מתוך medicontext.co.il
By Faith Reidenbach
NEW YORK (Reuters Health) – Among patients with knee osteoarthritis, the response to needle tidal interarticular irrigation is no greater than the response to sham irrigation, according to the results of a randomized, double-blinded study conducted at Indiana University, in Indianapolis.
"This study emphasizes that medical procedures, and particularly invasive procedures, have substantial placebo effects, and that these placebo effects may obscure the actual benefits of the procedure, if any," first author Dr. John D. Bradley told Reuters Health.
Irrigation of the osteoarthritic knee has been presumed to work by removing inflammatory and/or abrasive debris, Dr. Bradley and colleagues note in the January issue of Arthritis & Rheumatism. However, no adequately designed and powered placebo-controlled or sham-controlled study has ever been reported, they say.
Dr. Bradley's group devised a sham procedure whereby a needle was advanced to the joint capsule but not through it, and a small amount of saline was clysed into subcutaneous tissue while the rest was expelled through tubing. The researchers randomized 180 ambulatory patients with knee osteoarthritis to one tidal irrigation treatment or sham irrigation.
All but three study subjects completed the 12 months of follow-up. In comparing the two groups, Dr. Bradley's team observed "essentially identical improvement" at all time points with regard to global score and subscale scores on the Western Ontario and McMaster Universities Osteoarthritis Index, time required to walk 50 feet, and knee swelling and tenderness.
"Although it is possible that a sham procedure might have such a powerful placebo effect that a truly effective 'actual' procedure would not demonstrate superiority, that seems unlikely in this study because the magnitude of improvement in both treatment groups was modest (<30% relative to baseline, <20% of the outcome instrument scale) and improvement was slightly greater in the sham irrigation group than in the tidal irrigation group," the investigators remark.
Asked whether physicians might exploit the placebo effect and use tidal irrigation anyway, Dr. Bradley replied, "First, there is some risk associated with the procedure. Second, it is time-consuming, particularly for the physician, who would probably be reimbursed only for a joint aspiration. Third, there is an ethical issue regarding how such a procedure would be presented to the patient; if the patient was told that the aim was a placebo effect, there would probably be little or no benefit."
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