Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2

Pelvic floor dysfunction in postpartum women: A cross-sectional study

BACKGROUND

Pelvic floor dysfunction (PFD) is a disease of weakened pelvic floor support tissues, leading to changes in the pelvic organ position and function of pelvic organs, with long-term effects on women. This study aimed to assess pelvic floor function using electrophysiology and clinical symptoms, exploring the risk factors for PFD one month postpartum.

METHODS

This cross-sectional study included 845 women from postpartum outpatient clinic of Nantong Affiliated Hospital from August 2019 to October 2021. Pelvic floor muscle strength was evaluated via pelvic floor surface electromyography. Clinical symptoms (urinary incontinence (UI) and pelvic organ prolapse) were diagnosed by gynecologists. Sociodemographic, pregnancy, and obstetrical data were obtained from self-reported questionnaires and electronic records.

RESULTS

The study identified maternal age, parity, immigrant status, and economic income as factors were related to PFD. Gestational constipation increased the risk of abnormal resting muscle strength (OR:1.553, 95%CI: 1.022-2.359). Cesarean delivery was associated with higher rates of abnormal resting muscle strength than vaginal delivery (post-resting stage: OR, 2.712; 95% CI, 1.189-6.185), but a decreased incidence of UI (OR: 0.302; 95% CI, 0.117-0.782). Increased gestational weight gain was correlated with a greater risk of developing UI (OR:1.030, 95%CI: 1.002-1.058). Women with vaginal inflammation faced a higher risk of abnormal fast-twitch muscle (OR: 2.311, 95%CI: 1.125-4.748).

CONCLUSIONS

In addition to uncontrollable factors like mode of delivery, age, and parity, interventions targeting weight gain and constipation during pregnancy and vaginal flora could mitigate the risks of PFD. Educational programs for pregnant women should emphasize a proper diet and lifestyle. For women with vaginal inflammation, clinical treatment should be carried out as soon as possible to avoid further aggravating the damage to the pelvic floor muscles.

Multi-Regional Pelvic Floor Muscle Function Diagnosis System Based on Inflatable Stretchable Electrode Array

BACKGROUND

Effective prevention and treatment of pelvic floor dysfunction (PFD) necessitates the identification of lesions within the complex pelvic floor muscle (PFM) groups associated with various symptoms. Here, we developed a multi-region pelvic floor muscle functional diagnosis system (MPDS) based on an inflatable stretchable electrode array, which aids in accurately locating areas related to PFD.

METHODS

Clinical diagnostic experiments were conducted on 56 patients with postpartum stress urinary incontinence (PSUI) and 73 postpartum asymptomatic controls. MPDS collects pelvic floor electromyography from all participants. By assessing EMG parameters such as activation time differences (ATD) and using Jensen-Shannon (JS) divergence to verify, with the aim of locating target muscle groups with functional abnormalities.

RESULTS

Clinical test results showed that by observing the AT sequence of the PSUI group and the control group, muscle groups with functional abnormalities in the Pubococcygeus muscle (PC) and Puborectalis muscle (PR) regions could be preliminarily diagnosed. In the assessment of regional muscle contribution values based on JS divergence, it was verified that the contribution values of rapid contraction in the PC and PR regions of the PSUI group were relatively lower compared to those of the control group, which correlated with urinary control dysfunction.

CONCLUSIONS

These experiments demonstrate that the MPDS helps in accurately locating target muscle groups with functional abnormalities, showcasing its potential in precise assessment of complex muscle groups such as PFM, which may improve diagnostic precision and reliability.

