Spinal manipulative therapy for chronic low‐back pain
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
The objective of this review is to determine the effectiveness of spinal manipulation and mobilization for chronic low‐back pain.
We wish to test the following specific hypothesis:
Spinal manipulation and mobilization, either alone or in combination with another intervention results in better short‐ or long‐term outcomes compared to control treatments for patients with chronic low‐back pain as determined by percentage of patients recovered or numbers of patients with diminished pain and improved functional capacity.
Background
Low‐back pain is a common and disabling disorder in western society, which represents a great financial burden in the form of direct costs resulting from loss of work and medical expenses, as well as indirect costs (Dagenais 2008). Therefore, adequate treatment of low‐back pain is an important issue for patients, treating clinicians, and healthcare policy makers. To that end, spinal manipulative therapy is widely used for low‐back pain, which has been examined in many randomised controlled trials (RCTs). These trials have been summarized in numerous recent systematic reviews (Brønfort 2004; Brown 2007; Brox 1999; Cherkin 2003), which have formed the basis for recommendations in clinical guidelines (Airaksinen 2004; Chou 2007; Manchikanti 2003; Staal 2003; van Tulder 2006; Waddell 2001). Most notably, these guidelines are largely dependent upon an earlier version of this Cochrane review (Assendelft 2003; Assendelft 2004). That review concluded that spinal manipulative therapy was moderately superior to sham manipulation and therapies thought to be ineffective or harmful; however, the effect sizes were small and arguably not clinically relevant. Furthermore, spinal manipulative therapy was found to be no more effective than other standard therapies (e.g. general practitioner care, analgesics, exercise, or back schools) for short or long‐term pain relief or functional improvement.
Despite these findings, spinal manipulation has a prominent role in many national guidelines on the management of back pain (Koes 2001; van Tulder 2004); however, these recommendations vary. For example, spinal manipulative therapy is considered to be a therapeutic option in the acute phase of low‐back pain in many countries, while in other countries, such as the Netherlands, Australia, and Israel this is not recommended (Koes 2001). Similarly, spinal manipulative therapy is considered to be a useful option in the Danish and Dutch guidelines, but is either not recommended or is absent in the other national guidelines.
Our goal is to update the previous Cochrane systematic review following the most recent guidelines developed by the Cochrane Collaboration, in general and by the Cochrane Back Review Group, in specific (Furlan 2009; Handbook 5 2008). In contrast to the previous Cochrane review, the reviews have been split into two by duration of the complaint, namely acute and chronic low‐back pain. The current review is to report on chronic low‐back pain.
Description of the condition
Low‐back pain is defined as pain and discomfort, localised below the costal margin and above the inferior gluteal folds, with or without referred leg pain (Airaksinen 2004). Chronic low‐back pain is typically defined as pain persisting for more than 12 weeks. For the purposes of this review, studies will be included where the mean duration of the low‐back pain at baseline is greater than 12 weeks. Non‐specific low‐back pain is further defined as low‐back pain not attributed to recognisable, known specific pathology (e.g. infection, tumour, fracture, radicular syndrome or cauda equine syndrome) (van Tulder 2006).
Description of the intervention
Spinal manipulative therapy is considered here as any hands‐on treatment and includes both manipulation and mobilization (Assendelft 2003; Assendelft 2004). Mobilizations use low‐grade velocity, small or large amplitude passive movement techniques within the patient's range of motion and control. Manipulation, on the other hand, uses a high velocity impulse or thrust applied to a synovial joint over a short amplitude at or near the end of the passive or physiologic range of motion, which is often accompanied by an audible “crack” (Sandoz 1969). The cracking sound is caused by cavitation of the joint, which is a term used to describe the formation and activity of bubbles within the fluid (Evans 2002; Unsworth 1971). Various practitioners, including chiropractors, manual therapists (physiotherapists trained in manipulative techniques), orthomanual therapists (medical doctors trained in manipulation) or osteopaths use this intervention in their practices. However, the diagnostic techniques and philosophy of the various professions differ. The focus of orthomanual medicine is on abnormal positions of the skeleton and symmetry in the spine, while manual therapy focuses on functional disorders of the musculoskeletal system, and chiropractic focuses on the musculoskeletal and nervous systems in relation to the general health of the patient (van de Veen 2005).
