 |
|
Bipolar Permanent Magnets for the Treatment of Chronic Low Back Pain
A Pilot Study
Edward A. Collacott, MD;
John T. Zimmerman, PhD;
Donald W. White, PT;
Joseph P. Rindone, PharmD
JAMA. 2000;283:1322-1325.
ABSTRACT
| |
Context Chronic low back pain is one of the most prevalent and costly medical conditions in the United States. Permanent magnets have become a popular treatment for various musculoskeletal conditions, including low back pain, despite little scientific support for therapeutic benefit.
Objective To compare the effectiveness of 1 type of therapeutic magnet, a bipolar permanent magnet, with a matching placebo device for patients with chronic low back pain.
Design Randomized, double-blind, placebo-controlled, crossover pilot study conducted from February 1998 to May 1999.
Setting An ambulatory care physical medicine and rehabilitation clinic at a Veterans Affairs hospital.
Patients Nineteen men and 1 woman with stable low back pain of a mean of 19 years' duration, with no past use of magnet therapy for low back pain. Twenty patients were determined to provide 80% power in the study at P<.05 to detect a difference of 2 points (the difference believed to be clinically significant) on a visual analog scale (VAS).
Interventions For each patient, real and sham bipolar permanent magnets were applied, on alternate weeks, for 6 hours per day, 3 days per week for 1 week, with a 1-week washout period between the 2 treatment weeks.
Main Outcome Measures Pretreatment and posttreatment pain intensity on a VAS; sensory and affective components of pain on the Pain Rating Index (PRI) of the McGill Pain Questionnaire; and range of motion (ROM) measurements of the lumbosacral spine, compared by real vs sham treatment.
Results Mean VAS scores declined by 0.49 (SD, 0.96) points for real magnet treatment and by 0.44 (SD, 1.4) points for sham treatment (P = .90). No statistically significant differences were noted in the effect between real and sham magnets with any of the other outcome measures (ROM, P = .66; PRI, P = .55).
Conclusions Application of 1 variety of permanent magnet had no effect on our small group of subjects with chronic low back pain.
INTRODUCTION
Low back pain is a disabling, costly condition that is difficult to treat effectively. It is estimated that 85% of all people will have back pain during their lifetime. Annual prevalence reports range from 15% to 45%.1 Currently more than 5 million Americans are disabled with low back pain.2 The direct cost of treating low back pain is estimated at $15 billion, with indirect costs as high as $100 billion annually.3 According to one recent study, 75% of patients who visit a physician for an acute episode of low back pain are still symptomatic 1 year later.4 In view of the significant risks of some conventional treatments, there has been renewed interest in alternative methods5 for a variety of conditions. In the United States there has been a dramatic increase in visits to practitioners of alternative medicine, with expenditures in the range of $21.2 billion in 1997.6
There currently exists a media campaign promoting the use of permanent magnets for the treatment of pain,7-9 which has resulted in large profits: worldwide sales of $5 billion have been reported.10 Four reports of the use of permanent magnets for the treatment of pain have been published, only 1 of which used a double-blind randomized design.10-13 Vallbona and colleagues12 used active and placebo permanent magnets in a single 45-minute application to treat muscle pain in patients with postpolio syndrome. A statistically significant improvement was reported with the active magnets. Weintraub11 reported a statistically significant reduction in neuropathic pain in patients with diabetic polyneuropathy using magnetic foot pads for a total of 12 weeks. Because of public interest, and a lack of adequate scientific documentation, there has been a call for further clinical trials.14
Two types of permanent magnet therapy are popular: unipolar and bipolar. The terms unipolar and bipolar refer to the magnetic poles facing the patient's skin. Unipolar magnet therapy usually uses several discrete, individual magnets aligned with the same magnetic pole toward the skin. Usually the pole facing the patient is the biomagnetic north pole or negative pole (hence the term unipolar). The so-called biomagnetic south pole then faces away from the skin.
