[ clinical commentary ]

Transcription

1 Jackie L. Whittaker, PT, FCAMT 1 Judith A. Thompson, Dip PT, Post-grad Dip PT, PhD 2 Deydre S. Teyhen, PT, PhD, OCS 3 Paul Hodges, PhD, MedDr, BPhty (Hons) 4 Rehabilitative Ultrasound Imaging of Pelvic Floor Muscle Function It is well accepted that the pelvic floor muscles, specifically the levator ani, provide an important contribution to the continence mechanism. 17,18 However, there is growing evidence from biomechanical models, 65 as well as neurophysiological 40,76,77 and epidemiological 28,66,78 studies, that this muscle group also plays an important role in postural control of the lumbopelvic region. Both low back pain (LBP) and urinary incontinence (UI) are prevalent physical ailments, 42,90 and clinical experts have long alluded to their empirical association. In a recent epidemiological study, Smith et al 78 determined that disorders of continence are more strongly related to frequent LBP than obesity and levels of physical activity, while Eliasson et al 28 found that 78% of women with LBP report concurrent UI. As such, there is a need for physical therapists to have access to tools that accurately evaluate the various aspects of pelvic floor muscle function (elevating and occlusion functions, as well as neuromuscular control, strength, and endurance) both in laboratory and clinical environments. Ultrasound imaging is a potential tool that has been used to evaluate the morphology 7,52 and certain components of the function 24,27,67,81,82,86 of these muscles. Specifically, ultrasound imaging has been shown to be more specific than intravaginal palpation for measurement of the lifting action of the pelvic floor muscles on the bladder neck 31 and base, 20,31 and it provides information about the supporting function of the pelvic floor muscles during various maneuvers. 20,57,85 As the use of rehabilitative ultrasound imaging for assessment of pelvic floor muscles function is a relatively new procedure, the goal of this commentary t Synopsis: This commentary provides an overview of the current concepts and evidence related to rehabilitative ultrasound imaging of pelvic floor (levator ani) function. As this is an emerging topic, the goal is to provide a basic understanding of ultrasound imaging applications related to levator ani function: the available quantitative and qualitative information, the limitations, as well as how ultrasound imaging can be incorporated as a form of biofeedback during rehabilitation. Furthermore, as the ability to compile and compare existing evidence depends on the degree of similarity in methodology by investigators, this commentary highlights points of consideration and provides guidelines, as well as an agenda, for future investigation. J Orthop Sports Phys Ther 2007;37(8): doi: /jospt t Key Words: levator ani, sonography, therapeutic exercise, transabdominal ultrasound imaging, transperineal ultrasound imaging is to provide an understanding of current applications, the available quantitative and qualitative information, the associated limitations, and to show how rehabilitative ultrasound imaging can be incorporated as a form of biofeedback during rehabilitation. Furthermore, as the compilation and comparison of data depends on consistency of measurement techniques, this commentary highlights considerations for measurement accuracy and interpretation and provides generic guidelines for future investigation based upon international consensus. 80 QUANTITATIVE EVALUATION Ultrasound imaging has been used to measure the morphology 7,52 of the pelvic floor muscles. It has also been used to measure the impact of pelvic floor muscle contraction or increase in intra-abdominal pressure (straining, cough, sneeze, or leg-raising task) on the bladder from a variety of approaches (transperineal and transabdominal; Figure 1), planes (sagittal and transverse), and positions. 6,22,27,57,61,67,76,83,84,96 The transperineal approach (placement of the ultrasound transducer in a sagittal plane along the midline of the perineum) is considered advantageous to the transabdominal approach, as both the pubic symphysis and the proximal junction of the bladder neck and urethra are included within the field of view and can serve 1 MPhil/PhD Candidate, School of Health Professions and Rehabilitation Sciences, University of Southampton, Highfield Campus, Southampton, UK; Physical Therapist, Whittaker Physiotherapy Consulting, White Rock, BC, Canada 2 Lecturer, School of Physiotherapy, Curtin University of Technology, Perth, Western Australia; Physical Therapist, Body logic Physiotherapy, Shenton Park, Western Australia. 3 Assistant Professor, US Army-Baylor University Doctoral Program in Physical Therapy, San Antonio, TX; Director, Center for Physical Therapy Research, Fort Sam Houston, TX; Research Consultant, Spine Research Center and the Defense Spinal Cord and Column Injury Center, Walter Reed Army Medical Center, Washington, DC. 4 NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. The opinions or assertions contained here in are the private views of the authors and are not to be construed as official or as reflecting the views of the Departments of the Army, Air Force, or Defense. Address correspondence to Jackie Whittaker, Whittaker Physiotherapy Consulting, #101, th Ave, White Rock, BC, Canada V4A 1N2. J.L.Whittaker@soton.ac.uk journal of orthopaedic & sports physical therapy volume 37 number 8 august

