October 24, 2006
EFFICACY OF A STATIC MAGNETIC DEVICE AGAINST KNEE PAIN ASSOCIATED WITH INFLAMMATORY ARTHRITIS
Neil Segal, Joseph Houston, M.D., Howard Fuchs, M.D., Robert Holcomb, M.D, Ph.D. and Michael J. McLean, M.D, Ph.D.
Electromagnetic fields have been used therapeutically for 2000 years, for indications ranging from headaches to gout. There is considerable evidence that steady direct current and time-variant electromagnetic fields are produced by living bone through metabolic activity and pizoelectric activity upon bone deformation respectively. Pulsed electromagnetic fields (PEMF) have been used for acceleration of fracture and osteotomy healing. These effects have been shown to be mediated by reduction of osteoclastic resorption of bone, increased vascularization and increased rate of bone formation by osteoblasts, and these mechanisms have been studied on cellular and gene transcription levels.
Placebo-controlled trials have shown decreased pain and improved functional performance in patients with osteoarthritis of the knee with PEMF therapy. However, relatively few clinical studies have examined the effects of static magnetic fields. In this study, we examined the efficacy of treatment with a static magnetic field generator as adjunctive therapy for the joint pain in patients with inflammatory arthritis.
The MagnaBlocï (MB; U.S. patent no 5,312,321) is a non-invasive non-significant risk device, consisting of four permanent magnets arrayed with alternating polarity in a hypoallergenic plastic case. The MagnaBloc™ is approximately 3.5 centimeters in diameter, weighs approximately 30 grams and generates a magnetic field of 190 millitesla. This device reduced mechanical low back pain and knee pain significantly more than placebo. Much larger time invariant magnetic fields like those produced by magnetic resonance imaging devices have not been shown to be harmful to man or animals.
This study was designed to evaluate a protocol for use in a large double-blind, placebo-controlled study. The principal outcome measure was pain intensity in patients receiving MB therapy compared to baseline level of pain. In addition to assessment for anti-nociceptive and anti-inflammatory effects, this study also assessed the effect of MB treatment on the level of physical functioning. Volunteers for this study included patients over the age of eighteen with inflammatory arthritis (rheumatoid or psoriatic arthritis) and persistent knee pain despite appropriate use of medications.
The trial enrolled a cohort of 18 patients, drawn from a population consecutively presenting with the complaint of knee pain to their rheumatologist at Medical Specialists of Nashville or the Arthritis and Joint Replacement Center at Vanderbilt University Medical Center in Nashville, Tennessee during the 6 week period beginning August 31, 1998. Subjects included 16 females, 2 males, 16 Caucasians, and 2 African Americans, with an average age of 65.1 years-old. Patients were excluded if they had a cardiac pacemaker, prosthetic knee, unstable neurological condition, or morbid obesity. The magnetic field produced by the MagnaBloc™ device can interfere with cardiac pacemakers.
Morbid obesity results in technical difficulty both in affixing the devices and in field penetration of the fat layer which surrounds the nerve. Changes in analgesics were not allowed during the trial. Design of this study followed ACR recommended core set of disease activity measures for rheumatoid arthritis clinical trials.
The following assessments were made: patient’s and physician’s global assessments of disease activity (GADA); Westergren Sedimentation Rate (WSR); range of motion of the knee by goniometry; examination for tenderness; examination for swelling; patient’s assessment of physical function; 100mm horizontal visual analogue scale for pain (VAS); and, the Modified Health Assessment Questionnaire (MHAQ) for difficulty in daily activities. Patients with inflammatory arthritis who met inclusion criteria and consented to participation were included. The rheumatologist conducted a standardized joint examination, including assessment of tenderness and swelling and measurement of range of motion of the joint by goniometry. A Global Assessment of Disease Activity (GADA) was made by the rheumatologist by placing a mark on a 100mm line.
Patients reported baseline levels of pain on a Visual Analog Scale for pain (VAS), and completed the Modified Health Assessment Questionnaire (MHAQ). Westergren Sedimentation Rate (WSR) was assessed. With the patient seated and the leg flexed 90 degrees at the knee, four MB devices were applied: over the suprapatellar and infrapatellar bursae and over the medial collateral and lateral collateral ligaments to broadly cover joint swelling and inflamed synovium. Devices were affixed to the skin around the joint by double-stick adhesive tape and reinforced with Transpore™ (3M) tape over each device. One hour and 1 day after placement of the devices, MHAQ and VAS were repeated. Subjects were instructed to leave the devices taped in place until the 1 week follow-up visit.
One week after placement of devices, subjects were reassessed with GADA, ROM, VAS, WSR, and MHAQ, and devices were removed. This study was conducted with the approval of the Vanderbilt Committee for the Protection of Human Subjects.