed and processed by means of a specific mechanical model. Such computational model was developed with the purpose of interpreting the general pressure-volume-time response of biologic tubular structures. The model includes parameters that interpret the elastic and viscous behavior of hollow structures, directly correlated with the results from the experimental activities.
  
  
  RESULTS
  Post-processing of experimental data provided information about the non-linear elastic and time-dependent behavior of the urethral duct. In detail, statistically representative pressure-volume and pressure relaxation curves were identified, and summarized by structural parameters. Considering elastic properties, initial stiffness ranged between 0.677 ± 0.026kPa and 0.262 ± 0.006kPa moving from proximal to distal region of penile urethra. Viscous parameters showed typical values of soft biological tissues, as τ1=0.153±0.018s, τ2=17.458 ± 1.644s and τ1=0.201 ± 0.085, τ2= 8.514 ± 1.379s for proximal and distal regions respectively.
  
  
  CONCLUSIONS
  A general procedure for the mechanical characterization of the urethral duct has been provided. The proposed methodology allows identifying mechanical parameters that properly express the mechanical behavior of the biological tube. The approach is especially suitable for evaluating the influence of degenerative phenomena on the lower urinary tract mechanical functionality. The information are mandatory for the optimal design of potential surgical procedures and devices.
authors.affiliation: Department of Industrial Engineering, University of Padova, Via Venezia 1, I-35131 Padova Italy; Centre for Mechanics of Biological Materials, University of Padova, Italy.
authors.forename: Arturo Nicola
authors.initials: AN
authors.lastname: Natali
authors.affiliation: Department of Industrial Engineering, University of Padova, Via Venezia 1, I-35131 Padova Italy; Centre for Mechanics of Biological Materials, University of Padova, Italy. Electronic address: emanueleluigi.carniel@unipd.it.
authors.forename: Emanuele Luigi
authors.initials: EL
authors.lastname: Carniel
authors.affiliation: Centre for Mechanics of Biological Materials, University of Padova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Frigo
authors.affiliation: Centre for Mechanics of Biological Materials, University of Padova, Italy; Department of Biomedical Sciences, University of Padova, Italy.
authors.forename: Chiara Giulia
authors.initials: CG
authors.lastname: Fontanella
authors.affiliation: Centre for Mechanics of Biological Materials, University of Padova, Italy; Department of Biomedical Sciences, University of Padova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rubini
authors.affiliation: Centre for Mechanics of Biological Materials, University of Padova, Italy.
authors.forename: Yochai
authors.initials: Y
authors.lastname: Avital
authors.affiliation: Centre for Mechanics of Biological Materials, University of Padova, Italy; Department of Animal Medicine, Production and Health, University of Padova, Italy.
authors.forename: Giulia Maria
authors.initials: GM
authors.lastname: De Benedictis
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D006736:Horses; D008297:Male; D014521:Urethra / Q000033:anatomy & histology* / Q000503:physiopathology
keywords: Inflation tests; Mechanical behavior; Physio-mechanical parameters; Urethra