Pelvic muscles’ mechanical response to strains in the absence and presence of pregnancy-induced adaptations in a rat model

Catanzarite, Tatiana; Bremner, Shannon N.; Barlow, Caitlin L.; Bou-Malham, Laura; O’Connor, Shawn M.; Alperin, Marianna

doi:10.1016/j.ajog.2018.02.001

Cited by 35 publications

(74 citation statements)

References 44 publications

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“…1 Hence, levator ani muscle injury is related to the appearance of pelvic organ prolapse 1-3 (affecting mainly the anterior and middle compartments 4,5 ) as well as to fecal incontinence during the postpartum period [6][7][8] and in elderly women. 11 The main risk factor for the appearance of these levator ani muscle injuries is vaginal delivery, 12 which is associated with an increase in the levator muscle hiatus, 13,14 especially in cases of levator ani muscle avulsion. 11 The main risk factor for the appearance of these levator ani muscle injuries is vaginal delivery, 12 which is associated with an increase in the levator muscle hiatus, 13,14 especially in cases of levator ani muscle avulsion.…”

Section: Introductionmentioning

confidence: 99%

A comparable rate of levator ani muscle injury in operative vaginal delivery (forceps and vacuum) according to the characteristics of the instrumentation

García‐Mejido

Fernández‐Palacín

Barby

et al. 2019

Acta Obstet Gynecol Scand

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Abbreviations: CI, confidence interval; LAM, levator ani muscle; OR, odds ratio. AbstractIntroduction: Forceps delivery is associated with a high rate of levator ani muscle (LAM) trauma (avulsion) at 35%-65% whereas data on avulsion rates after vacuum delivery vary greatly. Nevertheless, a common characteristic of all previous studies carried out to evaluate the association between instrumental deliveries (forceps and vacuum) and LAM avulsion, is the fact that characteristics of the instrumentation have not been described or evaluated. The objective of this study is to compare the rate of LAM avulsion between forceps and vacuum deliveries according to the characteristics of the instrumentation. Material and methods: Prospective, observational study, including 263 nulliparous women, who underwent an instrumental delivery with either Malmström vacuum or Kielland forceps. The characteristics of the instrumentation, position (anterior position and other position) and height of the fetal head at the moment of instrumentation (low instrumentation [vertex at +2 station] and mid-instrumentation [head isinvolved but leading part above +2 station]) were assessed. Evaluation of LAM avulsion was performed at 6 months postpartum by three-/four-dimensional transperineal ultrasound. Using the multi-view mode, a complete avulsion was diagnosed when the abnormal muscle insertion was identified in all three central slices, that is, in the plane of minimal hiatal dimensions and the 2.5-mm and 5.0-mm slices cranial to this one. To detect a 30% or 15% difference in the LAM injury rate, with 80% power and 5% α-error, we needed, respectively 42 and 99 women per study group.Results: In all, 263 nulliparous individuals have been evaluated (162 vacuum deliveries, 101 forceps deliveries). Instrumentation in an occipito-anterior position was more frequent in vacuum deliveries (75.3% vs 56.4%, P = .002), whereas other positions were more frequent in the forceps deliveries group (24.7% vs 43.6%). No statistically significant differences were noted regarding the height of the fetal head at the moment of instrumentation. No statistically significant differences were found in the presence of LAM avulsion (41.4% vs 38.6%) between vacuum and forceps deliveries.The univariate analysis of the crude odds ratio was 1.17, 95% CI 0.67-1.98, P = .70 for

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Section: Introductionmentioning

confidence: 99%

A comparable rate of levator ani muscle injury in operative vaginal delivery (forceps and vacuum) according to the characteristics of the instrumentation

García‐Mejido

Fernández‐Palacín

Barby

et al. 2019

Acta Obstet Gynecol Scand

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“…Twenty‐two rats were used to establish the in vivo resting L s and to evaluate the impact of parturition‐related strains on muscle functional units (uninjured controls n = 4; animals subjected to SBI n = 16; and intrapartum: n = 2). For these L s measurements, physiological and supraphysiological strains were induced in rats subjected to SBI via vaginal distention with 3 and 5 ml volumes, respectively . SBI was performed without (n = 4/volume) and with (n = 4/volume) disarticulation of the pubic symphysis to allow a more cephalad positioning of the distention balloon to impact EUS over its entire length, which is located more rostrally than the human EUS .…”

Section: Methodsmentioning

confidence: 99%

“…Animals were anesthetized with 2.5% isoflurane in oxygen during the procedure. A 12‐French transurethral catheter (Bard Medical, Covington, GA) with the tip cut off was inserted into the vagina, as previously described . The balloon was inflated to either 3 or 5 ml, and a 130 g weight was attached to the end of the catheter, which was left in place for 2 hours to replicate circumferential and downward strains associated with parturition.…”

