Ultrasound Obstet Gynecol 2015; 45: 217–222 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.13456
Pelvic floor muscle contractility: digital assessment vs transperineal ultrasound K. VAN DELFT, R. THAKAR and A. H. SULTAN Croydon University Hospital, Department of Obstetrics and Gynaecology, Division of Urogynaecology, Croydon, UK
K E Y W O R D S: correlation; hiatus area; modified Oxford scale; pelvic floor muscle contractility; transperineal ultrasound
ABSTRACT
INTRODUCTION
Objectives A significant reduction in hiatal area and anteroposterior diameter can be induced by pelvic floor muscle contraction, and this has been demonstrated using three-dimensional/four-dimensional (3D/4D) transperineal ultrasound (TPS) in a small group of women. Our objective was to correlate pelvic floor muscle contractility using digital assessment with the change in TPS hiatus measurements during maximum pelvic floor muscle contraction.
Although clinical assessment of pelvic floor muscle structures is still regarded as being of great value, in recent years the use of three-dimensional/four-dimensional (3D/4D) transperineal ultrasound (TPS) to image pelvic floor muscle integrity has become the focus of considerable amounts of research. Research has been focused mainly on muscle morphology, such as levator ani muscle avulsion, and abnormal hiatus biometry, which are considered risk factors for pelvic organ prolapse1 , but not on functionality, which can be assessed using TPS. The functional capacity of the pelvic floor can be assessed by measuring pelvic floor muscle strength, and has been shown to be negatively associated with pelvic floor and sexual dysfunction2,3 . Various methods have been used to assess pelvic floor muscle contractility, such as digital assessment using the Modified Oxford Scale (MOS) and perineometry4 – 6 . Although MOS had previously been found to have poor inter-rater reliability7,8 , a recent study conducted by our group found substantial agreement between two raters9 . Weinstein et al.10 demonstrated a significant reduction, of approximately 10%, in hiatus area and anteroposterior diameter on contraction of the pelvic floor in 27 nulligravid women and Brækken et al.11 showed a reduction of 25% in 17 parous women. Their techniques of measuring the differences in hiatal area are related to the extent to which the levator ani muscle is lifted by pelvic floor muscle contraction10,11 . The reduction in hiatus measurements on maximum pelvic floor muscle contraction using TPS has not yet been evaluated in a large group of nulliparous and primiparous women, nor has it been correlated with digital assessment. Recently, based on clinical relevance, MOS has been suggested to be a superior measure of contraction than is ultrasound assessment12 , although no correlation study was performed. The MOS is an assessment of the degree of
Methods Nulliparous pregnant women were recruited from the antenatal clinic. Pelvic floor muscle contractility was assessed by digital palpation using the validated Modified Oxford Scale (MOS). Subsequently, women underwent 3D/4D TPS. Measurements of the hiatal area and anteroposterior diameter were taken from the rendered ultrasound images at rest and at maximum contraction, and differences in measurements were expressed as percentages. Spearman’s rank (ρ) was used to assess the correlation. Results Four hundred and fifty-nine assessments were performed, of which 268 were from women at around 36 weeks’ gestation, and 191 were from women following delivery at 3 months postpartum. The overall correlation between MOS and TPS was found to be ρ = 0.47 for hiatal area (P < 0.001) and ρ = 0.51 for hiatal anteroposterior diameter (P < 0.001). Conclusions Digital palpation using MOS and TPS can both be used as tools to assess pelvic floor muscle contractility. Although MOS is a simple clinical tool without the need for any equipment, TPS can provide good visual biofeedback when training patients in pelvic floor muscle exercises. As TPS is non-intrusive, it may be the method of choice for some women. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
Correspondence to: Dr R. Thakar, Croydon University Hospital, 530 London Road, Croydon, CR7 7YE, UK (e-mail: [email protected]) Accepted: 25 June 2014
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
ORIGINAL PAPER
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pressure against the examining finger, exerted by elevation of the levator ani muscle, during maximum pelvic floor muscle contraction. We hypothesized that digital and ultrasound measurements should correlate well in the assessment of pelvic floor muscle contractility. The aim of this study was to correlate pelvic floor muscle contractility using digital assessment and the change in hiatal measurements using TPS, during maximum pelvic floor muscle contraction.
