Hypothesis / aims of study
Identify instruments that assess contraction of the female pelvic floor muscles to characterize them in terms of pressure, strength, activation, location, and caudo-cranial and/or laterolateral displacements.
Study design, materials and methods
An integrative review was conducted, based on five steps to ensure adequate methodological rigor (1): problem formulation; data collection, data evaluation, data analysis and interpretation; and public presentation.
Using the PICo (Population-Interest-Context) strategy for non-clinical research, we asked: what are the instruments used to evaluate the contraction of female pelvic floor muscles (PFM) that can provide a pattern of contraction of these muscles? We included articles that contained the adult female pelvic floor - which, for this study should be understood as the anatomical-specific, biologically defined floor - with or without urogynecological dysfunctions, objective measurements of PFM - pressure in mmHg or cmHg or cmH2O; force in Newton (N); activation (muscle recruitment) by electromyography or electroneuromyography root mean square (RMS) in microvolts (μV); and/or contractile localization and displacement by ultrasonography, tomography, and magnetic resonance imaging (mm or cm), full text in Brazilian Portuguese, Spanish, or English published within the last 20 years (2000-2020) in the Medline, Embase, Lilacs, Scopus, Web of Science, PeDRO, or Cochrane Library databases. Studies exclusively involving pregnant women, children, male pelvic floor, or pelvic pain were excluded. All grey literature was also disregarded for this article.
The data were evaluated using the MMAT - Mixed Methods Appraisal Tool, capable of evaluating quantitative, qualitative, and mixed studies, to which a scoring system of 25%, 50%, 75%, and 100% quality was associated, with no exclusion. Data were collected and organized according to the collection tool validated by Ursi (2005) (2). Two reviewers independently graded the articles and discussed discrepancies when necessary. When consensus was not reached, a third reviewer, blinded to the other two, performed the ranking as a tie-breaker.
The results were categorized according to similar quantitative data, according to the measuring instrument used for measuring the PFM.
Results
The search strategy yielded 982 articles and followed the PRISMA criteria used for systematic reviews (Figure 1). In the end, were included 54 articles. Methodological evaluation by MMAT and classification resulted in 9 (16.67%) articles with a score of 25%, 19 (35.19%) of 50%, 13 (24.07%) of 75%, and 13 (24.07%) of 100%.
It was verified that fifteen studies (27.7%) used the manual assessment of PFM concomitantly with other methods. Of these, thirteen (86.6%) used the PERFECT scheme and nine (60%) were studies from Brazil. The mean strength was 2.74 (0.64) considering the studies analyzed. Manometry was the measure most used by the studies for measurements related to PFM. The most used equipment was the Peritron (Cardio Design Pty Ltd, Australia), being used in nineteen studies (63.3%) of the thirty (55.5%) found. Of these, eleven (36.6%) are exclusively Brazilian and two (6.66%) are in partnership with Norway. In addition, five studies (16.6%) from Norway used the Camtech AS device, developed in Norway. Among the studies that used Peritron, the mean peak pressure was 31.81 (16.97).
Eight studies (14.81%) used dynamometry, two articles (25%) most recent (2020) are Canadian, one of them being in partnership with New Zealand, used the Montreal Dynamometer. Three Brazilian studies (37.5%) were located, two of which, used the EMG System do Brasil equipment, model DFV 020101/10 (2015 and 2016). The other study is from 2011 and describes a speculum for measurement, without brand and measurement unit.
Electromyography was used in nineteen studies (35.18%), twelve (63.18%) of these Brazilian articles: four (21.05%) used EMG: EMG System do Brasil LTDA software and intracavitary electrode (Chattanooga Group, Hixson, USA); two (10.52%), more recent (2019, 2021) used MyoTrac® G, Montreal, Canada, and one (5.26%) older (2007) describes only Myotrac 3G, the others (52.65%) used Miotool 400 and 200 system (Miotec) and Physio-Med Services® vaginal probe and two (10.52%) did not describe the equipment.
Ultrasonography was used in eight studies (14.81%), two articles (25%) exclusively Brazilian, and one (12.5%) in partnership with Australia. Two studies (25%) are Norwegian, one Australian (12.5%), one Canadian (12.5%) and African (12.5%). The equipment most used was the GE Voluson ultrasound system (Norway or Austria), but the description of this equipment does not clearly state that it is the same measuring device. The South African study used the PhillipsTM HDIIXE equipment.
Interpretation of results
Through the evaluation of the PFM, the physiotherapist prepares the diagnosis and care of his patient, so understanding the state of the art on the measurement and functionality data of this musculature becomes important.
Arnold Kegel, in his works between 1948 and 1950, revolutionized the study and rehabilitation of the pelvic floor with proposals for intervention on these muscles. After 50 years, science continues to improve the knowledge about PFM and with the technological advances and accumulated knowledge, it has been making possible a better dialogue between subjectivity and practical issues.
A point in common among all the analyzed equipment was the prevalence of Brazilian studies, evidencing the growth of research in the area of women's health in the last 20 years. Through manual evaluation, we identified that the major reference for this evaluation is the PERFECT Scheme, described by Laycock and Jerwood (2001), which recommends the introduction of only one finger into the vaginal canal, with the evaluation of the right (at 4:00 am) and left (at 8:00 am) walls (3). Despite referring to such references, the descriptions of the way to evaluate are mostly unclear, indicating that the necessary evaluative rigor is not maintained.
Manometry, for historical reasons of availability, scientific basis, and cost-effectiveness, is the most used, and the Peritron device is the most prevalent. Electromyography was the second most used equipment by the researchers and presented the greatest equipment variability. This is possibly because it is a technology developed to evaluate muscles in general, and was then adapted by the companies to measure the PFM, using intracavitary probes and data collection programs.
Dynamometry and ultrasonography were less used. It is verified that dynamometry presents a history of research centers developing its equipment, also generating variability of devices, not always commercialized. Ultrasonography is a more expensive technology and depends on a specialized professional to collect and analyze the image data.
It was not possible to verify a pattern of contraction and the characteristics of PFM with the different instruments analyzed, due to the large population variability of the studies and the equipment used. However, it was possible to verify by the PERFECT scheme an average force of 2.74 (0.64) among women in the selected studies, and by the Peritron the average peak pressure was 31.81 (16.97) with an average pressure of 15.81 (9.97).