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By Yoon-Hang Kim, MD, MPH, DABMA
Back pain is the fifth most common reason for all physician visits.1 The direct health care expenditure for treating back pain is estimated to be more than $20 billion annually and as much as $50 billion per year when indirect costs are included.2 In the United States, 90% of adults experience back pain at some time in their lives, and 50% of the working population complains of back pain annually.3,4
Conventional medical approaches to back pain range from conservative management with non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy modalities to invasive interventions such as epidural steroid injection and back surgery.
Acupuncture is one of the most popular forms of complementary and alternative medicine and is rapidly gaining acceptance. In 1997, the NIH consensus panel concluded that acupuncture is effective for adult postoperative and chemotherapy-related nausea and vomiting and probably for the nausea of pregnancy.5 Furthermore, the panel concluded that there are reasonable studies showing relief with acupuncture on such diverse pain conditions as menstrual cramps, tennis elbow, and fibromyalgia.5
Mechanism of Action
Acupuncture analgesia is one of the most thoroughly researched physical modality in medicine and serves as a general model for basic science acupuncture research.6 Studies using animal and human subjects to evaluate acupuncture analgesia were started in China in 1965, and continue throughout the world to this day.
It is widely believed that acupuncture analgesia is initiated by stimulation of small diameter nerves in muscles, which send impulses to the spinal cord, midbrain, and pituitary gland, resulting in the release of neurotransmitters such as monoamines and endorphins, which in turn block pain signal transduction.6 The discovery of naloxone, an endorphin antagonist, helped elucidate the role of endorphins in acupuncture. Naloxone was shown to block acupuncture analgesia in human volunteers in a randomized, double-blind study.7 A subsequent study produced the same results, fashioned a dose-response curve for naloxone, and found that increasing doses created increasing blockade.8
In addition to endorphins, monoamines such as serotonin and norepinephrine have been shown to be involved in acupuncture analgesia. Microinjections of serotonin antagonists and norepinephrine antagonists have blocked the effect of acupuncture analgesia.9,10
It is likely that endorphins and monoamines represent but two classes of molecules involved in acupuncture analgesia, and that other classes of molecules also may be linked to this cascade.
In the West, acupuncture is most commonly used for the treatment of chronic pain, particularly musculoskeletal complaints. While there are many randomized controlled trials (RCTs) evaluating the effectiveness of acupuncture for back pain, the majority display poor quality, and provide conflicting evidence. One way to efficiently evaluate the confusing data is through the use of systematic review, applying scientific strategies in ways that limit bias. Two systematic reviews of acupuncture for back pain are summarized in Table 1.
Ernst and White selected 12 studies and pooled data from nine for meta-analysis.11 The primary outcome measure for the meta-analysis was numbers of patients whose symptoms were improved at the end of the treatment. The odds ratio of improvement with acupuncture compared with the control intervention was 2.30 (95% confidence interval [CI], 1.28-4.13). For sham-controlled, evaluator-blinded studies, the odds ratio was 1.37 (95% CI, 0.84-2.25). Ernst and White concluded that although acupuncture was shown to be superior to various control interventions, there was insufficient evidence to state whether it is superior to placebo.
van Tulder et al performed a qualitative review by assessing the methodological quality and outcome of the original studies and attributing levels of evidence to the effectiveness of acupuncture.12 Eleven RCTs were included in the review, but only two were determined to be high quality. In eight of the 11 trials, the individual authors had concluded that acupuncture provided benefits beyond those noted for the control group. In the remaining three trials they had concluded that acupuncture’s effectiveness was similar to the control group. By contrast, van Tulder et al disagreed with the original authors’ conclusions in seven of the 11 studies, stating that there was no difference between acupuncture and control in seven trials and that acupuncture was superior in only two of the 11 trials. The results were unclear in the remaining two trials.
In summary, conclusions of the primary authors were positive for eight of 11 studies and the conclusions of van Tulder et al were positive for only two of the 11 studies. van Tulder et al concluded that they would not recommend acupuncture as standard treatment for patients with low back pain and that there is a need for high-quality RCTs.
Methodological Challenges of Systematic Reviews
Many challenges face acupuncture researchers including having a solid foundational research base, non-specific (placebo) effect of needle insertion, and a lack of reliable and valid research protocols. A wide range of acupuncture styles exists including microsystems acupuncture (i.e., auricular, scalp, and hand acupuncture), French energetics, neuroanatomic acupuncture, five elements acupuncture, and traditional Chinese approaches to acupuncture. The differences of these styles are understood by its practitioners, but rarely are taken into account in systematic reviews.
The fact that Ernst and White11 and van Tulder et al12 included almost the same studies, yet arrived at opposite conclusions, attests to the difficulty of evaluating the existing evidence. The major difference is that Ernst and White utilized a statistical approach (meta-analysis) while van Tulder et al used qualitative analysis. Both authors agreed that more high-quality RCTs are needed.
