The Potential Complications of Chiropractic Therapy

Désirée Lie, MD, MSEd


April 20, 2011

A Tutorial on Chiropractic Therapy

Spinal manipulative therapy is a frequently applied therapy for headache, neck, and back pain and is often provided as part of chiropractic adjustment or manipulation. Although manual and manipulative methods are also applied by osteopaths and other disciplines, the evidence on adverse effects of chiropractic manipulation has focused on chiropractic practice.[1] Chiropractic is a discipline that focuses on the relationship between spinal structure and body function, mediated by the nervous system and originated in 1895 with D. D. Palmer, a hands-on healer. While sufficient evidence supports the use of chiropractic manipulative therapy for low back pain and tension-type headache, more is needed to justify manipulations for other conditions including vision problems, shoulder pain, thoracic pain, and whiplash injuries.[1]

Two main types of therapeutic interventions are described in chiropractic practice:

  • Manipulation described as high-velocity, low-amplitude thrusts that cannot be resisted by the patient; and

  • Mobilization defined as low-velocity passive motion that can be stopped by the patient.[2]

The cracking sound associated with manipulation has been attributed to cavitation in the zygapophyseal joints but has not been shown to be essential to manipulation. There is a higher reported occurrence of an audible crack during rotatory manipulation of the cervical spine than lower-level manipulations.[1]

At least 6 subtypes of techniques are recognized:

  1. Short-lever, dynamic thrust for vertebrae, muscle, or ligament;

  2. Long-lever manipulation of the shoulder, femur, head, or pelvis;

  3. Mobilization or articulation technique;

  4. Manual traction techniques;

  5. Soft-tissue massage; and

  6. Point pressure manipulation.

Adverse Effects of Chiropractic Treatment

The most common adverse effect reported after spinal manipulation is localized discomfort followed by dizziness, transient headache, or fatigue. A national survey of UK chiropractors found an incidence of mild to moderate adverse effects at rates of 1 per 10,000 treatment consultations and 6 per 10,000 cervical spine manipulations for a period of up to 7 days after treatment.[3] Headache, numbness, and tingling of the upper limbs were also reported within this 7-day period though symptoms subsequently subsided. The highest risk immediately after manipulation was faintness/dizziness (16 per 1000 treatments). The authors of this survey considered these rates to be low, and no serious adverse effects were reported by the respondents.

However, there have been case reports of serious sequelae and calls for more research and monitoring.[4] The case report literature suggests potentially more serious adverse effects including cervicothoracic epidural hematoma,[5,6] vertebrobasilar stroke,[7,8,9] neuropraxic injury of radicular nerves, cervical hematoma,[10] cervical disc herniation,[11] Boerhaave's syndrome,[12] cranial nerve palsy,[13] vertebral fracture,[14] subclavian artery occlusion,[15] and other potentially fatal outcomes.[16]

Case reports and series suggest that stroke occurring after cervical spine manipulation may be related to vascular instability of the vertebrobasilar artery. Cervical manipulation may cause dissection or occlusion of the posterior arteries as they are stretched during rotation or tilting of the neck, resulting in ischemia and brain injury in young persons.[8] Vertebrobasilar accidents (VBAs) have been associated with turning the head while driving, coughing, lifting, or sustaining a sports injury in addition to cervical manipulation.[8] A review of cases of VBAs associated with cervical spine manipulation occurring prior to 1993 as reported in the literature found a total of 165, though the total number of treatments in which these cases occurred is unknown; 27% recovered fully, 52% suffered residual effects, and 18% died.[8] These same authors cited other case series, which have estimated the risk at between 1 in 400,000-1,300,000 cervical manipulations.[8] In those 45 years of age and younger, VBA cases as reported by neurologists were 5 times more likely to occur in those who received 3 or more cervical manipulations within the preceding 4 weeks as compared with those who did not receive manipulation; no significant associations were found for those over 45 years of age.[8]

Reviews have reported rates of neurologic complication due to neck manipulations ranging from 1 in 50,000 to 1 in 5,000,000 manipulations.[17,18] These complications include stroke, myelopathy, and radiculopathy with a high rate of subsequent disability. The pathophysiology of the injuries includes C6-7 disc protrusion and hemorrhagic injury. The authors of 1 report suggested that the rate of prolapsed disc associated with cervical manipulation was unacceptably high and that misdiagnosis and failure to recognize the onset of neurological symptoms and signs contributed to subsequent morbidities.[8]

The most recent systematic review on the safety of chiropractic interventions examined reports and studies from 1966 to 2007 to establish both types of adverse events associated with chiropractic manipulations and their frequency.[2] The search identified 46 articles including 1 randomized trial, 2 case-control studies, 7 prospective studies, 12 surveys, 3 retrospective studies, and 115 case reports. The authors concluded that the frequency of all adverse events varied from 33.0%-60.9% and that most adverse effects were benign and transitory. Serious events did occur but were uncommon with a rate of 1.46 serious events and 2.68 deaths per 10,000,000 manipulations. Serious events included arterial dissection, myelopathy, vertebral disc protrusion, and epidural hematoma. For example, patients who had received spinal manipulation within 30 days had a 6.62 relative risk for cervical arterial dissection, ischemic stroke, and vertebral artery dissection compared with patients without such manipulation.

Strokes were found at a rate of 5 per 100,000 manipulations; a total of 64 cases of stroke temporally associated with cervical spine manipulation were identified as a result of legal action. Virtually all (92%) presented with history of head or neck pain, and 25% presented with sudden onset of new or unusual headache and neck pain. Data about incidence was incomplete and not robust, leading the authors to conclude that further research is needed to document the true risk for injuries.

Are There Predictors of Serious Adverse Events?

Attempts have been made to identify predictors of serious adverse events after manipulation. Women appear to be at higher risk as compared with men.[19,20] Those younger than 45 years of age are at higher risk when compared with those over that age.[19,20] Other risk factors have been identified though these appear to be predictive of primarily minor events, most notably headache. These are:

  • More adverse events were reported during a first treatment session[19];

  • Risk is greater if more than 1 region is treated[19];

  • Upper cervical manipulation is higher risk as is a longer duration of neck pain prior to treatment[20,21];

  • Use of medication is associated with higher risk[20]; and

  • Treatment of thoracic spine only also conveys higher risk.[21]

VBAs are difficult to predict because they occur in young, otherwise healthy adults. Some of the challenges of determining predictive factors include absence of accurate description of the manipulative procedure used, poor follow-up after treatment so that serious complications are not linked to the manipulative procedure, and lack of a national or international vigilance system to track the events.


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