Bipolar magnet therapy usually uses a flexible plastalloy (flexible plastic containing barium ferrite) sheet of magnetic material that has impressed upon it an alternating spatial pattern of north and south magnetic domains. Popular patterns in some bipolar magnetic designs are stripes, concentric circles, squares, and triangles. In each case, the adjacent shape is of the opposite magnetic polarity relative to its contiguous neighbor. Bipolar magnet therapy thus uses magnetic material arranged in an alternating pattern, so that both north and south poles face the skin.
The length of time the magnets must be worn to obtain maximum pain relief has not been established. Vallbona et al12 reported pain relief from a 45-minute application while Weintraub10 suggested continuous treatment.
Therapeutic permanent magnets are popular for a variety of musculoskeletal complaints.7-9 Low back pain was selected for study because it is 1 of the most common problems for which magnets are used. The objective of this study was to evaluate the effectiveness of a commonly used bipolar magnet, used repetitively for a fixed period, in the treatment of chronic low back pain.
METHODS
This was a randomized, double-blind, placebo-controlled, crossover pilot study. The trial was carried out in the physical medicine and rehabilitation outpatient facility of a Veterans Affairs hospital in Prescott, Ariz. The institutional review board of the Veterans Affairs hospital approved the study and all subjects gave written informed consent prior to participation. Randomization of devices was achieved using a computer-generated list of random numbers. The order of treatment (magnet first and placebo second or vice versa) also was randomized.
Study Population
Participants were recruited from the primary care and physical medicine and rehabilitation clinics of a Veterans Affairs hospital. Participants were recruited from February 1998 through March 1999. A total of 24 individuals met the study criteria. Two individuals did not wish to participate and 2 of the remaining 22 failed to complete the protocol because of time conflicts, leaving 20 subjects who completed the study. Their general characteristics are given in Table 1.
|
|
|
|
Table 1. Baseline Characteristics of Study Participants (N = 20)
|
|
|
All patients were examined by the same investigator (E.A.C.). Evaluations included radiography of the lumbosacral spine for all subjects. All imaging studies were consistent with spondylosis and some studies revealed additional diagnoses (Table 1). However, the source of subjects' existing back pain was thought to be degeneration of the "3-joint complex"15 (intervertebral disks and facet joints) in all cases. Subjects were required to have stable low back pain of at least 6 months' duration. None had a new neurological deficit. Exclusion criteria were past use of magnet therapy for low back pain; secondary gain issues such as recent application for disability or ongoing litigation; pregnancy; cardiac pacemaker; skin lesions over the site of pain; and difficulty understanding the directions.
Outcome Measures
The visual analog scale (VAS) was chosen as the primary outcome measure and used to quantify pain intensity. The VAS, shown to be a reliable and valid measure,16-17 consists of a standard 10-cm line with verbal anchors indicating "none" at one end (0) and "severe" at the other (10). Participants were told to estimate their current level of pain by an appropriate mark on the line, with severe indicating the worse imaginable pain. The McGill Pain Questionnaire was used to measure the affective component of pain.18 The Pain Rating Index (PRI) of the McGill Pain Questionnaire was the sole measure analyzed rather than the subscales.19-20 The PRI uses 20 category scales of verbal descriptors to demonstrate the sensory and affective components of pain, with a minimum score of 0 and a maximum score (most severe pain) of 78. Lacking a reliable measure of the physical response to pain, formal measurements of the range of motion (ROM) of the lumbosacral spine were obtained for all subjects by the same investigator (D.W.W.). The degree of flexion/extension of the lumbosacral spine was obtained using the 2-inclinometer method.21
Study Design
The trial lasted from February 9, 1998, to May 21, 1999. All subjects followed the treatment protocol for 2 weeks: 1 week with the magnets and 1 week with the sham devices. There was a 1-week washout period between the 2 treatment weeks. The protocol consisted of application of the devices 6 h/d, 3 d/wk (Monday, Wednesday, and Friday of each treatment week). Therefore, all participants were exposed to a total of 18 hours of treatment for both real and sham devices.
