Chiropractic manipulation has been known to lead to worsening symptoms or complications in a minority of patients. While most of these adverse events are relatively benign (i.e. muscle pain, stiffness, headache), more sinister outcomes some as disk herniation, neurological deficit or stroke have been reported. Most of the common adverse symptoms overlap with the natural history of neck and back pain, so it is difficult to know what to attribute to chiropractic care vs. the natural history of the underlying problem. Dr. Walker and his colleagues from Australia sought to find the answer to this question by performing a randomized, controlled, double blind trial comparing adverse events associated with usual chiropractic care to those reported following sham treatment (i.e. detuned ultrasound, random use of activator instrument). About 90 patients were randomized and underwent two treatment sessions and then filled out a questionnaire about adverse events 2 days after each treatment. Most of the adverse events were benign (stiffness, pain, or headache) and rated as moderate. Patients undergoing chiropractic care were more likely to report an adverse event (36% vs. 29%), but this difference was not significant. However, those undergoing real chiropractic treatment were almost twice as likely to report a severe adverse event, and this difference bordered on being statistically significant. At the conclusion of the trial, the patients were asked to guess to which group they had been assigned, and the majority of the patients were correct (67% sham, 85% chiropractic), indicating the blinding had not been particularly successful.
This is an interesting study that attempted to determine if chiropractic care actually led to increased adverse events or if patients reporting these outcomes were simply experiencing the natural history of their condition. While adverse events were quite common following sham treatment (29%), actual chiropractic care increased this rate by about 25%. The study was not powered to detect a difference of this size, so it is unclear if this represents a true difference or not. More notable was that chiropractic care increased the rate of “severe” adverse events almost two-fold, and this difference was essentially statistically significant. An important finding of this paper was that patients did not suffer any major complication such as stroke or neurological deficit, though many more patients would likely need to have been followed in order to have detected these rare events. The major limitations of this paper were the relatively low number of patients included that precluded study of rare adverse events and the fact that the blinding effectively failed. With the lack of blinding, it is difficult to know if the increased rate and severity of adverse events in the chiropractic group was due to a true difference or the tendency of patients to report more adverse events if they were aware they were in the treatment arm. As the authors suggested, future studies of chiropractic care should include larger numbers and use a more effective control intervention. Overall, this paper seems to suggest that chiropractic manipulation is reasonably safe, though it might exacerbate pain in some cases.
Please read Dr. Walker’s paper on this topic in the September 15 issue. Does it change how you view adverse events following chiropractic care? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor