SPINE Volume 34, Number 11, pp E405–E413 ©2009, Lippincott Williams & Wilkins Safety of Chiropractic Interventions A Systematic Review Liliana Olim Gouveia, MD,* Pedro Castanho, MD,† and Joaquim J. Ferreira, MD‡ Study Design. Systematic review of reported adverse events. Objective. To evaluate the tolerability and safety of chiropractic procedures. Summary of Background Data. Despite the increasing popularity of chiropractic, there are few properly de- signed prospective controlled trials, and there is a dispro- portionate lack of evaluation of its safety profile. The literature reports multiple neurologic complications of spinal manipulation, some of which are clinically relevant and even life threatening. Methods. We performed an electronic search in 2 da- tabases: Pubmed and the Cochrane Library for the years 1966 to 2007. All articles that reported adverse reactions associated with chiropractic were included irrespective of type of design. The outcome measures were the type of adverse events associated or attributed to chiropractic interventions and their frequency. Results. A total of 376 potential relevant articles were identified, 330 of which were discarded after abstract or complete article analysis. The search identified 46 articles that included data concerning adverse events: 1 randomized controlled trial, 2 case-control studies, 7 prospective studies, 12 surveys, 3 retrospective studies, and 115 case reports. Most of the adverse events reported were benign and transitory, however, there are reports of complications that were life threatening, such as arterial dissection, my- elopathy, vertebral disc extrusion, and epidural hema- toma. The frequency of adverse events varied between 33% and 60.9%, and the frequency of serious adverse events varied between 5 strokes/100,000 manipulations to 1.46 serious adverse events/10,000,000 manipulations and 2.68 deaths/10,000,000 manipulations. Conclusion. There is no robust data concerning the incidence or prevalence of adverse reactions after chiro- practic. Further investigations are urgently needed to as- sess definite conclusions regarding this issue. Key words: spinal manipulation, chiropractic, adverse events, safety. Spine 2009;34:E405–E413 Since the 19th century, chiropractic procedures have been applied to treat a vast number of conditions. 1 The World Health Organization (WHO) has recently defined chiropractic as a health care profession concerned with the diagnosis, treatment, and prevention of disorders of the neuromusculoskeletal system and the effects of these disorders on general health. WHO published guidelines focused on basic chiropractic training and the serious adverse reactions that can occur when safety issues are not respected. No information is reported about chiro- practic efficacy. (The WHO definition, WHO, Guide- lines on Chiropractic, 2005). 2 Although the multiple definitions of chiropractic are unclear in the discrimination of the type of therapeutic procedures included in this treatment, the 2 main types of therapeutic interventions are: manipulation (high ve- locity, low amplitude thrusts that cannot be resisted by the patient) and mobilization (low-velocity passive mo- tion that can be stopped by the patient). 3 Although the list of indications for which chiropractic is recommended is enormous, there is insufficient pub- lished evidence to support or refuse the efficacy of this treatment modality. 4,5 Recent reviews about its effective- ness in multiple indications concluded that the efficacy of spinal manipulation was not demonstrated for the treat- ment of any condition, 6 and that there were few properly designed randomized controlled trials, such that the re- sults were frequently inconclusive. 7–10 On the other hand, because it does not constitute a pharmacological in- tervention and is considered a nonconventional therapy, it has not been subjected to formal efficacy and safety evalu- ations demanded by the national drug agencies. Without a robust demonstration of effectiveness, and a disproportional overgrowth of popularity, the evalua- tion of the safety profile gains more relevance. Reinforc- ing this need, the literature reports multiple cases of pa- tients who experienced serious adverse neurologic events after chiropractic manipulations. 11–31 The aim of this systematic review was to identify and appraise all studies specifically designed to evaluate safety data concerning adverse events associated with chiropractic practice. Materials and Methods Study Identification We performed an electronic search in 2 databases: Pubmed and the Cochrane Library for the years 1966 to 2007. The key words used were: chiropractic, adverse reactions, adverse events, safety, and spinal manipulation. The search had no language restrictions, and we followed the approach presented in Appendix 1. We selected data regarding spinal manipulation safety. Additional references were identified from the bibliog- raphies of published articles that were relevant to the topic of spinal manipulation. We also analyzed all articles that reported adverse reactions related to spinal manipulation in the form of case series or case reports. Abstracts and other presentation formats were also included. From the *Department of Neurology, Hospital de Santa Maria, Lis- bon, Portugal; †Department of Neurosurgery, Hospital de Sa ˜o Jose ´, Lisbon, Portugal; and ‡Neurological Clinical Research Unit, Institute of Molecular Medicine, Lisbon, Portugal. Acknowledgment date: February 20, 2008. Revision date: December 1, 2008. Acceptance date: December 4, 2008. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence and reprint requests to Liliana Olim Gouveia, MD, Department of Neurology, Hospital de Santa Maria, Ave, Prof Egas Moniz, 1649 – 035 Lisbon, Portugal; E-mail: lilianafog@gmail.com E405