Computed tomography comparison of bony pelvis dimensions between women with and without genital prolapse

Objective: To compare bony pelvis dimensions between white women with and without genital prolapse using computed tomography (CT) pelvimetry. Methods: Thirty-four multiparous white women with vaginal prolapse beyond the hymen and 34 matched white controls with no signs or symptoms of pelvic support defects underwent CT pelvimetry. The anteroposterior and transverse diameters of the pelvic inlet, the interspinous diameter of the midpelvis, and the intertuberous diameter of the pelvic outlet were measured. Post hoc power analysis showed that 22 women were needed in each group to detect a 10% difference in the pelvic dimensions between groups, with an alpha error of 1% and a beta error of 10%, resulting in a 90% power. Results: Mean (+/- standard deviation [SD]) age of the subjects was 63.4 +/- 8.3 years, compared with 62.9 +/- 7.8 years for controls. Mean parity of the subjects was 3.3 +/- 1.7, compared with 3.6 +/- 1.7 for controls. Mean (+/- SD) anteroposterior (12.5 +/- 1.3 versus 12.8 +/- 1.0 cm), interspinous (11.5 +/- 0.8 versus 11.2 +/- 0.9 cm), and intertuberous (10.0 +/- 1.0 versus 9.8 +/- 0.8 cm) diameters were not significantly different between study groups. Mean transverse diameter of the pelvic inlet was significantly greater in women with prolapse than those without prolapse (12.9 +/- 0.7 versus 12.4 +/- 0.6 cm, P = .006). Conclusion: Women with advanced vaginal prolapse have larger transverse inlet diameters than do women with normal pelvic support. (Obstet Gynecol 1999;93:229-32. (C) 1999 by The American College of Obstetricians and Gynecologists.).