Both the real and sham devices consisted of a flexible rubberlike compound. The real devices were impregnated with active magnetic material; sham devices were identical, but had been demagnetized using a magnetizer/demagnetizer (Master Magnetics, Colorado Springs, Colo). After demagnetization the sham devices showed no detectable magnetism by gaussmeter. The magnetic strength measured on the cloth surface of the real devices approximated 300 G (range, 282-330 G). The devices were trapezoid in shape (19 x 11.5 x 14 cm) and about 2 mm thick. The surface applied to the participant's skin was covered with cloth fabric, while the outer surface was covered with smooth gold foil. The magnets were of the bipolar variety, with a magnetic design of multiple triangles of alternating north and south magnetic polarity. An abdominal binder, connected via Velcro straps, held the device in place. Subjects were advised not to manipulate the devices.
Participants completed VAS measurements before and after each treatment (ie, before and after either the real or sham device was applied). Measurements for ROM and PRI were obtained before and after the first day's treatment and at the end of each week. The same examiner (D.W.W.) applied all the devices and obtained all ROM measurements. Subjects were advised to avoid new treatments during the time of the study, and they were instructed not to alter their usual pattern of medication use.
Statistical Analysis
Statistical analysis of the data was performed using SigmaStat software (San Rafael, Calif). A 2-point difference in the VAS scores was selected as a clinically significant reduction in pain intensity. The power calculation was performed for the primary outcome measure (VAS). Analysis showed that enrolling 20 patients would provide an adequate sample size to achieve a power of 80%, assuming an SD of 1.5. The difference between baseline (preapplication) and posttreatment VAS scores and ROM measurements was analyzed using repeated measures analysis of variance and paired t test, respectively. The difference between baseline and posttreatment PRI scores (nonparametric) was analyzed and compared between treatments using the Wilcoxon signed rank test. Statistical significance was set at P<.05.
RESULTS
The mean (SD) cumulative baseline VAS score for all participants was 4.8 (2.2). The mean cumulative baseline score for the sham treatment was 5.0 (2.4) and for the magnet treatment, 4.7 (2.9). Table 2 shows the difference between baseline and posttreatment VAS scores, by day, for magnet and sham treatments. Table 3 shows the difference between baseline and posttreatment ROM and PRI measures for day 1. Table 4 compares cumulative change from baseline (day 1 vs posttreatment day 3) for VAS, ROM, and PRI. No statistically significant differences between magnet and sham treatment were found with any outcome measure. No adverse effects were reported by any of the participants.
|
|
|
|
Table 2. Baseline and Change in Visual Analog Scale (VAS) Scores After Treatment, by Day
|
|
|
|
|
|
|
Table 3. Baseline and Change in Outcome Measures After 1 Day of Treatment
|
|
|
|
|
|
|
Table 4. Change in Outcome Measures: Baseline vs Posttreatment Day 3
|
|
|
COMMENT
This study found no immediate or cumulative difference in the outcome measures of low back pain comparing real with demagnetized (sham) therapeutic magnets. Neither magnet nor sham treatment achieved the prospectively determined reduction in pain intensity (2-point reduction in the VAS score). To our knowledge, this is the only randomized, double-blind, placebo-controlled study reporting the use of permanent magnets on more than a single occasion and for more than 45 minutes. Our protocol treatment was 3 times a week for a total of 18 hours for both treatments. This was a pilot study and was not intended to prove or disprove the effectiveness of magnet therapy in general. Additional studies using different magnets (unipolar and bipolar), treatment times, and patient populations are needed.
A stronger magnet may be necessary to penetrate to the source of chronic low back pain. Expanding the treatment time in an ambulatory setting would require manipulation of the devices by the subjects, which would increase the chances of detecting whether the magnet/sham was magnetized. If a device with opposite polarity or of a certain design was found to be ineffective, it could serve as a placebo.
