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A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol夽 Mark H. Halliday a,∗ , Paulo H. Ferreira b , Mark J. Hancock c , Helen A. Clare d a
Physiotherapy Department, Concord Repatriation General Hospital, Hospital Rd., Concord, NSW 2139, Australia b Faculty of Health Sciences, The University of Sydney, 75 East St., Lidcombe, NSW 1825, Australia c Faculty of Human Sciences, Macquarie University, Balaclava Rd., North Ryde, NSW 2113, Australia d Physiotherapy Private Practice, 24/272 Pacific Highway, Crows Nest 2065, Australia
Abstract Objective To investigate if McKenzie exercises when applied to a cohort of patients with chronic LBP who have a directional preference demonstrate improved recruitment of the transversus abdominis compared to motor control exercises when measurements were assessed from ultrasound images. Design A randomized blinded trial with a 12-month follow-up. Setting The Physiotherapy department of Concord Hospital a primary health care environment. Participants 70-adults with greater than three-month history of LBP who have a directional preference. Interventions McKenzie techniques or motor control exercises for 12-sessions over eight weeks. Main outcome measures Transversus abdominus thickness measured from real time ultrasound images, pain, global perceived effect and capacity to self-manage. Discussion This study will be the first to investigate the possible mechanism of action that McKenzie therapy and motor control exercises have on the recruitment of the transversus abdominus in a cohort of low back pain patients sub-classified with a directional preference. Patients receiving matched exercises according to their directional preference are believed to have better outcomes than those receiving unmatched exercises. A better understanding of the mechanism of action that specific treatments such as motor control exercises or McKenzie exercises have on patients classified with a directional preference will allow therapist to make a more informed choice about treatment options. © 2014 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Keywords: McKenzie; Muscle; Recruitment; Ultrasound; Protocol; Low back pain
Introduction Low back pain (LBP) is a common complaint with 70% to 85% life time prevalence and an average point prevalence of 30% [1,2]. Recurrence of LBP is also high; 50% within one year, 60% within two years and 70% within five years [3]. Direct health care costs of LBP in the UK in 1998 were 夽 ∗
Clinical Trial Registration: CTRN12611000971932. Correspondence: Tel.: +61 297677042; fax: +61 297678448. E-mail address: [email protected] (M.H. Halliday).
estimated to be £1632 million while indirect societal costs were estimated to be £10 668 million [4]. It has been estimated that between 17% and 37% total medical costs for LBP are attributable to allied health [5,6]. Therefore it is appropriate that health professionals provide treatments that promote independence from therapist reliance. Treatment guidelines consistently recommend exercise in the management of chronic LBP. However, while some guidelines do not comment on the efficacy of different exercise approaches [7–9] others recommend specific exercises [10]. The American Physical Therapy Association
http://dx.doi.org/10.1016/j.physio.2014.07.001 0031-9406/© 2014 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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(APTA) produced clinical practice guidelines that recommend trunk stabilization or endurance exercises for sub-acute and chronic LBP in patients that demonstrate impaired movement coordination [11]. Directional preference (based on the McKenzie approach) exercises utilizing repeated end range movements in a specific direction are also recommended in the APTA and Danish guidelines [10,11]. Efficacy for MDT and motor control exercises for treatment of chronic LBP has been demonstrated in systematic reviews of the literature [12–14]. Two specific types of exercises utilized by therapists for managing chronic LBP are Mechanical Diagnosis and Therapy (MDT) commonly known as the McKenzie method and motor control exercises. The commonality between these treatment strategies is that they are patient-centered approaches and emphasize patients’ self-efficacy by requiring active patient participation. However, these interventions are based upon completely different rationale for achieving long term symptom relief. The principle that underpins MDT is to identify the non-specific mechanical syndromes that spinal pain can be classified into from a thorough examination of the patient. Each of the three syndromes: derangement, dysfunction and posture syndrome have typical and distinctive mechanical presentations. Derangement syndrome is characterized by a varied clinical presentation and typical responses to loading strategies, which may consist of changes in pain location centrally or peripherally and in intensity. These findings guide the therapist to implement the most appropriate mechanical therapy according to the patient’s classification [15]. Motor control exercises aim to restore optimum control of the spine to meet the functional demands of the trunk [16]. One of the strategies used to achieve spinal control is the retraining of the coordination of the trunk muscles such as transversus abdominus (TrA), obliquus internus (OI) and obliquus externus (OE). During the implementation of motor control exercises the therapist aims to integrate appropriate recruitment patterns of the trunk muscles with normal function of other systems such as respiration and pelvic floor control [16]. Despite the difference in theoretical rationale for how motor control exercises and MDT might help people with chronic LBP there is limited evidence that the mechanisms are specific to the approach and different to each other. The importance of TrA thickness is further underscored by findings that showed it to be reduced in patients with LBP while promising research showed that it can be increased after motor control training [17–19]. However, it is unclear if these changes are specific to motor control exercises. Studies using ultrasound measurements of TrA thickness as a prime outcome measurement have had varying results. One published case series found changes in TrA muscle thickness immediately after applying spinal manipulation therapy to LBP patients which suggests that TrA activation may be improved as pain and disability resolve with treatments that do not