2 as points of reference. Furthermore, the transperineal approach provides a direct view of the levator ani, facilitating study of its morphology. 52 Recently, there has been renewed interest in the transabdominal approach, as it is a noninvasive method 31 that can provide clinicians with novel information about some components of pelvic floor muscle function. Comparing sagittal transperineal and transabdominal approaches during pelvic floor muscle contraction, straining, and an abdominal curl in a group of women with incontinence and continent controls, Thompson et al 83,84 demonstrated that, although a divergence in bladder base (observed with transabdominal ultrasound imaging) and bladder neck motion (observed with transperineal ultrasound imaging) occurred in 15% of the subjects, there was a significant correlation between measurements across the tasks. Measurement Protocols for Bladder Base, Bladder Neck, and Anorectal Angle Motion Rehabilitative ultrasound imaging applications aimed at assessing pelvic floor muscle function generally employ a standard medical ultrasound imaging system used in conjunction with a 3.5- to 5.0- MHz curved array transducer (40-mm Trans abdominal Uterus Bladder neck Base Pubic symphysis Urethra Trans perineal Ultrasound transducers footprint) to generate 2-dimensional brightness mode (b-mode) images of the structures of interest. This convention is reflected in the following section; however, emerging applications that use motion-mode (m-mode) to investigate the endurance or ability to sustain an elevating contraction and the application of 3- dimensional imaging techniques for the evaluation of the pelvic floor 21 are being developed. Transperineal Ultrasound Imaging Transperineal ultrasound imaging provides a sagittal plane view of the junction between the bladder neck and proximal urethra, the anorectal angle (ARA), as well as the pubic symphysis, which serves as a fixed bony landmark from which measurements can be made (Figures 1 and 2). The technique for evaluation of bladder neck and ARA motion during pelvic floor muscles contraction and Valsalva maneuver are well established. 20,59-61,73,74 As measurements of bladder neck and ARA mobility can be influenced by a variety of factors, including bladder filling, subject and transducer position, measurement sites, and verbal instructions, 22,26,53,74 consistent methodology must be employed. Transperineal ultrasound imaging is most commonly performed with the subject in a dorsal lithotomy position with A PS Urethra the hips flexed, the knees slightly abducted, and the lumbar spine in neutral. 20 If circumstances demand, the technique can also be performed in standing 22 or sitting over a toilet chair 47 ; however, care must be taken when comparing images/ measures made in different positions. The ultrasound transducer is placed in the midline of the perineum, in the sagittal plane, after covering it with ultrasound gel followed by a nonpowdered surgical glove or plastic wrap for hygienic reasons, and further gel. The labia may need to be parted to obtain a clearer image, which should include the pubic symphysis, the urethra and bladder neck, the vagina, the cervix, rectum, and anal canal. For the assessment of bladder neck movement during pelvic floor muscle contraction and functional maneuvers, a measurement of the bladder neck relative to the pubic symphysis is taken using a standardized method (Figure 3). 61,74 As the bladder neck and proximal urethra exhibit greater mobility when the bladder is nearly empty, bladder filling should be specified. 26 With transperineal ultrasound imaging, voiding prior to evaluation is preferable. 20 Verbal instructions that have been used to encourage contraction of the pelvic floor muscles include draw in and lift the pelvic floor muscles while breathing normally. 83 Instructions that have B PS Urethra Bladder Bladder Rectum Vagina Sacrum FIGURE 1. Comparison of transperineal and transabdominal ultrasound. Note the different transducer locations and regions of the bladder where movement is visualized (bladder base for transabdominal and bladder neck for transperineal). Reproduced with permission of International Urogynecology Journal. 84 FIGURE 2. (A) Transperineal ultrasound image of the bladder (reproduced with permission of International Urogynecology Journal 84 ). (B) Labeled outline of the transperineal image. Abbreviation: PS, pubic symphysis. Cranial 488 august 2007 volume 37 number 8 journal of orthopaedic & sports physical therapy

3 been used to encourage an increase in intra-abdominal pressure via a Valsalva maneuver (a forced expiration against a closed glottis) include strain downwards with maximal effort. 83 Transabdominal Ultrasound Imaging Transabdominal ultrasound imaging of the bladder and pelvic floor was originally described by White 92 for the investigation of women with stress UI. However, the technique was abandoned in favor of the transperineal approach, due to the inability of transabdominal imaging to consistently provide a view of the bladder neck, which is a common point of investigation for women with incontinence. The transabdominal approach (both sagittal and transverse planes) has received renewed interest, as it is a relatively noninvasive method to provide clinicians with novel information about some components of pelvic floor muscle function, as well as serving as source of biofeedback when retraining the pelvic floor muscles. 27 Transabdominal ultrasound imaging is Valsalva Bladder neck Rest PFM contraction Pubic Symphysis y-axis (mm) A Cranial used to assess the lifting aspect of a pelvic floor muscle contraction by observation of movement of the bladder base as a marker for pelvic floor muscle activity during voluntary pelvic floor muscle contractions. 9,57,75,86 As with the transperineal approach, measurements of bladder base mobility, assessed transabdominally, can be influenced by a variety of factors, including bladder filling, subject and transducer position, measurement sites, and verbal instructions. Transabdominal ultrasound imaging can be performed in the supine, crooklying (supine with hips and knees flexed), sitting, and standing positions. 9,31,75,84,86 Reliability data have been reported for images gathered in crook lying 75,84 ; however, it has yet to be established for the other positions. Standardization of testing positions is critical, including the posture of the lumbar spine, as coactivation between the pelvic floor muscles and abdominal muscles varies with degree of lumbar lordosis 72 and may affect the displacement of the bladder base. Furthermore, the amount of bladder base displacement is influenced by subject position. For example, Frawley et al 31 demonstrated that a voluntary contraction of the pelvic floor muscles, viewed with transabdominal (sagittal) ultrasound imaging, resulted in greater displacement of the bladder base in standing than in the supine (P =.003) and sitting (P =.001) positions. A further consideration is the importance of testing pelvic floor muscle function in a variety of positions, as subjects who are unable to elevate the bladder base in supine lying may be able to do so in standing. 