METHODS All women were recruited as part of a prospective longitudinal study to establish the prevalence of levator ani muscle defects during childbirth and to correlate these with pelvic floor symptoms and pelvic floor muscle strength. Nulliparous pregnant women were recruited from the antenatal clinics at Croydon University Hospital, Croydon, UK13 . The primary study was approved by the National Research Ethics Service South West London Committee (REC 10/H0806/87). All women gave written informed consent. Examinations were performed at 36 weeks’ gestation and 3 months following childbirth, by one independent investigator (K.v.D.). We minimized technique variability by rigorous investigator training and observation by the principal investigator (R.T.). Before the examination, women were asked to empty their bladder, and examination was carried out in the supine position with knees semiflexed. During the follow-up assessment, the operator was blinded to the delivery details. Women were instructed to squeeze their pelvic floor muscle9 and subjective assessment of pelvic floor muscle contractility was performed by the examiner inserting the index finger approximately 4 cm into the vagina4,7,9 . The MOS was used to rate pelvic floor muscle contractility on a scale of 0–5: 0, no contraction; 1, minor muscle ‘flicker’; 2, weak muscle contraction without a circular contraction; 3, moderate muscle contraction; 4, good muscle contraction; and 5, strong muscle contraction against resistance by the examining finger4 , for which substantial agreement was found between two investigators9 . During examination, the researcher encouraged the women to perform a maximum pelvic floor muscle contraction. The weaker MOS of either levator ani muscle (left or right side of pelvis) was used for the correlation analysis, as we expected the weaker side to have the greatest influence on pelvic floor muscle contractility in the determination of maximum contraction9 . Subsequently, women underwent 3D- (to obtain images at rest) and 4D-TPS (to obtain images at maximum pelvic floor muscle contraction) using a Voluson 730 system with a 4–8-MHz transabdominal curved array 3D/4D transducer, with an acquisition angle of 85◦ (GE Medical Systems, Zipf, Austria). The midsagittal plane was used to identify the plane of minimal hiatal dimensions, from the symphysis pubis to the top of the levator plate9,14 . Imaging was performed at rest and at maximum pelvic floor muscle contraction (best of three contractions) and
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
for analysis the symmetric rendered volume was used (Figure 1). The 3D volume at rest was analyzed first, followed by the 4D cineloop obtained during muscle contraction, from which the best of three attempts was chosen for the analysis. Hiatal area and anteroposterior diameter were measured in the rendered axial plane of the minimal hiatal dimensions (Figure 2)14 . Previous research has revealed excellent interobserver reliability for hiatal area (intraclass correlation coefficient (ICC) at rest, 0.92 and at contraction, 0.92) and for anteroposterior diameter (ICC at rest, 0.96 and at contraction, 0.82)15 . Offline analysis was performed at least 2 months following examination, using software 4D View version 10.2 (GE Medical Systems) with the operator (K.v.D.) blinded to the clinical findings. Tomographic ultrasound imaging on maximum pelvic floor muscle contraction was used to assess the entire levator ani muscle and its attachment to the pubic bone. The central three slices were scored as positive or negative for levator ani muscle avulsion. The final unilateral score ranged from 0 (no avulsion) to 3 (complete avulsion). A summed total score, ranging from 0 to 6, for the left and right side levator ani muscle was then assigned and classified as no levator ani muscle avulsion (total score, 0), minor avulsion (total score, 1–3) or major avulsion (total score, 4–6 or a unilateral score of 3)16 . The formula used to calculate the difference in measurements between maximum contraction and rest was: difference = ((Mrest – Msqueeze )/Mrest ) × 100%.
Statistical analysis The MOS was not normally distributed and therefore Spearman’s rank test was used to assess the correlation between digital examination and TPS. An increasing rank correlation implied that there was increasing agreement between the two tests. The outcome of Spearman’s rank testing ranged from –1 (perfect disagreement) to +1 (perfect agreement), where 0 refers to completely independent rankings. Data were analyzed using SPSS 20.0 (SPSS Inc., Chicago, IL, USA) and two-sided P < 0.05 was considered as statistically significant.
RESULTS Between January 2011 and October 2012, 459 assessments were made: 268 of women at 36 (range, 34–41) weeks’ gestation and 191 of women at a median of 13 (range, 10–26) weeks postpartum. The mean ± SD age was 30.3 ± 5.8 years and mean body mass index was 25.4 ± 5.3 kg/m2 . Four antenatal and one postnatal ultrasound assessments were of poor quality, and one woman declined postnatal digital assessment. Statistically significant correlations were found between the weakest MOS and hiatus measurements on TPS for hiatal area (ρ = 0.45–0.47, P < 0.001), and for hiatal anteroposterior diameter (ρ = 0.44–0.57, P < 0.001) (Table 1). Figure 3 represents these results graphically.
Ultrasound Obstet Gynecol 2015; 45: 217–222.
Levator ani assessment
219
PB
PB
PB
PB
U
U V
V L
L
L
A
L
A
Figure 1 Antenatal rendered ultrasound images at rest (a) and on maximum pelvic floor muscle contraction (b), showing a decrease in hiatal area and anteroposterior diameter on maximum contraction. A, anus; L, levator ani muscle; PB, pubic bone; U, urethra; V, vagina.
DISCUSSION
PB
PB
1 2 L
L
Figure 2 Antenatal rendered transperineal ultrasound image showing hiatal area (1, outlined) and anteroposterior diameter (2, vertical line). L, levator ani muscle; PB, pubic bone.
