Adverse Reactions to Chiropractic Care in the UCLA Neck Pain Study: A Response

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Adverse Reactions to Chiropractic Care in the UCLA Neck Pain Study: A Response
Received 8 August 2005; received in revised form 2 December 2005
Anthony L. Rosner, PhDa
Journal of Manipulative and Physiological Therapeutics (JMPT)

Article Outline
Ô Significance and Time Sequence of Odds Ratios

Ô Comparative Odds Ratios and Frequencies

Ô Effect of Preceding Conditions

Ô Relativity to Other Interventions

Ô Lack of Details Regarding Technique and Number of Adjustments

Ô References

Ô Copyright

As an adjunct to the UCLA Neck Pain Study, in which outcomes of patients who undergo cervical manipulation have been compared to those of individuals treated by mobilization, Hurwitz et al11 have recently catalogued all the adverse symptoms apparently encountered by both groups during the clinical trial. As detailed a review as this study is, there are statements in the text as well as quirks and gaps in the data that must be brought to light for the actual risks of manipulation to be appreciated in their true perspective. Issues addressed include (1) problems with the time sequence of events; (2) comparative odds ratios and frequencies with procedures other than manipulation; (3) the effect of preceding conditions; (4) relativity to other interventions; and (5) the lack of details regarding technique and the number of adjustments.

During the past decade, the issues of cerebrovascular accidents (CVAs) and spinal manipulation have become linked in a debate of ever-increasing intensity. A copious number of studies have investigated spinal manipulation as a putative causative factor of CVAs.1, 2, 3, 4, 5, 6 Additional studies have examined more minor and transient events which have been observed to follow cervical manipulations, in the effort to more thoroughly assess the risk-benefit ratios of cervical manipulation as well as to attempt to gain a deeper understanding of the mechanisms that might possibly trigger more serious adverse events.7, 8, 9, 10

Adding to the latter body of evidence is an adjunct to the UCLA Neck Pain Study, in which the outcomes of patients who underwent cervical manipulation have been compared to those of individuals treated by mobilization. Hurwitz et al 11 catalogued all the adverse symptoms apparently encountered by both groups during the clinical trial. The investigators indicate that some 85 patients (30.4%) out of the 280 participants polled had adverse symptoms, most commonly increased neck pain or stiffness with less frequently reported instances of headache or radiating pain. Patients randomized to manipulation were reported to be more likely than those assigned to mobilization to report an adverse symptom (odds ratio, 1.44; 95% CI 0.83-2.49).11

If a true assessment of the risks and mechanisms that accompany cervical manipulation is to be made, however, one must examine more closely the design of those studies to be better equipped to provide more definitive data. Despite the extent of detail in the Hurwitz et al 11 study, in particular, there are statements in the text as well as inconsistencies and gaps in the data which are worth examining in order that the actual risks of manipulation are appreciated in a more complete perspective.

Significance and Time Sequence of Odds Ratios
A review of all the odds ratios reflecting the relative risks of manipulation vs mobilization raises several questions regarding their significance. To begin, all odds ratios are well within the confidence intervals shown in the data, indicating that they do not approach statistical significance. Secondly, one of the tables (Table 3 in Hurwitz et al11) in this investigation reports the increased risk of all adverse events attributed to manipulation compared to mobilization and reflects an odds ratio of 1.44 within 24 hours of the treatment. However, precisely the same odds ratio of 1.44 is shown for any time of onset. The odds ratios for neck pain, stiffness, and sorenessÛby far the most common symptom reported by the authorsÛactually decrease for onsets less than 24 hours, whereas the respective odds ratios for other conditions (radiating pain, fatigue, headache, neurological symptoms) are shown to increase. It has been suggested elsewhere that if the association with the treatment were to be real, a positive gradient linking presumed cause and outcome should be present.12

Therefore, one might anticipate a marked drop-off of the odds ratio as more time elapses between treatment and effect. That may not be the case here and contradicts a body of literature involving adverse reactions after cervical manipulation, in which the number of incidents did indeed decline as the time between treatment and effect increased beyond 24 hours.7, 8, 9, 10, 13 This argument must not be construed, however, to dismiss the significance of the effects of an intervention beyond 24 hours. Furthermore, the lack of statistical significance of the odds ratios may make any arguments about their presumed change or lack of change a moot issue.

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