Wednesday, August 29, 2012

Is Chiropractic for Low-Back Pain Effective?

Back PainLower back pain (LBP) is a common and costly musculoskeletal problem, affecting about 80% of all persons at some time in their lives. Many people with this condition seek the care of a chiropractor who may utilize a range of interventions such as spinal manipulation, massage, electrotherapy, mechanical devices, exercise, orthotics, and others. A recent large study found that chiropractic was effective in treating both acute and chronic LBP; however, there were considerable limitations of this study that question its external validity.

For this prospective cohort study adult patients with LBP who had not received chiropractic or manual therapy in the prior 3 months were recruited from multiple chiropractic practices in Switzerland [Peterson et al. 2012]. Patients were excluded if they had specific lumbar spine pathologies that are relative contraindications to chiropractic manipulative therapy, including tumors, infection, inflammatory spondyloarthropathies, fractures, severe osteoporosis, and Paget’s disease (bone deformities).

The purpose of the study was to evaluate outcomes in routine practice, so the 44 chiropractors volunteering to participate were allowed to administer their typical treatment methods (such as spinal manipulation, soft tissue mobilization, or others). Patients completed a numerical pain rating scale (NRS) and the Oswestry disability questionnaire at baseline immediately before treatment, and at 1 week, 1 month, and 3 months after the start of treatment. Subjects also self-reported perceived improvement on a Patient Global Impression of Change (PGIC) scale.

Writing in an early online edition of the Journal of Manipulative and Physiological Therapeutics, the researchers reported that 523 patients with acute LBP (<4 weeks duration prior to enrollment) and 293 with chronic LBP (>3 months) were included in study analyses. Patients with subacute LBP (>4 weeks to 3 months duration) were not assessed. At baseline, mean pain and disability scores were significantly higher in patients with acute LBP (P<0.001); although, mean pain scores for both cohorts on a 0-10 NRS were moderate: ≈6.0 (acute), ≈5.0 (chronic).

In both groups of patients, there were significant (P<0.0001) improvements in mean scores of pain and disability at 1 week, 1 month, and 3 months, although these change scores were significantly greater in the acute group at each followup point. The most consistent predictor of ongoing improvement in LBP over time was self-reported early improvement at 1 week after start of therapy. Whether or not patients had radiculopathy associated with their LBP at baseline did not appear to affect outcome success.

After 1 week of treatment, 65% of patients with acute pain and 32% with chronic pain reported that they were either “better” or “much better” on the PGIC assessment. And, these early responders to therapy were 4 to 5 times more likely to be improved at both 1 and 3 months compared with patients who were not similarly improved at 1 week.

In conclusion, the researchers observe that patients with acute LBP reported more severe pain and disability initially but recovered faster. However, patients with either chronic or acute LBP reported good outcomes, and most patients with radiculopathy also improved as a result of chiropractic therapy.

COMMENTARY: Jury Still Out on Chiropractic for LBP

This was a large-scale (ie, well-powered) study with an elaborate statistical analysis protocol. The outcome results favoring benefits of chiropractic will no doubt lead to this paper’s being frequently cited as evidence in future articles on this subject and reprints will probably appear on the literature tables at many chiropractic clinics. However, from an evidence-based pain management perspective, there are some strong limitations and potential biases of this study that challenge its quality and external validity.

  • There was a dual selection bias in this study. First, only 44 of 260 eligible chiropractors (17%) chose to participate, and the authors note that those practitioners might have self-selected themselves based on an interest in furthering research in the field. These also might have been practitioners who had achieved particular success in treating LBP in the past.

    The researchers do note that “certain practitioners seemed to obtain better patient outcomes compared with others”; however, the statistical influence of this subgroup of chiropractors on outcomes data and the characteristics defining their allegedly superior approaches — eg, practice environments, types of treatment and scheduling, communication styles, patient demographics, etc. — were not explored.

    Second, participating chiropractors were able to select patients at their convenience for inclusion in the study — a wide range of 5 to 85 patients were enrolled per chiropractic practice. The outcomes may have been strongly influenced toward favorable intervention effects by this sort of imbalanced and nonrandom selection process.

  • There was no standardization of therapeutic approach. The authors merely state that “it is likely that most patients were treated with diversified chiropractic spinal manipulation.” They concede that they do not know how many times patients were treated during the study period or specific details of the therapeutic interventions utilized.

  • There was no control group receiving either no chiropractic therapy or an alternate non-manipulative approach (eg, exercise or education alone) for comparison. Therefore, two confounding factors could have accounted for most, if not all, of the favorable outcome results: 1) the natural course of back pain resolution, and/or 2) placebo effects of chiropractic.