31 For sagittal plane transabdominal ultrasound imaging of the bladder base, the ultrasound transducer is placed in Bladder FIGURE 4. (A) Ultrasound transducer placement for sagittal ultrasound imaging of the bladder using the transabdominal approach. (B) A sagittal ultrasound image of the bladder. Reprinted from Ultrasound Imaging for Rehabilitation of the Lumbopelvic Region: A Clinical Approach, by Whittaker, 94 with permission from Elsevier. Abbreviation: BN, bladder neck. A B B Bladder BN FIGURE 3. Transperineal ultrasound assessment of bladder neck position at rest, during a pelvic floor muscle contraction and Valsalva. The measurement graph for calculation of vector length during Valsalva is shown. The displacement is measured by calculating a vector from the resting position (x 1 y 1 ) to the position at the end of the maneuver (x 2 y 2 ), using the following formula: vector length a 2 = b 2 + c 2, where b = y 1 y 2 and c = x 1 x 2. Reproduced with permission of International Urogynecology Journal. 84 Right FIGURE 5. (A) Ultrasound transducer placement for transverse ultrasound imaging of the bladder. (B) A transverse ultrasound image of the urinary bladder and midline pelvic floor structures using the transabdominal approach. Reprinted from Ultrasound Imaging for Rehabilitation of the Lumbopelvic Region: A Clinical Approach, by Whittaker, 94 with permission from Elsevier). MPFS journal of orthopaedic & sports physical therapy volume 37 number 8 august

4 a midline sagittal orientation immediately superior to the pubic symphysis on the lower abdomen. The angle of the transducer is manipulated until it points posterior and inferior to the symphysis pubis (towards the posteroinferior region or base of the bladder), allowing for a clear image of the bladder and the proximal aspect of its neck (Figure 4). The marker on the transducer, which indicates the left side of the screen, should be oriented towards the patient s head. For transverse plane transabdominal ultrasound imaging of the bladder base, the transducer is placed in a transverse orientation, across the midline of the abdomen, immediately superior to the pubic symphysis. The angle of the transducer is manipulated until it is approximately 60 from the vertical and aimed towards the base of the bladder (Figure 5). It is recommended that the marker on the transducer (indicating the left side of the display screen) is oriented according to standard radiological convention (eg, towards the right side of the supine subject) 15 ; however, this may not always be appropriate in clinical situations when assessing dynamic functional activities. The angle of the ultrasound transducer should be adjusted until there is a clear image of the bladder and midline pelvic floor structures (urethra, perineal body, rectum, etc). A key consideration in accurately interpreting bladder base motion with the transabdominal approaches is consistency of transducer position with respect to the bony pelvis. Abdominal muscle activity during functional tasks, inappropriate bracing of the abdominal muscles during voluntary contraction of the pelvic floor muscles, 83 and increases in intra-abdominal pressure are associated with a potential for the transducer to be pushed outward. This outward motion increases the distance from the transducer to the bladder base and may be misinterpreted as bladder descent. In these circumstances, the manual inward pressure of the transducer must be manipulated such that its position is maintained. Inclusion of the pubic symphysis in the transabdominal image by adjustment of the transducer angle can provide a landmark to assist with this control. The most commonly reported marker for the bladder base is the region of the posteroinferior bladder wall (junction of the hyper and hypoechoic structures) (Figure 1), which demonstrates the greatest displacement during the event being investigated (pelvic floor muscle contraction or Valsalva maneuver). It is important to note that with sagittal applications involving increases in intra-abdominal pressure (eg, Valsalva maneuver) this site has been shown to be less reliable. To obtain a clear image of the posteroinferior bladder wall the bladder must contain sufficient fluid. This can be accomplished by a standardized bladder-filling protocol, which involves asking the subject to void 1 hour before testing, then to drink 450 to 500 ml of water and to not void until after the test. 58,84 It is important to note that unlike other abdominal ultrasound scans, such as those associated with intrauterine fetal imaging, where the bladder needs to be near full capacity to serve as an acoustic window, overfilling in this situation may confound the assessment process by increasing the resting activity of the pelvic floor muscles. Reliability Reliability of Transperineal Ultrasound Imaging The position and mobility of the bladder neck have been reported to be reliable when assessed with transperineal ultrasound imaging. 20 The reference points used to generate this measurement are either the central axis or inferior margin of the symphysis pubis and the junction of the proximal urethra with the bladder. 20 This methodology has been shown to have good intra and interrater reliability (ICC, ) for the measurement of bladder neck movement during a pelvic floor muscle contraction and Valsalva maneuver. 19,61,74 Although measurement techniques used in the aforementioned investigations show good reliability, it is important to note that this is influenced by the skill of the operator, the degree of standardization of the performance of task by the subject/patient, as well as factors that affect the mobility of the bladder (bladder filling, 26 catheterization, and patient position 22,53,75 ). For instance, some women, particularly those who are nulliparous, find it difficult to perform an effective Valsalva maneuver 20 and therefore it is difficult to compare the strength and the quality of a maximal effort. Although investigators have attempted to standardize the degree of Valsalva maneuver 41,46 by either directly monitoring intra-abdominal pressure during the effort 41 or by monitoring rectal and intravesical (bladder) pressure while patients blew into a modified sphygmomanometer, 46 these techniques may represent different actions and may result in different patterns and levels of pelvic floor muscle activity. 