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Bipolar permanent magnets for the treatment of chronic low back pain: a pilot study.

CONTEXT
Chronic low back pain is one of the most prevalent and costly medical conditions in the United States. Permanent magnets have become a popular treatment for various musculoskeletal conditions, including low back pain, despite little scientific support for therapeutic benefit.


OBJECTIVE
To compare the effectiveness of 1 type of therapeutic magnet, a bipolar permanent magnet, with a matching placebo device for patients with chronic low back pain.


DESIGN
Randomized, double-blind, placebo-controlled, crossover pilot study conducted from February 1998 to May 1999.


SETTING
An ambulatory care physical medicine and rehabilitation clinic at a Veterans Affairs hospital.


PATIENTS
Nineteen men and 1 woman with stable low back pain of a mean of 19 years' duration, with no past use of magnet therapy for low back pain. Twenty patients were determined to provide 80% power in the study at P<.05 to detect a difference of 2 points (the difference believed to be clinically significant) on a visual analog scale (VAS).


INTERVENTIONS
For each patient, real and sham bipolar permanent magnets were applied, on alternate weeks, for 6 hours per day, 3 days per week for 1 week, with a 1-week washout period between the 2 treatment weeks.


MAIN OUTCOME MEASURES
Pretreatment and posttreatment pain intensity on a VAS; sensory and affective components of pain on the Pain Rating Index (PRI) of the McGill Pain Questionnaire; and range of motion (ROM) measurements of the lumbosacral spine, compared by real vs sham treatment.


RESULTS
Mean VAS scores declined by 0.49 (SD, 0.96) points for real magnet treatment and by 0.44 (SD, 1.4) points for sham treatment (P = .90). No statistically significant differences were noted in the effect between real and sham magnets with any of the other outcome measures (ROM, P = .66; PRI, P = .55).


CONCLUSIONS
Application of 1 variety of permanent magnet had no effect on our small group of subjects with chronic low back pain.