Spinal Manipulative Therapy for Low Back Pain

Context The role of spinal manipulation in the treatment of low back pain remains controversial, possibly because previous summaries of the evidence have compared spinal manipulation with a combination of traditional therapies rather than with individual therapies. Contribution This meta-analysis of randomized clinical trials found that spinal manipulation was more effective than sham therapy but was no more or less effective than general practitioner care, analgesics, physical therapy, exercise, or back school. Implications While some patients with low back pain may prefer spinal manipulation to traditional therapies, there is no evidence that it achieves better outcomes than standard treatments. The Editors Low back pain is a disabling disorder that greatly affects western society; it is a burden for the individual patient and an additional cost for society because of loss of work and medical expenses (1, 2). Therefore, adequate treatment of low back pain is an important issue for patients, treating clinicians, and health care policymakers. Spinal manipulative therapy is widely used for low back pain. It has been studied in many randomized, controlled trials (RCTs), which are heterogeneous in size, design, and quality of performance. These trials have been summarized in numerous systematic reviews (3). The conclusions of systematic reviews (4-6), which provided input for national guidelines, are partially discordant. None of these reviews has included the larger high-quality trials that have been published over the past few years (7-16). Furthermore, all of these reviews and meta-analyses have considered the treatments to which spinal manipulative therapy is being compared as equivalent, meaning, for example, that no distinction was made among studies comparing spinal manipulative therapy with bed rest and studies comparing spinal manipulative therapy with physical therapy. Only two recent reviews (17, 18) compared spinal manipulative therapy with a homogeneous control group (sham treatment in both reviews). Spinal manipulation has a prominent role in all national guidelines on the management of back pain (19). However, the recommendations in these guidelines vary. In most countries, spinal manipulative therapy is recommended for acute low back pain. However, in the Netherlands, Australia, and Israel, the evidence is interpreted differently (19). Recommendations also vary for chronic low back pain; spinal manipulative therapy is recommended in the Danish and Dutch guidelines but is not recommended or is absent in the other national guidelines. Our goal in this review is to update, improve, and resolve inconsistencies in previous systematic reviews through collaboration with the Cochrane Back Review Group (20). We incorporate relevant clinical variables and combine them with meta-analytic techniques to estimate the effectiveness of spinal manipulative therapy relative to other commonly used therapies (21). By presenting the most current information on this complicated issue, we provide support for individual and collective treatment decisions. Methods Literature Search One reviewer searched the following computerized bibliographic databases without language restrictions (22, 23): MEDLINE from January 1966 to January 2000, EMBASE from January 1988 to January 2000, and CINAHL from January 1982 to January 2000. The highly sensitive Cochrane Collaboration search strategy, which aims to identify all randomized, controlled trials, was used (20, 24). The same reviewer also searched for systematic reviews on low back pain and spinal manipulation (25). Additional specific subject headings and free text words were used to identify papers on low back pain and spinal manipulation (20). The Cochrane Controlled Trial Register was searched (24). Finally, references from retrieved articles were screened. To determine whether a study should be included, the abstracts of all identified papers were assessed by the same reviewer who performed the computerized bibliographic search. If there was any doubt, the full article was retrieved and read independently by both reviewers. Disagreements were resolved by consensus. Literature Selection We included studies that met the following conditions: 1) adult patients with low back pain, regardless of radiation pattern; 2) comparison of manipulation or mobilization for low back pain with another treatment or control [manipulation differs from mobilization in that it focuses on a different range of motion of the involved joint; unless otherwise indicated, spinal manipulative therapy refers to both hands-on treatments in this review; co-interventions were allowed]; 3) at least one clinically relevant outcome measure (pain, global improvement, back painspecific functional status, or generic functional status) [26]; 4) follow-up of at least 1 day; 5) publication as a full report before January 2001. Quality Assessment Quality can be assessed by using different