Multifunctional Evaluation Technology for Diagnosing Malfunctions of Regional Pelvic Floor Muscles Based on Stretchable Electrode Array Probe

The pelvic floor dysfunction (PFD) has become a serious public health problem. Accurate diagnosis of regional pelvic floor muscle (PFM) malfunctions is vitally important for the prevention and treatment of PFD. However, there is a lack of reliable diagnostic devices to evaluate and diagnose regional PFM abnormality. In this work, we developed a multifunctional evaluation technology (MET) based on a novel airbag-type stretchable electrode array probe (ASEA) for the diagnosis of malfunctions of regional PFM. The inflatable ASEA has specifically distributed 32 electrodes along the muscles, and is able to adapt to different human bodies for tight contact with the muscles. These allow synchronous collection of high-quality multi-channel surface electromyography (MC-sEMG) signals, and then are used to diagnose regional PFM malfunctions and evaluate inter-regional correlation. Clinical trial was conducted on 15 postpartum stress urinary incontinence (PSUI) patients and 15 matched asymptomatic women. Results showed that SUI patients responded slowly to the command and have symptoms of muscle strength degeneration. The results were consistent with the relevant clinical manifestations, and proved the reliability of MET for multifunctional PFM evaluation. Furthermore, the MET can diagnose malfunctions of regional PFM, which is inaccessible with existing technology. The results also showed that the dysfunction of PSUI patients is mainly located in iliococcygeus, pubococcygeus, and urethral sphincter regions, and there is a weak correlation between these specific regions and nearby regions. In conclusion, MET provides a point-of-care diagnostic method for abnormal function of regional PFM, which has a potential for the targeted point-to-point electrical stimulation treatment and PFD pathology research.

Fundamental Concepts of Bipolar and High-Density Surface EMG Understanding and Teaching for Clinical, Occupational, and Sport Applications: Origin, Detection, and Main Errors

Surface electromyography (sEMG) has been the subject of thousands of scientific articles, but many barriers limit its clinical applications. Previous work has indicated that the lack of time, competence, training, and teaching is the main barrier to the clinical application of sEMG. This work follows up and presents a number of analogies, metaphors, and simulations using physical and mathematical models that provide tools for teaching sEMG detection by means of electrode pairs (1D signals) and electrode grids (2D and 3D signals). The basic mechanisms of sEMG generation are summarized and the features of the sensing system (electrode location, size, interelectrode distance, crosstalk, etc.) are illustrated (mostly by animations) with examples that teachers can use. The most common, as well as some potential, applications are illustrated in the areas of signal presentation, gait analysis, the optimal injection of botulinum toxin, neurorehabilitation, ergonomics, obstetrics, occupational medicine, and sport sciences. The work is primarily focused on correct sEMG detection and on crosstalk. Issues related to the clinical transfer of innovations are also discussed, as well as the need for training new clinical and/or technical operators in the field of sEMG.

Cross-sectional study of early postpartum pelvic floor dysfunction and related bother in primiparous women 6-10 weeks postpartum

INTRODUCTION AND HYPOTHESIS

To study the prevalence of pelvic floor dysfunction and related bother in primiparous women 6-10 weeks postpartum, comparing vaginal and cesarean delivery.

METHODS

Cross-sectional study of 721 mothers with singleton births in Reykjavik, Iceland, 2015 to 2017, using an electronic questionnaire. Information on urinary and anal incontinence, pelvic organ prolapse and sexual dysfunction with related bother (trouble, nuisance, worry, annoyance) was collected. Main outcome measures were prevalence of pelvic floor dysfunction and related bother.

RESULTS

The overall prevalence of urinary and anal incontinence was 48% and 60%, respectively. Bother regarding urinary symptoms was experienced by 27% and for anal symptoms by 56%. Pelvic organ prolapse was noted by 29%, with less than half finding this bothersome. Fifty-five percent were sexually active, of whom 66% reported coital pain. Of all the women, 48% considered sexual issues bothersome. Urinary incontinence and pelvic organ prolapse were more prevalent in women who delivered vaginally compared to cesarean section, but no differences were observed for anal incontinence and coital pain. Compared to women with BMI < 25, obesity was a predictor for urinary incontinence after vaginal delivery (OR 1.94; 95% CI 1.20-3.14). Birthweight > 50th percentile was predictive for urgency incontinence after vaginal delivery (OR 1.53; 95% CI 1.05-2.21). Episiotomy predicted more anal incontinence (OR 2.19; 95% CI 1.30-3.67). No associations between maternal and delivery characteristics were found for pelvic floor dysfunction after cesarean section.

