Each year, pelvic floor dysfunction affects between 300,000 and 400,000 American women so severely that they require surgery. Approximately 30% of the operations performed are re-operations. The high ...prevalence of this problem indicates the need for preventive strategies, and the common occurrence of re-operation indicates the need for treatment improvement. Efforts at prevention and treatment improvement will only be possible if research clarifies causative mechanisms and scientifically valid studies discover why operations fail. By reaching a goal of 25% prevention we could save 90,000 women from experiencing pelvic floor dysfunction and with 25% treatment improvement we could avoid 30,000 women from needing a second operation. To achieve these goals we must discover specific events or behaviors in a woman's life that lead to these problems and that are amenable to preventive strategies. In addition, we must define specific biologic and behavioral factors that explain why certain women have recurrence after surgery. Because the pelvic organ support system is comprised of muscles, ligaments, and nerves arranged in a complex tension-based apparatus, the basic nature of this work must include biomechanical analyses of the overall mechanism and targeted research into the biology of muscle, ligament, nerve, and their complex interactions in normal pelvic floor function and in symptomatic patient. Each of these scientific disciplines is well developed so that engaging scientists in the effort to move forward will bring predictably important results. With an integrated approach to this problem over the next 20 years, it should be possible to achieve these goals and reduce the suffering for more than 100,000 afflicted women.
Objective
To determine whether all three components of the levator ani muscle (pubovisceral = pubococcygeal, puborectal and iliococcygeal) and the external anal sphincter are equally affected by ...oedema associated with muscle injury after vaginal birth.
Design
Observational cross‐sectional study.
Setting
Michigan Medicine, University of Michigan.
Population
Primiparous women classified as high risk for levator ani muscle injury during childbirth.
Method
MRI scans obtained 6–8 weeks postpartum were analysed. Muscle oedema was assessed on axial and coronal fluid‐sensitive magnetic resonance (MRI) scans. Presence of oedema was separately determined in each levator ani muscle component and in the external anal sphincter for all subjects. Descriptive statistics and correlation with obstetric variables were obtained.
Main outcome measures
Oedema score on fluid‐sensitive MRI scans.
Results
Of the 78 women included in this cohort, 51.3% (n = 40/78) showed muscle oedema in the pubovisceral (one bilateral avulsion excluded), 5.1% (n = 4/78) in the puborectal and 5.1% (n = 4/78) in the iliococcygeal muscle. No subject showed definite oedema on external anal sphincter. Incidence of oedema on the pubovisceral muscle was seven times higher than on any of the other analysed muscles (all paired comparisons, P < 0.001).
Conclusions
Even in the absence of muscle tearing, the pubovisceral muscle shows by far the highest incidence of injury, establishing that levator components are not equally affected by childbirth. External anal sphincter did not show oedema—even in women with sphincter laceration— suggesting a different injury mechanism. Developing a databased map of injured areas helps understand injury mechanisms that can guide us in honing research on treatment and prevention.
Tweetable
Injury‐associated levator ani muscle and anal sphincter oedema mapping on MRI reveals vulnerable muscle components after childbirth.
Tweetable
Injury‐associated levator ani muscle and anal sphincter oedema mapping on MRI reveals vulnerable muscle components after childbirth.
To identify obstetric factors associated with development of levator ani injury after vaginal birth.
Magnetic resonance images were taken of the pelvic floor of 160 women 9 to 12 months after first ...term vaginal delivery. Half the women had de novo stress incontinence and half were continent controls. Abnormalities of the pubovisceral portion were identified on magnetic resonance as present or absent. Defect severity was further scored in each muscle from 0 (no defect) to 3 (complete muscle loss). A summed score for the 2 sides (0 to 6) was assigned and grouped as minor (0-3) or major (4-6). Obstetric details were collected. The association between obstetric variables and muscle injury were analyzed using Fisher exact test and t tests.
The following increased odds ratios for levator defect were found: forceps use 14.7 (95% confidence interval CI 4.9-44.3), anal sphincter rupture 8.1 (95% CI 3.3-19.5) and episiotomy 3.1 (95% CI 1.4-7.2) but not vacuum delivery 0.9 (95% CI 0.19-4.3), epidural use 0.9 (95% CI 0.4-2.0), or oxytocin use 0.8 (95% CI 0.3-1.8). Women with levator injury were 3.5 years older and had a 78-minute longer second stage of labor. Differences in gestational age, birth weight, and head circumference were not statistically significant. A major defect in the pubovisceral muscle was seen in 22 women and a minor defect in 7 women.
Injuries to the levator ani muscles in women after their first vaginal delivery are associated with several obstetric factors indicating difficult vaginal birth and with older age.
II-3.
Levator Ani Muscle Stretch Induced by Simulated Vaginal Birth Lien, Kuo-Cheng; Mooney, Brian; DeLancey, John O. L. ...
