Abstract
Background The McKenzie method is widely used as an active intervention in the treatment of patients with nonspecific low back pain. Although the McKenzie method has been compared with several other interventions, it is not yet known whether this method is superior to placebo in patients with chronic low back pain.
Objective The purpose of this trial is to assess the efficacy of the McKenzie method in patients with chronic nonspecific low back pain.
Design An assessor-blinded, 2-arm, randomized placebo-controlled trial will be conducted.
Setting This study will be conducted in physical therapy clinics in São Paulo, Brazil.
Participants The participants will be 148 patients seeking care for chronic nonspecific low back pain.
Intervention Participants will be randomly allocated to 1 of 2 treatment groups: (1) McKenzie method or (2) placebo therapy (detuned ultrasound and shortwave therapy). Each group will receive 10 sessions of 30 minutes each (2 sessions per week over 5 weeks).
Measurements The clinical outcomes will be obtained at the completion of treatment (5 weeks) and at 3, 6, and 12 months after randomization. The primary outcomes will be pain intensity (measured with the Pain Numerical Rating Scale) and disability (measured with the Roland-Morris Disability Questionnaire) at the completion of treatment. The secondary outcomes will be pain intensity; disability and function; kinesiophobia and global perceived effect at 3, 6, and 12 months after randomization; and kinesiophobia and global perceived effect at completion of treatment. The data will be collected by a blinded assessor.
Limitations Therapists will not be blinded.
Conclusions This will be the first trial to compare the McKenzie method with placebo therapy in patients with chronic nonspecific low back pain. The results of this study will contribute to better management of this population.
Low back pain is a major health condition associated with a high rate of absenteeism from work and a more frequent use of health services and work leave entitlements.1 Low back pain recently was rated by the Global Burden of Disease Study as one of the 7 health conditions that most affect the world's population,2 and it is considered a debilitating health condition that affects the population for the greatest number of years over a lifetime.2 The point prevalence of low back pain in the general population is reported to be up to 18%, increasing to 31% in the last 30 days, 38% in the last 12 months, and 39% at any point in life.3 Low back pain also is associated with high treatment costs.4 It is estimated that in European countries, the direct and indirect costs vary from €2 to €4 billion a year.4 The prognosis of low back pain is directly related to the duration of the symptoms.5,6 Patients with chronic low back pain have a less favorable prognosis compared with patients with acute low back pain5,7 and are responsible for most of the costs for management of back pain, generating the need for research aimed at finding better treatments for these patients.
There is a great variety of interventions for the treatment of patients with chronic low back pain, including the McKenzie method developed by Robin McKenzie in New Zealand in 1981.8 The McKenzie method (also known as Mechanical Diagnosis and Therapy [MDT]) is an active therapy that involves repeated movements or sustained positions and has an educational component with the purpose of minimizing pain and disability and improving spinal mobility.8 The McKenzie method involves the assessment of symptomatic and mechanical responses to repeated movements and sustained positions. Patients' responses to this assessment are used to classify them into subgroups or syndromes called derangement, dysfunction, and posture.8–10 Classification according to one of these groups guides the treatment principles.
Derangement syndrome is the largest group and characterized by patients who demonstrate centralization (transition of pain from distal to proximal) or disappearance of pain11 with repeated movement testing in one direction. These patients are treated with repeated movements or sustained positions that could reduce pain. Patients classified as having dysfunction syndrome are characterized by pain that occurs only at the end of the range of motion of only one movement.8 The pain does not change or centralize with repeated movement testing. The treatment principle for patients with dysfunction is repeated movements in the direction that generated the pain. Finally, patients classified as having postural syndrome experience intermittent pain only during sustained positioning at the end of the range of motion (eg, sustained slumped sitting).8 The treatment principle for this syndrome consists of posture correction.11
The McKenzie method also includes a strong educational component based on the books titled The Lumbar Spine: Mechanical Diagnosis & Therapy: Volume Two11 and Treat Your Own Back.12 This method, unlike other therapeutic methods, aims to make the patients as independent of the therapist as possible and thus capable of controlling their pain through postural care and the practice of specific exercises for their problem.11 It encourages patients to move the spine in the direction that is not harmful to their problem, thus avoiding movement restriction due to kinesiophobia or pain.11
Two previous systematic reviews have analyzed the effects of the McKenzie method9,10 in patients with acute, subacute, and chronic low back pain. The review by Clare et al9 demonstrated that the McKenzie method showed better results in short-term pain relief and improvement of disability compared with active interventions such as physical exercise. The review by Machado et al10 showed that the McKenzie method reduced pain and disability in the short term when compared with passive therapy for acute low back pain. For chronic low back pain, the 2 reviews were unable to draw conclusions about the effectiveness of the McKenzie method due to the lack of appropriate trials. The randomized controlled trials that have investigated the McKenzie method in patients with chronic low back pain13–17 compared the method with other interventions such as resistance training,17 the Williams method,14 unsupervised exercises,16 trunk strengthening,15 and stabilization exercises.13 Better results in reducing pain intensity were obtained with the McKenzie method compared with resistance training,17 the Williams method,14 and supervised exercise.16 However, the methodological quality of these trials13–17 is suboptimal.
