L Chen1, Y Hsu, J A Ashton-Miller, J O L DeLancey. 1. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2125, USA. luyunc@umich.edu
Abstract
OBJECTIVE: Develop a method to quantify the cross-sectional area of the pubic portion of the levator ani muscle, validate the method in women with unilateral muscle defects, and report preliminary findings in those women. METHOD: Multi-planar proton density magnetic resonance images of 12 women with a unilateral defect in the pubic portion of their levator ani were selected from a larger study of levator ani muscle anatomy in women with and without genital prolapse. Three-dimensional bilateral models of the levator ani were reconstructed (using 3-D Slicer, version 2.1b1) and divided into iliococcygeal and pubic portions. Muscle cross-sectional areas were calculated at four equally spaced locations perpendicular to a line drawn from the pubic origin to the visceral insertion using the I-DEAS computer modeling software. RESULTS: The cross-sectional area of the muscle on the side with the defect was smaller than the normal side at all the four locations. The average bilateral difference was up to 81% at location 1 (nearest pubic origin). Almost all of the volume difference (13.7%, P=0.0004) was attributable to a reduction in the pubic portion (24.6%, P<0.0001), not the iliococcygeal portion (P=0.64), of the muscle. CONCLUSIONS: A method was developed to quantify cross-sectional area of the pubic portion of the levator ani perpendicular to the intact muscle direction. Significant bilateral cross-sectional area differences were found between intact and defective muscles in women with a unilateral defect.
OBJECTIVE: Develop a method to quantify the cross-sectional area of the pubic portion of the levator ani muscle, validate the method in women with unilateral muscle defects, and report preliminary findings in those women. METHOD: Multi-planar proton density magnetic resonance images of 12 women with a unilateral defect in the pubic portion of their levator ani were selected from a larger study of levator ani muscle anatomy in women with and without genital prolapse. Three-dimensional bilateral models of the levator ani were reconstructed (using 3-D Slicer, version 2.1b1) and divided into iliococcygeal and pubic portions. Muscle cross-sectional areas were calculated at four equally spaced locations perpendicular to a line drawn from the pubic origin to the visceral insertion using the I-DEAS computer modeling software. RESULTS: The cross-sectional area of the muscle on the side with the defect was smaller than the normal side at all the four locations. The average bilateral difference was up to 81% at location 1 (nearest pubic origin). Almost all of the volume difference (13.7%, P=0.0004) was attributable to a reduction in the pubic portion (24.6%, P<0.0001), not the iliococcygeal portion (P=0.64), of the muscle. CONCLUSIONS: A method was developed to quantify cross-sectional area of the pubic portion of the levator ani perpendicular to the intact muscle direction. Significant bilateral cross-sectional area differences were found between intact and defective muscles in women with a unilateral defect.
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