Characterizing and Quantifying Material Fatigue of the Artificial Urinary Sphincter Pressure Regulating Balloon

Abstract

ObjectiveTo characterize and quantify changes in elastic properties and in vivo pressure characteristics of pressure regulating balloons (PRB) over time, we conducted an analysis of the mechanical characteristics of the PRB after removal from patients for revision surgery. MethodsPressure and elasticity characteristics of new and used 61-70cmH20 PRBs were analyzed. Pressure-volume curves were generated using commercially available urodynamics equipment. PRB pressures were measured at a standard fill volume (23cc). Elastance was calculated by the slope of the tangent line at the inflection point of the pressure-volume curve. Tests were repeated 5 times per PRB and intraclass correlations were used to gauge test-retest reliability. Regression models were used for continuous variables based on data distribution. ResultsTwenty-seven used PRBs were analyzed after excluding three for alternative pressure ratings and two for occult pinpoint leaks. Time from AUS placement to removal ranged from 0.02 to 17.6 years (median 8.4, IQR 5.7-10.0). The mean pressure of all extracted PRBs: 58.8cmH2O (±7.4), 17 (62.9%) below the standard operating range. Each year of use in-vivo was associated with 1.09cmH20 pressure loss on linear regression (p<0.01 CI -1.52 to -0.65). PRB pressures were not significantly different according to indication for removal (one-way ANOVA p=0.11). Loss of elastance was non-linear, decreasing by 1.9% per year on Poisson regression (p<0.01, CI -0.03 to -0.01). When accounting for PRB age, PRB pressure was independently associated with detrusor overactivity. ConclusionsIn PRBs tested for pressure-volume characteristics, increasing PRB age was associated with decreased pressure and elasticity.