Levator ani avulsion: a Systematic evidence review (LASER)

In vivo measurement of the elastic properties of pelvic floor muscles in pregnancy using shear wave elastography

OBJECTIVE

We aimed to investigate changes in the elastic properties of levator ani muscle (LAM) and external anal sphincter (EAS) during pregnancy using shear wave elastography (SWE). Our secondary objective was to examine the association between the elastic properties of pelvic floor muscles (PFM) and perineal tears at childbirth.

METHODS

This was a prospective monocentric study, including nulliparous women. Three visits were planned (14-18, 24-28, and 34-38 weeks) with a SWE assessment of the LAM and EAS at rest and during Valsalva maneuver. Then, we collected data about the delivery's characteristics. Assessments were performed using an Aixplorer V12® device (SL 18-5 linear probe) using a transperineal approach, reporting the shear modulus in kPa. We looked for changes in PFM's elastic properties during pregnancy using one-way ANOVA for repeated measures. We compared the mean shear modulus in late pregnancy for each muscle and condition between women with an intact perineum at delivery and those with a perineal tear using Student's t test.

RESULTS

Forty-seven women were considered. Forty-five women had vaginal delivery of which 38 (84.4%) had perineal tears. We did not report any significant changes in the elastic properties of PFM during pregnancy. Women with an intact perineum at delivery had a stiffer EAS at Valsalva maneuver in late pregnancy (27.0 kPa vs. 18.2 kPa; p < 0.005).

CONCLUSIONS

There were no significant changes in the elastic properties of the PFM in pregnancy. Stiffer EAS in late pregnancy appears to be associated with a lower incidence of perineal tears.

A unified pelvic floor conceptual model for studying morphological changes with prolapse, age, and parity

Several 2-dimensional and 3-dimensional measurements have been used to assess changes in pelvic floor structures and shape. These include assessment of urogenital and levator hiatus dimensions, levator injury grade, levator bowl volume, and levator plate shape. We argue that each assessment reflects underlying changes in an individual aspect of the overall changes in muscle and fascial structures. Vaginal delivery, aging, and interindividual variations in anatomy combine to affect pelvic floor structures and their connections in different ways. To date, there is no unifying conceptual model that permits the evaluation of how these many measures relate to one another or that reflects overall pelvic floor structure and function. Therefore, this study aimed to describe a unified pelvic floor conceptual model to better understand how the aforementioned changes to the pelvic floor structures and their biomechanical interactions affect pelvic organ support with vaginal birth, prolapse, and age. In this model, the pelvic floor is composed of 5 key anatomic structures: the (1) pubovisceral, (2) puborectal, and (3) iliococcygeal muscles with their superficial and inferior fascia; (4) the perineal membrane or body; and (5) the anal sphincter complex. Schematically, these structures are considered to originate from pelvic sidewall structures and meet medially at important connection points that include the anal sphincter complex, perineal body, and anococcygeal raphe. The pubovisceral muscle contributes primarily to urogenital hiatus closure, whereas the puborectal muscle is mainly related to levator hiatus closure, although each muscle contributes to the other. Dorsally and laterally, the iliococcygeal muscle forms a shelflike structure in women with normal support that spans the remaining area between these medial muscles and attachments to the pelvic sidewall. Other features include the levator plate, bowl volume, and anorectal angle. The pelvic floor conceptual model integrates existing observations and points out evident knowledge gaps in how parturition, injury, disease, and aging can contribute to changes associated with pelvic floor function caused by the detachment of one or more important connection points or pubovisceral muscle failure.

Obstetric risk factors for levator ani muscle avulsion: A systematic review and meta-analysis

OBJECTIVES

Women have a 11% lifetime risk of undergoing surgery for vaginal prolapse. Levator ani muscle (LAM) avulsion is one etiological factor associated with primary and recurrent pelvic organ prolapse. Pelvic organ prolapse has been shown to greatly affect the quality of life and well-being of women. Conduct a meta-analysis identifying risk factors associated with LAM avulsion recognised on transperineal ultrasound (TPUS) or magnetic resonance imaging (MRI) in primiparous women after vaginal birth.