Obstetrics and gynecology (New York. 1953),
2004-January, 2004, 2004-Jan, 2004-01-00, 20040101, Letnik:
103, Številka:
1
Journal Article
Recenzirano
Odprti dostop
OBJECTIVE:To develop a three-dimensional computer model to predict levator ani muscle stretch during vaginal birth.
METHODS:Serial magnetic resonance images from a healthy nulliparous 34-year-old ...woman, published anatomic data, and engineering graphics software were used to construct a structural model of the levator ani muscles along with related passive tissues. The model was used to quantify pelvic floor muscle stretch induced during the second stage of labor as a model fetal head progressively engaged and then stretched the iliococcygeus, pubococcygeus, and puborectalis muscles.
RESULTS:The largest tissue strain reached a stretch ratio (tissue length under stretch/original tissue length) of 3.26 in medial pubococcygeus muscle, the shortest, most medial and ventral levator ani muscle. Regions of the ileococcygeus, pubococcygeus, and puborectalis muscles reached maximal stretch ratios of 2.73, 2.50, and 2.28, respectively. Tissue stretch ratios were proportional to fetal head sizeFor example, increasing fetal head diameter by 9% increased medial pubococcygeus stretch by the same amount.
CONCLUSION:The medial pubococcygeus muscles undergo the largest stretch of any levator ani muscles during vaginal birth. They are therefore at the greatest risk for stretch-related injury.
The purpose of this study was to determine whether the degree of anterior compartment (bladder) and apical compartment (cervix) prolapse are correlated, and whether 2 anterior compartment elements ...(urethra and bladder) are related at maximal Valsalva.
Women with a complete spectrum of pelvic support were recruited for a pelvic support study. Dynamic magnetic resonance scans were taken during Valsalva. A convenience sample of 153 women with a mean age of 53.3 ± 12.5 (SD) years with a uterus in situ was studied. Anterior compartment status was assessed by the most caudal bladder point and the internal urinary meatus. The external cervical os was used to assess the apical compartment. The position of the bladder, urethra, and uterus were determined in 20 nulliparous women to determine their reference locations. The distances of each structure below the reference positions were calculated at maximum Valsalva.
Average distances of the bladder base, urethra, and uterus from the reference positions at maximal Valsalva were 4.1 ± 2.4 cm, 3.1 ± 1.3 cm, and 4.3 ± 2.4 cm, respectively. The Pearson correlation coefficient of the relationship between the bladder base and uterine distances was r = 0.73 (r2 = 0.53). The Pearson correlation coefficient of the bladder distance and urethral distance was r = 0.82 (r2 = 0.67).
Half of the observed variation in anterior compartment support may be explained by apical support.
Objective: Our purpose was to assess the structural integrity of individual elements of the urethral and anterior vaginal wall support system. Study Design: Notes were made during retropubic ...operations for cystourethrocele and stress incontinence in 71 women aged 52 ± 12.4 (SD) years. Vaginal support was assessed with the Baden-Walker system with the following average findings: urethra 1.9 ± 0.6, bladder 1.9 ± 1.0, apex 0.8 ± 1.1, upper posterior wall 0.3 ± 0.8, and rectocele 1.1 ± 0.7. The presence of the following features was noted: paravaginal defect, integrity of the pubic and ischial attachments of the arcus tendineus fascia pelvis (ATFP), appearance of the ATFP on the sidewall, and abnormalities in the pubococcygeal muscle. Results: Paravaginal defects were present in 87.3% on the left and in 88.7% on the right. Detachment of the ATFP from the pubic bone was present in 1.4% (left) and 2.8% (right). The ATFP was detached from the ischial spine in 97.6% (left) and 95.1% (right). Remnants of the ATFP were present on the sidewall in 62% (left) and 63% (right). Of these, 9% extended one fourth the distance to the spine, 21% one half the distance, 3% three fourths the distance, and 17% all the way to the spine. The pubococcygeal muscle was visibly normal in 45% (left) and 39% (right). It showed localized atrophy in 22% (left) and 30% (right) and generalized atrophy in 22.5% (left) 30.0% (right). Conclusion: The ATFP usually detaches from the ischial spine, but not from the pubis; slightly less than half of these women have visibly abnormal levator ani muscles. (Am J Obstet Gynecol 2002;187:93-8.)
The purpose of this study was to estimate the incidence of urinary and bowel incontinence in relation to anal sphincter laceration in primiparous women and to identify factors that are associated ...with anal sphincter laceration in a unit that uses primarily midline episiotomy.
