Biomechanical properties of vaginal tissue in women with pelvic organ prolapse.

BACKGROUND/AIMS: To compare biomechanical properties of vaginal tissues between women with and without pelvic organ prolapse (POP) and investigate factors that may influence these properties. METHODS: Forty patients submitted to POP surgery and 15 non-POP cadavers were evaluated. The tissue was excised from anterior and posterior middle third vagina. The biomechanical properties considered were stiffness (E) and maximum stress (S), and they were evaluated by means of uniaxial tension tests. RESULTS: POP patients were associated with higher values of E (13.1 ± 0.8 vs. 9.5 ± 0.7 MPa; p < 0.001) and S (5.3 ± 0.5 vs. 3.2 ± 0.9 MPa; p < 0.001) in the anterior vaginal wall compared to the posterior wall. In contrast, non-POP women presented lower values of E (6.9 ± 1.1 vs. 10.5 ± 1.0 MPa; p = 0.01) and S (2.6 ± 0.4 vs. 3.5 ± 0.4 MPa; p = 0.043) in the anterior wall. The occurrence of POP was the only independent predictor of higher values of E and S in anterior vaginal samples (p = 0.003 and p = 0.008, respectively). Women with severe anterior vaginal prolapse presented higher levels of E and S in the anterior sample compared to those with lower POP stages (p = 0.001 and p = 0.01; respectively). CONCLUSION: Women with POP present significant changes of biomechanical properties in the vagina.

The influence of muscles activation on the dynamical behaviour of the tympano-ossicular system of the middle ear.

The human ear is a complex biomechanical system and is divided into three parts: outer, middle and inner ear. The middle ear is formed by ossicles (malleus, incus and stapes), ligaments, muscles and tendons, which transfers sound vibrations from the eardrum to the inner ear, linking with mastoid and Eustachian tube. In this work, a finite element modelling of the tympano-ossicular system of the middle ear was developed. A dynamic study based on a structural response to harmonic vibrations, for a sound pressure level (SPL) of 110, 120 and 130 dB SPL applied in the eardrum, is presented. The connection between the ossicles is made using a contact formulation. The model includes the different ligaments considering its hyperelastic behaviour. The activation of the muscles is based on the constitutive model proposed by previous work. The harmonic responses of displacement and pressure obtained on the stapes footplate, for a frequency range between 100 Hz and 10 kHz, are obtained simulating the muscle activation. The results are compared considering the passive and active states. The results are discussed and they are in accordance with audiological data published with reference to the effects of the middle ear muscles contraction.

Uniaxial mechanical behavior of the human female bladder.

INTRODUCTION AND HYPOTHESIS: The objective of the present study was to investigate the tensile biomechanical properties of the human female bladder. METHODS: Tissue samples were obtained from 13 cadavers without pelvic floor dysfunctions. We performed uniaxial tensile tests to measure the stiffness and maximum stress of the bladder tissue. Correlations were calculated using the Pearson correlation coefficient. RESULTS: The bladder tissue stiffness ranged from 1 to 4.1 MPa (mean stiffness, 1.9 ± 0.2 MPa) and the maximum stress ranged from 0.5 to 2.6 MPa (mean maximum stress, 0.9 ± 0.1 MPa). There was a strong positive correlation between stiffness and maximum stress in the bladder tissue (ρ = 0.829, p < 0.001). Tissue from women younger than 50 years presented higher bladder stiffness than did tissue from older subjects (2.1 ± 0.2 versus 1.3 ± 0.1 MPa, p = 0.02). Maximum bladder stress, however, was not associated with age (1.0 ± 0.2 versus 0.7 ± 0.1 MPa, p = 0.349). In addition, body mass index and menopausal status were not associated with these biomechanical properties. CONCLUSIONS: Age may influence the uniaxial mechanical behavior of the human female bladder.