STUDY DESIGN

OVID Medline, Embase and the Cochrane Library from inception to January 2021 were searched. Review Manager 5.3 (The Cochrane Collaboration) was used to analyse data. Odds ratios (OR) with 95% confidence intervals (95% CIs) were calculated. The heterogeneity among studies was calculated using the I2statistic.

RESULTS

Twenty-five studies were eligible for inclusion (n = 9333 women). Major LAM avulsion was diagnosed in an average of 22 % (range 12.7-39.5 %) of cases. Twenty-two studies used TPUS and three used MRI to diagnose avulsion. Modifiable and non-modifiable risk factors were identified. Significant predictors identified were forceps (OR 6.25 [4.33 - 9.0]), obstetric anal sphincter injuries (OR 3.93 [2.85-5.42]), vacuum (OR 2.41 [1.40-4.16]), and maternal age (OR 1.06 [1.02-1.10]).

CONCLUSIONS

This is the first meta-analysis of both modifiable and non-modifiable risk factors associated with LAM avulsion. This information could be used to develop a clinically applicable risk prediction model to target postnatal women at risk of LAM avulsion with a view to prevent the onset of pelvic floor organ prolapse.

Analysis of the obstetrician's posture and movements during a simulated forceps delivery

BACKGROUND

The objective of this study was to identify and qualify, by means of a three-dimensional kinematic analysis, the postures and movements of obstetricians during a simulated forceps birth, and then to study the association of the obstetricians' experience with the technique adopted.

METHOD

Fifty-seven volunteer obstetricians, 20 from the Limoges and 37 from the Poitiers University hospitals, were included in this multi-centric study. They were classified into 3 groups: beginners, intermediates, and experts, beginners having performed fewer than 10 forceps deliveries in real conditions, intermediates between 10 and 100, and experts more than 100. The posture and movements of the obstetricians were recorded between December 2020 and March 2021 using an optoelectronic motion capture system during simulated forceps births. Joint angles qualifying these postures and movements were analysed between the three phases of the foetal traction. These phases were defined by the passage of a virtual point associated with the forceps blade through two anatomical planes: the mid-pelvis and the pelvic outlet. Then, a consolidated ascending hierarchical classification (AHC) was applied to these data in order to objectify the existence of groups of similar behaviours.

RESULTS

The AHC distinguished four different postures adopted when crossing the first plane and three different traction techniques. 48% of the beginners adopted one of the two raised posture, 22% being raised without trunk flexion and 26% raised with trunk flexion. Conversely, 58% of the experts positioned themselves in a "chevalier servant" posture (going down on one knee) and 25% in a "squatting" posture before initiating traction. The results also show that the joint movement amplitude tends to reduce with the level of expertise.

CONCLUSION

Forceps delivery was performed in different ways, with the experienced obstetricians favouring postures that enabled observation at the level of the maternal perineum and techniques reducing movement amplitude. The first perspective of this work is to relate these different techniques to the traction force generated. The results of these studies have the potential to contribute to the training of obstetricians in forceps delivery, and to improve the safety of women and newborns.

Functional Anatomy of Urogenital Hiatus Closure: the Perineal Complex Triad Hypothesis

INTRODUCTION

Urogenital hiatus enlargement is a critical factor associated with prolapse and operative failure. This study of the perineal complex was performed to understand how interactions among its three structures: the levator ani, perineal membrane, and perineal body-united by the vaginal fascia-work to maintain urogenital hiatus closure.

METHODS

Magnetic resonance images from 30 healthy nulliparous women with 3D reconstruction of selected subjects were used to establish overall geometry. Connection points and lines of action were based on perineal dissection in 10 female cadavers (aged 22-86 years), cross sections of 4 female cadavers (aged 14-35 years), and histological sections (cadavers aged 16 and 21 years).

