Effect of static magnetic field on pain associated with frozen shoulder

Abstract

To examine the effectiveness of application of a static magnetic field (SMF) in reducing pain associated with frozen shoulder, a pathophysiological study of shoulder pain was performed using thermography and deep body thermometry in conjunction with the patients' subjective and objective symptoms. A total of 40 patients (18 men and 22 women; age range, 27 to 83 years; mean age, 57.3 years) with pain associated with frozen shoulder for a duration of 1 week to 36 years (mean, 7 years) were investigated. The subjective and objective symptoms were evaluated with inspection and palpation in conjunction with a visual analogue scale. Patients were randomly assigned to be exposed to active or dummy magnets in a doubleblind test. Active magnets [Ferrite Magnets (130 ± 10 mT, 15 mm in diameter and 7.2 mm in height)] were applied externally to the painful area. In other patients, dummy magnets (0 mT) were applied externally as a placebo. All patients wore 12 pieces of active or dummy magnets for 3 weeks, after which the magnets were removed. Before the treatment, the skin temperature of the painful area was generally lower than that of a healthy or painless area. Upon application of the active magnets, the subjective and objective symptoms significantly improved at 3 weeks, accompanied by an increase in the skin temperature of the painful area. The pain relief persisted in the patients with shoulder pain up through 1 week after removal of the active magnets. These findings suggest that SMF application gradually increases the blood circulation in areas with ischemic pain, thereby improving the subjective and objective symptoms.