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E. Ernst, MD, PhD, FRCP

The author is with the Department of Complementary Medicine, School of Sport and Health Sciences, University of Exeter, England.

Correspondence: Requests for reprints should be sent to E. Ernst, MD, PhD, FRCP, Department of Complementary Medicine, School of Sport and Health Sciences, University of Exeter, 25 Victoria Park Rd, Exeter EX2 4NT, England (e-mail: E.Ernst{at}exeter.ac.uk).

	INTRODUCTION

TOP INTRODUCTION EFFECTIVENESS SAFETY CONCLUSIONS References

 
There are about 5000 chiropractors in active practice in North America, predominantly treating spinal problems, particularly neck and back pain.¹ Worldwide, single-year prevalence rates for use of chiropractors among the general population vary from 10% in Austria to 33% in the United Kingdom.² This level of popularity renders a critical risk–benefit analysis of chiropractic care a desirable exercise.

	EFFECTIVENESS

TOP INTRODUCTION EFFECTIVENESS SAFETY CONCLUSIONS References

 
Several evaluations of the effectiveness of chiropractic treatment have been published (e.g., Shekelle et al.,³ Meeker and Haldeman⁴). Invariably, they include studies of manual therapies other than chiropractic treatments. Because the chiropractic approach is distinct from that of other professions,⁴ it is important to evaluate this approach separately.

In 1996, Assendelft and colleagues⁵ published a rigorous assessment of treatments performed by chiropractors. Their review included 8 randomized clinical trials of chiropractic for treatment of low back pain. All of these studies had serious flaws in their design, execution, and reporting. The authors found "no convincing evidence for the effectiveness of chiropractic for acute or chronic low back pain."⁵

Since the publication of the Assendelft et al. article, several additional randomized controlled trials of chiropractic spinal manipulation for back pain have emerged.^6–9 Results of these trials, which included a total of 741 patients suffering from acute, subacute, or chronic back pain, did not show an advantage of chiropractic over control treatments (i.e., physiotherapy, educational booklets, oral medications, acupuncture, or steroid injections). Thus, the conclusions drawn by Assendelft et al.⁵ 6 years ago seem to be still valid today.

Of course, use of these data to evaluate the effectiveness of chiropractic presents problems for several reasons. First, few of the studies available to date have controlled for a potentially powerful placebo effect. A recent systematic review revealed no compelling evidence to suggest that chiropractic yields clinical effects that are distinct from those of placebo manipulation.¹⁰

Second, chiropractic treatment often comprises more than spinal manipulation.⁴ It is therefore difficult to judge the relative contribution of any element in this "chiropractic treatment package." Most of the trial data just described refer to chiropractic spinal manipulation.

Third, chiropractors do not treat only back pain. Yet, back pain is the indication that has been researched more thoroughly than any other condition, and the evidence for other complaints is (even) less encouraging.⁴ Thus, a preliminary conclusion as to the effectiveness of chiropractic is that its benefits are by no means certain.

	SAFETY

TOP INTRODUCTION EFFECTIVENESS SAFETY CONCLUSIONS References

 
And what about the risks? Prospective investigations into the risks of chiropractic are scarce. The methodologically best studies show that mild, transient adverse effects such as localized pain are experienced by about 50% of all chiropractic patients.¹¹ In addition to such minor events, dramatic complications have been noted with some degree of regularity.¹² These complications typically involve upper spinal manipulation, which has been associated with cerebrovascular accidents. To date, it has not been possible to identify risk factors.¹³ As a result, essentially everyone receiving chiropractic treatment is at risk.

The question is, How large is that risk? Estimates by chiropractors of the risk of serious events vary from 1 in 400 000 to 1 in 3.85 million cervical spine manipulations.¹³ These estimates are based on certain assumptions, such as that complications are underreported. However, rates of underreporting can be as high as 100%¹⁴; this, in turn, implies that the existing estimates are meaningless.

The most compelling data in this respect originate from a recent Canadian population-based, nested case–control study conducted by Rothwell et al.¹² That study matched 582 patients who had experienced vertebrobasilar accidents with control subjects (i.e., nonpatients) who did not have a history of stroke. Patients younger than 45 years who had experienced a vertebrobasilar accident were 5 times more likely than control subjects to have visited a chiropractor in the preceding week and 5 times more likely to have made more than 3 cervical treatment visits in the preceding month. No significant associations with past-week receipt of chiropractic services were found among older patients.

The Rothwell et al. study also indicated that for every 100 000 chiropractic patients below the age of 45 years, approximately 1.3 cases of vertebrobasilar accidents attributable to chiropractic treatment would be observed within 1 week of treatment.¹² It seems to follow that the frequency of serious complications of chiropractic has been underestimated in the past.