The mean antenatal difference calculated between rest and contraction on TPS was 19.1 ± 12.3% for hiatal area and 17.3 ± 9.1% for hiatal anteroposterior diameter. The mean postnatal difference between rest and contraction on TPS was 16.6 ± 12.9% for hiatal area and 16.0 ± 8.9% for hiatal anteroposterior diameter. Subanalysis on women with postnatal levator ani muscle avulsion (n = 30) revealed that the correlation coefficient between the weakest MOS and hiatal area was ρ = 0.37 (P = 0.044) and for anteroposterior diameter it was ρ = 0.54 (P = 0.002). Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
In this prospective study, we found a moderate, significantly positive correlation between the MOS and the difference in hiatal measurements on TPS induced by maximum pelvic floor muscle contraction, implying that both TPS and the MOS can be used to assess pelvic floor muscle contractility. Ultrasound has been shown previously to be useful in establishing the direction of pelvic floor movement on contraction, based on a moderate correlation between the MOS, perineometry and bladder-neck movement on TPS17 – 20 . However, bladder-neck mobility does not reflect muscle strength, but is the result of muscle action18 . More recently, TPS has been used to evaluate the change in hiatal measurements on pelvic floor muscle contraction10 – 12 . As in these studies, we found that hiatal area and hiatal anteroposterior diameter were significantly smaller during contraction than at rest, indicating that a genuine contraction was ´ Rojas et al.12 found being performed10 – 12 . Guzman that pelvic floor muscle contractility assessed by ultrasonography decreased significantly following childbirth, although no significant pattern was seen on digital assessment. The present study reveals a correlation between pelvic floor muscle contractility measured by digital and ultrasound assessment. Ultrasound, as well as digital, assessment of pelvic floor muscle contraction evaluates the elevation of the levator ani muscle induced by the contraction. These two techniques therefore seem to be comparable, supported by the moderate significant correlation we found in this study. These results do not depend on the presence of levator ani muscle avulsion. MOS is a relatively easy clinical examination and widely available, with no additional costs or need for equipment. Furthermore, recent research has shown a substantial inter-rater agreement9 . Apart from
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Table 1 Results of pelvic floor muscle contractility assessment by Modified Oxford Scale (MOS) and difference between transperineal ultrasound measurements of hiatal area and anteroposterior diameter (AP) at rest and on maximum contraction
Parameter
Visit
MOS weakest contraction hiatal area (%) hiatal AP (%) MOS weakest contraction hiatal area (%) hiatal AP (%) MOS weakest contraction hiatal area (%) hiatal AP (%)
Overall Overall Overall Antenatal Antenatal Antenatal Postnatal Postnatal Postnatal
n
Measurement (median (range) or mean ± SD)
458 454 454 268 264 264 190 190 190
3 (0–5) 18.1 ± 12.6 16.8 ± 9.0 3 (0–5) 19.1 ± 12.3 17.3 ± 9.1 3 (0–5) 16.6 ± 12.9 16.0 ± 8.9
Spearman’s rank (ρ)*
P
0.465 0.506
< 0.001 < 0.001
0.452 0.438
< 0.001 < 0.001
0.457 0.573
< 0.001 < 0.001
Difference () in hiatal measurements calculated as: difference = ((Mrest – Msqueeze )/Mrest ) × 100%. ρ = –1 indicates perfect disagreement; ρ = 0, independent ranking; ρ = +1, perfect agreement. *Correlation between ultrasound measurements and MOS score.
(b) 60 Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
(a) 60 40 20 0
–20 –40 1 2 3 4 MOS score for hiatal area
0 –20
5
(c) 60
0
1 2 3 4 MOS score for hiatal AP diameter
5
0
1 2 3 4 MOS score for hiatal AP diameter
5
0
1 2 3 4 MOS score for hiatal AP diameter
5
(d) 60 Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
20
–40 0
40 20 0
–20 –40
40 20 0 –20 –40
0
1 2 3 4 MOS score for hiatal area
5
(e)
(f) 40 40
Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
40
20
0
–20
30 20 10 0 –10
0
1 2 3 4 MOS score for hiatal area
5
Figure 3 Graphical presentation of Spearman’s correlation between Modified Oxford Scale (MOS) and difference () in transperineal ultrasound (TPS) measurements of the hiatal area and anteroposterior (AP) diameter at rest and at maximum contraction: (a,b) overall (n = 454), (c,d) antenatal assessments (n = 264) and (e,f) postnatal assessments (n = 190).
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
Ultrasound Obstet Gynecol 2015; 45: 217–222.