71 Furthermore, attempts to limit the amount of effort during a Valsalva maneuver may limit the amount of bladder descent observed. 20 Therefore, it is important to consider that the method of the Valsalva maneuver may affect reliability and that the technique of the Valsalva maneuver must be specified. Reliability of Transabdominal Ultrasound Imaging Transabdominal ultrasound imaging is primarily used to assess the lifting aspect of a pelvic floor muscle contraction by observation of movement of the bladder base as a marker for pelvic floor muscle activity during voluntary pelvic floor muscle contraction. 9,57,75,86 The technique has also been used to assess the amount of movement at the bladder base during various functional maneuvers that increase intra-abdominal pressure, such as the Valsalva maneuver, an abdominal curl-up, and lower extremity lifting tasks. 56,57,83,84 Good intrarater and interrater reliability for measurement of bladder base displacement (transverse and sagittal views) during a pelvic floor muscle contraction (ICC, ), 76 as well as good intrarater reliability (transverse view) during functional, active, straightleg raise testing (ICC, 0.98), 57 have been reported. In contrast, Thompson et al 83, august 2007 volume 37 number 8 journal of orthopaedic & sports physical therapy

5 reported only moderate reliability for the measurement of bladder base displacement (sagittal view) during an abdominal curl-up (ICC, 0.53) and Valsalva maneuver (ICC, 0.51). This is likely explained by the difficulty in maintaining a consistent transducer position when the abdominal wall is stiffened or displaced outward during contraction of the abdominal muscles or an increase in intra-abdominal pressure, and may limit the use of this view during these postural tasks. Although both the transverse and sagittal transabdominal views have good reliability for assessment of bladder base movement during pelvic floor muscle contraction, the transverse view may provide additional information about the symmetry of the contraction based on the symmetry of the bladder base movement. However, the clinical significance of this measure has not been assessed. It is important to note that movement of the bladder base during pelvic floor muscle contraction may only be visible in 1 plane in some individuals, and therefore the use of both views is recommended. Interpretation of Pelvic Floor Displacement Motion of the pelvic floor is dependent on a range of factors that complicate the interpretation of ultrasound imaging. Two main issues require consideration: intra-abdominal pressure and the starting position of the pelvic floor. Increased intra-abdominal pressure due to contraction of the diaphragm and abdominal muscles directly opposes the elevation of the bladder base during a pelvic floor muscle contraction. Consequently, elevation of the bladder base may not be evident during functional tasks that involve activation of the abdominal and diaphragm muscles, despite increased activity of the pelvic floor muscles, if the increase in intra-abdominal pressure prevents shortening of the pelvic floor muscles. It has been suggested in specific populations that increased intra-abdominal pressure may overcome the contraction of the pelvic floor muscles and lead to caudal displacement of the bladder base. 57 During voluntary contraction of the pelvic floor muscles, some women activate abdominal muscles in addition to the pelvic floor muscles, with a resultant caudal displacement of the bladder base. 81 Thus consideration of the activity of the other muscles that surround the abdominal cavity and the associated increase in intra-abdominal pressure must be considered during ultrasound imaging evaluation of pelvic floor displacement. Motion of the pelvic floor also depends on its starting position, which is dependent on preexisting pelvic floor muscle activity and the laxity of the myofascial system. For instance, if the bladder base is already elevated due to resting activity of the pelvic floor muscles, further elevation may not occur when the pelvic floor muscles are contracted voluntarily or during a functional task. Similarly, decreased laxity of the myofascial system could maintain the bladder base in an elevated position. Conversely, greater laxity may result in a more caudal start position and therefore greater potential for motion. Thus the amount of bladder base elevation seen with ultrasound imaging is dependent on a number of interdependent factors that are likely to complicate the interpretation of pelvic floor muscle function. Furthermore, the amount of elevation is not likely to be directly correlated with pelvic floor muscle activity except in very specific situations in which the pelvic floor muscles contract from rest with no concurrent activity of abdominal or diaphragm muscles. For these reasons, clinical assessment requires diligent inquiry as well as the amalgamation of information from a range of assessment tools, including a detailed history, digital palpation, evaluation of abdominal muscle activity, and changes in breathing as well as ultrasound imaging. Ultimately, it is the opinion of the authors that, due to the interplay of the above-mentioned factors, the ability to generate accurate, reliable, and meaningful measurements with transperineal and transabdominal ultrasound imaging of the bladder and pelvic floor structures requires specialized training, diligent inquiry, and considerable experience. Validity of Transperineal and Transabdominal Ultrasound Imaging Magnetic resonance imaging (MRI) and indwelling electromyography (EMG) have been used to establish the validity of ultrasound with respect to measurement of the morphology (using MRI) and activation (using EMG) of other muscles, including the transversus abdominis 37,39,49 and lumbar multifidus. 