It is known from the literature that the McKenzie method yields beneficial results when compared with some clinical interventions in patients with chronic low back pain; however, to date, no studies have compared the McKenzie method against a placebo treatment in order to identify its actual efficacy. Clare et al9 highlighted the need to compare the McKenzie method with placebo therapy and to study the effects of the method in the long term. In other words, it is not known whether the positive effects of the McKenzie method are due to its real efficacy or simply to a placebo effect.
The objective of this study will be to assess the efficacy of the McKenzie method in patients with chronic nonspecific low back pain using a high-quality randomized placebo-controlled trial.
Method
Study Design
This will be an assessor-blinded, 2-arm, randomized placebo-controlled trial.
Study Setting
This study will be conducted in physical therapy clinics in São Paulo, Brazil.
Eligibility Criteria
The study will include patients seeking care for chronic nonspecific low back pain (defined as pain or discomfort between the costal margins and the inferior gluteal folds, with or without referred symptoms in the lower limbs, for at least 3 months18), with a pain intensity of at least 3 points as measured with the 0- to 10-point Pain Numerical Rating Scale, aged between 18 and 80 years, and able to read Portuguese. Patients will be excluded if they have any contraindication to physical exercise19 or ultrasound or shortwave therapy, evidence of nerve root compromise (ie, one or more motor, reflex, or sensation deficits), serious spinal pathology (eg, fracture, tumor, inflammatory and infectious diseases), serious cardiovascular and metabolic diseases, previous back surgery, or pregnancy.
Procedure
First, the patients will be interviewed by the study's blinded assessor, who will determine eligibility. Eligible patients will be informed about the objectives of the study and asked to sign a consent form. Next, the patient's sociodemographic data and medical history will be recorded. The assessor will then collect the data related to the study outcomes at the baseline assessment, after completion of 5 weeks of treatment, and 3, 6, and 12 months after randomization. With the exception of baseline measurements, all other assessments will be collected over the telephone. All data entry will be coded, entered into an Excel (Microsoft Corporation, Redmond, Washington) spreadsheet, and double-checked prior to the analysis.
Outcome Measures
The clinical outcomes will be measured at the baseline assessment, after treatment, and 3, 6, and 12 months after random allocation. The primary outcomes will be pain intensity (measured with the Pain Numerical Rating Scale)20 and disability (measured with the Roland-Morris Disability Questionnaire)21,22 after completion of 5 weeks of treatment. The secondary outcomes will be pain intensity and disability 3, 6, and 12 months after randomization and disability and function (measured by the Patient-Specific Functional Scale),20 kinesiophobia (measured with the Tampa Scale of Kinesiophobia),23 and global perceived effect (measured with the Global Perceived Effect Scale)20 after treatment and 3, 6, and 12 months after randomization. On the day of the baseline assessment, each patient's expectancy for improvement also will be assessed using the Expectancy of Improvement Numerical Scale,24 followed by assessment using the McKenzie method.8 Patients may experience an exacerbation of symptoms after the baseline assessment due to the MDT physical examination. All measurements were previously cross-culturally adapted into Portuguese and clinimetrically tested and are described below.
Pain Numerical Rating Scale.
The Pain Numerical Rating Scale is a scale that assesses the levels of pain intensity perceived by the patient using an 11-point scale (varying from 0 to 10), in which 0 represents “no pain” and 10 represents the “worst possible pain.”20 The participants will be instructed to select the average of pain intensity based on the last 7 days.
Roland-Morris Disability Questionnaire.
This questionnaire consists of 24 items that describe daily activities that patients have difficulty performing due to low back pain.21,22 The higher the number of affirmative answers, the higher the level of disability associated with low back pain.21,22 The participants will be instructed to complete the questionnaire based on the last 24 hours.
Patient-Specific Functional Scale.
