Three-dimensional shape differences in the bony pelvis of women with pelvic floor disorders.

INTRODUCTION AND HYPOTHESIS: The objective of this study was to determine whether the three-dimensional shape of the bony pelvis differs between women with and without pelvic floor disorders (PFDs). We predict that the levator ani attachment points for the pelvic floor are further displaced from one another in affected relative to unaffected women.
METHODS: Pelvic shape was quantified by collecting coordinate data from landmarks located on three-dimensional reconstructions of magnetic resonance images of 19 PFD cases and 16 matched controls. Euclidean distance matrix analysis (EDMA) was used to quantify and compare pelvic shape using these landmark data.
RESULTS: There were no significant group differences in age, parity, body mass, racial attribution, cesarean section, or hysterectomy status. After controlling for size as a confounding factor, EDMA results identified significant differences (p = 0.05) in the bispinous diameter (4 % proportionally larger) and distances defining lateral displacement of ischia from pubis (5-6 % proportionally larger) in cases compared to controls.
CONCLUSIONS: Pelvic shape in women with PFDs is characterized by the proportional mediolateral enlargement of the pelvic midplane and ischial eversion near the subpubic arch, consistent with inferolateral migration of the attachment points for the levator ani and correspondingly lateral displacement. These movements may result in increased strain on the pelvic floor's muscular and connective tissues, increasing the risk of failure over a woman's lifetime.