Viscoelastic properties measurement of the prolapsed anterior vaginal wall: a patient-directed methodology.

OBJECTIVE

In-vivo measurement of the viscoelastic properties of the prolapsed anterior vaginal wall (AVW) in post-menopausal women undergoing cystocele repair.

STUDY

DESIGN

A BTC-2000 cutometer-like instrument was introduced during vaginal repair of symptomatic stage 2-3 AVW prolapse. Under anesthesia, 10-mm orifice probe was applied to the AVW at the level of the bladder neck. A suction pressure ramp (0 to -147 mmHg in 6s) was delivered causing tissue uplift, followed by immediate release to 0 mmHg, measuring tissue relaxation for 20s. Similar measurements were performed over the suprapubic region (SP) for comparison purpose. The rate of tissue recovery was obtained by fitting a Voigt model to the data and expressing results as the ratio E/η [(spring modulus E)/(dashpot viscosity η)]. The effective strain energy (SE) was calculated from the pressure-uplift data and evaluated from initiation to: (1) maximum storage in tissue at peak vacuum; (2) tissue recovery after vacuum release; (3) net SE loss over the entire loading-unloading cycle.

RESULTS

In 22 women, higher AVW peak and residual tissue uplift values, and lower E/η ratios were found compared with SP results. The AVW stored less elastic strain energy at peak vacuum than did the SP, and AVW net energy loss over the uplift-recovery cycle was greater than for SP controls. Not only was the AVW more compliant than the SP, with higher viscous damping, but the tissue was also less able to store recoverable energy upon distension.

CONCLUSION

Such in-vivo measurements quantify the biomechanical properties of the prolapsed AVW and may assist in its management.