The Patient-Specific Functional Scale is a global scale; therefore, it can be used for any part of the body.25,26 The patients will be asked to identify up to 3 activities that they feel unable to perform or that they have difficulty performing due to their low back pain.25,26 Measurement will be taken using Likert-type, 11-point scales for each activity, with higher average scores (ranging from 0 to 10 points) representing better ability to perform the tasks.25,26 We will calculate the average of these activities based on the last 24 hours, with a final score ranging from 0 to 10.
Global Perceived Effect Scale.
The Global Perceived Effect Scale is a Likert-type, 11-point scale (ranging from −5 to +5) that compares the patient's current condition with his or her condition at the onset of symptoms.20 Positive scores apply to patients who are better and negative scores apply to patients who are worse in relation to the onset of symptoms.20
Tampa Scale of Kinesiophobia.
This scale assesses the level of kinesiophobia (fear of moving) by means of 17 questions that deal with pain and intensity of symptoms.23 The scores from each item vary from 1 to 4 points (eg, 1 point for “strongly disagree,” 2 points for “partially disagree,” 3 points for “agree,” and 4 points for “strongly agree”).23 For the total score, it is necessary to invert the scores of questions 4, 8, 12, and 16.23 The final score can vary from 17 to 68 points, with higher scores representing a higher degree of kinesiophobia.23
Expectancy of Improvement Numerical Scale.
This scale assesses the patient's expectancy for improvement after treatment in relationship to a specific treatment.24 It consists of an 11-point scale varying from 0 to 10, in which 0 represents “no expectancy for improvement” and 10 represents “expectancy for the greatest possible improvement.”24 This scale will be administered only on the first day of assessment (baseline) before the randomization. The reason for including this scale is to analyze whether the expectation of improvement will influence the outcomes.
Random Allocation
Before the treatment begins, the patients will be randomly allocated to their respective intervention groups. The random allocation sequence will be implemented by one of the researchers not involved with recruiting and assessing the patients and will be generated on Microsoft Excel 2010 software. This random allocation sequence will be inserted into sequentially numbered, opaque, sealed envelopes (to ensure that allocation is concealed from the assessor). The envelopes will be opened by the physical therapist who will treat the patients.
Blinding
Given the nature of the study, it is not possible to blind the therapists to the conditions of treatment; however, the assessor and the patients will be blinded to the treatment groups. At the end of the study, the assessor will be asked whether the patients were allocated to the real treatment group or to the placebo group in order to measure assessor blinding. A visual representation of the study design is presented in the Figure.
Flow diagram of the study.
Interventions
The participants will be allocated to groups receiving 1 of 2 interventions: (1) placebo therapy or (2) MDT. Participants in each group will receive 10 sessions of 30 minutes each (2 sessions per week over 5 weeks). The studies on the McKenzie method do not have a standard number of sessions given that some studies propose low doses of treatment,16,17,27 and others recommend higher doses.13,15
For ethical reasons, on the first day of treatment, patients from both groups will receive an information booklet called The Back Book,28 based on the same recommendations as the existing guidelines.29,30 This booklet will be translated into Portuguese so that it can be completely understood by the study's participants, who will receive additional explanations regarding the content of the booklet, if needed. Patients will be asked in each session if they have felt any different symptom. The chief investigator of the study will periodically audit the interventions.
Placebo Group
The patients allocated to the placebo group will be treated with detuned pulsed ultrasound for 5 minutes and detuned shortwave diathermy in pulsed mode for 25 minutes. The devices will be used with the internal cables disconnected to obtain the placebo effect; however, it will be possible to handle them and adjust doses and alarms as if they were connected to simulate the pragmatism of clinical practice as well as to increase credibility of use of these devices on the patients. This technique has been used successfully in previous trials with patients with low back pain.31–35
McKenzie Group
The patients of the McKenzie group will be treated according to the principles of the McKenzie method,8 and the choice of therapeutic intervention will be guided by the physical examination findings and classification. Patients also will receive written instructions from the Treat Your Own Back12 book and will be asked to perform home exercises based on the principles of McKenzie method.11 The descriptions of the exercises that will be prescribed in this study are published elsewhere.27 Adherence to home exercises will be monitored by means of a daily log that the patient will fill in at home and bring to the therapist at each subsequent session.
Statistical Methods
Sample size calculation.
The study was designed to detect a difference of 1 point in pain intensity measured with the Pain Numerical Rating Scale20 (estimate for standard deviation=1.84 points)31 and a difference of 4 points in disability associated with low back pain measured with the Roland-Morris Disability Questionnaire21,22 (estimate for standard deviation=4.9 points).31 The following specifications were considered: statistical power of 80%, alpha level of 5%, and follow-up loss of 15%. Therefore, the study will require a sample of 74 patients per group (148 in total).
Analysis of the effects of treatment.
