We conducted a double-blind placebo-controlled randomized clinical trial in which 30 patients with pain attributed to carpal tunnel syndrome had either a 1000 gauss magnet or a placebo metal disk applied to the carpal tunnel area using a Velcro wrap for a period of 45 minutes. Pain was measured on a visual analogue scale using 0 and 10 as anchors.
Presenting symptoms including numbness, tingling, burning, and pain did not differ significantly between the 2 groups. There was significant pain reduction across the 45-minute period for both groups. However, t test comparisons found no significant differences between the groups for beginning pain, pain at 15 minutes, pain at 30 minutes, or pain at 45 minutes. The use of a magnet for reducing pain attributed to carpal tunnel syndrome was no more effective than use of the placebo device.
Four recent randomized trials have provided conflicting results concerning the efficacy of magnets in relieving pain. Two double-blind randomized trials have found that magnets relieve pain in postpolio subjects1 and in patients with postoperative wounds.2 However, double-blind randomized studies of magnet therapy for treatment of low back pain3 and foot pain4 showed no benefit.
In an attempt to find alternate forms of therapy,5,6 many chronic sufferers of carpal tunnel syndrome have resorted to using magnets to alleviate their symptoms. The purpose of our study was to determine the efficacy of magnet therapy on pain attributed to carpal tunnel syndrome when compared with a placebo device.
We contacted 160 patients who had wrist pain attributed to carpal tunnel syndrome by their primary care physicians. These patients were identified from the billing databases at a university-operated family practice clinic and a rural private practitioner’s office. The inclusion criteria for participation were presence of chronic wrist pain in the area of the carpal tunnel and the willingness to accept randomization into treatment or control group. Individuals were excluded before randomization if the source of pain had been attributed to some cause other than carpal tunnel syndrome, if they had taken pain medication within 4 hours of beginning treatment, if their body mass index was greater than 35, or if they were not experiencing pain at the time treatment was started.
The magnets and placebo devices used in our study were custom made by Medical Magnetics of Houston, Texas. The devices consisted of 5 stacked magnetic pads. Four of these were flexible (2500 gauss, residual induction). The fifth pad was a neodymium disk (10,000 gauss, residual induction). The flexible pads were 1.7 inches in diameter, and the neodymium disk was 0.5 inches in diameter. All 5 pads were glued together to form a single unit. Actual magnetic energy was determined to be 1000 gauss at the surface of the center of the magnet, and depth of penetration was estimated to be adequate for the carpal tunnel area. The placebo disks appeared identical to the magnets. Each magnet and placebo was labeled with a computer-generated random number, wrapped in foam, and boxed individually. Individual boxes were selected at the time of the patient appointment without regard for the order or numerical identifier, which served as a blinding device. Codes identifying placebo or control were not broken until the completion of the study.
After giving written consent, patients were asked to complete a short questionnaire collecting demographic and symptom information. They were then asked to rate the pain at the most painful point in the wrist using the visual analog scale (VAS) of the McGill Pain Questionnaire.7 The VAS consisted of a standard length line labeled 0 on the left and 10 on the right. The patient was instructed to place a mark on that line at the appropriate position relative to the degree of pain experienced (0 = no pain; 10 = the worst pain ever experienced). The distance of the mark from 0 was then measured in millimeters to provide the pain score. A new pain scale was provided for each measurement, and patients were not allowed to view previous measurements, to insure the objectivity of the patient’s pain perception.
A device, either magnet or placebo, was then placed on the wrist overlying the carpal tunnel. The device was secured with foam and a wrist bracelet fastened with Velcro. Each patient was then asked to remain seated and to keep the device in place for the next 45 minutes. This time period was selected based on the experience of the postpolio pain trial.1 Throughout the 45 minutes a research assistant observed the patients to ensure that they did not tamper with their device. The patients were asked to rate their pain on the VAS at 15-minute intervals. After 45 minutes the device was removed, and the patient again rated his or her pain on a VAS.