Levator ani assessment assessing pelvic floor muscle contraction by vaginal digital palpation, MOS also helps the therapist provide effective feedback to women regarding the performance of their pelvic floor muscle exercises7 . However, TPS is available to many gynecologists and can be performed fairly quickly in a clinical setting. TPS has the advantage of providing women with effective visual biofeedback of their pelvic floor muscle contractility without a finger or instrument inserted into the vagina17 . It is therefore a more physiological approach to help in teaching women about pelvic floor muscle exercises. TPS has also been shown to be readily accepted by women17 . Although possibly not always indicated, TPS can provide additional information on pelvic floor muscle structures using dynamic evaluation1,14 . TPS may therefore be the assessment of choice in women with intact hymens or those with vaginismus and female sexual dysfunction, and the availability of a less invasive tool in the initial assessment could help to enhance their confidence and optimize therapy. It has been shown that this group of women benefit from better pelvic floor muscle function, as it is related to arousal, orgasm and improved sexual function3 . Furthermore, a randomized controlled trial by Bø et al.21 has shown that pelvic floor muscle exercises reduce problems related to sex life, social life and physical activity in women with urodynamically proven stress incontinence. The 18% change in hiatal dimensions on contraction in our group of pregnant women was larger than the 10% found in nulligravid women by Weinstein et al.10 . The likely explanation for this lies in the fact that pregnant women probably perform more pelvic floor muscle exercises, as this is recommended during pregnancy. The 16.6% change in hiatal dimensions on contraction in our group of women 3 months postpartum was smaller than the 25% found in parous women by Brækken et al.11 . However, their group was not homogeneous regarding parity and the assessment was performed much later after childbirth than in our study. A recent systematic review has shown that pelvic floor muscle training during pregnancy and following childbirth can prevent or treat urinary incontinence22 . Supervised pelvic floor muscle training is most effective, and it is advised that it be incorporated into women’s exercise programs22 . Furthermore, a randomized controlled trial on supervised pelvic floor muscle training in women with pelvic organ prolapse has shown that it increases muscle volume and pelvic floor muscle strength, and closes the levator hiatus23 . It is therefore essential that all women with pelvic organ prolapse should have an adequate assessment of their pelvic floor, including guidance on the performance of pelvic floor muscle exercises. The number of women included in this study is large, making the results reliable and robust. The vast majority of measurements on TPS could be taken successfully and these correlated with the findings on digital assessment, which supports its clinical relevance for assessing pelvic floor muscle contractility.
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We acknowledge that there are limitations to our study. Although muscle contractility can be altered by nerve trauma or neurological disease, we did not perform a neurological examination before inclusion of the subjects, as they were young, healthy women. Only one investigator analyzed the TPS measurements. However, our study was commenced after appropriate training and previous reliability studies had shown good correlation15 . Thirdly, the experience and satisfaction of the women included, regarding which method they preferred for the assessment of their pelvic floor muscle contractility, was not rated and we cannot therefore make recommendations based on women’s preferences. In conclusion, this study confirms that both digital and ultrasound assessment can be used to evaluate pelvic floor muscle contractility. Therefore, either modality of assessment can be used in isolation or as a combination in appropriate women. Although MOS is simple, TPS can be a good visual biofeedback tool for patients and may be the assessment of choice in women with sexual dysfunction.
ACKNOWLEDGMENTS R.T. and A.S. have received speaker honorariums from Pfizer and Astellas. R.T. is secretary of the International Urogynecology Association. Kim van Delft was funded by the Mayday Childbirth Charity Fund.
REFERENCES 1. Dietz HP, Simpson JM. Levator trauma is associated with pelvic organ prolapse. BJOG 2008; 115: 979–984. 2. Dietz HP, Shek C. Levator avulsion and grading of pelvic floor muscle strength. Int Urogynecol J Pelvic Floor Dysfunct 2008; 19: 633–636. 3. Lowenstein L, Gruenwald I, Gartman I, Vardi Y. Can stronger pelvic muscle floor improve sexual function? Int Urogynecol J 2010; 21: 553–556. 4. Laycock J. Clinical evaluation of the pelvic floor. In Pelvic floor ¨ re-education, Principles and Practice, Schussler B, Laycock J, Norton PA, Stanton SL (eds). Springer-Verlag: London, 1994; 42–48. 5. Isherwood PJ, Rane A. Comparative assessment of pelvic floor strength using a perineometer and digital examination. BJOG 2000; 107: 1007–1011. 6. Riesco ML, Caroci Ade S, de Oliveira SM, Lopes MH. Perineal muscle strength during pregnancy and postpartum: the correlation between perineometry and digital vaginal palpation. Rev Lat Am Enfermagem 2010; 18: 1138–1144. 7. Bø K, Finckenhagen HB. Vaginal palpation of pelvic floor muscle strength: inter-test reproducibility and comparison between palpation and vaginal squeeze pressure. Acta Obstet Gynecol Scand 2001; 80: 883–887. ˆ 8. Ferreira CH, Barbosa PB, de Oliveira Souza F, Antonio FI, Franco MM, Bø K. Inter-rater reliability study of the modified Oxford Grading Scale and the Peritron manometer. Physiotherapy 2011; 97: 132–138. 9. van Delft K, Schwertner-Tiepelmann N, Thakar R, Sultan AH. Inter-rater reliability of assessment of levator ani muscle strength and attachment to the pubic bone in nulliparous women. Ultrasound Obstet Gynecol 2013; 42: 341–346.