Recent Clinical Trials
Several recent RCTs not included in the two systematic reviews are summarized below and in Table 2.
A study by Ghoname et al utilized percutaneous electrical nerve stimulation (PENS) acupuncture, a contemporary neuroanatomic style of acupuncture utilizing trigger points and electric stimulation.13 Ghoname et al demonstrated PENS acupuncture to be more effective in decreasing visual analog scale (VAS) pain score compared to sham, transcutaneous electrical nerve stimulation (TENS), and exercise. Additional benefits included decreased medication use and improved physical activity, quality of sleep, and sense of well-being (P < 0.05 for each). A weakness of the study is that the patients (n = 60) were divided into four groups leaving a small number of subjects for each treatment arm.
In a study published in 2004, Sator-Katzenschlager et al compared auricular acupuncture and auricular electro-acupuncture.14 Although both groups showed improvement during the observation period, the pain relief was significantly better in the auricular electro-acupuncture group than in the conventional auricular acupuncture group (P < 0.001). In addition, psychological well-being, physical activity, and quality of sleep during the six-week acupuncture treatment and follow-up were significantly improved in the auricular electro-acupuncture group compared to the conventional auricular acupuncture group (P < 0.05).
In another study, Meng et al compared medical treatment with acupuncture.15 The acupuncture group showed significant improvement in the Roland Disability Questionnaire (P = 0.001). Effects were maintained for up to four weeks after treatment (P = 0.007). Kerr et al conducted a similarly designed study comparing TENS and acupuncture.16 The result showed overall improvement of back pain in both groups; however, no differences between the two groups were observed. Both studies failed to control for potential placebo response resulting from needle insertion (by using sham acupuncture, for example). The fact that both acupuncture and TENS benefited back pain patients and no difference was observed between groups means both may be acceptable for treating back pain. Other studies document similar findings.17
In 2002, Leibing et al compared physical therapy, acupuncture, and sham acupuncture.18 At the end of the treatment phase, acupuncture was superior to the control intervention (physiotherapy) regarding pain intensity (P < 0.001), pain disability (P < 0.001), and psychological distress (P = 0.020). However, no differences were observed between sham acupuncture and acupuncture. The authors concluded that a non-specific or placebo effect had been shown through this trial.
Molsberger et al conducted a study comparing a combination of acupuncture and conservative orthopedic treatment (OT) vs. sham acupuncture + OT vs. OT.19 Percent improvements after three months appear below:
The effects were significant for acupuncture + OT over sham acupuncture + OT (P < 0.001) and over OT (P < 0.001). While Leibing et al18 attributed the benefits of acupuncture to a non-specific effect, Molsberger et al19 and Ghoname et al13 demonstrated a difference between sham and true acupuncture.
Cherkin et al conducted a trial comparing acupuncture, massage, and self-education for treatment of lower back pain.20 At 10 weeks, massage was superior to self-care on both symptom and disability scales (P = 0.01). The massage group used the least medications (P < 0.05) and had the lowest costs of subsequent care. The authors concluded that the therapeutic massage was effective for persistent low back pain and traditional Chinese medical acupuncture was relatively ineffective.
Gadsby and Flowerdew concluded that electro-acupuncture and TENS reduce pain and improve range of motion in chronic back pain patients in their Cochrane Database System Review.21 Carlsson and Sjolund conducted a RCT comparing acupuncture and mock TENS, concluding that a significant decrease in pain intensities occurred at one and three months in the acupuncture group compared with the mock TENS group.22
Another study by Giles and Muller compared acupuncture, medication, and spinal manipulation and concluded that manipulation results in greater short-term improvement than acupuncture or medication.23
Cherkin et al performed a review of evidence for the effectiveness, safety, and cost of acupuncture, massage therapy, and spinal manipulation for back pain utilizing existing systematic reviews and updated literature.24 The conclusions reached by Cherkin et al are summarized in Table 3.
Table 3: Conclusions of Cherkin et al24
Notably, the review by Cherkin et al24 left out at least four acupuncture RCTs documenting positive results and categorized Grant et al17 as a negative study when the results showed that both TENS and acupuncture showed positive effects.
An abundant amount of conflicting information exists on the efficacy of acupuncture for treating back pain. The waters are muddied further by systematic reviews that arrived at opposite conclusions while analyzing almost identical studies. Despite the lack of clear clinical evidence, basic science research shows plausible mechanisms of action for acupuncture with respect to reducing pain.
Back pain is a prevalent medical problem with huge social, economical, and medical implications. While most patients with back pain improve, a segment of the patient population requires intensive therapy or invasive procedures including surgery.
Given the low risk of acupuncture and existing range of therapeutic options, a trial of acupuncture should be considered a potentially useful option for some patients with persistent back pain.
Dr. Kim is a Fellow in the Program in Integrative Medicine at the University of Arizona in Tucson.
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