Levator plate angle in women with pelvic organ prolapse compared to women with normal support using dynamic MR imaging

Objective The purpose of this study was to determine whether the levator plate is (1) horizontal in women with normal support, (2) different between women with and without prolapse, (3) related to levator hiatus and perineal body descent. Study design Cohorts of cases with prolapse at least 1 cm below the hymen and normal controls with all points 1 cm or more above the hymen were prospectively enrolled in a study of pelvic organ support to be of similar age, race, and parity. Subjects underwent supine midsagittal dynamic magnetic resonance imaging (MRI) during Valsalva. Levator plate angle (LPA) was measured relative to a horizontal reference line. Levator hiatus length (LH) and perineal body location (PB) were also measured. Student t tests and Pearson correlation coefficients (r) were performed. Results Sixty-eight controls and 74 cases were analyzed. During Valsalva, controls had a mean LPA of 44.3°. Cases, compared to controls, had 9.1° (21%) more caudally directed LPA (53.4° vs 44.3°, P< .01), 15% larger LH length (7.8 cm vs 6.8 cm, P< .01), and 24% more caudal PB location (6.8 cm vs 5.5 cm, P< .01). Increases in LPA were correlated with increased LH length (r = 0.42, P< .0001) and PB location (r =.51, P< .0001). Conclusion The measured levator plate angle in women with normal support is 44.3°. During Valsalva, women with prolapse have a modest (9.1°) though statistically greater levator plate angle compared to controls. This larger angle showed moderate correlation with larger levator hiatus length and greater displacement of the perineal body in women with prolapse compared to controls.