Interaction among apical support, levator ani impairment, and anterior vaginal wall prolapse.
OBJECTIVE
To use a biomechanical model to explore how impairment of the pubovisceral portion of the levator ani muscle, the apical vaginal suspension complex, or both might interact to affect anterior vaginal wall prolapse severity.


METHODS
A biomechanical model of the anterior vaginal wall and its support system was developed and implemented. The anterior vaginal wall and its main muscular and connective tissue support elements, namely the levator plate, pubovisceral muscle, and cardinal and uterosacral ligaments were included, and their geometry was based on midsagittal plane magnetic resonance scans. Material properties were based on published data. The change in the sagittal profile of the anterior vaginal wall during a maximal Valsalva was then predicted for different combinations of pubovisceral muscle and connective tissue impairment.


RESULTS
Under raised intra-abdominal pressure, the magnitude of anterior vaginal wall prolapse was shown to be a combined function of both pubovisceral muscle and uterosacral and cardinal ligament ("apical supports") impairment. Once a certain degree of pubovisceral impairment was reached, the genital hiatus opened and a prolapse developed. The larger the pubovisceral impairment, the larger the anterior wall prolapse became. A 90% impairment of apical support led to an increase in anterior wall prolapse from 0.3 cm to 1.9 cm (a 530% increase) at 60% pubovisceral muscle impairment, and from 0.7 cm to 2.4 cm (a 240% increase) at 80% pubovisceral muscle impairment.


CONCLUSIONS
These results suggest that a prolapse can develop as a result of impairment of the muscular and apical supports of the anterior vaginal wall.
Chen
Luyun
L
Department of Biomedical Engineering, University of Michigan, Ann Arbor, 48109-2125, USA. luyunc@umich.edu
Ashton-Miller
James A
JA
Hsu
Yvonne
Y
DeLancey
John O L
JO
D001699:Biometry; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008022:Ligaments / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009130:Muscle, Smooth / Q000473:pathology; D017773:Pelvic Floor / Q000473:pathology*; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D014596:Uterine Prolapse / Q000473:pathology / Q000503:physiopathology*