The statistical analysis of our study will follow intention-to-treat principles.36 The normality of the data will be tested by visual inspection of histograms, and the characterization of the participants will be calculated using descriptive statistical tests. The between-group differences (effects of treatment) and their respective 95% confidence intervals will be calculated by constructing mixed linear models37 using interaction terms of treatment groups versus time. We will conduct a secondary exploratory analysis to assess whether patients classified as having derangement syndrome have a better response to the McKenzie method (compared with placebo) than those with other classifications. For this assessment, we will use a 3-way interaction for group, time, and classification. For all of these analyses, we will use the IBM SPSS software package, version 19 (IBM Corp, Armonk, New York).
Ethics
This study was approved by the Research Ethics Committee of the Universidade Cidade de São Paulo (#480.754) and prospectively registered at ClinicalTrials.gov (NCT02123394). Any protocol modifications will be reported to the Research Ethics Committee as well as to the trial registry.
Discussion
Potential Impact and Significance of the Study
The existing randomized controlled trials investigating the McKenzie method in patients with chronic low back pain have all used an alternative intervention as the comparison group.14–17 To date, no study has compared the McKenzie method with a placebo treatment in patients with low back pain in order to identify its real efficacy, which is an important gap in the literature.9 Interpretation of the previous comparative effectiveness studies is limited by the lack of knowledge of the efficacy of the McKenzie method for people with chronic low back pain. This study will be the first to compare McKenzie method with placebo therapy in patients with chronic nonspecific low back pain. A proper comparison against a placebo group will provide more unbiased estimates of the effects of this intervention. This type of comparison has already been done in trials aiming to assess the efficacy of motor control exercises for patients with chronic low back pain,31 spinal manipulative therapy and diclofenac for patients with acute low back pain,38 and exercise and advice for patients with subacute low back pain.39
Contribution to the Physical Therapy Profession and for Patients
The McKenzie method is one of the few methods used in physical therapy that advocates for the independence of patients.8,12 This method also provides patients with tools to promote their autonomy in managing the current pain and even future recurrences.12 We expect that patients treated with the McKenzie method will benefit more than the patients treated with the placebo treatment. If this hypothesis is confirmed in our study, the results will contribute to better clinical decision making of physical therapists. Moreover, the approach has the potential to reduce the burden associated with the recurrent nature of low back pain if patients can better self-manage future episodes.
Strengths and Weaknesses of the Study
This trial contemplates a substantial number of patients to minimize bias, and it was prospectively registered. We will use true randomization, concealed allocation, blinded assessment, and an intention-to-treat analysis. The treatments will be conducted by 2 therapists who were extensively trained to perform the interventions. We will monitor the home exercise program. Unfortunately, due to the interventions, we will not be able to blind the therapists to the treatment allocation. It is known from the literature that the McKenzie method yields beneficial results when compared with some clinical interventions in patients with chronic low back pain.14–17 To date, however, no studies have compared the McKenzie method with a placebo treatment in order to identify its actual efficacy.
Future Research
The intention of this study group is to submit the results of this study to a top-level, international peer-reviewed journal. These published results may provide a basis for future trials that investigate the effectiveness of the McKenzie method when delivered at different doses (different numbers of sets, repetitions, and sessions), which is still unclear in the literature. Our secondary exploratory analysis aims to assess whether patients classified as having derangement syndrome have a better response to the McKenzie method (compared with placebo treatment) than those with other classifications. This assessment will contribute to a better understanding of possible subgroups of patients with chronic low back pain who respond best to specific interventions. This is an important issue, as exploring subgroups is currently considered the most important research priority in the field of low back pain.40
Footnotes
All authors provided concept/idea/research design and writing. Mr de Almeida and Mr de Souza provided data collection, participants, and facilities/equipment. Dr L.O.P. Costa provided data analysis and institutional liaisons. Ms Garcia and Dr L.O.P. Costa provided project management. Dr L.C.M. Costa provided fund procurement. Ms Garcia and Dr L.C.M. Costa provided consultation (including review of the manuscript before submission). The authors thank Research Foundation of São Paulo (FAPESP) (grant number 2013/20075-5) for funding the study.
This study was fully funded by São Paulo Research Foundation (FAPESP) (grant number 2013/20075-5). Ms Garcia is funded by a scholarship from the Coordination for the Improvement of Higher Education Personnel/Brazilian Government (CAPES/Brazil).
The study was prospectively registered at ClinicalTrials.gov (trial registration: NCT02123394).
- Received May 6, 2014.
- Accepted September 26, 2014.
- © 2015 American Physical Therapy Association
References
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