Section: Methodsmentioning

confidence: 99%

“…These acute events result in decreased overlap between actin and myosin, inflammation, fibrosis, ultimately leading to muscle dysfunction . We have previously identified that excessive strains during the simulated birth injury (SBI) lead to sarcomere hyperelongation of the rat pelvic floor muscles . Published studies examining the impact of SBI on the rat pelvic sphincters focus on important mechanisms of muscle dysfunction, specifically hypoxia and pudendal neuropathy .…”

Section: Introductionmentioning

confidence: 99%

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Mechanical impact of parturition‐related strains on rat pelvic striated sphincters

Duran

Ward

Christman

et al. 2019

Neurourology and Urodynamics

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Aims To define the operational resting sarcomere length (Ls) of the female rat external urethral sphincter (EUS) and external anal sphincter (EAS) and to determine the mechanism of parturition‐related injury of EUS and EAS using a simulated birth injury (SBI) vaginal distention model. Methods EUS and EAS of 3‐month‐old Sprague‐Dawley control and injured rats were fixed in situ, harvested, and microdissected for Ls measurements and assessment of ultrastructure. EUS and EAS function was determined at baseline, and immediately and 4 weeks after SBI, using leak point pressure (LPP) and anorectal manometry (ARM), respectively. Operational L s was compared to species‐specific optimal L s using one sample Student's t test. Data (mean ± SD) were compared between groups and time points using repeated measures one‐way analysis of variance, followed by Tukey's post hoc pairwise comparisons, with significance set to 0.05. Results The operational resting Ls of both sphincters (EUS: 2.09 ± 0.07 µm, EAS: 2.02 ± 0.03 µm) was significantly shorter than optimal rat Ls of 2.4 µm. Strains imposed on EUS and EAS during SBI resulted in significant sarcomere elongation and disruption, compared with the controls (EUS: 3.09 ± 0.11 µm, EAS: 3.37 ± 0.09 µm). Paralleling structural changes, LPP and ARM measures were significantly lower immediately (LPP: 21.5 ± 1.0 cmH2O, ARM: 5.1 ± 2.31 cmH2O) and 4 weeks (LPP: 27.7 ± 1.3cmH2O, ARM: 2.5 ± 1.0 cmH2O) after SBI relative to the baseline (LPP: 43.4 ± 8.5 cmH2O, ARM: 8.2 ± 2.0 cmH2O); P < 0.05. Conclusions Analogous to humans, the short resting Ls of rat EUS and EAS favors their sphincteric function. The insult experienced by these muscles during parturition leads to sarcomere hyperelongation, myofibrillar disruption, and dysfunction of the sphincters long‐term.

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“…The above is the first step in the continuum of research focused on deciphering what segregates women who do and do not sustain PFM birth trauma (Catanzarite et al. ). In addition, the rat has been extensively used as a simulated birth injury model to study the mechanisms of maternal injury and postpartum recovery, and to investigate various treatments that directly target the injured pelvic soft tissues (Wood et al.…”

Section: Introductionmentioning

confidence: 99%

Multimodal imaging assessment and histologic correlation of the female rat pelvic floor muscles’ anatomy

et al. 2019

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Pelvic floor disorders negatively impact millions of women worldwide. Although there is a strong epidemiological association with childbirth, the mechanisms leading to the dysfunction of the integral constituents of the female pelvic floor, including pelvic floor skeletal muscles, are not well understood. This is in part due to the constraints associated with directly probing these muscles, which are located deep in the pelvis. Thus, experimental models and non-invasive techniques are essential for advancing knowledge of various phenotypes of pelvic floor muscle injury and pathogenesis of muscle dysfunction, as well as developing minimally invasive approaches for the delivery of novel therapeutics. The most widely used animal model for pelvic floor disorders is the rat. However, the radiological anatomy of rat pelvic floor muscles has not been described. To remedy this gap, the current study provides the first detailed description of the female rat pelvic floor muscles’ radiological appearance on MR and ultrasound images, validated by correlation with gross anatomy and histology. We also demonstrate that ultrasound guidance can be used to target rat pelvic floor muscles for possible interventional therapies.

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Pelvic muscles’ mechanical response to strains in the absence and presence of pregnancy-induced adaptations in a rat model

Cited by 35 publications

References 44 publications

A comparable rate of levator ani muscle injury in operative vaginal delivery (forceps and vacuum) according to the characteristics of the instrumentation

A comparable rate of levator ani muscle injury in operative vaginal delivery (forceps and vacuum) according to the characteristics of the instrumentation

Mechanical impact of parturition‐related strains on rat pelvic striated sphincters

Multimodal imaging assessment and histologic correlation of the female rat pelvic floor muscles’ anatomy

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