Accupuncture for knee pain (and two other articles)

In the Annals of Internal Medicine due out on December 21 are three “alternative medicine” articles.

The lead article, effectiveness of acupuncture as adjunctive therapy in osteoarthritis of the knee, randomized 570 patients with osteoarthritis of the knee to one of three interventions: a 26 week tapering schedule of acupuncture, sham acupuncture, or six 2-hour group sessions of education. The patients were evaluated at 4, 8, 14 and 26 weeks for improvement in five areas: a pain score, a function score, a global assessment score, a physical health score and a 6-minute walking distance test.

Acupuncture provided statistically significant benefit over sham acupuncture and over the education alone approach at 26 weeks in terms of the pain, function and global assessment scores. The authors conclude: “Acupuncture seems to provide improvement in function and pain relief as an adjunctive therapy for osteoarthritis of the knee when compared with credible sham acupuncture and education control groups.”

I have two comments to make about this paper. First, similarly to my remarks about the paper on effectiveness of vestibular rehabilitation for the treatment of vertigo, I would have liked to see some measure that expresses in plainer english the results of the study. What percentage of patients would, at the end of trial, consider repeating the therapy? How many would consider recommending it to their family or friends? Clearly there is a benefit, but it’s hard to contextualize that benefit, to get a handle on how clinically worthwhile it is.

A second point relates to the results themselves, presented in Table 2 of the paper. The change from baseline for all five measurements is reported for the three groups (true acupuncture, sham acupuncture and education) at weeks 4, 8, 14 and 26. Taking one example, the WOMAC pain score was approximately 8.95 at baseline in the three groups. At week 4, it improved by 2.22 in the true acupuncture group, by 1.98 in the sham acupuncture group and by 0.84 in the education group.

This means that the benefit of true acupuncture over education was 2.22-0.84 = 1.38. Similarly, the benefit of sham acupuncture over education was 1.98-0.84 = 1.14. In this case, if the benefit of true acupuncture over education was 1.38, and that of sham acupuncture over education was 1.14, then one might conclude that 1.14/1.38 = 83% of the benefit of true acupuncture was due to the placebo (sham acupuncture) effect. I realize that this may not be a statistically correct assumption, but I believe it does represent a reasonable approximation. I would love to hear what statisticians have to say about this.

At any rate, I performed the same calculation for the other results given in Table 4, and came up with the following numbers:

  • For the improvement in WOMAC pain score, at weeks 4, 8, 14 and 26, the percentages of the improvement attributable to placebo acupuncture were: 83%, 74%, 55% and 59%.
  • For the improvement in WOMAC function score, at weeks 4, 8, 14 and 26, the percentages attributable to placebo acupuncture were: 43%, 46%, 58% and 52%.
  • For the patient global assessment score, the corresponding percentages were: 50%, 38%, 52% and 0% (no effect from sham acupuncture).

Although these numbers are derived by me and may not be strictly correct, I think they do give an idea that about half of the benefit from acupuncture in this study was due to a generic placebo effect equivalent to sham acupuncture, and about half of the effect was specific to the real treatment. That’s not a bad overall result for acupuncture, considering how important the placebo effect is pain therapy.

Two other articles from the same issue:

Acupuncture versus placebo for the treatment of chronic mechanical neck pain was a single-blind randomized study comparing acupuncture with sham electrical stimulation of acupuncture points (placebo) for chronic neck pain. Although there was a statistically significant benefit of acupuncture over the placebo, this benefit was only of modest degree and felt to be not clinically significant.

More interesting was a clinical prediction rule to identify patients with low back pain most likely to benefit from spinal manipulation. The authors used a clinical prediction rule with 5 components:

  • length of current episode (component positive if < 16 days)
  • symptoms below the knee (absent)
  • level of fear of pain and avoidance of activity (low)
  • presence of hypomobile lumbar spine segments (at least one)
  • internal rotation at the hip (> 35 degrees)

When four out of five of these components were positive (about 1/3 of patients), there was a substantially better outcome with spinal manipulation than with exercise alone and also better than with spinal manipulation in the 2/3 of patients who did not score well on the prediction rule. The only problem I have with the applicability of this study is that the prediction rule was evaluated by a physical therapist. How easy it would be for primary practitioners to successfully perform the same evaluation is unclear to me.

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