One could also argue that serious complications mostly involve upper spinal manipulation and that these data should not be associated with the preceding evidence on effectiveness, which relates to low back pain. However, chiropractors view the spine as a functional entity; thus, they frequently manipulate the spine at levels in which subluxations, or partial dislocations, are detected regardless of the location of pain. In other words, patients with low back pain often receive upper spinal manipulation.

	CONCLUSIONS

TOP INTRODUCTION EFFECTIVENESS SAFETY CONCLUSIONS References

 
Where does all of this leave us when attempting a risk–benefit analysis? On one side we have uncertain benefits; on the other we must consider common nonserious adverse effects as well as serious complications that occur at an unknown rate. Given this situation, a tentative risk–benefit analysis cannot produce a positive result. The conclusion must therefore be that, according to the evidence to date, chiropractic spinal manipulation does not demonstrably do more good than harm. In view of the incompleteness of our current knowledge and the popularity of chiropractic, research into this complex area should be intensified.

	Acknowledgments

 
Human Participant Protection
No protocol approval was needed for this study.

	Footnotes

 
Peer Reviewed

Accepted for publication May 27, 2002.

	References

TOP INTRODUCTION EFFECTIVENESS SAFETY CONCLUSIONS References

 
1. Coulter ID, Hurwitz EL, Adams AH, Genovese BJ, Hays R, Shekelle PG. Patients using chiropractors in North America. Spine. 2002;27:291–298.[Medline]

2. Ernst E. Prevalence of use of complementary/alternative medicine: a systematic review. Bull World Health Organ. 2000;78:252–257.[Medline]

3. Shekelle PG, Adams AH, Chassin MR, Hurwitz EL, Brook RH. Spinal manipulation for low back pain. Ann Intern Med. 1992;117:590–598.

4. Meeker WC, Haldeman S. Chiropractic: a profession at the crossroads of mainstream and alternative medicine. Ann Intern Med. 2002;136:216–227.[Abstract/Free Full Text]

5. Assendelft WJJ, Koes BW, van der Heijden GJMG, Bouter LM. The effectiveness of chiropractic for treatment of low back pain: an update and attempt at statistical pooling. J Manipulative Physiol Ther. 1996;19:499–507.[Medline]

6. Skargren EI, Oberg BE, Carlsson PG, Gade M. Cost and effectiveness analysis of chiropractic and physiotherapy treatment for low back and neck pain—six-month follow-up. Spine. 1997;22:2167–2177.[Medline]

7. Cherkin DC, Deyo RA, Battie M, Street J, Barlow W. An important trial of chiropractic for acute low back pain. N Engl J Med. 1998;339:1021–1029.[Abstract/Free Full Text]

8. Giles LGF, Müller R. Chronic spinal pain syndromes: a clinical pilot trial comparing acupuncture, a nonsteroidal anti-inflammatory drug, and spinal manipulation. J Manipulative Physiol Ther. 1999;22:376–381.[Medline]

9. Bronfort G, Evans RL, Anderson AV, et al. Nonoperative treatments for sciatica: a pilot study for a randomized clinical trial. J Manipulative Physiol Ther. 2000;23:536–544.[Medline]

10. Ernst E, Harkness EF. Spinal manipulation: a systematic review of sham-controlled, double-blind, randomized clinical trials. J Pain Symptom Manage. 2001;24:879–889.

11. Ernst E. Prospective investigations into the safety of spinal manipulation. J Pain Symptom Manage. 2001;21:238–242.[Medline]

12. Rothwell DM, Bondy SJ, Williams SJ. Chiropractic manipulation and stroke: a population-based case-control study. Stroke. 2001;32:1054–1060.[Abstract/Free Full Text]

13. Haldeman S, Kohlbeck FJ, McGregor M. Unpredictability of cerebrovascular ischemia associated with cervical spine manipulation. Spine. 2002;27:49–55.[Medline]

14. Stevinson C, Honan W, Cooke B, Ernst E. Neurological complications of cervical spine manipulation. J R Soc Med. 2001;94:107–110.[Abstract/Free Full Text]

This article has been cited by other articles:

				W. Evans CHIROPRACTIC CARE: ATTEMPTING A RISK-BENEFIT ANALYSIS Am J Public Health, April 1, 2003; 93(4): 522 - 523. [Full Text] [PDF]

				E. L. Hurwitz, W. C. Meeker, and M. Smith CHIROPRACTIC CARE: A FLAWED RISK-BENEFIT ANALYSIS? Am J Public Health, April 1, 2003; 93(4): 523 - 524. [Full Text] [PDF]

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