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222 10. Weinstein MM, Jung SA, Pretorius DH, Nager CW, den Boer DJ, Mittal RK. The reliability of puborectalis muscle measurements with 3-dimensional ultrasound imaging. Am J Obstet Gynecol 2007; 197: 68.e1–6. 11. Braekken IH, Majida M, Engh ME, Bø K. Test–retest reliability of pelvic floor muscle contraction measured by 4D ultrasound. Neurourol Urodyn 2009; 28: 68–73. ´ Rojas R, Wong V, Shek KL, Dietz HP. Impact of 12. Guzman levator trauma on pelvic floor muscle function. Int Urogynecol J 2014; 25: 375–380. 13. van Delft K, Schwertner-Tiepelmann N, Thakar R, Sultan AH. Recruitment of pregnant women in research. J Obstet Gynaecol 2013; 33: 442–446. 14. Dietz HP, Shek C, Clarke B. Biometry of the pubovisceral muscle and levator hiatus by three-dimensional pelvic floor ultrasound. Ultrasound Obstet Gynecol 2005; 25: 580–585. 15. Majida M, Braekken IH, Umek W, Bø K, Saltyte Benth J, Ellstrøm Engh M. Interobserver repeatability of three- and four-dimensional transperineal ultrasound assessment of pelvic floor muscle anatomy and function. Ultrasound Obstet Gynecol 2009; 33: 567–573. 16. van Delft K, Thakar R, Sultan AH, Schwertner-Tiepelmann N, Kluivers K. Levator ani muscle avulsion during childbirth: a risk prediction model. BJOG 2014; 121: 1155–1163; discussion 1163. 17. Dietz HP, Wilson PD, Clarke B. The use of perineal ultrasound to quantify levator activity and teach pelvic floor muscle
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exercises. Int Urogynecol J Pelvic Floor Dysfunct 2001; 12: 166–168; discussion 168–169. Peschers UM, Gingelmaier A, Jundt K, Leib B, Dimpfl T. Evaluation of pelvic floor muscle strength using four different techniques. Int Urogynecol J Pelvic Floor Dysfunct 2001; 12: 27–30. Dietz HP, Jarvis SK, Vancaillie TG. The assessment of levator muscle strength: a validation of three ultrasound techniques. Int Urogynecol J Pelvic Floor Dysfunct 2002; 13: 156–159; discussion 159. Thompson JA, O’Sullivan PB, Briffa NK, Neumann P. Assessment of voluntary pelvic floor muscle contraction in continent and incontinent women using transperineal ultrasound, manual muscle testing and vaginal squeeze pressure measurements. Int Urogynecol J Pelvic Floor Dysfunct 2006; 17: 624–630. Bø K, Talseth T, Vinsnes A. Randomized controlled trial on the effect of pelvic floor muscle training on quality of life and sexual problems in genuine stress incontinent women. Acta Obstet Gynecol Scand 2000; 79: 598–603. Mørkved S, Bø K. Effect of pelvic floor muscle training during pregnancy and after childbirth on prevention and treatment of urinary incontinence: a systematic review. Br J Sports Med 2014; 48: 299–310. Brækken IH, Majida M, Engh ME, Bø K. Morphological changes after pelvic floor muscle training measured by 3-dimensional ultrasonography: a randomized controlled trial. Obstet Gynecol 2010; 115: 317–324.
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Pelvic floor muscle contractility: digital assessment vs transperineal ultrasound K. VAN DELFT, R. THAKAR and A. H. SULTAN Croydon University Hospital, Department of Obstetrics and Gynaecology, Division of Urogynaecology, Croydon, UK
K E Y W O R D S: correlation; hiatus area; modified Oxford scale; pelvic floor muscle contractility; transperineal ultrasound
ABSTRACT
INTRODUCTION
Objectives A significant reduction in hiatal area and anteroposterior diameter can be induced by pelvic floor muscle contraction, and this has been demonstrated using three-dimensional/four-dimensional (3D/4D) transperineal ultrasound (TPS) in a small group of women. Our objective was to correlate pelvic floor muscle contractility using digital assessment with the change in TPS hiatus measurements during maximum pelvic floor muscle contraction.
Although clinical assessment of pelvic floor muscle structures is still regarded as being of great value, in recent years the use of three-dimensional/four-dimensional (3D/4D) transperineal ultrasound (TPS) to image pelvic floor muscle integrity has become the focus of considerable amounts of research. Research has been focused mainly on muscle morphology, such as levator ani muscle avulsion, and abnormal hiatus biometry, which are considered risk factors for pelvic organ prolapse1 , but not on functionality, which can be assessed using TPS. The functional capacity of the pelvic floor can be assessed by measuring pelvic floor muscle strength, and has been shown to be negatively associated with pelvic floor and sexual dysfunction2,3 . Various methods have been used to assess pelvic floor muscle contractility, such as digital assessment using the Modified Oxford Scale (MOS) and perineometry4 – 6 . Although MOS had previously been found to have poor inter-rater reliability7,8 , a recent study conducted by our group found substantial agreement between two raters9 . Weinstein et al.10 demonstrated a significant reduction, of approximately 10%, in hiatus area and anteroposterior diameter on contraction of the pelvic floor in 27 nulligravid women and Brækken et al.11 showed a reduction of 25% in 17 parous women. Their techniques of measuring the differences in hiatal area are related to the extent to which the levator ani muscle is lifted by pelvic floor muscle contraction10,11 . The reduction in hiatus measurements on maximum pelvic floor muscle contraction using TPS has not yet been evaluated in a large group of nulliparous and primiparous women, nor has it been correlated with digital assessment. Recently, based on clinical relevance, MOS has been suggested to be a superior measure of contraction than is ultrasound assessment12 , although no correlation study was performed. The MOS is an assessment of the degree of
Methods Nulliparous pregnant women were recruited from the antenatal clinic. Pelvic floor muscle contractility was assessed by digital palpation using the validated Modified Oxford Scale (MOS). Subsequently, women underwent 3D/4D TPS. Measurements of the hiatal area and anteroposterior diameter were taken from the rendered ultrasound images at rest and at maximum contraction, and differences in measurements were expressed as percentages. Spearman’s rank (ρ) was used to assess the correlation. Results Four hundred and fifty-nine assessments were performed, of which 268 were from women at around 36 weeks’ gestation, and 191 were from women following delivery at 3 months postpartum. The overall correlation between MOS and TPS was found to be ρ = 0.47 for hiatal area (P < 0.001) and ρ = 0.51 for hiatal anteroposterior diameter (P < 0.001). Conclusions Digital palpation using MOS and TPS can both be used as tools to assess pelvic floor muscle contractility. Although MOS is a simple clinical tool without the need for any equipment, TPS can provide good visual biofeedback when training patients in pelvic floor muscle exercises. As TPS is non-intrusive, it may be the method of choice for some women. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
Correspondence to: Dr R. Thakar, Croydon University Hospital, 530 London Road, Croydon, CR7 7YE, UK (e-mail: [email protected]) Accepted: 25 June 2014
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
ORIGINAL PAPER
van Delft et al.