CONCLUSIONS

Bothersome pelvic floor dysfunction symptoms are prevalent among first-time mothers in the immediate postpartum period.

Sphincter muscle activity before and after delivery: Does it depend on the type of birth?

AIM

There are ongoing discussions whether cesarean section is the safest mode of childbirth to prevent pelvic floor disorders. Pelvic floor electromyography (EMG) allows the analysis of external anal sphincter (EAS) function during voluntary contractions. The primary objective of this study was the evaluation of EMG amplitude of external anal sphincter in women who had vaginal delivery, compared to women who had cesarean section. The secondary objective was to evaluate the anal incontinence score changes before and after delivery between the groups, and to look for any relationship between the clinical and EMG findings.

METHODS

Multichannel surface EMG was detected during maximal contractions in three sessions: (i) during pregnancy, (ii) 6 weeks after delivery and (iii) 1 year after delivery. Women were divided into two groups: cesarean section and vaginal delivery.

RESULTS

External anal sphincter EMG amplitude decreases 6 weeks after vaginal deliveries from 10.1 to 8.6 μV with effect size of 0.4, but returns to baseline after 1 year. No differences were observed between groups in all other variables.

CONCLUSION

No differences were observed after 1 year in EMG activity between the two groups; however, a slight decrease of sphincter muscle amplitude was noted 6 weeks after vaginal delivery. The delivery mode does not have effect on the EAS amplitude 1 year after delivery. Incontinence score slightly increased in both groups after delivery, with no significant differences between the two groups. No association was observed between the increase of incontinence score and the decrease of EMG signal amplitude.

Tools for fecal incontinence assessment: lessons for inflammatory bowel disease trials based on a systematic review

BACKGROUND

Fecal incontinence is a disabling condition affecting up to 20% of women.

OBJECTIVE

We investigated fecal incontinence assessment in both inflammatory bowel disease and non-inflammatory bowel disease patients to propose a diagnostic approach for inflammatory bowel disease trials.

METHODS

We searched on Pubmed, Embase and Cochrane Library for all studies on adult inflammatory bowel disease and non-inflammatory bowel disease patients reporting data on fecal incontinence assessment from January 2009 to December 2019.

RESULTS

In total, 328 studies were included; 306 studies enrolled non-inflammatory bowel disease patients and 22 studies enrolled inflammatory bowel disease patients. In non-inflammatory bowel disease trials the most used tools were the Wexner score, fecal incontinence quality of life questionnaire, Vaizey score and fecal incontinence severity index (in 187, 91, 62 and 33 studies). Anal manometry was adopted in 41.2% and endoanal ultrasonography in 34.0% of the studies. In 142 studies (46.4%) fecal incontinence evaluation was performed with a single instrument, while in 64 (20.9%) and 100 (32.7%) studies two or more instruments were used. In inflammatory bowel disease studies the Wexner score, Vaizey score and inflammatory bowel disease quality of life questionnaire were the most commonly adopted tools (in five (22.7%), five (22.7%) and four (18.2%) studies). Anal manometry and endoanal ultrasonography were performed in 45.4% and 18.2% of the studies.

CONCLUSION

Based on prior validation and experience, we propose to use the Wexner score as the first step for fecal incontinence assessment in inflammatory bowel disease trials. Anal manometry and/or endoanal ultrasonography should be taken into account in the case of positive questionnaires.

Surface EMG in Clinical Assessment and Neurorehabilitation: Barriers Limiting Its Use