Our study population was small and had special requirements. The subjects had to travel to the clinic twice daily at specific times, conditions that eliminated many employed and younger individuals. Other potential subjects lived too far away or had no transportation. Since we recruited from the Veterans Affairs clinic population there were too few women. Thus, it is difficult to generalize these results to the population at large with chronic low back pain.
Our results did not support the findings of Vallbona et al12 and Weintraub.10 However, there were considerable differences in the study designs and populations, including the cause of pain. The patients of Vallbona and colleagues had muscle pain while Weintraub's subjects had neuropathic pain. The source of pain in our participants would appear to be deeper than that of the former, and may explain the lack of beneficial effect from the magnets used (300 G).
AUTHOR INFORMATION
Corresponding Author and Reprints: Edward A. Collacott, MD, Physical Medicine and Rehabilitation, 500 N Hwy 89, Veterans Affairs Medical Center, Prescott, AZ 86313 (e-mail: edward.collacott{at}med.va.gov).
Author Affiliations: Bio-Electro-Magnetics Institute, Reno, Nev (Dr Zimmerman); and Veterans Affairs Medical Center, Prescott, Ariz (Drs Collacott and Rindone and Mr White).
REFERENCES
| |
1. Research on low back pain and common spinal disorders. NIH Guide. May 16, 1997;26:1-6. Also available at: http://www.ninds.nih.gov/scientists/grntcn/PA-97-058.htm. Accessed January 26, 2000.
2. Frymoyer JW. Back pain and sciatica. N Engl J Med. 1988;318:291-300.
WEB OF SCIENCE
| PUBMED
3. White AH. The socioeconomic cascade. In: White AH, Schofferman JA, eds. Spine Care: Diagnosis and Conservative Care. Part 1. St Louis, Mo: Mosby–Year Book Inc; 1995:27-34.
4. Croft PR, Macfarlane GJ, Papageorgiou AC, Thomas E, Silman AJ. Outcome of low back pain in general practice: a prospective study. BMJ. 1998;316:1356-1359.
FREE FULL TEXT
5. Fontanarosa PB, Lundberg GD. Complementary, alternative, unconventional, and integrative medicine: call for papers for the annual coordinated theme issues of the AMA journals [editorial]. JAMA. 1997;278:2111-2112.
FREE FULL TEXT
6. Eisenberg DM, Davis RB, Ettner SL, et al. Trends in alternative medicine use in the United States, 1990-1997: results of a follow-up national survey. JAMA. 1998;280:1569-1575.
FREE FULL TEXT
7. Ruibal S. Ironclad cures for pain? athletes put their faith in power of magnets. USA Today. August 20, 1997:C3.
8. The power to heal? [transcript]. "Dateline." NBC television. May 10, 1998.
9. Nikken Inc Web site. Available at: http://www.nikken.com/index.htm. Accessed January 24, 2000.
10. Weintraub M. Magnetic biostimulation in painful diabetic peripheral neuropathy: a novel intervention—a randomized, double-placebo crossover study. Am J Pain Manage. 1999;9:8-17.
11. Weintraub M. Chronic submaximal magnetic stimulation in peripheral neuropathy: is there a beneficial therapeutic relationship? Am J Pain Manage. 1998;8:9-13.
12. 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;78:1200-1203.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
13. Hong CZ, Lin JC, Bender LF, Schaeffer JN, Meltzer RJ, Causin P. Magnetic necklace: its therapeutic effectiveness on neck and shoulder pain. Arch Phys Med Rehabil. 1982;63:462-466.
WEB OF SCIENCE
| PUBMED
14. Montrey JS for the VHA National Leadership Board. Quality forum on pain management. Veterans Health Syst J. 1999;4:21-28.
