Comparison of levator ani muscle defects and function in women with and without pelvic organ prolapse

Abstract

Background: To compare levator ani defects and pelvic floor function among women with prolapse and controls.

Methods: Levator ani structure and function were measured in a case-control study with group matching for age, race, and hysterectomy status among 151 women with prolapse (cases) and 135 controls with normal support (controls) determined by pelvic organ prolapse quantification examination. Magnetic resonance imaging was used to determine whether there were "major" (more than half missing), "minor" (less than half of the muscle missing), or no defects in the levator ani muscles. Vaginal closure force at rest and during maximal pelvic muscle contraction was measured with an instrumented vaginal speculum.

Results: Cases were more likely to have major levator ani defects than controls (55% compared with 16%), with an adjusted odds ratio of 7.3 (95% confidence interval 3.9-13.6, P<.001) but equally likely to have minor defects (16% compared with 22%). Of women who reported delivery by forceps, 53% had major defects compared with 28% for the nonforceps women, adjusted odds ratio 3.4 (95% confidence interval 1.95-5.78). Women with prolapse generated less vaginal closure force during pelvic muscle contraction than controls (2.0 Newtons compared with 3.2 Newtons P<.001), whereas those with defects generated less force than women without defects (2.0 Newtons compared with 3.1 Newtons, P<.001). The genital hiatus was 50% longer in cases than controls (4.7+/-1.4 cm compared with 3.1+/-1.0 cm, P<.001).

Conclusion: Women with prolapse more often have defects in the levator ani and generate less vaginal closure force during a maximal contraction than controls.

Level of evidence: II.