Segal NA, et al. Two configurations of static magnetic fields for treating rheumatoid arthritis of the knee: a double-blind clinical trial. Arch Phys Med Rehabil 2001;82:1453-60.A randomized, double-blind, controlled, multicenter trial evaluated magnetic pads in 64 patients with rheumatoid arthritis and persistent knee pain rated > 40/100 mm. Patients were randomized to wear MagnaBloc quadrapolar 1900 G magnets, measured to penetrate 5 cm into cadaveric tissue (n=38), or unipolar 720 G control device containing 1 functional and 3 sham magnets (n=26). Rheumatologist's global assessment of disease activity (R-GADA), erythrocyte sedimentation rate (ESR) and/or C-reactive protein, knee range of motion (ROM), examination for tenderness and swelling, patients' assessment of physical function, 100mm VAS score for pain, subjects' global assessment of disease activity (S-GADA), and the Modified Health Assessment Questionnaire (MHAQ) were measured at baseline, 1 hour, 1 day, and 1 week after placement of devices. Patients were asked to keep a pain diary. Both treatment arms showed a significant reduction in pain from baseline at 1 day and 1 week post-treatment (p<.0001). Though the MagnaBloc group showed a greater reduction in pain, the difference was not statistically significant (p<.23). S-GADA decreased significantly at 1 week in the MagnaBloc group (33%), while declining only 2% in controls. At 1 week, 68% of MagnaBloc patients and 27% of controls reported feeling better or much better (c2 = 10.64, p = .001). No other outcome changed significantly. No power analysis was performed to assess adequate sample size and length of intervention may be too short.
Collacott EA, et al. Bipolar permanent magnets for the treatment of chronic low back pain. JAMA 2000;283:1322-5.
A small, randomized, double-blind, placebo-controlled, crossover pilot study of the use of bipolar magnetic devices in 20 patients with low back pain. Subjects were randomized to receive one week of 282-330 G magnets and one week of sham, or vice versa, with one week washout between. Subjects applied devices 6 h/d, Mon/Wed/Fri. Outcomes measured were pre- and post-treatment pain on a Visual Analog Scale (VAS), Pain Rating Index (PRI) of the McGill Pain Questionnaire, and range of motion (ROM) of the lumbosacral spine. No significant differences were noted in any outcome for real or sham magnets; post-treatment pain declined slightly for both groups. Subjects reported no adverse effects. This study has been criticized for sex bias (95% of subjects male), selection bias (55% subjects were disabled, 85% were retired), and a weak intervention compared to other studies requiring 24 h/d use of stronger magnets.
Vallbona C, Hazlewood CF, Jurida G. Response of pain to static magnetic fields in postpolio patients: a double-blind pilot study. Arch Phys Med Rehabil 1997;78:1200-3.
A prospective double-blind study of bipolar 300-500 G Bioflex magnets versus sham in 50 patients with postpolio syndrome experiencing muscular or arthritic pain for at least 4 weeks. No significant differences in demographics or location of pain existed between study groups. However, a higher prevalence of muscular pain (compared to arthritic) and a higher female:male ratio were present in the experimental group. Only the most sensitive area of pain was evaluated per patient. Four different magnet sizes were used, depending on site of pain, applied to the skin with adhesive tape. Patients wore the device for 45 minutes; position or activity during this time was not monitored. Outcomes measured were McGill Pain Questionnaire and pain as assessed by palpation of a trigger point pre- and post-treatment. Both outcomes improved significantly for the treatment group compared to control, but pressure of palpation was not measured, so consistency is questionable. This study does not address the efficacy of long-term magnet use for chronic pain relief. Additional, larger studies are necessary and should control for magnet size between groups, female-male ratio, position during treatment, and source of pain.
Caselli MA, et al. Evaluation of magnetic foil and PPT Insoles in the treatment of heel pain. J Am Podiatr Med Assoc 1997;87:11-6.
Prospective, randomized evaluation of effect of insoles with or without magnetic foil on 34 otherwise healthy patients with medial plantar calcaneal heel pain. Primary outcome was foot function index, measured before and after 4 weeks of constant insole use. Eleven of 19 (58%) patients in the treatment group and 9 of 15 (60%) controls reported improvement, and no significant difference in the percentage improvement was measured. The authors conclude that the molded insole alone was effective in treating heel pain.