specifically aim to improve TrA thickness [20]. Conversely, Ferreira et al. found that patients who received general exercises or spinal mobilizations had a negative change in TrA thickness, while those who received motor control exercises had a 7% improvement in muscle thickness [19]. One study comparing MDT and motor control exercises in a heterogeneous cohort of patients with chronic LBP who received non-standard treatment found a greater increase in TrA thickness in patients receiving motor control exercises compared to McKenzie exercises [21]. The primary aim is to investigate if MDT results in similar changes to TrA thickness as motor control exercises in a cohort of patients with chronic LBP and a directional preference. A secondary aim of this study is to compare the effectiveness of MDT to motor control exercises on short and long term disability in patients with chronic LBP and a directional preference. To do this we will recruit only people who demonstrate a directional preference. While previous studies have demonstrated centralization to be associated with a favorable prognosis [22,23], there is no strong evidence the presence of a directional preference identifies people who respond better to MDT than other exercise approaches including motor control exercises. A tertiary aim of this trial is to compare the effectiveness of MDT to motor control on the number of flare-ups after discharge. This will provide a measure of the impact of these intervention on the ability of participants to self-manage their symptoms. A recent systematic review found moderate evidence to support self-management of LBP [24]. One study found patients with LBP treated with MDT sort less care than those managed by a general practitioner [25]. We are interested to explore if patients were able to use the skills provided to them to manage any exacerbation without the need to seek care from a health professional. Self-management is a core principle of MDT, while motor control exercise principles do not specifically address self-management as a formal part of the intervention. Therefore we will investigate if a greater proportion of people having an exacerbation, who were in the MDT group were able to manage a flare-up without seeking additional care (Fig. 1).
Methods Design This study will be a randomized blinded clinical trial. Power analysis A sample size of 70 will provide 80% power for detecting differences between groups of 7% in the recruitment of trunk muscles assessed with ultrasonography and based on the percentage of increase in muscle thickness as a function of resting thickness levels. The 7% effect size is based on our previous studies of ultrasonography for deep trunk muscles
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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Potential participants approached (n=140)
Enrollment
Subjects excluded because did not meet inclusion criteria (n=70)
Participants randomized (n=70)
Participants allocated to motor control exercises (n=35)
Participants allocated to MDT (n=35)
Follow-up 2 months
Estimated lost to follow-up (n=1)
Estimated lost to follow-up (n=1)
Follow-up 12 months
Estimated lost to follow-up (n=2)
Estimated lost to follow-up (n=2)
Fig. 1. Flow of participants through the trial.
and shown to be a clinical important difference between treatment groups [19]. These calculations assume a worst-case loss to follow-up of 10% in sample size calculation. Inclusion and exclusion criteria Seventy-adult patients will be recruited from the physiotherapy musculoskeletal waiting list for treatment of LBP. To be included patients must have had LBP for more than three months. The location of the pain must be between the twelfth rib and the buttock crease; it may refer to the lower limbs extending to the foot and can be accompanied by paraesthesia, anesthesia or myotomal weakness. Patients must demonstrate a directional preference immediately following lumbar spine mechanical assessment. We will record centralization by asking the patient to shade in a body chart while standing, indicating all of the pain they are experiencing immediately prior to and after the mechanical assessment. A standardized grid numbered 1 to 6 will be then placed
across the body charts and if the location of the pain has shifted proximally by one point when comparing the postassessment grid to the pre-assessment grid then centralizing can be considered as having occurred. Inter-rater reliability for this procedure is high (ICC = 0.96) [26]. If the pain has not changed location but the most distal pain has reduced in intensity by at least two points on an 11 point visual analog scale immediately following mechanical assessment then a directional preference can be considered to have occurred even if centralization was not demonstrated. Patients who have no pain immediately prior to the mechanical assessment must produce pain on the first movement and then abolish this pain immediately following mechanical loading in the opposite direction from the provocative movement. Patients will be excluded if they: do not demonstrate a directional preference, are under eighteen or over seventy years of age, cannot follow simple verbal instructions or read trial information in English, have an intellectual impairment, known metastatic disease, history of spinal fracture, previous spinal surgery or
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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known osteoporosis. Pregnancy is also an exclusion criteria and if a woman should become pregnant during the treatment phase of the study they will be withdrawn. Therapists, centers, ethics Therapists who are classifying patients prior to admission or applying MDT have obtained a certificate of Credentialed Therapist from the McKenzie Institute International. Therapists conducting motor control exercise have previous training and are experienced in applying the protocol for these techniques. The operator of the real time ultrasound will receive training from an experienced operator who will then assess the quality of the images obtained from a reliability study of ten healthy individuals. The research assistant responsible for ultrasound image analysis has conducted previous research in this area and is familiar with the protocol [27]. This study will be conducted in the Physiotherapy Department of Concord Hospital which is a major metropolitan public hospital in Sydney, Australia. Ethical approval was granted by the Sydney Local Health District Human Ethics Committee. The study was registered with the Australian New Zealand Clinical Trials Registry, trial number CTRN12611000971932. Interventions Following randomization patients will be given an appointment with a Physiotherapist to commence treatment. The exact number of treatments will be up to the clinical judgment of the treating Physiotherapist. Patients will be expected to receive twelve sessions of treatment over an eight-week period with no minimum amount of sessions required for an intention to treat analysis. The specific application of techniques will be delivered according to the patients’ needs based on the principles of treatment to which the patient has been randomized to receive. MDT MDT treatment will be prescribed according to the principles outlined by McKenzie [15]. Treatment involves mechanical therapy of both patient and therapist generated forces utilizing sustained or repeated end range movements in either loaded or unloaded postures according to the patients’ directional preference. The amount of force required and the loading strategy to apply the force will be guided by symptom response. The aim of treatment is to use forces such that peripheral symptoms will be reduced, centralized, and abolished; patients with central symptoms only will be reduced and abolished with repeated end range movements or sustained end range loading strategies. Once symptoms have been stabilized any loss of range will be addressed by the application of repeated end range movements in the direction of movement loss. Postural education will be continuously