218
pressure against the examining finger, exerted by elevation of the levator ani muscle, during maximum pelvic floor muscle contraction. We hypothesized that digital and ultrasound measurements should correlate well in the assessment of pelvic floor muscle contractility. The aim of this study was to correlate pelvic floor muscle contractility using digital assessment and the change in hiatal measurements using TPS, during maximum pelvic floor muscle contraction.
METHODS All women were recruited as part of a prospective longitudinal study to establish the prevalence of levator ani muscle defects during childbirth and to correlate these with pelvic floor symptoms and pelvic floor muscle strength. Nulliparous pregnant women were recruited from the antenatal clinics at Croydon University Hospital, Croydon, UK13 . The primary study was approved by the National Research Ethics Service South West London Committee (REC 10/H0806/87). All women gave written informed consent. Examinations were performed at 36 weeks’ gestation and 3 months following childbirth, by one independent investigator (K.v.D.). We minimized technique variability by rigorous investigator training and observation by the principal investigator (R.T.). Before the examination, women were asked to empty their bladder, and examination was carried out in the supine position with knees semiflexed. During the follow-up assessment, the operator was blinded to the delivery details. Women were instructed to squeeze their pelvic floor muscle9 and subjective assessment of pelvic floor muscle contractility was performed by the examiner inserting the index finger approximately 4 cm into the vagina4,7,9 . The MOS was used to rate pelvic floor muscle contractility on a scale of 0–5: 0, no contraction; 1, minor muscle ‘flicker’; 2, weak muscle contraction without a circular contraction; 3, moderate muscle contraction; 4, good muscle contraction; and 5, strong muscle contraction against resistance by the examining finger4 , for which substantial agreement was found between two investigators9 . During examination, the researcher encouraged the women to perform a maximum pelvic floor muscle contraction. The weaker MOS of either levator ani muscle (left or right side of pelvis) was used for the correlation analysis, as we expected the weaker side to have the greatest influence on pelvic floor muscle contractility in the determination of maximum contraction9 . Subsequently, women underwent 3D- (to obtain images at rest) and 4D-TPS (to obtain images at maximum pelvic floor muscle contraction) using a Voluson 730 system with a 4–8-MHz transabdominal curved array 3D/4D transducer, with an acquisition angle of 85◦ (GE Medical Systems, Zipf, Austria). The midsagittal plane was used to identify the plane of minimal hiatal dimensions, from the symphysis pubis to the top of the levator plate9,14 . Imaging was performed at rest and at maximum pelvic floor muscle contraction (best of three contractions) and
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
for analysis the symmetric rendered volume was used (Figure 1). The 3D volume at rest was analyzed first, followed by the 4D cineloop obtained during muscle contraction, from which the best of three attempts was chosen for the analysis. Hiatal area and anteroposterior diameter were measured in the rendered axial plane of the minimal hiatal dimensions (Figure 2)14 . Previous research has revealed excellent interobserver reliability for hiatal area (intraclass correlation coefficient (ICC) at rest, 0.92 and at contraction, 0.92) and for anteroposterior diameter (ICC at rest, 0.96 and at contraction, 0.82)15 . Offline analysis was performed at least 2 months following examination, using software 4D View version 10.2 (GE Medical Systems) with the operator (K.v.D.) blinded to the clinical findings. Tomographic ultrasound imaging on maximum pelvic floor muscle contraction was used to assess the entire levator ani muscle and its attachment to the pubic bone. The central three slices were scored as positive or negative for levator ani muscle avulsion. The final unilateral score ranged from 0 (no avulsion) to 3 (complete avulsion). A summed total score, ranging from 0 to 6, for the left and right side levator ani muscle was then assigned and classified as no levator ani muscle avulsion (total score, 0), minor avulsion (total score, 1–3) or major avulsion (total score, 4–6 or a unilateral score of 3)16 . The formula used to calculate the difference in measurements between maximum contraction and rest was: difference = ((Mrest – Msqueeze )/Mrest ) × 100%.
