Static Magnetic Field Therapy for Carpal Tunnel Syndrome: A Feasibility Study

Colbert AP, Markov MS, Carlson N, Gregory WL, Carlson H, Elmer PJ. Static magnetic field therapy for carpal tunnel syndrome: a feasibility study. Arch Phys Med Rehabil 2010;91:1098-104. Objectives: To assess the feasibility of conducting trials of static magnetic field (SMF) therapy for carpal tunnel syndrome (CTS), to collect preliminary data on the effectiveness of 2 SMF dosages, and to explore the influence of an SMF on median nerve conduction. Design: Randomized, double-blind, sham-controlled trial with a 6-week intervention and a 12-week follow-up. Setting: University hospital outpatient clinics. Participants: Women and men (N=60), ages 21 to 65 years, with an electrophysiologically confirmed CTS diagnosis recruited from the general population. Interventions: Participants wore nightly either neodymium magnets that delivered either 15 or 45mTesla (mT) to the contents of the carpal canal or a nonmagnetic disk. Main Outcome Measures: Symptom Severity Scale (SSS) and Function Severity Scale (FSS) of the Boston Carpal Tunnel Questionnaire (BCTQ) and 4 median nerve parameters: sensory distal latency, sensory nerve action potential amplitude, motor distal latency and compound motor action potential amplitude. Results: Fifty-eight of 60 randomized participants completed the study. There were no significant between-group differences for change in the primary endpoint SSS or for FSS or median nerve conduction parameters. For the SSS and the FSS, each group showed a reduction at 6 weeks indicating improvement in symptoms. Conclusions: This study showed the feasibility and safety of testing SMF therapy for CTS. There were no between-group differences observed for the BCTQ or median nerve parameters after 6 weeks of SMF therapy. Significant within-group, symptomatic improvements of the same magnitude were experienced by participants in both active and sham magnet groups. Future studies are needed to optimize SMF dosimetry and resolve issues related to the use of sham controls in SMF trials.