15. Kirkaldy-Willis WH. Managing Low Back Pain. New York, NY: Churchill Livingstone; 1983.
16. Duncan GH, Bushnell MC, Lavigne GJ. Comparison of verbal and visual analogue scales for measuring the intensity and unpleasantness of experimental pain. Pain. 1989;37:295-303.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
17. Price DD, McGrath PA, Rafii A, Buckingham B. The validation of the visual analogue scales as ratio scale measures for chronic and experimental pain. Pain. 1983;17:45-56.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
18. Melzack R. The McGill Pain Questionnaire: major properties and scoring methods. Pain. 1975;1:277-299.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
19. Holroyd KA, Holm JE, Keefe FJ, et al. A multi-center evaluation of the McGill Pain Questionnaire: results from more than 1700 chronic pain patients. Pain. 1992;48:301-311.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
20. Turk DC, Rudy TE, Salovey P. The McGill Pain Questionnaire reconsidered: confirming the factor structure and examining appropriate uses. Pain. 1985;21:385-397.
FULL TEXT
|
WEB OF SCIENCE
| PUBMED
21. Guides to the Evaluation of Permanent Impairment, Fourth Edition. Chicago, Ill: American Medical Association; 1993:127.
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter
What's this?
RELATED LETTERS
Reporting Drug Abuse in the Emergency Department
Judy Ball, Samuel Korper, Albert Woodward, David E. Joranson, Karen M. Ryan, Aaron M. Gilson, and June L. Dahl
JAMA. 2000;284(5):564.
EXTRACT
| FULL TEXT
Are Magnets Effective for Pain Control?
Craig G. Burkhart, Craig N. Burkhart, Michael I. Weintraub, Abraham M. Blechman, Windsor Ting, Saran Jonas, and Edward A. Collacott
JAMA. 2000;284(5):564-566.
EXTRACT
| FULL TEXT
RELATED ARTICLE
March 8, 2000
JAMA. 2000;283(10):1361-1362.
EXTRACT
| FULL TEXT
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
|
Static Magnetic Field Therapy: A Critical Review of Treatment Parameters
Colbert et al.
Evid Based Complement Alternat Med 2009;6:133-139.
ABSTRACT
| FULL TEXT
Analgesic effects of treatments for non-specific low back pain: a meta-analysis of placebo-controlled randomized trials
Machado et al.
Rheumatology (Oxford) 2009;48:520-527.
ABSTRACT
| FULL TEXT
Static magnets for reducing pain: systematic review and meta-analysis of randomized trials
Pittler et al.
CMAJ 2007;177:736-742.
ABSTRACT
| FULL TEXT
Nonsurgical Management of Acute and Chronic Low Back Pain
Shen et al.
J Am Acad Orthop Surg 2006;14:477-487.
ABSTRACT
| FULL TEXT
Magnet therapy
Finegold and Flamm
BMJ 2006;332:4-4.
FULL TEXT
Effect of Magnetic vs Sham-Magnetic Insoles on Nonspecific Foot Pain in the Workplace: A Randomized, Double-Blind, Placebo-Controlled Trial
Winemiller et al.
Mayo Clin Proc. 2005;80:1138-1145.
ABSTRACT
The power of placebo
McCrory
Br. J. Sports. Med. 2005;39:125-125.
FULL TEXT
Randomised controlled trial of magnetic bracelets for relieving pain in osteoarthritis of the hip and knee
Harlow et al.
BMJ 2004;329:1450-1454.
ABSTRACT
| FULL TEXT
Effect of Magnetic vs Sham-Magnetic Insoles on Plantar Heel Pain: A Randomized Controlled Trial
Winemiller et al.
JAMA 2003;290:1474-1478.
ABSTRACT
| FULL TEXT
Comparative effect of positive and negative static magnetic fields on heart rate and blood pressure in healthy adults
Hinman
Clin Rehabil 2002;16:669-674.
ABSTRACT
Unproven Therapies
Hirsch
Clin. Diabetes 2002;20:1-3.
FULL TEXT
Are Magnets Effective for Pain Control?
Burkhart et al.
JAMA 2000;284:564-566.
FULL TEXT
|