How the intervention might work
Many hypotheses exist regarding the mechanism of action for spinal manipulation and mobilization (Brønfort 2008; Khalsa 2006; Pickar 2002), and some have postulated that mobilization and manipulation should be assessed as separate entities given their theoretically different mechanisms of action (Evans 2002). The modes of action might be roughly divided into mechanical and neurophysiologic. The mechanistic approach suggests that spinal manipulative therapy acts on a manipulable lesion (often called the functional spinal lesion or subluxation) which proposes that forces to reduce internal mechanical stresses will result in reduced symptoms (Triano 2001). However, given the non‐nociceptive behaviour of chronic low‐back pain, a purely mechanistic theory alone cannot explain clinical improvement (Evans 2002). Much of the literature focuses on the influence on the neurological system, where it is suggested that spinal manipulation therapy impacts the primary afferent neurons from paraspinal tissues, the motor control system and pain processing (Pickar 2002), although the actual mechanism remains debatable (Evans 2002; Khalsa 2006).
Why it is important to do this review
Spinal manipulative therapy is a worldwide, extensively practiced intervention provided by a variety of professions. The efficacy of this therapy for chronic low‐back pain is, however, not without dispute. This review with its comprehensive and rigorous methodology is thought to provide better insight to this problem. Although numerous systematic reviews have examined efficacy of spinal manipulative therapy for low‐back pain (Chou 2007; Airaksinen 2004), very few have conducted a meta‐analysis, especially for chronic low‐back pain. The previous version of the Cochrane review was published in 2003 and many new trials have been published since. Also, the methodology of systematic reviews has recently been updated (Furlan 2009; Handbook 5 2008).
Objectives
The objective of this review is to determine the effectiveness of spinal manipulation and mobilization for chronic low‐back pain.
We wish to test the following specific hypothesis:
Spinal manipulation and mobilization, either alone or in combination with another intervention results in better short‐ or long‐term outcomes compared to control treatments for patients with chronic low‐back pain as determined by percentage of patients recovered or numbers of patients with diminished pain and improved functional capacity.
Methods
Criteria for considering studies for this review
Types of studies
Only truly randomized studies will be included; studies with quasi‐random procedures (e.g. alternate allocation, birth dates) will be excluded.
Types of participants
Inclusion criteria
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adult participants (>18 years of age)
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mean duration of the current episode of low‐back pain is greater than 12 weeks for the study population.
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studies with patients from primary, secondary and tertiary care
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no limitations were placed on data regarding patients with or without radiating pain.
Exclusion criteria
Subjects with:
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post‐partum low‐back pain or pelvic pain due to pregnancy
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pain not related to the low‐back, e.g. coccydynia
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post‐operative studies or subjects with “failed‐back syndrome”
Studies on “maintenance” care or on prevention.
Studies which examine specific pathologies, such as sciatica.
Types of interventions
Experimental intervention
The experimental intervention to be examined in this review includes both spinal manipulation and mobilisation for chronic low‐back pain; unless otherwise indicated, spinal manipulative therapy refers to both hands‐on treatments.
Types of comparison
A study design will be used which suggests that the observed differences were due to the unique contribution of spinal manipulation or mobilization (i.e. which excludes studies with a multimodal treatment as one of the interventions and different type of intervention as the comparison therapy).
Comparison therapies are to be combined into the following main clusters:
1) spinal manipulative therapy versus no treatment or waiting list control
2) spinal manipulative therapy versus sham spinal manipulative therapy
3) spinal manipulative therapy versus all other therapies
4) spinal manipulative therapy in addition to any intervention versus the intervention alone.
Any other comparisons are to be considered secondary analysis.
Types of outcome measures
Primary outcomes
Only patient‐centered outcome measures are to be evaluated:
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pain expressed on a visual analogue or similar scale [e.g. visual analogue scale (VAS), numerical rating scale (NRS), McGill pain score]
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functional status, expressed on a back pain‐specific scale (e.g. Roland‐Morris Disability Questionnaire, Oswestry Disability Index)
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global improvement
Secondary outcomes
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Quality of life (on validated indexes, such as the SF‐36)
Physiological variables, such as spinal flexibility or degrees achieved with a straight leg raise test (i.e. Lasegue’s) are not considered clinically relevant outcomes and will not be evaluated.