38,45 No studies have described the relationship between the amount of EMG activity of the pelvic floor muscles and pelvic floor elevation. However, as mentioned above, it is likely that this relationship would be affected by the complex interrelationship between elevation, intraabdominal pressure, start position, and preexisting myofascial laxity. Several MRI studies have investigated the behavior of the pelvic floor muscles during voluntary contraction and straining in both continent and incontinent populations, 8,14,29 and have provided data that are consistent with the findings of ultrasound imaging. Using MRI with subjects in a supine position, Christensen et al 14 reported on bladder wall movement during a voluntary pelvic floor muscle contraction in continent females. They specifically reported that the greatest amount of motion (mean 6 SD, mm) occurs at the posteroinferior region of the bladder wall (bladder base), and that this displacement is most easily observed from the sagittal plane. Bo et al 8 reconfirmed the elevating function of the pelvic floor muscles through dynamic MRI in a seated position and measured the inward motion of the bladder base ( mm) in a group consisting of both continent and incontinent women. Furthermore, these authors demonstrated a mean outward motion of mm associated with straining. Although not directly compared, these values are within the range measured with transabdominal ultrasound imaging. 9,75 journal of orthopaedic & sports physical therapy volume 37 number 8 august

6 Comparison of Transperineal and Transabdominal Ultrasound Imaging As indicated above, transperineal ultrasound imaging has advantages over the transabdominal approach, as it allows visualization of the junction between the proximal urethra and bladder neck, as well as providing a fixed bony landmark from which all measurement can be made, thus increasing the reliability for comparisons between subjects. However, the transperineal technique requires extensive training, interpretation of transperineal images necessitates experience, transducer location is more invasive and may interfere with some functional maneuvers, and measurement is complex and time consuming. By comparison, transabdominal ultrasound imaging is a relatively easy technique to learn, measurements and image interpretation are less complex, and transducer placement does not restrict movement of the lower extremities, which has been argued to be important for assessment of people with lumbopelvic pain. 57 Furthermore, transabdominal ultrasound imaging is totally noninvasive (the patient does not need to undress), which may be important in specific populations where internal examination may not be desirable (eg, children, adolescents, men, victims of sexual abuse, and some ethnic groups). This technique provides an alternative source of biofeedback when learning pelvic floor muscle exercises in individuals who are reluctant to undergo internal examination. This may overcome a major barrier to some patients seeking professional help for incontinence. However, transabdominal ultrasound imaging does not always allow for direct visualization of the bladder neck, requires a moderately full bladder (which may be difficult in women with a reduced functional bladder capacity or bladder urgency), and may be difficult in individuals with dense abdominal scar tissue. 84 Furthermore, movement of the bladder base does not always reflect movement at the bladder neck. 84 As mentioned above, descent of the bladder base only indicates that there has been an increase in distance between it and the transducer. This can reflect either an actual descent of the bladder wall or outward movement of the abdominal wall. One other possible disadvantage of the transabdominal approach is the difficulty of visualizing the bladder in obese individuals. 92 However, this did not prove to be a limitation in a study by Thompson et al, 83,84 in which the bladder base was visualized in all subjects, despite a body mass index range of 17 to 39 kg/m 2. Comparison of Ultrasound Imaging With Other Methods of Pelvic Floor Muscle Assessment As mentioned earlier, it is important to consider that interpretation of bladder base or neck displacement observed with ultrasound imaging requires integration with the information attained from other methods of assessment due to the range of factors that influence their motion. Although ultrasound imaging does provide valuable and previously unavailable information, it does not allow for definitive assessment of clinically important information, such as resting pelvic floor muscle activity, myofascial laxity, pelvic floor muscle strength, abdominal activation strategy (eg, excessive bracing), or other important subjective information such as the presence of pain. Although the amount of bladder neck (transperineal ultrasound imaging) and bladder base (transabdominal ultrasound imaging) movement during a pelvic floor muscle contraction has been shown to correlate with pelvic floor muscle strength (assessed by manual muscle testing and perineometry), 27,82,83 there have been some findings to the contrary. 75 Precaution should be taken with the interpretation of larger displacements, as they do not necessarily represent a more forceful contraction. For instance, a larger lift may result from either a forceful pelvic floor muscle contraction or increased fascial laxity. In contrast, a small lift observed during a voluntary pelvic floor muscle contraction may indicate either a weak contraction or high pelvic floor muscle resting activity. Furthermore, transabdominal ultrasound imaging does not allow direct assessment of the perineal area or vaginal wall support. Consequently, the information that it provides must be considered in light of findings attained through traditional assessment, including digital examination when possible. Muscle Morphology and Structural Assessment In addition to its ability to provide information about pelvic floor muscle (levator ani) function through the analysis of bladder neck and bladder base motion, ultrasound imaging has been used to quantify the thickness of the levator ani, 7,52 measure residual bladder volume, 34 investigate uterovaginal prolapse 20,64 and new surgical procedures, 25,91 as well as detect paravaginal defects 48,55 and space-occupying lesions (cysts, fibroids). Applications