Vault prolapse I: Dynamic supports of the vagina.

The relative contributions of muscle forces and vaginal suspensory ligaments to the anatomical support of the vagina have been long disputed. The aim of this study was to gain further insights into the role of striated muscle forces. Fifty consecutive patients presenting to a pelvic floor clinic were tested with perineal ultrasound, lateral X-rays at rest and on straining, 10 ml of radio-opaque dye having been injected into bladder, vagina, rectum and, in 12 patients, into the levator plate also. The relevance of muscle forces to the three anatomical levels of support, the cardinal/uterosacral ligament complex (level 1), the rectovaginal fascia (level 2) and the perineal body (level 3), was analyzed. Biopsies of the suspensory ligaments were performed per vaginam. During effort, the upper part of the vagina was stretched backwards and downwards against the perineal body. Compression of level 2 on standing lateral X-ray appeared to be related to the angle of the upper vagina to the horizontal at rest. In 23 patients in whom the angle was 45 degrees or more to the horizontal, only 2 demonstrated significant angulation of the upper vagina and therefore compression of level 2 on straining. In contast, all 27 patients with an angle less than 45 degrees to the horizontal demonstrated both vaginal angulation and compression. Histology demonstrated smooth muscle and nerves in the suspensory ligaments, indicating an active contractile role for these structures. Analysis of the directional forces suggests that inability ot angulate the vagina sufficiently may predispose to herniations of the walls of the vagina owing to the twin influences of gravity and downward muscle forces exerted by the levator muscles.