Only studies with a follow‐up longer than 1 day are to be included.
Search methods for identification of studies
Electronic searches
We will identify RCTs and systematic reviews by electronically searching the following databases:
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The Cochrane Central Register of Controlled Trials (CENTRAL) from 2000‐2009 (Appendix 1)
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MEDLINE from 2000‐2009 (Appendix 2)
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EMBASE from 2000‐2009 (Appendix 3)
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CINAHL from 2000‐2009 (Appendix 4)
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PEDro up to 2009
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Index to Chiropractic Literature up to 2009
The search strategy developed by the Cochrane Back Group is to be followed using free text words and MeSH headings (Furlan 2009). A search will not be conducted for studies published before 2000 because they were included in the previous Cochrane reviewAssendelft 2003; Assendelft 2004).
Searching other resources
The following strategies will also be followed:
1) screen the reference lists of all relevant papers
2) search the main electronic sources of ongoing trials (National Research Register, meta‐Register of Controlled Trials; Clinical Trials).
Data collection and analysis
Selection of studies
Two review authors (SMR, MM) will independently screen the titles and abstracts from the search results. Potentially relevant studies will be obtained in full text and independently assessed for inclusion. Disagreements will be resolved through discussion. A third review author (MWvT) will be contacted if disagreements persist. Only full papers will be included. Abstracts will be excluded. Studies published in English, German, French and Dutch will be included because the authors are able to read and understand these languages. Trials published in other languages will be reported and included in a future update of the review if we are able to find translators for these papers.
Data extraction and management
A standardized data extraction form will be prepared and used to extract data from the included papers. Data extracted will include: study design (RCT), study characteristics (e.g. country, recruitment modality, study funding, risk of bias), patient characteristics (e.g. number of participants, age, sex, severity of low‐back pain at baseline), description of the experimental and control interventions, co‐interventions, duration of follow up, outcomes assessed and results. Data will be extracted independently by the same two review authors who are to conduct the selection of studies. Any disagreement will be discussed and a third review author consulted if necessary. Key findings will be summarized in a narrative format. Data relating to the primary outcomes will be assessed for inclusion in the meta‐analysis, where possible.
Assessment of risk of bias in included studies
The risk of bias assessment for RCTs will be performed using the 12‐criteria recommended by the Cochrane Back Review Group, which is to be evaluated independently by same two review authors who performed the search (SMR, MM). The criteria used are standard for all other interventions evaluating effectiveness for low‐back pain (Appendix 5; Furlan 2009; Handbook 5 2008). Admittedly, this may raise objections in some because blinding the practitioner, patient and therefore, also the outcome assessor, is nearly impossible. However, studies that do not fulfil these criteria items have a potential risk of bias. To drop these items from the assessment is to negate the observation that “blinding” provides less biased data.
The criteria will be scored as ’yes’, ’no’ or ‘unclear’ and will be reported in the Risk of Bias table. Any disagreement between the review authors will be resolved by discussion, including input from a third independent reviewer if required (MWvT). A study with a low risk of bias is to be defined as fulfilling six or more of these items, and subgroup analyses will be performed based upon this assessment. The reviewers will not be blinded to authors of the individual studies, institution or journal because they are familiar with the literature. All studies will subsequently be evaluated for risk of a fatal flaw. Quantitative data from those studies are not to be extracted; therefore, these data are to be excluded from the meta‐analyses.
