Quantification of Levator Ani Cross-Sectional Area Differences Between Women With and Those Without Prolapse

OBJECTIVE: Compare levator ani cross-sectional area as a function of prolapse and muscle defect status. METHODS: Thirty women with prolapse and 30 women with normal pelvic support were selected from an ongo-ing case-control study of prolapse. For each of the two groups, 10 women were selected from three categories of levator defect severity: none, minor, and major iden-tified on supine magnetic resonance scans. Using those scans, three-dimensional (3D) models of the levator ani muscles were made using a modeling program (3D Slicer), and cross-sections of the pubic portion were calculated perpendicular to the muscle fiber direction using another program, I-DEAS. An analysis of variance was performed. RESULTS: The ventral component of the levator muscle of women with major defects had a 36 % smaller cross-sectional area, and women with minor defects had a 29% smaller cross-sectional area compared with the women with no defects (P<.001). In the dorsal component, there were significant differences in cross-sectional area ac-cording to defect status (P.03); women with major levator defects had the largest cross-sectional area com-pared with the other defect groups. For each defec