Feasibility and benefits of the ewe as a model for vaginal surgery training.

INTRODUCTION AND HYPOTHESIS: The objective was to evaluate the ewe as an animal model for teaching and training in vaginal surgery. METHODS: Twenty-nine postgraduate surgeons attended a training course on vaginal prolapse surgery. After a review of human and sheep anatomy, the participants performed transvaginal meshes, vaginal hysterectomy, SSLF (Richter), and OAS repair in ewes and human cadavers. Participants completed questionnaires on the whole course. RESULTS: Questionnaires showed the significant superiority of ewes over human cadavers for all items evaluated regarding surgical dissections. Only identification of the sacrospinous ligament and the spine were judged to be similar in ewes and human cadavers. Participants noticed that ewe model is appropriate for vaginal prolapse surgery training for resident and for postgraduate surgeons. Two vaginal hysterectomies were also performed. Operating time, surgery, and anatomy were nearly identical to that of humans. The same conclusions were made while performing sacrospinous ligament fixation (Richter) and obstetric anal sphincter injury repair. CONCLUSION: This series indicates that the ewe is a useful animal model for teaching vaginal surgery.

Comparative analysis of pelvic ligaments: a biomechanics study.

INTRODUCTION AND HYPOTHESIS: Pelvic organ prolapse (POP) affects one third of women of all ages and is a major concern for gynecological surgeons. In pelvic reconstructive surgery, native ligaments are widely used as a corrective support, while their biomechanical properties are unknown. We hypothesized differences in the strength of various pelvic ligaments and therefore, aimed to evaluate and compare their biomechanical properties. MATERIALS AND METHODS: Samples from the left and right broad, round, and uterosacral ligaments from 13 fresh female cadavers without pelvic organ prolapse were collected. Uniaxial tension tests at a constant rate of deformation were performed and stress-strain curves were obtained. RESULTS: We observed a non-linear stress-strain relationship and a hyperelastic mechanical behavior of the tissues. The uterosacral ligaments were the most rigid whether at low or high deformation, while the round ligament was more rigid than the broad ligament. CONCLUSION: Pelvic ligaments differ in their biomechanical properties and there is fairly good evidence that the uterosacral ligaments play an important role in the maintenance of pelvic support from a biomechanical point of view.

Biomechanical properties of human pelvic organs.

OBJECTIVE: To comparatively define the biomechanical characteristics of the pelvic organs (the vagina, bladder, and rectum), which are crucial for the maintenance of pelvic support. Despite minimal fundamental studies, meshes are increasingly implanted into the vesicovaginal and rectovaginal spaces to replace disrupted native tissues and to treat pelvic organ prolapse. However, the mechanical characteristics of these materials have not yet been compared with those of the "functional unit," the vagina, bladder, and rectum. METHODS: Samples from 5 fresh female cadavers without prolapse were collected. Uniaxial tension tests under monotonic and cyclic loading were performed and the stress-strain curves obtained. RESULTS: The biomechanical properties of the vaginal, bladder, and rectal tissues differed significantly. We were able to demonstrate a nonlinear relationship between the stress and strain and a visco-hyperelastic behavior with a Mullins effect of damage of the tissues examined. Comparable rigidity was found between the investigated tissues at low strains; however, at large strain levels, marked differences could be observed. The vagina was much more rigid and less extendible than the rectal tissue, which, in turn, was more rigid than the bladder tissue. The anterior and posterior vagina revealed a different stiffness, and the bladder tissue was anisotropic at large strain levels. CONCLUSION: Our results underline the pivotal role of the vaginal tissue for the maintenance of pelvic support. The observed differences with respect to tissue rigidity should have pronounced effects on the physiologic organ function, pointing to the necessity of a differentiated view on using the same prosthetic material for different anatomic locations.