related to quantification of the thickness of the levator ani or residual bladder volumes have a direct relevance to physical therapists. For instance, Bernstein et al 7 used a transperineal ultrasound imaging to assess the reliability of pelvic floor muscle thickness measurements at rest and during contraction in 9 healthy, young (25-38 years of age) females. Although the methodology is poorly described, they reported a mean (6SD) resting thickness of mm and contracted thickness of mm, which represented an increase of 23% 6 8%. In a more recent study, Morkved et al 52 investigated the relationship between pelvic floor muscle strength (vaginal squeeze pressure) and increased thickness of the pelvic floor muscles (transperineal ultrasound imaging) in both continent and incontinent women. They determined that the continent group (n = 71) had significantly thicker muscles at rest (P =.018) and with contraction (P =.006), and they demonstrated higher mean increments in muscle thickness (P =.021) between the resting and contracted states. Moreover, a moderate to good correlation between measurements of pelvic floor muscle 492 august 2007 volume 37 number 8 journal of orthopaedic & sports physical therapy

7 strength and muscle thickness (r = 0.703) was demonstrated. Specialized radiological training is required for evaluation of tissue pathology. Further, the diagnosis of a paravaginal defect, uterovaginal prolapse, fibroid, or cyst via an imaging study is challenging and, in the case of the paravaginal defect, a controversial undertaking. 20,54 Furthermore, such investigations are beyond the scope of practice and training of physical therapists. However, if therapists employ ultrasound imaging in this region they must be prepared to handle suspicions of such findings in a timely and professional manner. It is recommended that physical therapists ensure that all patients are aware of the scope of practice of physical therapists with respect to the use of ultrasound imaging, and that all patients provide consent prior to ultrasound imaging examination, enabling the therapist to contact the patient s physician if a questionable structure is identified during the ultrasound imaging examination. For instance, Stokes et al 79 recommend the use of a consent form that clearly states that the purpose of the rehabilitative ultrasound imaging evaluation is to examine muscle function and is not intended for the identification of other pathology. Further, if during the course of study a questionable finding is identified, the information is to be passed onto the patient s physician in a timely manner. QUALITATIVE EVALUATION The use of ultrasound imaging to analyze the effect of a muscle contraction is complex. Although changes in static architectural parameters (eg, position of the bladder base) can contribute some elements of the story, this analysis does not take into account the timing of a contraction, or its influence on other structures (eg, tension in the endopelvic fascia). As alteration in the neuromuscular control of the pelvic floor muscles and abdominal muscles have been reported in individuals with dysfunctions such as stress UI, 5,16,77 it is imperative that methods to assist in the detection of these changes are developed. It is likely that detailed evaluation of qualitative components of changes in the pelvic floor muscles, bladder base, etc, may provide additional insight to aid in the interpretation of pelvic floor muscle function. Qualitative analysis of resting characteristics and dynamic features that occur with muscle contraction or increased intra-abdominal pressure may provide additional insight when added to the measurement of quantitative parameters. For instance, important information that may assist in the clinical interpretation of a neuromuscular strategy may be provided by analysis of the following: the resting shape of the bladder; factors suggesting simultaneous abdominal splinting versus a lift of the bladder base; phasic versus sustained lifting of the bladder base with a pelvic floor muscle contraction; return of the bladder base to its starting position once a pelvic floor muscle contraction ceases; or motion of the bladder with a task (such as an active straight-leg raise) that loads the region. Although components of qualitative analysis have been proposed by several authors, 68,93,94 these factors have not been adequately examined in the peer-reviewed literature. Current analysis is based on clinical interpretation and extrapolation of related and emerging evidence. Further investigation is required to evaluate the validity and psychometric properties of these analyses. However, it may be possible to combine the applications outlined above with traditional assessment findings and a knowledge of the neuromuscular mechanisms that underlie postural control of the trunk and continence. This may enable analysis of the neuromuscular strategy employed by an individual at rest, during a task that loads the region, or during a pelvic floor muscle contraction and correlate this to various qualitative features observed with ultrasound imaging (Table). For instance, one might be able to determine if an individual can produce and maintain a coordinated isometric contraction of the pelvic floor muscles and sustain it during limb-loading activities, as well as to speculate on resting activity of the pelvic floor muscles and the ability of the endopelvic fascia to transmit tension. 94 Although this reasoning appears to have clinical utility, it is speculative and requires further investigation. TREATMENT: ULTRASOUND IMAGING AND BIOFEEDBACK TRAINING The real-time information provided by ultrasound imaging has been proposed as a possible source of biofeedback that can be valuable during re-education of the pelvic floor muscles and lateral abdominal wall muscles in individuals with incontinence, 27,36 and possible low back and pelvic girdle pain. This section describes the role of biofeedback in pelvic floor muscle training, presents the unique benefits of ultrasound biofeedback in comparison to more traditional biofeedback devices, and outlines basic gaps in the current knowledge base with respect to these topics. Nonoperative care of individuals with SUI has been advocated since the late 1940s when Kegel reported that 90% of 455 patients treated with pelvic floor muscle training improved. 