reinforced including provision of a standard McKenzie lumbar roll when an extension preference is identified. Patients will also be given instructions on how to self-manage future exacerbations of their LBP including a copy of Treat Your Own Back by Robyn McKenzie for reference [28]. Motor control exercises The protocol for motor control exercises being used in this study is based on principles published by Hodges and Ferreira [16]. There are progressive phases to this protocol and patients can only progress when specific criteria are met for each phase. Initially promotion of independent contraction of the deep stabilizing muscles such as TrA and multifidus being facilitated by pelvic floor contraction leading to their co-contraction is encouraged. Patients will also be given instructions to control breathing with resting tidal volumes throughout deep trunk activation maneuvers. Progression is achieved by precision of contraction in static tasks and the implementation of deep muscle contraction into dynamic tasks. Therapists will provide feedback on the performance of exercises while less prompting is provided as the patient masters the skill. Patients will be instructed to practice exercises daily at home for 30-minutes. Patients will be encouraged to attend twice a week for the first four weeks and once per week for the second four weeks even if their symptoms should resolve during the treatment episode. Data collection procedures Once the patient has accepted an invitation to participate they will be asked to read the patient information booklet and give written consent before being assessed for inclusion. Included participants will then proceed to ultrasound examination. Ultrasound images will be collected using a 5 cm T5 MHz linear array ultrasound transducer using settings for musculoskeletal exam, depth 6 focus 2.8. Measures will be taken during resting and while patients perform isometric contractions of the lower limbs against a 7.5% body weight target. Body weight will be self-reported. Investigations of self-reporting of body weight have shown less than a 2 kg error which for this protocol will have a minimal effect [29–31]. Patient will be asked to lie supine with arms crossed on a plinth with their knees suspended in a harness from a supporting frame. The hips are positioned at 50◦ flexion while the knees are at 70◦ flexion with the feet supported on a bar connected to a spring balance. The operator then positions the real time ultrasound transducer laterally on the abdominal wall and instructs the patient to perform low load isometric knee flexion and knee extension movements in a random fashion. When the desired amount of force is reached then a row of lights are illuminated and the operator obtains the image. A buzzer will sound if excessive force is used, the operator may also give verbal feedback to help achieve the desired maneuver. Twelve images are taken; four at rest, four during knee flexion and four during knee extension. The ultrasound
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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transducer is placed transversely across the left abdominal wall along a line mid-way between the inferior angle of the costal margin and the iliac crest. The medial edge of the transducer is positioned so that the medial edge of TrA is aligned in the left-hand one-third of the ultrasound image when the subject is relaxed. The images are then stored for analysis. This process is described in detail elsewhere by Ferreira et al. [17]. A research assistant then randomizes the images prior to assessment by a blinded researcher who has had previous experience in ultrasound analysis of trunk muscle thickness. Customized software will be used to analyze the images. Measurements are taken of muscle thickness in the center and 1 cm to the left and right of the muscle center from both resting and contracted images. The sum of all 12-measurements is then averaged to give a mean measurement of muscle thickness. The baseline measurement is expressed as 100% muscle thickness and is then compared to follow-up measurements which will be expressed as a percentage change in muscle thickness. Secondary outcome questionnaires will be collected by a blinded research assistant at baseline, following discharge and at 12 months, while data regarding patients’ capacity to self-manage exacerbations of LBP will be collected by a blinded research assistant via email or telephone interview every two months from discharge to 12-month follow-up. Randomization Following collection of baseline measurements patients will then be randomized to treatment allocation by a blinded investigator with sequentially numbered opaque sealed envelopes. The randomization process was created using computer generated numbers. Outcome measures The primary outcome measurement is recruitment of the trunk muscles TrA, OI and OE expressed as percentage changes in muscle thickness increases obtained from real time ultrasound images. The reliability for this outcome measure was good to excellent for single measurements and poor too good for changes in thickness from base line measurements [32]. This outcome will be collected at baseline, following treatment discharge and again at 12-month followup. Secondary outcomes will be patients’ perception of function measured by the Patient Specific Functional Scale [3 to 30 point scale) [33], global improvement measured by the Global Perceived Effect questionnaire (rated from −5 to 5) [34] and pain intensity using an eleven point Visual Analogue Scale (VAS). Data will be collected at enrolment, following treatment discharge and at 12 months. Data will also be collected regarding patients who reported an exacerbation of more than two points on an eleven point visual analog scale over the preceding two months and whether they were able
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to self-manage or required further intervention from a health professional. Data analysis The software to be used for statistical analysis will be SPSS 22.0 (IBM Corporation, NY, USA). The primary measures of effect of treatment will be recruitment of TrA at treatment discharge. The statistician will be given grouped data, but data will be coded so that the statistician will remain blinded to patients’ group allocation. Separate analyses will be conducted to determine the effects of treatment at discharge and 12 months. Analysis will be by intention-to-treat, with data being analyzed for all randomized subjects for whom follow-up data are available. The emphasis in the analysis will be on estimation of the effects of intervention rather than hypothesis testing. We will use analysis of covariance with the baseline value of the outcome being used as a covariate in each separate analysis.
