Original articleThe relationship of transversus abdominis and lumbar multifidus clinical muscle tests in patients with chronic low back pain
Introduction
There has been considerable debate about the role of trunk muscles such as the transversus abdominis (TrA) and lumbar multifidus muscles in lumbo-pelvic stability and low back pain (LBP). There is considerable evidence that these muscles provide an important contribution. For example, there is evidence that the TrA muscle is controlled independently of the other abdominal muscles in a range of tasks (Hodges and Richardson, 1996, Hodges and Richardson, 1998). It has been proposed that the TrA muscle may contribute to stability of the lumbo-pelvic region via its effects on intra-abdominal pressure and by affecting fascial tension (Hodges et al., 2003a, Hodges et al., 2005, Barker et al., 2006). In addition, biomechanical models have proposed that the TrA muscle may play a role in support of the lumbo-pelvic region for weight-bearing (Snijders et al., 1995).
Changes in motor control of abdominal muscles have been reported in subjects with LBP. There is evidence of delayed activation of the TrA muscle in clinical and experimental studies of LBP (Hodges and Richardson, 1996, Hodges and Richardson, 1998, Hodges et al., 2003b). Imaging studies using magnetic resonance imaging (MRI) and ultrasound imaging have documented alterations in motor control of the abdominal muscles (Hides et al., 2008b, Hides et al., 2010). It has been proposed that the documented motor control changes, such as dysfunction of the TrA muscle, are associated with higher long-term incidence of LBP (Moseley, 2004).
There is also considerable evidence for the role of the lumbar multifidus muscle in stabilization of the lumbar spine. Biomechanical studies have highlighted the role of the multifidus muscle in provision of segmental stiffness (Panjabi, 1992a, Panjabi, 1992b, Wilke et al., 1995), control of the spinal segment’s neutral zone (Panjabi et al., 1989, Panjabi, 1992b), and its capacity to stabilize the spine when spinal stability is challenged (Keifer et al., 1997, Keifer et al., 1998, Moseley, 2004).
Among subjects with LBP, impairments of the multifidus muscle have been documented using imaging techniques. There is evidence that the cross-sectional area (CSA) of the multifidus is selectively decreased compared with other lumbo-pelvic muscles in patients with chronic LBP (Danneels et al., 2000). Multifidus muscle atrophy has been successfully quantified using MRI and Computerized Tomography (CT) scanning in terms of both decreased muscle CSAs (Barker et al., 2004) and presence of alterations in muscle consistency (due to fatty deposits or fibrous/connective tissue infiltration) and atrophy (Kader et al., 2000). Researchers have used real-time ultrasound imaging to demonstrate segmental decrease in the CSA of the multifidus, ipsilateral to painful symptoms, in patients with acute unilateral LBP (Hides et al., 1994, Hides et al., 1996). A similar localized (rather than generalized) pattern of muscle atrophy of the multifidus muscle has been demonstrated in subjects with chronic LBP with unilateral pain presentations (Hides et al., 2008a, Wallwork et al., 2009). This study also provided evidence of a corresponding reduced ability to voluntarily contract the atrophied muscle (Wallwork et al., 2009).
In the clinical setting, possible methods of testing TrA muscle function involve palpation of the abdominal wall (Hides et al., 2000) and the use of a pressure cuff (pressure biofeedback unit Chattanooga, USA) placed under the abdomen with the patient in a prone lying position (Hides et al., 2004). This test represents an inner range concentric contraction of the TrA muscle to lift the abdominal contents and wall and thereby decrease the pressure in the pressure biofeedback unit. The multifidus muscle can be assessed by the palpation of muscle bulk and by the quality of voluntary contraction at each lumbar vertebral level (Hides et al., 2004). Real-time ultrasound imaging is another method that is used in physiotherapy clinical practice both for assessment of TrA and multifidus muscle function and size as well as for retraining purposes (Bunce et al., 2004, Teyhen et al., 2005, Koppenhaver et al., 2009, Wallwork et al., 2009, Hides et al., 2010).
It would seem from previous research that changes in the TrA and multifidus muscles are common, and may even possibly represent a marker of chronic LBP. However, studies of impairments of the TrA and multifidus muscles have been performed in isolation. While it may be assumed that these impairments are related, no studies have tested and documented this association. In clinical practice, these muscles are often rehabilitated together (Hides et al., 2004), based on the assumption that a relationship exists between these muscles. This is an important point as there is evidence to support the efficacy of this approach. Macedo et al. (2009) examined motor control training for persistent LBP (subacute, chronic and recurrent). Of the 14 randomized controlled trials included, the results of 7 trials showed that motor control exercise (alone or as supplement to another intervention), was better than a minimal intervention in reducing pain at short-term, intermediate and long-term follow-up, and in reducing disability at long-term follow-up. In addition to the lack of current information of the relationship between the two muscles, it is unknown if there is a relationship between the results of muscle tests of the TrA and multifidus muscles and other clinical measures. The relationship between the distribution of reported symptoms, findings of manual joint examination and clinical assessment of TrA and multifidus muscle function has not been established in a clinical population with chronic LBP.
Therefore, this study was designed to investigate the relationships between clinical muscle testing and other measures taken in the course of a clinical assessment at a back clinic. The aims of the study were to test for concordance between (i) clinical assessments of TrA muscle contraction and multifidus muscle contraction, and (ii) multifidus muscle contraction and multifidus muscle size and asymmetry, and (iii) the association of these measures and other clinical outcome measures such as pain on manual examination and pain distribution.
Section snippets
Subjects
Data for this study was based on chart audits from the files of 82 patients (42 females, 40 males) presenting to a hospital based back pain clinic between 1998 and 2005 for assessment and management of chronic LBP. The mean age of the patients was 43.21 ± 13.09 years. Patients who attended the clinic during these years and were included in this study had a history of LBP in excess of three months, with LBP defined as pain localized between the T12 vertebral level and the gluteal fold.
Results
The mean (SD) of the VAS pain scores was 4.41 ± 2.47, with individual pain ratings ranging between zero and maximum (10/10) at the time of examination. HAQ scores ranged between 3.75 and 10.35 (out of a possible 15) with a mean score of 7.22 ± 1.45. Baseline RMQ disability scores ranged between 0 and 21 (out of a possible 24) with a mean score of 8.61 ± 5.81. The mean duration of symptoms was 51.21 ± 91.72 months, with a range of 3 months–40 years (480 months), reflecting the prolonged
Discussion
The main result of the current study was that the ability to contract the multifidus muscle (at the L5 vertebral level) was related to the ability to contract the TrA muscle, i.e. the odds of a good contraction of the multifidus muscle were 4.45 times higher for patients who had a good contraction of the TrA muscle compared with those who had a poor ability.
The muscle test for the TrA muscle was performed formally in prone lying, which is an anti-gravity position for this muscle (Hides et al.,
Acknowledgements
The authors would like to acknowledge the subjects studied, Ms Linda Blackwell (Director of Physiotherapy, Mater Health Services), Skye Shaw (Receptionist, Mater/ACU Back Stability Clinic), Craig Gilmore (Physiotherapist), and Megan Bambeery for administering and scoring the questionnaires. The contribution of Amanda Bromley, Rebecca Davis, Angela Phillott and Rebecca Robinson in compiling information for this report is acknowledged.
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