Measures of treatment effect
A mean difference (MD) will be calculated for pain where a VAS or NRS is reported. All results for pain will be converted to 100‐points, where necessary. Given that a number of different instruments are typically used to measure functional status [e.g. Roland‐Morris Disability Questionnaire (RMDQ), Oswestry Disability Index (ODI)], a standardized mean differences (SMD) will be calculated. A negative effect size indicates that spinal manipulative therapy is more beneficial than the comparison therapy, meaning, subjects have less pain and better functional status. For dichotomous outcomes (i.e. recovery), a risk ratio (RR) will be calculated and the event will be defined as the number of subjects recovered. A random‐effects model will be used for all analyses. In those cases where more than two interventions are evaluated in the same study, a single “pair‐wise” comparison will be calculated, where this seems clinically logical. This step is necessary in order to correct for error introduced by “double‐counting” of subjects of “shared” interventions in the meta‐analyses. Funnel plots will be examined for publication bias. For each treatment comparison, an effect size and a 95% confidence interval (CI) will be calculated. All analyses will be conducted in Review Manager 5.0.
Dealing with missing data
In cases where data are reported as a median and interquartile range (IQR), it will be assumed that the median is equivalent to the mean and the width of the IQR is equivalent to 1.35 times the standard deviation (Handbook 5 2008, section 7.7.3.5) assuming the sample sizes are large and the distribution of the outcome is similar to the normal distribution. Where data are reported in a graph and not in a table, the means and standard deviations will be estimated. When standard deviations are not reported, these will be estimated from the confidence intervals if possible. If the standard deviation for follow‐up measurements is missing, the standard deviation for that measure at baseline will be used for subsequent follow‐up measurements. Finally, if no measure of variation is reported anywhere in the text, the standard deviation will be estimated based upon other studies with a similar population and risk of bias.
Assessment of heterogeneity
Heterogeneity will be explored by vision (eye‐ball test) and formally tested by the Q‐test (chi‐square) and I²; however, the decision regarding heterogeneity will be dependent upon the I² (Handbook 5 2008).
Data synthesis
The outcome measures from the individual trials will be combined through meta‐analysis where possible depending upon homogeneity between studies. The overall quality of the evidence and strength of recommendations is to be evaluated using GRADE (Guyatt 2008), which is recommended by the Cochrane Back Review Group (Furlan 2009). The quality of the evidence for a specific outcome is based on five principal domains: 1) limitations (due to risk of bias), 2) consistency of results, 3) directness (i.e. generalizability), 4) precision (sufficient data with narrow confidence intervals) and 5) other (e.g. publication bias). Single studies are considered to provide “low” or “very low quality evidence”, depending upon whether they are associated with a low or high risk of bias, respectively. The following levels of the quality of the evidence will be applied:
High quality: Further research is very unlikely to change the level of evidence and recommendations based upon consistent findings from at least two RCTs with low risk of bias and generalizable to the population in question. There are sufficient data with narrow confidence intervals. There are no known or suspected reporting biases.
Moderate quality: Further research is likely to have an important impact on confidence in the estimate of effect and may change the estimate; one of the domains is not met.
Low quality: Further research is very likely to have an important impact on confidence in the estimate of effect and is likely to change it; two of the domains are not met
Very low quality: Great uncertainty about the estimate; three of the domains are not met.
No evidence: No evidence from RCTs
Subgroup analysis and investigation of heterogeneity
Regardless of possible heterogeneity of the included studies, the following stratified analyses will be conducted: 1) by control groups as defined in types of intervention (see specifically types of comparisons); 2) by time, that is, short‐term (closest to 1 month), intermediate (closest to 6 months) and long‐term follow‐up (closest to 12 months); and 3) by type of low‐back pain (i.e. non‐specific low‐back pain, including subjects with radiating pain to the knee versus those subjects with pain below the knee or those with clear neurological deficit). If a study reports outcomes at three months only, these will be considered short‐term. Similarly, outcomes at nine months will be considered long‐term.
Sensitivity analysis
The following sensitivity analyses are pre‐planned and will be conducted in order to explain possible sources of heterogeneity between studies: 1) for risk of bias, 2) for studies with an adequate allocation procedure versus studies with no adequate or unclear allocation procedure; 3) by duration of the low‐back pain (studies which included subacute and chronic versus studies of exclusively chronic low‐back pain); 4) by type of technique (manipulation versus mobilization versus unspecified); 5) by type of manipulator (chiropractor, osteopath, or manual therapist).
The type of comparison therapy will be examined (therapies in which the patient receives treatment without their active involvement, e.g. massage versus those therapies in which the patient is an active participant, e.g. exercise).