Discussion The main purpose of this study is to compare the effect of MDT and motor control exercises on the thickness of the TrA, OI and OE. The results will provide evidence on whether changes in recruitment of trunk muscles occur only as a result of exercises targeting motor control or if changes can also occur as a result of a MDT exercise program aimed at reducing pain and increasing function in a cohort of people with chronic LBP who have a directional preference. By establishing trunk muscle recruitment as our primary outcome we will be able to investigate the mechanisms underlying MDT and motor control exercises and further our understanding of the mechanisms responsible for TrA recruitment work in people with chronic LBP who have a directional preference. Findings for the secondary outcomes of pain function and global perceived effect will make an important contribution to the knowledge regarding treatment subgroups for LBP. Previous research suggests outcomes for patients with low back pain can be improved by targeting different approaches, including directional preference exercises and motor control exercises, to patients likely to respond best to a specific approach [35]. Our results will test whether patients previously reported to be responders to McKenzie who have been classified as presenting with a derangement syndrome do in fact respond better to repeated end range or sustained loading strategies including therapist generated forces and postural education when compared to utilizing motor control exercises for this sub-group of patients’ with mechanical LBP. Finally the outcome pertaining to patients’ capacity to self-manage exacerbations of their LBP following discharge will shed some light on whether an approach such as MDT that emphasizes prophylaxis, results in any difference when compared to motor control exercises that does not
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emphasize self-management following discharge in a subgroup of people who demonstrate a directional preference who have chronic LBP.
Limitations The authors acknowledge several limitations in this study. As we will only include patients with directional preference our results cannot be generalized to the entire population of patients with LBP. As with all long-term follow-up studies the dropout rate can be substantial although we have accounted for that in our sample size calculations.
Acknowledgements Steven May and Mark Werneke assisted with creation of working definitions for the inclusion criteria related to the mechanical assessment of patients. Gavin Robertson and Rafael Pinto collected and analyzed the real time ultrasound images. Yin Yee Lie collected data on patients’ ability to self-manage. David Roberts and Tim Morcombe provided treatment and Margareta Otero managed the randomization process. Ethical approval: This clinical trial received ethical approval from the Sydney Local Health District Human Ethics Committee of Concord Repatriation General Hospital, approved by the National Ethics Committee, Human research ethics approval number: HREC/10/CRGH/153. Funding: The trial received competitive funding from the International MDT Research Foundation, funder approval number: 2011-01346. We also received a donation of 35 copies of ‘Treat Your Own Back’ by Robyn McKenzie from Spinal Publications New Zealand Ltd. Back Care Products Australia supplied McKenzie lumbar rolls. The International MDT Research Foundation, Spinal Publications New Zealand Ltd. and Back Care Products Australia took no part in design of the trial or publication of this manuscript. Conflict of interest: Helen Clare is currently a board member of the McKenzie Institute International and head of the teaching faculty of the McKenzie Institute International.
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[31] Dekkers JC, van Wier MF, Hendriksen IM, Twisk JW, van Mechelen W. Accuracy of self-reported body weight, height and waist circumference in a Dutch overweight working population. BMC Med Res Methodol 2008;8:69 http://www.biomedcentral.com/1471-2288/ 8/69 [32] Costa LO, Maher CG, Latimer J, Hodges PW, Shirley D. An investigation of the reproducibility of ultrasound measures of abdominal muscle activation in patients with chronic non-specific low back pain. Eur Spine J 2009;18:1059–65. [33] Westaway MD, Stratford PW, Binkley JM. The Patient-Specific Functional Scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther 1998;27:331–8. [34] Ross R, LaStayo P. Clinical assessment of pain. Assess Occup Ther Phys Ther 1997:122–33. [35] Bennan GP, Fritz JM, Hunter SJ, Thackeray A, Delitto A, Erhard RE. Identifying subgroups of patients with acute/subacute nonspecific low back pain: results of a randomized clinical trial. Spine (Phila Pa 1976) 2006;31:623–31.
