Kinematic Analysis for Repetitive Peripheral Magnetic Stimulation of the Intrinsic Muscles of the Hand

The intrinsic muscles of the hand are responsible for finger flexion and extension. The purpose of this study was to investigate the usefulness of stimulating the intrinsic muscles of the hand using repetitive peripheral magnetic stimulation (rPMS). We evaluated angular changes in the finger joints by studying active motion and rPMS. Ten healthy adults were instructed to perform the following tests in random order: (1) maximum active metacarpophalangeal joint flexion; (2) maximum active metacarpophalangeal joint abduction; and (3) repetitive peripheral magnetic stimulation for 2 s at maximum stimulation intensity. A three-dimensional motion analysis system was used to measure angular changes. Pain during stimulation was graded on a numerical rating scale (NRS). The maximum flexion and abduction of the metacarpophalangeal joint were not significantly different between active motion and rPMS. The proximal interphalangeal joint (p = 0.009) and distal interphalangeal joint (p = 0.005) were significantly extended by rPMS. The median NRS score for pain during rPMS was 2. rPMS can produce the same extent of metacarpophalangeal joint flexion and abduction as active movement with less pain. This technique can effectively stimulate the intrinsic muscles of the hand and may be used as a treatment for various diseases that cause immobility of the metacarpophalangeal joints.