43,44 In a more recent systematic review, as part of the Cochrane Database, the widespread use of pelvic floor muscle training as a firstline conservative management strategy for women with stress, urge, or mixed urinary incontinence has been advocated. 35 Although pelvic floor muscle training has success rates reported between 21% to 84%, 2 investigators have found that between 25% to 57% of individuals with incontinence or bladder prolapse have difficulty performing a proper pelvic floor muscle contraction when only verbal and/or tactile cueing is provided. 10,27,81,86 As improper performance of a pelvic floor muscle contraction may actually facilitate urine leakage, 10,81 pelvic floor muscle training augmented with a biofeedback device that ensures accuracy of contraction may decrease the number journal of orthopaedic & sports physical therapy volume 37 number 8 august

8 Qualitative Transabdominal and Transperineal Ultrasound Imaging Features Associated With Analysis of Pelvic Floor Function and the Possible Insights That They Provide 94 Point of Consideration Shape, size, and symmetry of bladder at rest Resting relationship of bladder and pelvic floor height Caudodorsal motion of bladder with an ASLR Dorsal motion of bladder with an ASLR Lateral shift or rotation of bladder with an ASLR Observable PFM contraction during an ASLR Change in shape of the bladder with an ALSR Caudal encroachment of bladder with PFM contraction Cranioventral motion of bladder with PFM contraction Abdominal encroachment of bladder with PFM contraction Caudodorsal motion of bladder with PFM contraction Observable relaxation of the PFM after PFM contraction of individuals that do not respond to conservative care. Biofeedback training has been advocated as an adjunct during the training of a proper pelvic floor muscle contraction in people with poor ability to contract or perceive contraction of the pelvic floor muscles, weak, injured, and edematous muscles, or altered neuromuscular control resulting in delayed or inconsistent activation. 87,88 However, traditional biofeedback training utilizing surface or intravaginal EMG and pressure perinometry has demonstrated mixed success. 2,11,35,51 Several cohort studies have shown a decrease in the number of leakage accidents resulting in leakage per week, the cost of protective garments, and an increase in strength and endurance of the pelvic floor muscles when biofeedback training was included as an adjunct to pelvic floor muscle exercises. 1,2,4,11,12 More specifically, Burgio et al 11 and Morkved et al 51 found a 19% to 25% increase in success rates when individuals participated in an augmented biofeedback training program compared to a control group. However, the results are more equivocal when assessed using systematic reviews of randomized control trials. Two recent reviews by the Cochrane Database 35 and the International Continence Society 96 were unable to determine the benefit of augmented biofeedback training (primarily employing pressure perinometry and EMG) for the pelvic floor muscles. However, methodological problems within the original studies were cited. A key issue is that biofeedback may not lead to a substantially better outcome when it is Contribution to PFM Analysis* May assist in detection of PFM resting activity, residual bladder volume, and the possibility of a PVD or encroaching structure (eg, cyst) May assist in detection of increased PFM resting activity or as an early indicator of prolapse May assist in the detection of factors that contribute to inappropriate bladder descent, such as insufficient PFMs, delayed activation of the PFMs, fascial laxity, and/or a motor control strategy that employs unsuitable increases in IAP 57 May assist in detection of competent PFM activation in association with a motor control strategy that employs inappropriate increases in IAP resulting from abdominal splinting May assist in detection of either a unilateral insufficiency of the PF, or excessive unilateral activation of the oblique abdominals May assist in the detection of an effective PFM May assist in the detection of a motor control strategy that employs excessive increases in IAP May suggest some degree of voluntary control over the PFMs May suggest some degree of voluntary control over the PFMs May suggest a lack of voluntary control over the PFMs May suggest a lack of voluntary control over the PFMs. Bladder base depression has been associated with increased activity of the upper abdominal and chest wall muscles 85 May suggest some degree of voluntary control over the PFMs. Difficulty returning to the rest position or a slow return may indicate over active PFMs Abbreviations: ASLR, active straight-leg raise; IAP, intra-abdominal pressure; PF, pelvic floor (muscles and associated fascial support system); PFM, pelvic floor muscle (levator ani); PVD, paravaginal defect; TA, transabdominal; QTA, qualitative transabdominal; TP, transperineal. *Appropriate interpretation of these qualitative features must take into account findings attained through traditional assessment, including where possible internal digital examination, and requires appropriate ultrasound imaging training and an understanding of the neuromuscular mechanisms associated with postural control of the trunk and the continence mechanism. applied in a blanket manner to all individuals, but may be effective when used with a specific subset of patients who have particular difficulty learning how to activate the pelvic floor muscles. The use of ultrasound imaging as a source of biofeedback is relatively new and may be advantageous in comparison to traditional biofeedback training devices (eg, pressure perinometry or EMG). Although all of these devices provide immediate visual feedback during a pelvic floor muscle contraction, both pressure perinometry and EMG can increase with either an elevating or a straining pelvic floor muscle contraction. 85 In contrast, ultrasound imaging can provide real-time visual information about the direction of pelvic floor movement during a pelvic floor muscle contraction, straining ma- 494 august 2007 volume 37 number 8 journal of orthopaedic & sports physical therapy