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A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol夽 Mark H. Halliday a,∗ , Paulo H. Ferreira b , Mark J. Hancock c , Helen A. Clare d a
Physiotherapy Department, Concord Repatriation General Hospital, Hospital Rd., Concord, NSW 2139, Australia b Faculty of Health Sciences, The University of Sydney, 75 East St., Lidcombe, NSW 1825, Australia c Faculty of Human Sciences, Macquarie University, Balaclava Rd., North Ryde, NSW 2113, Australia d Physiotherapy Private Practice, 24/272 Pacific Highway, Crows Nest 2065, Australia
Abstract Objective To investigate if McKenzie exercises when applied to a cohort of patients with chronic LBP who have a directional preference demonstrate improved recruitment of the transversus abdominis compared to motor control exercises when measurements were assessed from ultrasound images. Design A randomized blinded trial with a 12-month follow-up. Setting The Physiotherapy department of Concord Hospital a primary health care environment. Participants 70-adults with greater than three-month history of LBP who have a directional preference. Interventions McKenzie techniques or motor control exercises for 12-sessions over eight weeks. Main outcome measures Transversus abdominus thickness measured from real time ultrasound images, pain, global perceived effect and capacity to self-manage. Discussion This study will be the first to investigate the possible mechanism of action that McKenzie therapy and motor control exercises have on the recruitment of the transversus abdominus in a cohort of low back pain patients sub-classified with a directional preference. Patients receiving matched exercises according to their directional preference are believed to have better outcomes than those receiving unmatched exercises. A better understanding of the mechanism of action that specific treatments such as motor control exercises or McKenzie exercises have on patients classified with a directional preference will allow therapist to make a more informed choice about treatment options. © 2014 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.
Keywords: McKenzie; Muscle; Recruitment; Ultrasound; Protocol; Low back pain
Introduction Low back pain (LBP) is a common complaint with 70% to 85% life time prevalence and an average point prevalence of 30% [1,2]. Recurrence of LBP is also high; 50% within one year, 60% within two years and 70% within five years [3]. Direct health care costs of LBP in the UK in 1998 were 夽 ∗
Clinical Trial Registration: CTRN12611000971932. Correspondence: Tel.: +61 297677042; fax: +61 297678448. E-mail address: [email protected] (M.H. Halliday).
estimated to be £1632 million while indirect societal costs were estimated to be £10 668 million [4]. It has been estimated that between 17% and 37% total medical costs for LBP are attributable to allied health [5,6]. Therefore it is appropriate that health professionals provide treatments that promote independence from therapist reliance. Treatment guidelines consistently recommend exercise in the management of chronic LBP. However, while some guidelines do not comment on the efficacy of different exercise approaches [7–9] others recommend specific exercises [10]. The American Physical Therapy Association
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Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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(APTA) produced clinical practice guidelines that recommend trunk stabilization or endurance exercises for sub-acute and chronic LBP in patients that demonstrate impaired movement coordination [11]. Directional preference (based on the McKenzie approach) exercises utilizing repeated end range movements in a specific direction are also recommended in the APTA and Danish guidelines [10,11]. Efficacy for MDT and motor control exercises for treatment of chronic LBP has been demonstrated in systematic reviews of the literature [12–14]. Two specific types of exercises utilized by therapists for managing chronic LBP are Mechanical Diagnosis and Therapy (MDT) commonly known as the McKenzie method and motor control exercises. The commonality between these treatment strategies is that they are patient-centered approaches and emphasize patients’ self-efficacy by requiring active patient participation. However, these interventions are based upon completely different rationale for achieving long term symptom relief. The principle that underpins MDT is to identify the non-specific mechanical syndromes that spinal pain can be classified into from a thorough examination of the patient. Each of the three syndromes: derangement, dysfunction and posture syndrome have typical and distinctive mechanical presentations. Derangement syndrome is characterized by a varied clinical presentation and typical responses to loading strategies, which may consist of changes in pain location centrally or peripherally and in intensity. These findings guide the therapist to implement the most appropriate mechanical therapy according to the patient’s classification [15]. Motor control exercises aim to restore optimum control of the spine to meet the functional demands of the trunk [16]. One of the strategies used to achieve spinal control is the retraining of the coordination of the trunk muscles such as transversus abdominus (TrA), obliquus internus (OI) and obliquus externus (OE). During the implementation of motor control exercises the therapist aims to integrate appropriate recruitment patterns of the trunk muscles with normal function of other systems such as respiration and pelvic floor control [16]. Despite the difference in theoretical rationale for how motor control exercises and MDT might help people with chronic LBP there is limited evidence that the mechanisms are specific to the approach and different to each other. The importance of TrA thickness is further underscored by findings that showed it to be reduced in patients with LBP while promising research showed that it can be increased after motor control training [17–19]. However, it is unclear if these changes are specific to motor control exercises. Studies using ultrasound measurements of TrA thickness as a prime outcome measurement have had varying results. One published case series found changes in TrA muscle thickness immediately after applying spinal manipulation therapy to LBP patients which suggests that TrA activation may be improved as pain and disability resolve with treatments that do not