RESULTS

The perineal membrane originates laterally from the ventral two thirds of the ischiopubic rami and attaches medially to the perineal body and vaginal wall. The levator ani attaches to the perineal membrane's cranial surface, vaginal fascia, and the perineal body. The levator line of action in 3D reconstruction is oriented so that the levator pulls the medial perineal membrane cranio-ventrally. In cadavers, simulated levator contraction and relaxation along this vector changes the length of the membrane and the antero-posterior diameter of the urogenital hiatus. Loss of the connection of the left and right perineal membranes through the perineal body results in diastasis of the levator and a widened hiatus, as well as a downward rotation of the perineal membrane.

CONCLUSION

Interconnections involving the levator ani muscles, perineal membrane, perineal body, and vaginal fascia form the perineal complex surrounding the urogenital hiatus in an arrangement that maintains hiatal closure.

Levator ani muscle avulsion and subsequent vaginal delivery: 8-year longitudinal follow-up

OBJECTIVES

To assess the evolution of levator ani muscle (LAM) avulsion from 1 year to 8 years after first delivery in women with and those without subsequent vaginal delivery. In addition, to assess whether women with full or partial avulsion 8 years after first delivery have larger LAM hiatal area and more symptoms of pelvic organ prolapse compared to women with normal LAM insertion.

METHODS

In this single-center longitudinal study, 195 women who were primiparous at the start of the study were included and underwent transperineal ultrasound examination 1 year and 8 years after first delivery. Muscle insertion was assessed by tomographic ultrasound imaging in the axial plane. Full LAM avulsion was defined as abnormal muscle insertion in all three central slices. Partial LAM avulsion was defined as abnormal muscle insertion in one or two central slices. Eight years after the first delivery, LAM hiatal area was assessed at rest, during maximum pelvic floor muscle contraction and on maximum Valsalva maneuver. To assess symptoms of pelvic organ prolapse, the vaginal symptoms module of the International Consultation on Incontinence Questionnaire was used.

RESULTS

At 1-year follow-up, 25 (12.8%) women showed signs of LAM avulsion, of whom 20 fulfilled the sonographic criteria of full avulsion and five of partial avulsion. Eight years after the first delivery, 35 (17.9%) women were diagnosed with avulsion, of whom 25 were diagnosed with full avulsion and 10 with partial avulsion. No woman with partial or full avulsion at 1 year had improved avulsion status at the 8-year follow-up. Of the 150 women who had subsequent vaginal delivery, 21 (14.0%) women were diagnosed with partial or full LAM avulsion 1 year after first delivery, and 31 (20.7%) women were diagnosed with partial or full avulsion 8 years after first delivery. Of the 45 women without subsequent vaginal delivery, one woman with partial avulsion 1 year after first delivery was diagnosed with full avulsion at the 8-year follow-up. All women with full avulsion at 1-year follow-up were diagnosed with full avulsion at the 8-year follow-up regardless of whether they had subsequent vaginal delivery. At 8-year follow-up, women with full avulsion had statistically significantly larger LAM hiatal area compared to women with normal muscle insertion. Mean ± SD vaginal symptom scores ranged between 5.5 ± 5.7 and 6.0 ± 4.0 and vaginal symptom quality of life scores ranged between 0.9 ± 1.4 and 1.5 ± 2.2 and did not differ significantly between women with normal muscle insertion and women with partial or full avulsion at 8-year follow-up.