This article addresses the potential clinical value of techniques based on surface electromyography (sEMG) in rehabilitation medicine with specific focus on neurorehabilitation. Applications in exercise and sport pathophysiology, in movement analysis, in ergonomics and occupational medicine, and in a number of related fields are also considered. The contrast between the extensive scientific literature in these fields and the limited clinical applications is discussed. The "barriers" between research findings and their application are very broad, and are longstanding, cultural, educational, and technical. Cultural barriers relate to the general acceptance and use of the concept of objective measurement in a clinical setting and its role in promoting Evidence Based Medicine. Wide differences between countries exist in appropriate training in the use of such quantitative measurements in general, and in electrical measurements in particular. These differences are manifest in training programs, in degrees granted, and in academic/research career opportunities. Educational barriers are related to the background in mathematics and physics for rehabilitation clinicians, leading to insufficient basic concepts of signal interpretation, as well as to the lack of a common language with rehabilitation engineers. Technical barriers are being overcome progressively, but progress is still impacted by the lack of user-friendly equipment, insufficient market demand, gadget-like devices, relatively high equipment price and a pervasive lack of interest by manufacturers. Despite the recommendations provided by the 20-year old EU project on "Surface EMG for Non-Invasive Assessment of Muscles (SENIAM)," real international standards are still missing and there is minimal international pressure for developing and applying such standards. The need for change in training and teaching is increasingly felt in the academic world, but is much less perceived in the health delivery system and clinical environments. The rapid technological progress in the fields of sensor and measurement technology (including sEMG), assistive devices, and robotic rehabilitation, has not been driven by clinical demands. Our assertion is that the most important and urgent interventions concern enhanced education, more effective technology transfer, and increased academic opportunities for physiotherapists, occupational therapists, and kinesiologists.

A Novel High-Density Electromyography Probe for Evaluating Anorectal Neurophysiology: Design, Human Feasibility Study, and Validation with Trans-Sacral Magnetic Stimulation

Fecal incontinence (FI) substantially impairs quality of life and imparts a major socioeconomic burden. Anal sphincter injury and possibly pudendal nerve damage are considered common causes, however, current clinical methods for evaluating their function remain suboptimal. Electromyography (EMG) and pudendal nerve terminal latencies have been applied with some success, but are not considered standard practice due to uncertain accuracy and clinical value. In this study we developed and applied a novel anorectal high-density (HD) EMG probe in humans and pigs to acquire quantitative electrophysiological metrics of the anorectum. In the human trial we assessed somatic pathways and showed that EMG amplitude was greater for tight voluntary squeezes than light voluntary squeezes (0.03 ± 0.02 mV vs. 0.05 ± 0.03 mV). In a porcine model we applied trans-sacral magnetic stimulation to evoke extrinsically activated involuntary pathways and the resulting motor evoked potentials (MEP) were captured using the HD-EMG probe. The mean MEP amplitude at 50% magnetic stimulation intensity output (MSO) was significantly lower that the MEP amplitude at 85, 95 and 100% MSO (1.52 ± 0.50 mV vs. 3.10 ± 0.60 mV). In conclusion, the use of HD-EMG probe in conjunction with trans-sacral magnetic stimulation, for spatiotemporal mapping of anorectal EMG and MEP activity is anticipated to achieve new insights into FI and could offer improved diagnostic and prognostic biomarkers for anorectal dysfunction.

Global Innervation Zone Identification With High-Density Surface Electromyography

OBJECTIVE

The aim of this study is to compare the performance of three strategies in determining the global innervation zone (IZ) distribution.

METHODS

High-density surface electromyography was recorded from the biceps brachii muscle of seven healthy subjects under isometric voluntary contractions at 20%, 50%, and 100% of the maximal voluntary contraction and supramaximal musculocutaneous nerve stimulations. IZs were detected: first, by visual identification in a column-specific manner (IZ-1D); second, based on decomposed bipolar mapping of motor unit action potentials (IZ-2D); and third, by source imaging in the three-dimensional muscle space (IZ-3D).

RESULTS

All three IZ detection approaches have exhibited excellent trial-to-trial repeatability. Consistent IZ results were found in the axial direction of the arm across all three approaches, yet a difference was observed in the mediolateral direction.

CONCLUSIONS

Among all three approaches, IZ-3D is capable of providing the most comprehensive information regarding the global IZ distribution, while maintaining high consistency with IZ-1D and IZ-2D results.

SIGNIFICANCE

IZ-3D approach can be a potential tool for global IZ imaging, which is critical to the clinical diagnosis and treatment of neuromuscular disorders.