    The authors disclose that much of the improvement among patients with acute pain was likely “due to the natural history of LBP, and any specific treatment effects cannot be determined from a prospective cohort study of this type.” They still maintain, however, that observed improvements in patients with chronic LBP probably ensued beyond the point when natural recovery might occur.

    In subjects with chronic LBP, placebo effects might have played an especially important role. For example, effect sizes for NRS score improvements were considerably smaller in the chronic pain cohort, and placebo effects — which some authorities long ago estimated can exert as much as a 50% reduction in pain [see UPDATE here] — may have accounted for a significant proportion of the improvement. Without a control group, it is impossible to assess the magnitude of potential placebo effects.

  • Favorable outcomes reported in this study relied extensively on results from the Owestry pain and disability questionnaire. However, the authors disclose that this was “not the best outcome measure for this patient population, having been designed for more severe and surgical cases.” They acknowledge this instrument was used mainly because it was available in German and French translation, so these data might not be relevant or valid in this study.

  • At baseline, 44% of patients with acute pain and 28% of those with chronic pain were taking unspecified analgesics for their back conditions. Logistic regression analyses suggested this was not a significant statistical factor affecting outcome results; however, it is unknown whether concurrent analgesic regimens were increased, decreased, or eliminated in many patients after the start of chiropractic therapy and this could have been a confounding influence on overall outcomes. The researchers did not separately assess results in subgroups taking analgesics compared with those who did not.

  • Contrary to prior evidence, the presence of radiculopathy was not found to be a limiting factor in achieving beneficial effects of chiropractic in this study. However, diagnosis of radiculopathy — defined broadly as signs/symptoms of nerve root compression rather than just leg pain — was left up to the participating chiropractors, and it is unknown if all of them had necessary skills to accurately identify this disorder.

  • Finally, this study was funded in part by the European Academy of Chiropractic, and the researchers are engaged in the chiropractic field, so there is an obvious potential for vested interests and bias in study initiation, design, and interpretation. At the same time, however, it must be recognized that without such support chiropractic research would most likely not be done at all.

In sum, this was an interesting study, but due to the many limitations and potential sources of bias it represents a low quality of evidence for recommending chiropractic for acute or chronic low-back pain. In fact, there may be some concern regarding the quantity and quality of evidence in the chiropractic field overall to support the modality as effective for LBP.

In a fairly recently reported Cochrane review of evidence on this topic, a team of Australian researchers examined all randomized controlled trials comparing “combined chiropractic interventions” with no treatment or other therapies [Walker et al. 2011]. Combined chiropractic was defined as encompassing a range of therapies such as spinal manipulation, massage, heat and cold therapies, electrotherapies, the use of mechanical devices, exercise programs, nutritional advice, orthotics, lifestyle modification, and patient education. The primary interest was treatment in adults for nonspecific LBP that was acute (≤4 weeks duration) or subacute (>4 weeks to 3 months duration). Chronic LBP (>3 months) was not investigated.

The literature search discovered 12 qualifying studies involving 2,887 participants who received various combinations of chiropractic care for LBP, but only 3 of the trials were considered to be of good quality and have a low risk of bias. Based on outcomes data the researchers found that, while combined chiropractic interventions slightly improved pain and disability in the short term and pain in the medium term for acute and subacute LBP, the effect sizes were small and only seen in the lowest quality studies. Overall, the evidence was judged to be of poor quality.

Walker and colleagues [2011] concluded that there is currently no evidence to support or refute that combined chiropractic interventions provide a clinically meaningful advantage over other treatments for pain or disability in people with LBP. It is important to note that this review focused on a pragmatic approach — similar to that used in the above study by Peterson et al. 2012 — with chiropractic incorporating diverse and varied procedures as commonly occurs in everyday practice settings. So the evidence, as revealed in these two studies, does not necessarily repudiate the efficacy of any specific interventions, such as spinal manipulation, clinical massage, and so forth.

Certainly, further and better research is necessary to define the specific interventions and characteristics of chiropractors that might be most beneficial for treating low-back pain, whether acute, subacute, or chronic. Until then, it seems that this modality might be best considered with some circumspection.

REFERENCES:
> Peterson CK, Bolton J, Humphreys BK. Predictors of Improvement in Patients With Acute and Chronic Low Back Pain Undergoing Chiropractic Treatment. J Manip Physiol Ther. 2012(Aug 2), online ahead of print [
abstract here].
> Walker BF, French SD, Grant W, Green S. A Cochrane review of combined chiropractic interventions for low-back pain. Spine. 2011;36(3):230-242 [
abstract here].

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