Biomechanical study on the bladder neck and urethral positions: Simulation of impairment of the pelvic ligaments

Excessive mobility of the bladder neck and urethra are common features in stress urinary incontinence. We aimed at assessing, through computational modelling, the bladder neck position taking into account progressive impairment of the pelvic ligaments. Magnetic resonance images of a young healthy female were used to build a computational model of the pelvic cavity. Appropriate material properties and constitutive models were defined. The impairment of the ligaments was simulated by mimicking a reduction in their stiffness. For healthy ligaments, valsalva maneuver led to an increase in the alpha angle (between the bladder neck-symphysis pubis and the main of the symphysis) from 91.8 degrees(at rest) to 105.7 degrees, and 5.7 mm of bladder neck dislocation, which was similar to dynamic imaging of the same woman (alpha angle from 80 degrees to 103.3 degrees, and 5 mm of bladder neck movement). For 95% impairment, they enlarged to 124.28 degrees and 12 mm. Impairment to the pubourethral ligaments had higher effect than that of vaginal support (115 degrees vs. 108 degrees, and 9.1 vs. 73 mm). Numerical simulation could predict urethral motion during valsalva maneuver, for both healthy and impaired ligaments. Results were similar to those of continent women and women with stress urinary incontinence published in the literature. Biomechanical analysis of the pubourethral ligaments complements the biomechanical study of the pelvic cavity in urinary incontinence. It may be useful in young women presenting stress urinary incontinence without imaging evidence of urethral and muscle lesions or organ descend during valsalva, and for whom fascial damage are not expected. (C) 2014 Elsevier Ltd. All rights reserved.