specifically aim to improve TrA thickness [20]. Conversely, Ferreira et al. found that patients who received general exercises or spinal mobilizations had a negative change in TrA thickness, while those who received motor control exercises had a 7% improvement in muscle thickness [19]. One study comparing MDT and motor control exercises in a heterogeneous cohort of patients with chronic LBP who received non-standard treatment found a greater increase in TrA thickness in patients receiving motor control exercises compared to McKenzie exercises [21]. The primary aim is to investigate if MDT results in similar changes to TrA thickness as motor control exercises in a cohort of patients with chronic LBP and a directional preference. A secondary aim of this study is to compare the effectiveness of MDT to motor control exercises on short and long term disability in patients with chronic LBP and a directional preference. To do this we will recruit only people who demonstrate a directional preference. While previous studies have demonstrated centralization to be associated with a favorable prognosis [22,23], there is no strong evidence the presence of a directional preference identifies people who respond better to MDT than other exercise approaches including motor control exercises. A tertiary aim of this trial is to compare the effectiveness of MDT to motor control on the number of flare-ups after discharge. This will provide a measure of the impact of these intervention on the ability of participants to self-manage their symptoms. A recent systematic review found moderate evidence to support self-management of LBP [24]. One study found patients with LBP treated with MDT sort less care than those managed by a general practitioner [25]. We are interested to explore if patients were able to use the skills provided to them to manage any exacerbation without the need to seek care from a health professional. Self-management is a core principle of MDT, while motor control exercise principles do not specifically address self-management as a formal part of the intervention. Therefore we will investigate if a greater proportion of people having an exacerbation, who were in the MDT group were able to manage a flare-up without seeking additional care (Fig. 1).
Methods Design This study will be a randomized blinded clinical trial. Power analysis A sample size of 70 will provide 80% power for detecting differences between groups of 7% in the recruitment of trunk muscles assessed with ultrasonography and based on the percentage of increase in muscle thickness as a function of resting thickness levels. The 7% effect size is based on our previous studies of ultrasonography for deep trunk muscles
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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Potential participants approached (n=140)
Enrollment
Subjects excluded because did not meet inclusion criteria (n=70)
Participants randomized (n=70)
Participants allocated to motor control exercises (n=35)
Participants allocated to MDT (n=35)
Follow-up 2 months
Estimated lost to follow-up (n=1)
Estimated lost to follow-up (n=1)
Follow-up 12 months
Estimated lost to follow-up (n=2)
Estimated lost to follow-up (n=2)
Fig. 1. Flow of participants through the trial.
and shown to be a clinical important difference between treatment groups [19]. These calculations assume a worst-case loss to follow-up of 10% in sample size calculation. Inclusion and exclusion criteria Seventy-adult patients will be recruited from the physiotherapy musculoskeletal waiting list for treatment of LBP. To be included patients must have had LBP for more than three months. The location of the pain must be between the twelfth rib and the buttock crease; it may refer to the lower limbs extending to the foot and can be accompanied by paraesthesia, anesthesia or myotomal weakness. Patients must demonstrate a directional preference immediately following lumbar spine mechanical assessment. We will record centralization by asking the patient to shade in a body chart while standing, indicating all of the pain they are experiencing immediately prior to and after the mechanical assessment. A standardized grid numbered 1 to 6 will be then placed
across the body charts and if the location of the pain has shifted proximally by one point when comparing the postassessment grid to the pre-assessment grid then centralizing can be considered as having occurred. Inter-rater reliability for this procedure is high (ICC = 0.96) [26]. If the pain has not changed location but the most distal pain has reduced in intensity by at least two points on an 11 point visual analog scale immediately following mechanical assessment then a directional preference can be considered to have occurred even if centralization was not demonstrated. Patients who have no pain immediately prior to the mechanical assessment must produce pain on the first movement and then abolish this pain immediately following mechanical loading in the opposite direction from the provocative movement. Patients will be excluded if they: do not demonstrate a directional preference, are under eighteen or over seventy years of age, cannot follow simple verbal instructions or read trial information in English, have an intellectual impairment, known metastatic disease, history of spinal fracture, previous spinal surgery or