CONCLUSIONS

More LAM avulsions were present 8 years compared with 1 year after first delivery in women with subsequent vaginal delivery. Except for one primipara, all women without subsequent vaginal delivery had unchanged LAM avulsion status between 1 year and 8 years after their first delivery. Larger LAM hiatal area was found in women with full avulsion compared to those with normal muscle insertion at 8-year follow-up. Vaginal symptoms scores were low and did not differ between women with normal muscle insertion and those with partial or full avulsion at 8-year follow-up. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

A new approach to assessing the obstetrician's posture and movement during an instrumental forceps delivery

INTRODUCTION

The number of deliveries by forceps decreases significantly in favour of the vacuum. Now, when the use of forceps is necessary, physicians less experimented with this procedure are likely to induce serious and preventable perineal or foetal injuries. Training therefore becomes essential. However, there are no clear recommendations on the technique to perform a delivery by forceps, namely the body posture and gesture to adopt. Our goal is then to provide a protocol that can help to determine if there is an optimal technique to perform a delivery by forceps.

METHOD

We will include voluntary participants whose level of experience and type of practice differ. We will propose to record their postures and gestures using an optoelectronic motion analysis system during a forceps delivery simulated on a mannequin. We will also measure the traction force produced by the subject on the forceps using force platforms and technical markers placed on the forceps. We will then perform a principal component analysis to look for similar motion patterns.

EXPECTED RESULTS

We plan to analyse about fifty participants (25 seniors and 25 juniors). Our hypothesis is that the realism of the simulation will be deemed satisfactory by the participants, that the experimental conditions will not modify their gestures, and that the degree of experience will result in different techniques.

CONCLUSION

A better knowledge on the posture and gesture to adopt to realise a forceps delivery should improve the safety of women and new-borns. The results of this study could also be a valuable contribution for the training of obstetricians.

A comparison of MRI-based pelvic floor support measures between young and old women with prolapse

INTRODUCTION AND HYPOTHESIS

We sought to 1) test the hypothesis that young women (≤45 years) with pelvic organ prolapse have a higher prevalence of major levator ani muscle (LAM) defects than old women (≥70 years) with prolapse and 2) compare level II/III measurements between young and old women with prolapse and age-matched controls to evaluate age-related mechanistic differences in the disease process.

METHODS

A secondary analysis examined four groups of parous women: young prolapse (YPOP, n = 17); old prolapse (OPOP, n = 17); young controls (YC, n = 15); old controls, (OC, n = 13). Prolapse was defined as any compartment at or beyond the hymen with vaginal bulge symptoms. Genital hiatus (GH) was measured on clinical exam. Major LAM defects and level II/III measurements (UGH: urogenital hiatus, LA: levator area, and apex location) were assessed on MRI at rest and strain, and the difference (Δ) between measurements calculated. Principal component analysis was used to evaluate levator plate (LP) shape.

RESULTS

Major LAM defects occurred in 42% of YPOP and 47% of OPOP (p > .99). GHrest was 1.5 cm larger in OPOP versus YPOP (p < .001) and 2 cm larger in OPOP versus OC (p < .001). Regardless of prolapse status, LArest and UGHrest on MRI increased with age. YPOP had larger ΔLA (p = .04), ΔUGH (p = .03), and Δapex than OPOP (p = .01). Resting LP shape was more dorsally oriented in OPOP versus YPOP (p = .02) and OC versus YC (p = .004).

CONCLUSIONS

Prolapse in young women cannot be solely explained by a higher LAM defect prevalence. GH size and other measures of level II/III pelvic support worsen with age regardless of prolapse status.

Hiatal failure: effects of pregnancy, delivery, and pelvic floor disorders on level III factors

INTRODUCTION AND HYPOTHESIS

The failure of the levator hiatus (LH) and urogenital hiatus (UGH) to remain closed is not only associated with pelvic floor disorders, but also contributes to recurrence after surgical repair. Pregnancy and vaginal birth are key events affecting this closure. An understanding of normal and failed hiatal closure is necessary to understand, manage, and prevent pelvic floor disorders.

METHODS

This narrative review was conducted by applying the keywords "levator hiatus" OR "genital hiatus" OR "urogenital hiatus" in PubMed. Articles that reported hiatal size related to pelvic floor disorders and pregnancy were chosen. Weighted averages for hiatal size were calculated for each clinical situation.