checklists or scales. We used the quality list from the Cochrane Back Review Group (20) to assess methodologic quality. This list contains items relevant to the description, internal validity, and statistical issues of the study (Table 1). Each criterion was rated as positive, negative, or inconclusive (insufficient information presented). Equal weights were applied, resulting in a total score for internal validity of each study, by adding the number of positive criteria (range, 0 to 10); higher scores indicated a lower likelihood of bias. In addition, we scored the list of Jadad and colleagues (27, 28). We used multiple criteria and scales because of the absence of a consensus on a gold standard for quality, especially for interventions such as spinal manipulative therapy, for which true double-blinding is not feasible. Table 1. Criteria for the Methodologic Assessment of Randomized Clinical Trials (Cochrane Back Review Group and Editorial Board Quality List) The articles were not blinded for authors, journal, or year of publication (27) because the two reviewers were familiar with most of the articles from their previous reviews. Included articles were independently assessed for methodologic quality by the two authors. Disagreements were discussed and resolved in a consensus meeting. Data Extraction Data were independently extracted by the two reviewers and checked for accuracy by two other authors. Statistical Analysis We briefly describe the analysis here. The Appendix describes the analysis in detail. We classified studies by the duration of back pain (acute, chronic, mixed, and unsure), presence of leg pain, profession of manipulator, comparison therapy, outcome measured, and follow-up time. Short-term follow-up was less than 6 weeks; for the meta-analysis, we chose the outcome measurement closest to 3 weeks. Long-term follow-up was more than 6 weeks; for the meta-analysis, we chose the outcome measurement closest to 6 months. For each study that had data available for each of the four outcomes (short-term pain, long-term pain, short-term function, and long-term function), we calculated the effect sizes of the changes in outcome between the reference spinal manipulative therapy group and all comparison therapy groups in the study. An effect size is the ratio of the difference in mean outcomes between the spinal manipulative therapy and comparison therapy groups divided by its standard deviation; it is a unitless measure of comparison for results reported by using different measurement scales (for example, pain measured by using a 100-mm visual analogue scale [VAS] or a 7-point pain rating scale). A positive effect size indicates that spinal manipulative therapy was beneficial, that is, function increased or pain decreased, as compared with the alternative therapy. For each outcome, we assessed the degree of heterogeneity in all effect sizes within each back pain stratum by use of a forest plot and chi-square test (29). Ideally, we would have liked to compare spinal manipulative therapy with each different therapy for each outcome within each back pain stratum, but this was not possible because the data were sparse. Therefore, we used available research evidence and the clinical judgment of similar effectiveness of the Editorial Board of the Cochrane Back Review Group to group the comparison therapies into the following clusters of presumed effectiveness: 1. Sham: Used to assess efficacy rather than effectiveness. 2. Conventional general practitioner care and analgesics: Although general practitioners may suggest other therapy for back pain in addition to prescribing medication, empirical evidence shows that 80% of initial visits to primary care providers for back pain result in an analgesic prescription (38); consequently, we considered these two categories sufficiently similar to pool. 3. Physical therapy and exercise: Both are considered to be activating therapies; in general, exercises are often a key component of physical therapy, making up 30%, 33%, and 100% of the treatment delivered in three studies of physical therapy for patients with low back pain (7-10, 39). 4. Traction, corset, bed rest, home care, topical gel, no treatment, diathermy, and minimal massage: Treatments that were considered to lack evidence of benefit or have evidence of harm (40). 5. Back school: Treatments that did not conceptually fit with any other group. For each outcome, we fit a random-effects meta-regression (33) model, in which effect size is the unit of observation, to compare the effect of spinal manipulative therapy with that of alternative therapies while controlling for other variables. The model contained indicator variables for the five alternative therapy clusters and main effects for duration of back pain (chronic, acute, mixed, or unsure). Although we also developed estimates for patients with mixed pain patterns and unsure, we do not present them because the number of studies was too small. We also fit a series of models with increas