9 neuver, 82,83 or functional task (eg, active straight-leg raise test). 57 Furthermore, traditional biofeedback techniques are susceptible to measurement error due to crosstalk from lower extremity muscle activity (eg, gluteus maximus, hamstrings, and adductors), while assessment of pelvic floor elevation with ultrasound imaging is not. 62 It is important to point out that the crosstalk from lower extremity muscles may be a result of either the intensity or technique employed by subjects when contracting their pelvic floor muscles (eg, subjects asked to perform strong contractions likely coactivated the limb muscles with the pelvic floor muscles) and not a shortcoming of the biofeedback device itself, as a recent investigation addressing this problem has shown. 40 As with all pelvic floor muscle biofeedback devices, substitution patterns associated with abdominal and chest wall muscle activity may confound interpretation and contribute to measurement error. For instance, a recent study identified increased activity of these muscles in individuals with both UI and LBP, highlighting that they need to be monitored concurrently. 78,81 One further consideration is that, due to the noninvasive nature of transabdominal ultrasound imaging, measurement error associated with poor patient compliance and apprehension, as seen with the more invasive traditional methods, may be minimized. Beyond the advantages highlighted above, ultrasound biofeedback training can assist some individuals in performing an effective pelvic floor muscle contraction in a relatively short time. In a study of 212 women, Dietz et al 27 reported that 26% of subjects (n = 56) were unable to perform a proper pelvic floor muscle contraction; but 57% of these subjects (32 individuals) were successful after 5 minutes of training with ultrasound biofeedback. In a smaller study (n = 13), 62% of incontinent women identified to be depressing the pelvic floor when attempting to perform an elevating pelvic floor muscle contraction (transabdominal ultrasound imaging) were able to perform an elevating contraction within 1 biofeedback session. 81 As with any form of biofeedback, the optimal protocol and feedback schedule, as well as the subgroup(s) of patients that would receive the greatest benefit from training with ultrasound biofeedback, must be determined. 50 As ultrasound biofeedback training is relatively new, many of these concepts have not been investigated. Considerations of biofeedback during specific phases of motor learning, timing (immediate versus delayed), the type (knowledge of results or performance), and amount of feedback need to be determined. Furthermore, how to match the specific needs of a patient (deficits of strength, endurance, or timing) to an appropriate ultrasound biofeedback training protocol needs to be investigated. 30,69,70 The use of treatment-based subgroups aimed at determining patients who would most benefit from the addition of ultrasound biofeedback training during a pelvic floor muscle training protocol may prove valuable. This type of classification scheme has been demonstrated to be beneficial in the treatment of patients with low back pain 13,32,33 and may serve as a template for further research in the development of a treatment-based classification system for UI. In addition to the use of ultrasound biofeedback of pelvic floor muscle contraction in patients with incontinence, this technique may be useful for the rehabilitation of pelvic floor muscle function in people with low back and pelvic pain. Although early data suggest dysfunction of the pelvic floor muscles in a subset of people with pain in this region 57,66 and pelvic floor muscle training has been advocated as a component of the rehabilitation of trunk muscle control, 68,72 further work is required to determine whether this approach is effective in this population. In conclusion, there appears to be agreement among investigators that a proportion of the population who require pelvic floor muscle training are unable to perform the exercise properly when only verbal and/or tactile cueing are provided. 27,84 Further, there is initial evidence to suggest that ultrasound biofeedback may be beneficial in the assessment and initial training of the pelvic floor muscles and could potentially increase the proportion of the population with these conditions who received benefit from exercise management of pelvic floor dysfunction. 27 Although current evidence for the use of ultrasound biofeedback in pelvic floor muscle training is limited, there is emerging evidence to suggest that ultrasound biofeedback training of other trunk muscles is valuable. 36,89 More research is needed and in particular it must be determined if ultrasound biofeedback can positively influence motor learning and clinical outcomes. RESEARCH AGENDA Ultrasound imaging can be used to assess the morphology of the pelvic floor muscles and associated structures. 7,20,52,54 It also provides a means to measure the supporting function of the pelvic floor muscles through the objective dynamic assessment of a voluntary pelvic floor muscle contraction that results in elevation of the bladder neck or bladder base, and the mobility of the bladder base and neck during maneuvers than increase intra-abdominal pressure. Ultrasound imaging has the advantage of provision of real-time information, thereby providing instantaneous visual feedback to both the client and therapist, and is more clinically accessible and affordable than MRI. Furthermore, transabdominal ultrasound imaging has been found to be more sensitive than digital palpation for the detection of an elevating pelvic floor muscle contraction. 31 In a study by Dietz et al, 23 4-dimensional transperineal ultrasound imaging (eg, real-time 3-dimensional imaging) was found to be more sensitive for detection of defects in the levator ani than digital palpation. Although asymmetries of the bladder base have been observed using conventional 2-dimensional transabdominal ultrasound imaging, there is a need for further studies that correlate journal of orthopaedic & sports physical therapy volume 37 number 8 august