Statistical analysis The MOS was not normally distributed and therefore Spearman’s rank test was used to assess the correlation between digital examination and TPS. An increasing rank correlation implied that there was increasing agreement between the two tests. The outcome of Spearman’s rank testing ranged from –1 (perfect disagreement) to +1 (perfect agreement), where 0 refers to completely independent rankings. Data were analyzed using SPSS 20.0 (SPSS Inc., Chicago, IL, USA) and two-sided P < 0.05 was considered as statistically significant.
RESULTS Between January 2011 and October 2012, 459 assessments were made: 268 of women at 36 (range, 34–41) weeks’ gestation and 191 of women at a median of 13 (range, 10–26) weeks postpartum. The mean ± SD age was 30.3 ± 5.8 years and mean body mass index was 25.4 ± 5.3 kg/m2 . Four antenatal and one postnatal ultrasound assessments were of poor quality, and one woman declined postnatal digital assessment. Statistically significant correlations were found between the weakest MOS and hiatus measurements on TPS for hiatal area (ρ = 0.45–0.47, P < 0.001), and for hiatal anteroposterior diameter (ρ = 0.44–0.57, P < 0.001) (Table 1). Figure 3 represents these results graphically.
Ultrasound Obstet Gynecol 2015; 45: 217–222.
Levator ani assessment
219
PB
PB
PB
PB
U
U V
V L
L
L
A
L
A
Figure 1 Antenatal rendered ultrasound images at rest (a) and on maximum pelvic floor muscle contraction (b), showing a decrease in hiatal area and anteroposterior diameter on maximum contraction. A, anus; L, levator ani muscle; PB, pubic bone; U, urethra; V, vagina.
DISCUSSION
PB
PB
1 2 L
L
Figure 2 Antenatal rendered transperineal ultrasound image showing hiatal area (1, outlined) and anteroposterior diameter (2, vertical line). L, levator ani muscle; PB, pubic bone.
The mean antenatal difference calculated between rest and contraction on TPS was 19.1 ± 12.3% for hiatal area and 17.3 ± 9.1% for hiatal anteroposterior diameter. The mean postnatal difference between rest and contraction on TPS was 16.6 ± 12.9% for hiatal area and 16.0 ± 8.9% for hiatal anteroposterior diameter. Subanalysis on women with postnatal levator ani muscle avulsion (n = 30) revealed that the correlation coefficient between the weakest MOS and hiatal area was ρ = 0.37 (P = 0.044) and for anteroposterior diameter it was ρ = 0.54 (P = 0.002). Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
In this prospective study, we found a moderate, significantly positive correlation between the MOS and the difference in hiatal measurements on TPS induced by maximum pelvic floor muscle contraction, implying that both TPS and the MOS can be used to assess pelvic floor muscle contractility. Ultrasound has been shown previously to be useful in establishing the direction of pelvic floor movement on contraction, based on a moderate correlation between the MOS, perineometry and bladder-neck movement on TPS17 – 20 . However, bladder-neck mobility does not reflect muscle strength, but is the result of muscle action18 . More recently, TPS has been used to evaluate the change in hiatal measurements on pelvic floor muscle contraction10 – 12 . As in these studies, we found that hiatal area and hiatal anteroposterior diameter were significantly smaller during contraction than at rest, indicating that a genuine contraction was ´ Rojas et al.12 found being performed10 – 12 . Guzman that pelvic floor muscle contractility assessed by ultrasonography decreased significantly following childbirth, although no significant pattern was seen on digital assessment. The present study reveals a correlation between pelvic floor muscle contractility measured by digital and ultrasound assessment. Ultrasound, as well as digital, assessment of pelvic floor muscle contraction evaluates the elevation of the levator ani muscle induced by the contraction. These two techniques therefore seem to be comparable, supported by the moderate significant correlation we found in this study. These results do not depend on the presence of levator ani muscle avulsion. MOS is a relatively easy clinical examination and widely available, with no additional costs or need for equipment. Furthermore, recent research has shown a substantial inter-rater agreement9 . Apart from
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Table 1 Results of pelvic floor muscle contractility assessment by Modified Oxford Scale (MOS) and difference between transperineal ultrasound measurements of hiatal area and anteroposterior diameter (AP) at rest and on maximum contraction
Parameter
Visit
MOS weakest contraction hiatal area (%) hiatal AP (%) MOS weakest contraction hiatal area (%) hiatal AP (%) MOS weakest contraction hiatal area (%) hiatal AP (%)
Overall Overall Overall Antenatal Antenatal Antenatal Postnatal Postnatal Postnatal
n
Measurement (median (range) or mean ± SD)
458 454 454 268 264 264 190 190 190
3 (0–5) 18.1 ± 12.6 16.8 ± 9.0 3 (0–5) 19.1 ± 12.3 17.3 ± 9.1 3 (0–5) 16.6 ± 12.9 16.0 ± 8.9
Spearman’s rank (ρ)*
P
0.465 0.506
< 0.001 < 0.001
0.452 0.438
< 0.001 < 0.001
0.457 0.573
< 0.001 < 0.001
Difference () in hiatal measurements calculated as: difference = ((Mrest – Msqueeze )/Mrest ) × 100%. ρ = –1 indicates perfect disagreement; ρ = 0, independent ranking; ρ = +1, perfect agreement. *Correlation between ultrasound measurements and MOS score.