Effects of delivery mode and age on motor unit properties of the external anal sphincter in women

INTRODUCTION AND HYPOTHESIS

This study aimed to assess the individual and interactive effects of delivery mode and age on the function of the external anal sphincter (EAS) by analyzing the motor unit properties with intramuscular electromyography (EMG). Results are expected to improve the understanding of delivery-related occult obstetric EAS injuries and its development over the aging process and further support early clinical detection and intervention.

METHODS

A total of 49 postpartum women were recruited into four test groups according to their age and delivery mode: young vaginal delivery (Y-VD), elderly vaginal delivery (E-VD), young cesarean section (Y-CS), and elderly cesarean section (E-CS) groups. Anorectal ultrasonography, manometry, and intramuscular EMG were employed for comprehensive evaluation of EAS function.

RESULTS

No significant difference in anorectal ultrasonography and most manometry measurements was associated with delivery age or mode. Intramuscular EMG, however, revealed a statistically significant difference in the characteristics of motor unit potentials (MUPs), including duration, turns, phases, and multiphase wave ratio between four subject groups. No significant interaction effect between age and delivery mode was found.

CONCLUSIONS

Delivery mode and age have a significant effect on the neuromuscular function of the EAS, suggesting a potential protectiveness of cesarean section against impairment to the EAS. Our results do not provide significant evidence regarding the interaction effect of delivery mode and age; further investigations are needed to confirm this conclusion.

Intuitive Visualization of Innervation Zones Based on Surface-EMG Signals

The purpose of this study was to develop a user-friendly presentation of surface-EMG data in near-time for intraoperative nerve-monitoring. We have built a novel surface-EMG probe as a diagnostic device to investigate innervation patterns of sphincter muscles in further clinical diagnostic studies. S-EMG data were recorded from 20 healthy volunteers from the orbicularis oris muscles. We developed an automated analysis based on correlation in order to find phase inversions and thus innervation zones automatically. We compared our automated analysis with manual, visual analysis. Both techniques were reviewed for variance and showed reproducible results. Data from automated analysis were compared to visually analyzed data showing high consistency. Based on our automated analysis, we created an intuitive visualization of all measurements per person. We displayed the quality and quantity of the phase inversions found in a subject thus allowing for simple identification of innervation zones. We conclude that our set-up showed sufficient reliability for detection of motoric endplate activity and can be used for further clinical neurophysiological studies.

[Fetal expulsion: Which interventions for perineal prevention? CNGOF Perineal Prevention and Protection in Obstetrics Guidelines]

OBJECTIVE

The objective for all obstetricians and midwifes who intervene during the release of the fetal presentation is to prevent at best the perineal lesions. This work consisted in analyzing the literature, researching and evaluating interventions that reduce this perineal risk during the release.

METHODS

A keyword search for each medical intervention during the expulsion phase was conducted by selecting studies assessing perineal risk. Interventions during pregnancy and during delivery before the expulsion phase were specifically addressed in other sections of the recommendations.

RESULTS

Firstly, the degree of perineal stretching during the second stage of labour does not appear to be a risk factor for OASIS, postpartum incontinence, or sexual disorders (LE3) and that a substantial stretching of the perineum is not an indication of episiotomy (Professional consensus). Then, manual control of the expulsion of the fetus at the end of the second stage of labour and support of the posterior perineum during this time appear to reduce the rate of OASIS (LE3). The crowning of the baby's head should be manually controlled and the posterior perineum manually supported manually to reduce the risk of OASIS (GradeC). There is no recognised benefit to episiotomy in normal deliveries (LE1); the liberal practice of episiotomy results in fewer intact perineums than its restrictive practice, and the latter does not result in increasing the number of cases of OASIS. No evidence indicates that an episiotomy for women with a breech presentation, twin pregnancy, or posterior position prevents OASIS (LE3). Indication for episiotomy during delivery depends on individual risk factors and obstetric conditions (Professional consensus). It is recommended that the indication for episiotomy be explained and the woman's consent received before its performance. The performance of an episiotomy during normal deliveries is not recommended to reduce the risk of OASIS (Grade A). The liberal practice of episiotomy to prevent OASIS is not recommended for women with a breech presentation, twin pregnancy, or posterior position (GradeC). Episiotomy during an instrumental delivery appears to be associated with a reduction of the risk of OASIS (LE3). The vacuum extractor appears to induce fewer cases of OASIS than other instruments (LE3). Episiotomy may be indicated in instrumental deliveries to avoid OASIS (GradeC). Training in perineal protection in obstetrics is recommended (Grade B). In operative vaginal deliveries when several instruments can be used, a vacuum extractor is preferentially recommended to reduce the risk of OASIS (GradeC). When forceps or spatulas are used, it is preferable that they be withdrawn just before cephalic deflexion so that the fetal head is not "capped" with these instruments at birth (Professional consensus). Couder's maneuver, which consists of lowering the forearm during the release of the fetal shoulders, appears to decrease the rate of second-degree perineal tears and increase the rate of intact perineum (LE3).