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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known osteoporosis. Pregnancy is also an exclusion criteria and if a woman should become pregnant during the treatment phase of the study they will be withdrawn. Therapists, centers, ethics Therapists who are classifying patients prior to admission or applying MDT have obtained a certificate of Credentialed Therapist from the McKenzie Institute International. Therapists conducting motor control exercise have previous training and are experienced in applying the protocol for these techniques. The operator of the real time ultrasound will receive training from an experienced operator who will then assess the quality of the images obtained from a reliability study of ten healthy individuals. The research assistant responsible for ultrasound image analysis has conducted previous research in this area and is familiar with the protocol [27]. This study will be conducted in the Physiotherapy Department of Concord Hospital which is a major metropolitan public hospital in Sydney, Australia. Ethical approval was granted by the Sydney Local Health District Human Ethics Committee. The study was registered with the Australian New Zealand Clinical Trials Registry, trial number CTRN12611000971932. Interventions Following randomization patients will be given an appointment with a Physiotherapist to commence treatment. The exact number of treatments will be up to the clinical judgment of the treating Physiotherapist. Patients will be expected to receive twelve sessions of treatment over an eight-week period with no minimum amount of sessions required for an intention to treat analysis. The specific application of techniques will be delivered according to the patients’ needs based on the principles of treatment to which the patient has been randomized to receive. MDT MDT treatment will be prescribed according to the principles outlined by McKenzie [15]. Treatment involves mechanical therapy of both patient and therapist generated forces utilizing sustained or repeated end range movements in either loaded or unloaded postures according to the patients’ directional preference. The amount of force required and the loading strategy to apply the force will be guided by symptom response. The aim of treatment is to use forces such that peripheral symptoms will be reduced, centralized, and abolished; patients with central symptoms only will be reduced and abolished with repeated end range movements or sustained end range loading strategies. Once symptoms have been stabilized any loss of range will be addressed by the application of repeated end range movements in the direction of movement loss. Postural education will be continuously
reinforced including provision of a standard McKenzie lumbar roll when an extension preference is identified. Patients will also be given instructions on how to self-manage future exacerbations of their LBP including a copy of Treat Your Own Back by Robyn McKenzie for reference [28]. Motor control exercises The protocol for motor control exercises being used in this study is based on principles published by Hodges and Ferreira [16]. There are progressive phases to this protocol and patients can only progress when specific criteria are met for each phase. Initially promotion of independent contraction of the deep stabilizing muscles such as TrA and multifidus being facilitated by pelvic floor contraction leading to their co-contraction is encouraged. Patients will also be given instructions to control breathing with resting tidal volumes throughout deep trunk activation maneuvers. Progression is achieved by precision of contraction in static tasks and the implementation of deep muscle contraction into dynamic tasks. Therapists will provide feedback on the performance of exercises while less prompting is provided as the patient masters the skill. Patients will be instructed to practice exercises daily at home for 30-minutes. Patients will be encouraged to attend twice a week for the first four weeks and once per week for the second four weeks even if their symptoms should resolve during the treatment episode. Data collection procedures Once the patient has accepted an invitation to participate they will be asked to read the patient information booklet and give written consent before being assessed for inclusion. Included participants will then proceed to ultrasound examination. Ultrasound images will be collected using a 5 cm T5 MHz linear array ultrasound transducer using settings for musculoskeletal exam, depth 6 focus 2.8. Measures will be taken during resting and while patients perform isometric contractions of the lower limbs against a 7.5% body weight target. Body weight will be self-reported. Investigations of self-reporting of body weight have shown less than a 2 kg error which for this protocol will have a minimal effect [29–31]. Patient will be asked to lie supine with arms crossed on a plinth with their knees suspended in a harness from a supporting frame. The hips are positioned at 50◦ flexion while the knees are at 70◦ flexion with the feet supported on a bar connected to a spring balance. The operator then positions the real time ultrasound transducer laterally on the abdominal wall and instructs the patient to perform low load isometric knee flexion and knee extension movements in a random fashion. When the desired amount of force is reached then a row of lights are illuminated and the operator obtains the image. A buzzer will sound if excessive force is used, the operator may also give verbal feedback to help achieve the desired maneuver. Twelve images are taken; four at rest, four during knee flexion and four during knee extension. The ultrasound
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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transducer is placed transversely across the left abdominal wall along a line mid-way between the inferior angle of the costal margin and the iliac crest. The medial edge of the transducer is positioned so that the medial edge of TrA is aligned in the left-hand one-third of the ultrasound image when the subject is relaxed. The images are then stored for analysis. This process is described in detail elsewhere by Ferreira et al. [17]. A research assistant then randomizes the images prior to assessment by a blinded researcher who has had previous experience in ultrasound analysis of trunk muscle thickness. Customized software will be used to analyze the images. Measurements are taken of muscle thickness in the center and 1 cm to the left and right of the muscle center from both resting and contracted images. The sum of all 12-measurements is then averaged to give a mean measurement of muscle thickness. The baseline measurement is expressed as 100% muscle thickness and is then compared to follow-up measurements which will be expressed as a percentage change in muscle thickness. Secondary outcome questionnaires will be collected by a blinded research assistant at baseline, following discharge and at 12 months, while data regarding patients’ capacity to self-manage exacerbations of LBP will be collected by a blinded research assistant via email or telephone interview every two months from discharge to 12-month follow-up. Randomization