(b) 60 Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
(a) 60 40 20 0
–20 –40 1 2 3 4 MOS score for hiatal area
0 –20
5
(c) 60
0
1 2 3 4 MOS score for hiatal AP diameter
5
0
1 2 3 4 MOS score for hiatal AP diameter
5
0
1 2 3 4 MOS score for hiatal AP diameter
5
(d) 60 Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
20
–40 0
40 20 0
–20 –40
40 20 0 –20 –40
0
1 2 3 4 MOS score for hiatal area
5
(e)
(f) 40 40
Δ AP diameter on TPS (%)
Δ hiatal area on TPS (%)
40
20
0
–20
30 20 10 0 –10
0
1 2 3 4 MOS score for hiatal area
5
Figure 3 Graphical presentation of Spearman’s correlation between Modified Oxford Scale (MOS) and difference () in transperineal ultrasound (TPS) measurements of the hiatal area and anteroposterior (AP) diameter at rest and at maximum contraction: (a,b) overall (n = 454), (c,d) antenatal assessments (n = 264) and (e,f) postnatal assessments (n = 190).
Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.
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Levator ani assessment assessing pelvic floor muscle contraction by vaginal digital palpation, MOS also helps the therapist provide effective feedback to women regarding the performance of their pelvic floor muscle exercises7 . However, TPS is available to many gynecologists and can be performed fairly quickly in a clinical setting. TPS has the advantage of providing women with effective visual biofeedback of their pelvic floor muscle contractility without a finger or instrument inserted into the vagina17 . It is therefore a more physiological approach to help in teaching women about pelvic floor muscle exercises. TPS has also been shown to be readily accepted by women17 . Although possibly not always indicated, TPS can provide additional information on pelvic floor muscle structures using dynamic evaluation1,14 . TPS may therefore be the assessment of choice in women with intact hymens or those with vaginismus and female sexual dysfunction, and the availability of a less invasive tool in the initial assessment could help to enhance their confidence and optimize therapy. It has been shown that this group of women benefit from better pelvic floor muscle function, as it is related to arousal, orgasm and improved sexual function3 . Furthermore, a randomized controlled trial by Bø et al.21 has shown that pelvic floor muscle exercises reduce problems related to sex life, social life and physical activity in women with urodynamically proven stress incontinence. The 18% change in hiatal dimensions on contraction in our group of pregnant women was larger than the 10% found in nulligravid women by Weinstein et al.10 . The likely explanation for this lies in the fact that pregnant women probably perform more pelvic floor muscle exercises, as this is recommended during pregnancy. The 16.6% change in hiatal dimensions on contraction in our group of women 3 months postpartum was smaller than the 25% found in parous women by Brækken et al.11 . However, their group was not homogeneous regarding parity and the assessment was performed much later after childbirth than in our study. A recent systematic review has shown that pelvic floor muscle training during pregnancy and following childbirth can prevent or treat urinary incontinence22 . Supervised pelvic floor muscle training is most effective, and it is advised that it be incorporated into women’s exercise programs22 . Furthermore, a randomized controlled trial on supervised pelvic floor muscle training in women with pelvic organ prolapse has shown that it increases muscle volume and pelvic floor muscle strength, and closes the levator hiatus23 . It is therefore essential that all women with pelvic organ prolapse should have an adequate assessment of their pelvic floor, including guidance on the performance of pelvic floor muscle exercises. The number of women included in this study is large, making the results reliable and robust. The vast majority of measurements on TPS could be taken successfully and these correlated with the findings on digital assessment, which supports its clinical relevance for assessing pelvic floor muscle contractility.
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We acknowledge that there are limitations to our study. Although muscle contractility can be altered by nerve trauma or neurological disease, we did not perform a neurological examination before inclusion of the subjects, as they were young, healthy women. Only one investigator analyzed the TPS measurements. However, our study was commenced after appropriate training and previous reliability studies had shown good correlation15 . Thirdly, the experience and satisfaction of the women included, regarding which method they preferred for the assessment of their pelvic floor muscle contractility, was not rated and we cannot therefore make recommendations based on women’s preferences. In conclusion, this study confirms that both digital and ultrasound assessment can be used to evaluate pelvic floor muscle contractility. Therefore, either modality of assessment can be used in isolation or as a combination in appropriate women. Although MOS is simple, TPS can be a good visual biofeedback tool for patients and may be the assessment of choice in women with sexual dysfunction.
ACKNOWLEDGMENTS R.T. and A.S. have received speaker honorariums from Pfizer and Astellas. R.T. is secretary of the International Urogynecology Association. Kim van Delft was funded by the Mayday Childbirth Charity Fund.
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