CONCLUSION

Manual control of the expulsion and perineal support reduce the risk of perineal injury. There is no benefit to episiotomy in normal delivery, nor in special cases such the breech presentation for example. On the other hand, in case of instrumental delivery, an episiotomy may be indicated to avoid OASIS (GradeC), and it is recommended if it is possible to use the ventouse preferentially. The Couder's maneuver seems to reduce the rate of 2^nd degree perineal lesions (LE3). Finally, training in perineal obstetric protection is recommended (Grade B).

Innervation asymmetry of the external anal sphincter in aging characterized from high-density intra-rectal surface EMG recordings

AIMS

The innervation zone asymmetry of the external anal sphincter (EAS) has been investigated as a risk factor for the development of fecal incontinence (FI). This study aims to utilize an intra-rectal high-density surface electromyogram (HD-sEMG) recording and advanced HD-sEMG decomposition technique to characterize the effects of aging on the asymmetry of EAS functional innervation.

METHODS

HD-sEMG signals were recorded intra-rectally from six healthy young and seven healthy elderly women during voluntary contractions of the EAS. EMG signals were decomposed into constituent motor unit action potentials (MUAPs) and the innervation zone of each decomposed motor unit was identified. Asymmetry index (AI) was defined and calculated for all subjects. The maximum squeezing pressures of the EAS were also measured for all subjects as a comparison.

RESULTS

The HD-sEMG decomposition and AI calculation were successfully performed from EMG data acquired from all the subjects. The AI values were 28.7 ± 17.0% for the young group and 55.6 ± 18.8% for the elderly group. The AI and EAS contraction strength were found to be negatively correlated (P < 0.05). A two-tailed student's t-test demonstrated a significant increase in AI with age by comparison between two groups (P < 0.05).

CONCLUSIONS

Our work demonstrates, for the first time, that EAS functional innervation tends to become increasingly asymmetrical with advancing age, and this increase is associated with a compromised anorectal function. Results suggest that the intra-rectal HD-sEMG will serve as an advanced tool for assessing and monitoring the anorectal neuromuscular function minimally invasively under different pathophysiological conditions.

Could the correct side of mediolateral episiotomy be determined according to anal sphincter EMG?

INTRODUCTION AND HYPOTHESIS

Mediolateral episiotomy is one of the most frequent surgical interventions performed in obstetrics. There is conflicting evidence as to whether mediolateral episiotomy reduces the risk of obstetric anal sphincter injuries (OASI). Recent studies suggest that functional asymmetry of pelvic floor innervation exists in healthy women and is strongly associated with postpartum incontinence when the trauma occurs on the dominant side of innervation. Mediolateral episiotomy is the most common cause of perineal trauma during delivery, and the surgical incision is usually performed on the mediolateral right side. Surface electromyography (EMG) has been recently applied in obstetrics for detecting electrical activity of the external anal sphincter (EAS).

