Biomechanical Analyses of Anterior Vaginal Wall Prolapse: MR Imaging andComputer Modeling Studies.

[摘要] Pelvic organ prolapse is a distressing and debilitating condition for which 200,000 U.S. women will undergo surgery each year.Anterior vaginal prolapse (AVP), clinically referred to as ;;cystocele,” is the most common form of pelvic organ prolapse.The pathomechanics of cystocele remains poorly understood.In this dissertation, magnetic resonance (MR) imaging was used to help develop biomechanical models in order to test a new hypothesis related to the mechanism of cystocele formation. We hypothesized that the occurrence and magnitude of AVP cannot be explained by a single failure mechanism: rather, a defect has to be present in the levator ani muscle and/or more than one connective tissue site. In women with and without prolapse we found that the presence of a major levator ani muscle defect on MR images is associated with a 50% reduction in the cross-sectional area of the ventral portion of their levator ani muscle compared with those having intact levator ani (Chapter 2).Apical descent and vaginal length explained 77% of the variation in cystocele size (Chapter 3).A 2-D sagittal plane, lumped parameter model (Chapter 4) and a 3-D, subject-specific, anatomically accurate, finite element model (Chapter 5) were developed to analyze the effect on cystocele formation of different combinations of connective tissue and muscle impairments. The models suggest that a larger cystocele formed in the presence of both muscular and mesenteric connective tissue support impairments than with either support element impairment alone. In particular, an impaired levator ani muscle caused a larger hiatus size, longer exposed vaginal length, larger apical descent and resulted in larger cystocele size.Synchronous measurements of intra-abdominal pressure and displacements of the most dependent bladder point on dynamic MR images were used to make the first in vivo estimates of the compliance of anterior vaginal wall support (Chapter 6). Women with cystocele had 67% greater compliance of their support system compared to controls.This dissertation provides insights into the biomechanical mechanisms underlying the development of anterior vaginal wall prolapse.Hopefully, these insights will help lead to improvements in the treatment of this distressing condition.

[发布机构] University of Michigan

[效力级别] MR Imaging

[关键词] Anterior Vaginal Wall Prolapse;MR Imaging;Biomechanics Modeling;Mechanism;Biomedical Engineering;Engineering;Biomedical Engineering