By Dr. Christopher Kent and Dr. Patrick Gentempo, Jr.
In recent years, a great deal of attention has been focused on the use of surface EMGs in chiropractic practice. In this special article, EMG experts Christopher Kent, D.C., and Patrick Gentempo, D.C., give their views on some important questions.
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QUESTION: Is there any research to support the reliability and clinical utility of surface electromyography? Has it been published in reputable, indexed journals?
ANSWER: Yes. A computer search of Medline, the computer database of the National Library of Medicine, lists over 280 references on surface EMG published since 1966. There are additional refereed works on the subject in other indexes. For example, CHIROLARS is a computer database which indexes all refereed chiropractic publications, as well as selected papers from popular journals. There are also papers on surface EMG in refereed behavioral medicine and psychology journals.
Q. Does the research show that surface EMG is reliable?
A. Yes, and high reliability is an essential characteristic of any outcome measurement. Reliability is expressed as a coefficient from 0.00 to 1.00. Values above .50 are considered evidence of adequate reliability. [1]
Surface EMG has demonstrated very good to excellent reliability in a number of studies. For example, Cram [2] reported a mean reliability coefficient of 0.83 for surface EMG scanning with handheld electrodes. Spector [3] used affixed surface electrodes to assess paraspinal muscle activity.
Results of the study yielded correlation coefficients ranging from 0.73 to 0.97. Ahern et al [4] elevated the reliability of lumbar paraspinal SEMG for dynamic ROM studies. Reliability coefficients ranged from 0.66 to 0.97.
Q. Are handheld scanning electrode techniques reliable?
A. Yes. The Cram study used handheld scanning electrodes. Furthermore, Thompson et al [5] of the Mayo Clinic found that readings using handheld electrodes correlated highly with readings taken using attached electrodes.
Q. Isn’t needle EMG more accurate?
A. Surface EMG and needle EMG are not interchangeable techniques. They have different clinical objectives and indications. Some critics of SEMG have attempted to discredit the procedure by listing the things it cannot do.
For example, SEMG cannot demonstrate the denervation waveforms seen on needle EMG studies. On the other hand, Cobb et al [6] found SEMG is superior to needle EMG in demonstrating even mild muscle spasm. Furthermore, Komi and Buskirk [7] found that the testretest reliability of surface EMG was superior to that of inserted electrode EMG.
Q. Doesn’t the scientific literature state that EMG studies should not be performed until after the acute stage of an injury?
A. This issue is a result of confusing surface EMG with needle EMG. Needle EMG exams should not be performed in the acute stage of an injury case. In contrast, surface studies performed prior to the initiation of care are indicated to establish a baseline. SEMG exams also disclose the amount of muscle activity in a given region, and provide a means of measuring symmetry of function.
Q. Is surface EMG valid?
A. Yes, as a measurement of muscle electrical activity. Validity relates to whether an instrument is actually measuring what it is claimed to measure. Some critics of SEMG have stated that it is “not valid” since it does not discriminate between pain vs. nonpain patients. However, we have never claimed that it can measure or detect pain. Thus, that argument is without merit. SEMG measures the electrical activity produced in groups of muscles, not pain.
Q. Are there any negative studies on surface EMG?
A. Some individuals have attempted to relate surface EMG potentials to back pain. Since EMG is not a sensory nerve test, it is not surprising that the results of such studies have been equivocal.
Q. Can’t a chiropractor obtain the same information by palpation?
A. Consider an analogy. A doctor can feel a patient’s forehead, and detect a fever if the temperature is high enough. Such a procedure, however, does not result in a precise, reproducible measurement. By using a thermometer, a specific temperature is obtained. Changes in temperature help to monitor case progress. The presence or absence of fever is very useful diagnostic information. Yet, a thermometer cannot tell the doctor if there is an infection or which pathogens are present. Similarly, EMG cannot tell you if a person is in pain. It can, however, provide a reliable measurement of muscle activity.
Q. Are there specific protocols and indications for SEMG in chiropractic practice?
A. Yes, and they have been published in refereed journals. [8,9]
Q. Some have charged that your research is tainted because you manufacture EMG equipment. What is your response?
A. Such charges suggest that the individuals involved do not understand the process of blind peer review. When a paper undergoes such review, the names of the authors are not revealed. Thus, the paper is judged solely on the basis of merit.