METHODS

Two hundred and forty-five pregnant nulliparous women at their second and third trimester of pregnancy were recruited, and EMG signals were detected using a multichannel cylindric anal probe. Measurements were repeated and compared 6-8 weeks after delivery on a subgroup of 167 women who were divided in two groups according to EMG amplitude asymmetry before delivery and two subgroups according to type of delivery: (1A) asymmetric left, episiotomy right; (1B) asymmetric left, other types of deliveries; (2A) asymmetric right, episiotomy right; (2B) asymmetric right, other type of deliveries.

RESULTS

The reduction of EMG amplitude after right episiotomy was larger in women with right asymmetric sphincter compared with women with left asymmetry and women with other types of delivery.

CONCLUSIONS

Prenatal EMG may be used to predict the impact of right-sided mediolateral episiotomy on EAS and perhaps also function following delivery.

Modern Theories of Pelvic Floor Support : A Topical Review of Modern Studies on Structural and Functional Pelvic Floor Support from Medical Imaging, Computational Modeling, and Electromyographic Perspectives

PURPOSE OF REVIEW

Weakened pelvic floor support is believed to be the main cause of various pelvic floor disorders. Modern theories of pelvic floor support stress on the structural and functional integrity of multiple structures and their interplay to maintain normal pelvic floor functions. Connective tissues provide passive pelvic floor support while pelvic floor muscles provide active support through voluntary contraction. Advanced modern medical technologies allow us to comprehensively and thoroughly evaluate the interaction of supporting structures and assess both active and passive support functions. The pathophysiology of various pelvic floor disorders associated with pelvic floor weakness is now under scrutiny from the combination of (1) morphological, (2) dynamic (through computational modeling), and (3) neurophysiological perspectives. This topical review aims to update newly emerged studies assessing pelvic floor support function among these three categories.

RECENT FINDINGS

A literature search was performed with emphasis on (1) medical imaging studies that assess pelvic floor muscle architecture, (2) subject-specific computational modeling studies that address new topics such as modeling muscle contractions, and (3) pelvic floor neurophysiology studies that report novel devices or findings such as high-density surface electromyography techniques. We found that recent computational modeling studies are featured with more realistic soft tissue constitutive models (e.g., active muscle contraction) as well as an increasing interest in simulating surgical interventions (e.g., artificial sphincter). Diffusion tensor imaging provides a useful non-invasive tool to characterize pelvic floor muscles at the microstructural level, which can be potentially used to improve the accuracy of the simulation of muscle contraction. Studies using high-density surface electromyography anal and vaginal probes on large patient cohorts have been recently reported. Influences of vaginal delivery on the distribution of innervation zones of pelvic floor muscles are clarified, providing useful guidance for a better protection of women during delivery. We are now in a period of transition to advanced diagnostic and predictive pelvic floor medicine. Our findings highlight the application of diffusion tensor imaging, computational models with consideration of active pelvic floor muscle contraction, high-density surface electromyography, and their potential integration, as tools to push the boundary of our knowledge in pelvic floor support and better shape current clinical practice.

High spatial resolution pressure distribution of the vaginal canal in Pompoir practitioners: A biomechanical approach for assessing the pelvic floor

BACKGROUND

Pompoir is a technique poorly studied in the literature that claims to improve pelvic floor strength and coordination. This study aims to investigate the pelvic floor muscles' coordination throughout the vaginal canal among Pompoir practitioners and non-practitioners by describing a high resolution map of pressure distribution.

METHODS

This cross-sectional, study included 40 healthy women in two groups: control and Pompoir. While these women performed both sustained and "waveform" pelvic floor muscle contractions, the spatiotemporal pressure distribution in their vaginal canals was evaluated by a non-deformable probe fully instrumented with a 10×10 matrix of capacitive transducers.

FINDINGS

Pompoir group was able to sustain the pressure levels achieved for a longer period (40% longer, moderate effect, P=0.04). During the "waveform" contraction task, Pompoir group achieved lower, earlier peak pressures (moderate effect, P=0.05) and decreased rates of contraction (small effect, P=0.04) and relaxation (large effect, P=0.01). During both tasks, Pompoir group had smaller relative contributions by the mid-region and the anteroposterior planes and greater contributions by the caudal and cranial regions and the latero-lateral planes.