RESULTS

Women with prolapse have a 22% and 30% larger LH area measured by ultrasound at rest and during Valsalva than parous women with normal support. Women with persistently enlarged UGH have 2-3 times higher postoperative failure rates after surgery for prolapse. During pregnancy, the LH area at Valsalva increases by 29% from the first to the third trimester in preparation for childbirth. The enlarged postpartum hiatus recovers over time, but does not return to nulliparous size after vaginal birth. Levator muscle injury during vaginal birth, especially forceps-assisted, is associated with increases in hiatal size; however, it only explains a portion of hiatus variation-the rest can be explained by pelvic muscle function and possibly injury to other level III structures.

CONCLUSIONS

Failed hiatal closure is strongly related to pelvic floor disorders. Vaginal birth and levator injury are primary factors affecting this important mechanism.

Multicenter study of the evolution of different types of avulsion over the 12 months after delivery

OBJECTIVE

To perform a multicenter study of muscle recovery in levator ani muscle (LAM) avulsion during the first 12 months postpartum according to the type of LAM avulsion suffered.

METHODS

This was a multicenter prospective observational study including 242 primiparas. Transperineal ultrasound was performed at 6 months and 12 months after delivery. Type I LAM avulsion was present when most of the lateral fibers of the pubovisceral muscle were observed at the muscle's insertion at the pubic level. Type II LAM avulsion was defined as complete detachment of the pubovisceral muscle from its insertion at the pubic level.

RESULTS

Among the 56 patients who completed the study (with ultrasound at 6 and 12 months after delivery), 76 avulsions (10 cases of bilateral avulsion) were identified at 6 months after delivery, and the total number of avulsions had decreased to 58 at 12 months after delivery (P < 0.001; 95% confidence interval [CI] 13.9%-33.5%). This decrease was due to the disappearance of 69.2% of the cases of Type I LAM avulsions (P < 0.001; 95% CI: 50.2%-88.2%). However, the number of Type II LAM avulsions remained constant at 6 months and 12 months after delivery.

CONCLUSION

The spontaneous resolution of LAM avulsion during the first 12 months postpartum occurs in cases of Type I LAM avulsion but is not observed in Type II LAM avulsion.

Episiotomy in vacuum extraction, do we cut the levator ani muscle? A prospective cohort study

INTRODUCTION AND HYPOTHESIS

Vaginal delivery may lead to levator ani muscle (LAM) injury or avulsion. Episiotomy may reduce obstetric anal sphincter injury in operative vaginal delivery, but may increase the risk of LAM injury. Our aim was to assess whether lateral episiotomy in vacuum extraction (VE) in primiparous women causes LAM injury.

METHODS

A prospective cohort study of 58 primiparous women with episiotomy nested within an ongoing multicenter randomized controlled trial of lateral episiotomy versus no episiotomy in VE (EVA trial) was carried out in Sweden. LAM injury was evaluated using 3D endovaginal ultrasound 6-12 months after delivery and Levator Ani Deficiency (LAD) score. Episiotomy scar properties were measured. Characteristics were described and compared using Chi-squared tests. We stipulated that if a lateral episiotomy cuts the LAM, ≥50% would have a LAM injury. Among those, ≥50% would be side specific. We compared the observed prevalence with a test of one proportion.

RESULTS

Twelve (20.7%, 95% CI 10.9-32.9) of 58 women had a LAD (p < 0.001, compared with the stipulated 50%). Six (50.0%, 95% CI 21.1% to 78.9%) of 12 women had a LAD on the episiotomy side, including those with bilateral LAD (p = 1.00). Two (16.7%, 95% CI 2.1% to 48.4%) of 12 women had a LAD exclusively on the episiotomy side (p = 0.02).

CONCLUSIONS

There was no excessive risk of cutting the LAM while performing a lateral episiotomy. LAD was not seen in women with episiotomies shorter than 18 mm.