Furthermore, the normative values we obtained were within one standard deviation of those obtained by other investigators. Such corroboration lends additional strength to our findings. For the record, it should also be noted that Dr. Kent has no equity interest in any EMG company.
Q. Is the use of SEMG taught through any chiropractic colleges?
A. Yes. Postgraduate faculty from several colleges offer SEMG courses.
Q. Are there any controlled studies using surface EMG as outcome measures for chiropractic adjustment or spinal manipulation?
A. Yes. Studies by Shambaugh [10] and Ellestad [11] have reported that significant changes in paraspinal SEMG occurred following chiropractic adjustments or osteopathic manipulations. No significant changes were observed in control subjects. Few chiropractic procedures have undergone blinded controlled studies. Even fewer have been studies by two professions, published in refereed indexed journals, and produced independent corroboration of their respective findings.
Q. Is surface EMG investigational?
A. No. The Food and Drug Administration (FDA) has an investigational device category, and surface EMG equipment is not classified as an “investigational device,” It is classified as a 510(K) certified medical device, and may be marketed for general clinical use by licensed practitioners.
Q. Why do some chiropractic researchers and insurance consultants claim that it is investigational and not valid?
A. They may be unaware of the scientific studies which have been published. Some are paid to review and cut insurance claims, and will try to justify their actions by using the “experimental” or “medically necessary” clauses of policies. It is very common for a far more burdensome standard to be applied to SEMG than other chiropractic procedures. In other cases, professional jealousy may be involved. This may be due in part to the lack of clinically useful research produced by SEMG detractors. Most critics of SEMG have never used it in clinical practice to monitor subluxation related paraspinal muscle changes.
Q. What is the future of SEMG?
A. The future of SEMG is exciting. Protocols are being developed for additional applications. Since SEMG provides quantitative data, it is useful as an outcome assessment for chiropractic care. SEMG is one technology which is demonstrating that the vertebral subluxation complex is not a philosophical construct, but a clinical reality.
References
1. Adams AH: “Methodological considerations in the selection of outcome measures for chiropractic practice.” Proceedings of the 1991 International Conference on Spinal Manipulation. Arlington, VA. P. 911.
2. Cram JR: “Clinical EMG: Muscle Scanning for Surface Recordings.” Seattle, WA. Biofeedback Institute of Seattle 1986. P. 8183.
3. Spector B: “Surface electromyography as a model for the development of standardized procedures and reliability testing.” Journal of Manipulative and Physiological Therapeutics 1979; 2(4):214222.
4. Ahern DK, Follick MJ, Council JR, LaserWolston N: “Reliability of lumbar paravertebral EMG assessment in chronic low back pain. Arch Phys Med Rehabil 1986; 67:762765.
5. Thompson JM, Erickson RP, Offord KP: “EMG muscle scanning: stability of handheld electrodes.” Biofeedback and Self Regulation 1989; 14(1):5562.
6. Cobb CR, DeVries HA, Urban RT, Luekens CA, Bagg RJ: “Electrical activity in muscle pain.” American Journal of Physical Medicine 1975; 54(2):8087.
7. Komi PV, Buskirk ER: “Reproducibility of electromyographic measurements with inserted wire electrodes and surface electrodes.” Electromyography 1970; 10(4):357367.
8. Gentempo P, Kent C: “Establishing medical necessity for paraspinal EMG scanning.” Chiropractic: The Journal of Chiropractic Research, Study, and Clinical Investigation 1990 3(1):2225.
9. Kent C, Gentempo P: “Protocols and normative data for paraspinal EMG scanning in chiropractic practice.” Chiropractic: The Journal of Chiropractic Research and Clinical Investigation 1990 6(3):6467.
10. Shambaugh P: “Changes in electrical activity in muscles resulting from chiropractic adjustment: a pilot study.” Journal of Manipulative and Physiological Therapeutics 1987 10(6):300304.
11. Ellestad SM, Nagle RV, Boesler DR, Kilmore MA: “Electromyographic and skin resistance responses to osteopathic manipulative treatment for low back pain.” Journal of the American Osteopathic Association 1988 88(8):991997.