INTERPRETATION

Results suggest that specific coordination training of the pelvic floor muscles alters the pressure distribution profile, promoting a more-symmetric distribution of pressure throughout the vaginal canal. Therefore, this study suggests that pelvic floor muscles can be trained to a degree beyond strengthening by focusing on coordination, which results in changes in symmetry of the spatiotemporal pressure distribution in the vaginal canal.

Detection of Multiple Innervation Zones from Multi-Channel Surface EMG Recordings with Low Signal-to-Noise Ratio Using Graph-Cut Segmentation

Knowledge of the location of muscle Innervation Zones (IZs) is important in many applications, e.g. for minimizing the quantity of injected botulinum toxin for the treatment of spasticity or for deciding on the type of episiotomy during child delivery. Surface EMG (sEMG) can be noninvasively recorded to assess physiological and morphological characteristics of contracting muscles. However, it is not often possible to record signals of high quality. Moreover, muscles could have multiple IZs, which should all be identified. We designed a fully-automatic algorithm based on the enhanced image Graph-Cut segmentation and morphological image processing methods to identify up to five IZs in 60-ms intervals of very-low to moderate quality sEMG signal detected with multi-channel electrodes (20 bipolar channels with Inter Electrode Distance (IED) of 5 mm). An anisotropic multilayered cylinder model was used to simulate 750 sEMG signals with signal-to-noise ratio ranging from -5 to 15 dB (using Gaussian noise) and in each 60-ms signal frame, 1 to 5 IZs were included. The micro- and macro- averaged performance indices were then reported for the proposed IZ detection algorithm. In the micro-averaging procedure, the number of True Positives, False Positives and False Negatives in each frame were summed up to generate cumulative measures. In the macro-averaging, on the other hand, precision and recall were calculated for each frame and their averages are used to determine F1-score. Overall, the micro (macro)-averaged sensitivity, precision and F1-score of the algorithm for IZ channel identification were 82.7% (87.5%), 92.9% (94.0%) and 87.5% (90.6%), respectively. For the correctly identified IZ locations, the average bias error was of 0.02±0.10 IED ratio. Also, the average absolute conduction velocity estimation error was 0.41±0.40 m/s for such frames. The sensitivity analysis including increasing IED and reducing interpolation coefficient for time samples was performed. Meanwhile, the effect of adding power-line interference and using other image interpolation methods on the deterioration of the performance of the proposed algorithm was investigated. The average running time of the proposed algorithm on each 60-ms sEMG frame was 25.5±8.9 (s) on an Intel dual-core 1.83 GHz CPU with 2 GB of RAM. The proposed algorithm correctly and precisely identified multiple IZs in each signal epoch in a wide range of signal quality and is thus a promising new offline tool for electrophysiological studies.

Functional mapping of the pelvic floor and sphincter muscles from high-density surface EMG recordings

INTRODUCTION AND HYPOTHESIS

Knowledge of the innervation of pelvic floor and sphincter muscles is of great importance to understanding the pathophysiology of female pelvic floor dysfunctions. This report presents our high-density intravaginal and intrarectal electromyography (EMG) probes and a comprehensive innervation zone (IZ) imaging technique based on high-density EMG readings to characterize the IZ distribution.

METHODS

Both intravaginal and intrarectal probes are covered with a high-density surface electromyography electrode grid (8 × 8). Surface EMG signals were acquired in ten healthy women performing maximum voluntary contractions of their pelvic floor. EMG decomposition was performed to separate motor-unit action potentials (MUAPs) and then localize their IZs.

RESULTS

High-density surface EMG signals were successfully acquired over the vaginal and rectal surfaces. The propagation patterns of muscle activity were clearly visualized for multiple muscle groups of the pelvic floor and anal sphincter. During each contraction, up to 218 and 456 repetitions of motor units were detected by the vaginal and rectal probes, respectively. MUAPs were separated with their IZs identified at various orientations and depths.

CONCLUSIONS

The proposed probes are capable of providing a comprehensive mapping of IZs of the pelvic floor and sphincter muscles. They can be employed as diagnostic and preventative tools in clinical practices.