From January 1, 1997, to March 30, 2000, 2941 questionnaires concerning pelvic floor function 6 months after delivery were mailed to primiparous women who were delivered vaginally at the University of Michigan Medical Center. Charts were reviewed for 2858 deliveries to assess the use of episiotomy and the degree of perineal trauma, along with demographic and pertinent delivery variables. There were 943 women who completed the urinary function questionnaire and 831 women who completed the bowel function questionnaire. Univariate analysis was performed on all covariates. Multiple logistic regression was used for the analysis of the presence of third- or fourth-degree lacerations as the outcome.
Nineteen percent of the women who completed the survey had sustained third- or fourth-degree lacerations during childbirth. The women in the sphincter laceration group were more likely (23.0%) to have bowel incontinence than the women in the control group (13.4%) (
P<.05). The incidence of worse bowel control was nearly 10 times higher in women with fourth-degree lacerations (30.8%) compared with women with third-degree lacerations (3.6%,
P<.001). Macrosomia (odds ratio, 2.19; 95% CI, 1.61, 2.99), forceps-assisted delivery (odds ratio, 4.75; 95% CI, 3.43, 6.57), and vacuum-assisted delivery (odds ratio, 3.51; 95% CI, 2.64, 4.66) were associated with higher risks of third- and fourth-degree lacerations. Midline episiotomy (odds ratio, 2.24; 95% CI, 1.81, 2.77), but not mediolateral (odds ratio, 0.66; 95% CI, 0.375, 1.19), episiotomy was associated with anal sphincter lacerations. More than one half of the women had new onset of urinary incontinence after delivery and reported several lifestyle modifications to prevent leakage.
Women with third- and fourth-degree lacerations were more likely to have bowel incontinence than women without anal sphincter lacerations. Fourth-degree lacerations appear to affect anal continence greater than third-degree lacerations.
To examine the published literature and suggest a resolution to the confusion that exists in levator ani muscle descriptions and terminology.
A MEDLINE search was performed using the keyword "levator ...ani," limited to human studies in women. References found in these articles were reviewed to identify research reported before 1966 and articles not included in the search.
Studies were accepted if they contained direct observations of female specimens. Only those that contained specific descriptions or illustrations of the muscle origins and insertions in more than 5 female specimens were included. Review of 265 human studies yielded 9 qualifying articles, and reference tracing disclosed 3 additional reports.
The literature review identified 5 origin-insertion pairs consistently described in studies directly examining the levator ani muscle in women, but 16 terms were used by authors for these 5 components of the muscle. Labeled illustrations often provided more precise information than was provided in the text. Terms were reviewed for inconsistencies of usage and appropriateness of term choice. The terms puboperineal, pubovaginal, and puboanal (for components of the pubovisceral "pubococcygeal" muscle), along with puborectal and iliococcygeal, are sufficient to describe the divisions of the levator ani muscle.
Although there was great diversity and conflict in terms chosen among the original articles, the number of origin and insertion pairs was relatively consistent among authors and confusion can be avoided by standardizing terminology.
This study examines the anatomic factors that could explain the mechanical basis for transmission of abdominal pressure to the urethra.
Dissection of 19 embalmed and 42 fresh cadavers and examination ...of 13 sets of serial pelvic sections were performed to study the structures involved in urethral support. The effect of simulated increases in abdominal pressure on the pelvic floor and urethra was observed in fresh specimens.
The urethra lies on a supportive layer that is composed of the endopelvic fascia and the anterior vaginal wall. This layer gains structural stability through its lateral attachment to the arcus tendineus fascia pelvis and levator ani muscle. Pressure from above compresses the urethra against this hammock-like supportive layer, compressing its lumen closed. The stability of the suburethral layer depends on the intact connection of the vaginal wall and endopelvic fascia to the arcus tendineus fasciae pelvis and levator ani muscles.
Increases in urethral closure pressure during a cough probably arise because the urethra is compressed against a hammock-like supportive layer, rather than the urethra being truly "intraabdominal."
Objective: This study was undertaken to define posterior compartment structural anatomy relevant to rectocele.
Study Design: Dissection of 42 fresh and 22 fixed cadavers was supplemented by ...examination of histologic (n = 3) and macroscopic (n = 5) serial sections.
Results: Distal posterior compartment support involves connection of the halves of the perineal membrane (urogenital diaphragm) through the perineal body, preventing downward protrusion of the lower rectum. Above this level the posterior vaginal wall is held in place by sheets of bilateral endopelvic fascia that attach each side of the posterior vaginal wall to the pelvic diaphragm. Most of these fascial fibers attach to the vaginal wall and a few fibers unite in the midline. Pelvic floor closure by the levator ani muscles relieves pressure-induced stress on the midvaginal fascial supports.
Conclusions: Midline perineal membrane union supports the distal posterior compartment and a fascial connection between the pelvic diaphragm and vagina supports the mid vagina. Muscular pelvic floor closure helps to relieve fascial stress. (Am J Obstet Gynecol 1999;180:815-23.)
PDF