Following collection of baseline measurements patients will then be randomized to treatment allocation by a blinded investigator with sequentially numbered opaque sealed envelopes. The randomization process was created using computer generated numbers. Outcome measures The primary outcome measurement is recruitment of the trunk muscles TrA, OI and OE expressed as percentage changes in muscle thickness increases obtained from real time ultrasound images. The reliability for this outcome measure was good to excellent for single measurements and poor too good for changes in thickness from base line measurements [32]. This outcome will be collected at baseline, following treatment discharge and again at 12-month followup. Secondary outcomes will be patients’ perception of function measured by the Patient Specific Functional Scale [3 to 30 point scale) [33], global improvement measured by the Global Perceived Effect questionnaire (rated from −5 to 5) [34] and pain intensity using an eleven point Visual Analogue Scale (VAS). Data will be collected at enrolment, following treatment discharge and at 12 months. Data will also be collected regarding patients who reported an exacerbation of more than two points on an eleven point visual analog scale over the preceding two months and whether they were able
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to self-manage or required further intervention from a health professional. Data analysis The software to be used for statistical analysis will be SPSS 22.0 (IBM Corporation, NY, USA). The primary measures of effect of treatment will be recruitment of TrA at treatment discharge. The statistician will be given grouped data, but data will be coded so that the statistician will remain blinded to patients’ group allocation. Separate analyses will be conducted to determine the effects of treatment at discharge and 12 months. Analysis will be by intention-to-treat, with data being analyzed for all randomized subjects for whom follow-up data are available. The emphasis in the analysis will be on estimation of the effects of intervention rather than hypothesis testing. We will use analysis of covariance with the baseline value of the outcome being used as a covariate in each separate analysis.
Discussion The main purpose of this study is to compare the effect of MDT and motor control exercises on the thickness of the TrA, OI and OE. The results will provide evidence on whether changes in recruitment of trunk muscles occur only as a result of exercises targeting motor control or if changes can also occur as a result of a MDT exercise program aimed at reducing pain and increasing function in a cohort of people with chronic LBP who have a directional preference. By establishing trunk muscle recruitment as our primary outcome we will be able to investigate the mechanisms underlying MDT and motor control exercises and further our understanding of the mechanisms responsible for TrA recruitment work in people with chronic LBP who have a directional preference. Findings for the secondary outcomes of pain function and global perceived effect will make an important contribution to the knowledge regarding treatment subgroups for LBP. Previous research suggests outcomes for patients with low back pain can be improved by targeting different approaches, including directional preference exercises and motor control exercises, to patients likely to respond best to a specific approach [35]. Our results will test whether patients previously reported to be responders to McKenzie who have been classified as presenting with a derangement syndrome do in fact respond better to repeated end range or sustained loading strategies including therapist generated forces and postural education when compared to utilizing motor control exercises for this sub-group of patients’ with mechanical LBP. Finally the outcome pertaining to patients’ capacity to self-manage exacerbations of their LBP following discharge will shed some light on whether an approach such as MDT that emphasizes prophylaxis, results in any difference when compared to motor control exercises that does not
Please cite this article in press as: Halliday MH, et al. A randomized controlled trial comparing McKenzie therapy and motor control exercises on the recruitment of trunk muscles in people with chronic low back pain: a trial protocol. Physiotherapy (2014), http://dx.doi.org/10.1016/j.physio.2014.07.001
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emphasize self-management following discharge in a subgroup of people who demonstrate a directional preference who have chronic LBP.
Limitations The authors acknowledge several limitations in this study. As we will only include patients with directional preference our results cannot be generalized to the entire population of patients with LBP. As with all long-term follow-up studies the dropout rate can be substantial although we have accounted for that in our sample size calculations.
Acknowledgements Steven May and Mark Werneke assisted with creation of working definitions for the inclusion criteria related to the mechanical assessment of patients. Gavin Robertson and Rafael Pinto collected and analyzed the real time ultrasound images. Yin Yee Lie collected data on patients’ ability to self-manage. David Roberts and Tim Morcombe provided treatment and Margareta Otero managed the randomization process. Ethical approval: This clinical trial received ethical approval from the Sydney Local Health District Human Ethics Committee of Concord Repatriation General Hospital, approved by the National Ethics Committee, Human research ethics approval number: HREC/10/CRGH/153. Funding: The trial received competitive funding from the International MDT Research Foundation, funder approval number: 2011-01346. We also received a donation of 35 copies of ‘Treat Your Own Back’ by Robyn McKenzie from Spinal Publications New Zealand Ltd. Back Care Products Australia supplied McKenzie lumbar rolls. The International MDT Research Foundation, Spinal Publications New Zealand Ltd. and Back Care Products Australia took no part in design of the trial or publication of this manuscript. Conflict of interest: Helen Clare is currently a board member of the McKenzie Institute International and head of the teaching faculty of the McKenzie Institute International.
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