Related Terms

• Chiropractic adjustment, chiropractic manipulation, chiropractic manipulative therapy, chiropractic spinal manipulation, manual physiotherapy, manual therapy, spinal adjustive manipulation, spinal manipulation, spinal manipulative therapy, SMT.

• Not included in this review: Osteopathic manipulative therapy, mobilization, mobilization therapy, physical therapy. Traction is a physical modality used primarily in physical therapy, and is inconsistently utilized in chiropractic offices.

Background

• Overview: Chiropractic is a health care discipline that focuses on the relationship between musculoskeletal structure (primarily the spine) and body function (as coordinated by the nervous system), and how this relationship affects the preservation and restoration of health. The broad term "spinal manipulative therapy" incorporates all types of manual techniques, including chiropractic.

• History: Spinal manipulation was used medicinally as early as 2700 B.C. in ancient Chinese medicine. Hippocrates and Galen used manipulative techniques, and the word "chiropractic" is derived from Greek chiropraktikos, meaning "effective treatment by hand."

• In the late 1800s, David Daniel Palmer systematized the principles upon which modern chiropractic is based, suggesting that abnormal nerve function is the primary cause of disorders, and recommending adjustment of the spine as an effective therapy. The Palmer School of Chiropractic opened in 1895, and one-third of students were physicians. Acceptance of Palmer's principles in the medical community varied, and some early chiropractors were imprisoned (including Palmer himself). A schism between chiropractors and medical doctors persisted, and between 1977-1987, an antitrust lawsuit was brought against the American Medical Association for systematic bias against the chiropractic profession (which was ultimately successful).

• Divisions existed within the chiropractic community as well, and during the early 20th century, two schools of thought emerged: One group ("straights") asserted that subluxation is the underlying cause of disease. A second group ("mixers") worked in a multidisciplinary setting with physicians, and accepted other pathophysiologic theories of disease. Two different chiropractic associations were founded between 1920-1926 reflecting this division: the International Chiropractic Association (ICA) and the American Chiropractic Association (ACA), respectively.

• In 1972, chiropractic treatment became reimbursable by Medicare. In 1974, nationally recognized standards were adopted by the Council on Chiropractic Education (CCE), and were recognized by the U.S. Department of Education. All U.S. chiropractic colleges achieved accreditation by the CCE by 1975. Currently, all 50 U.S. states have statutes recognizing and regulating the practice of chiropractic.

• Currently: In the United States, chiropractors are the most frequently used non-physician primary health providers, after dentists (1;2). There are more than 60,000 licensed American chiropractors (3), a number expected to reach 100,000 by 2010 (4). Almost 80% of all visits to chiropractors are for musculoskeletal complaints (5), and more than 40% are for back pain (6). In 1999, 11% of adults and more than 30% of patients with low back pain visited a chiropractor (7). For two-thirds of patients, a chiropractor was the only provider seen for these complaints (8).

• The cost effectiveness of chiropractic care remains controversial and is not clearly established (9-12).

• Techniques: There are more than 100 distinct chiropractic and spinal manipulative adjusting techniques, and there is variability between practitioners. Some approaches use highly specialized tables or hand-held equipment. Techniques that are widely taught in chiropractic schools include: Diversified, Extremity Adjusting, Activator, Gonstead, Cox Flexion-Distraction, and Thompson. Other techniques are taught on chiropractic campuses outside of the established curriculum, and many are taught in seminars that are not sanctioned as a part of the established chiropractic curriculum. Categories of therapeutic approaches include the following:

• Manipulation: A primary chiropractic therapeutic application that involves applying a specific amount of force vectored through a specific plane of motion of a spinal or peripheral joint, in order to reduce joint restriction and facilitate normal range of motion. Long-lever manipulation uses the femur, shoulder, head, or pelvis to affect larger sections of the spine in a non-specific manner. Specific short lever, dynamic thrusts utilize a specific contact on a transverse spinous process of vertebra, muscle, or ligament. Point pressure manipulation includes the gouging or manual stimulation of specific points without attempting to actually massage a muscle or move a joint.

• Mechanical traction: A technique that incorporates the use of an external system of applied resistance to facilitate joint decompression of the spine or extremity. Manual traction is often performed on a segment of the spine without attempting to mobilize the joint through a specific passive movement.

• Massage/soft tissue mobilization: A category of soft tissue therapeutic techniques used to reduce muscle spasm, soreness, or tightness. These procedures are directed at the subcutaneous, muscular, or tendinous tissues and do not result in significant joint movement. Example techniques include myofascial trigger point therapy, cross friction massage, active release therapy, muscle stripping, and rolfing. Mobilization or articulation technique uses slow rhythmic movements rather than quick sharp thrusts, and may be performed within the passive range of motion of the spine.

• Electrical muscle stimulation (EMS)/interferential therapy: A therapeutic modality using two medium-frequency currents that intersect. The intersecting current is believed by some practitioners to reduce muscle spasm and pain.

• Diathermy: A technique that uses high-frequency electrical currents to produce specific "thermal" effects.

• Ultrasound: A technique that uses high-frequency sound waves with the goal of producing "micromassage" and "deep tissue heat."

• Cryotherapy: A technique that uses ice therapy or icepacks for control of joint pain and inflammation.

• Hydroculator packs: A technique that uses therapeutic heat application.

• Rehabilitation/exercise prescription: Exercise-based programs designed to improve function (rehabilitation programs) are sometimes used as part of an overall management strategy.

• Dietary counseling/nutritional support: Weight modulation and dietary change may be recommended as part of an overall management strategy.

• Health promotion/preventative services: Chiropractors often provide health promotion and prevention services, including an emphasis on exercise, adjustment/manipulation, dietary advice, vitamins, and relaxation.

• Diagnostic procedures: Chiropractors use a number of diagnostic imaging tests, including x-ray, computerized tomography (CT) scans, magnetic resonance imaging (MRI), and thermography.

Theory

• There are traditional and scientifically-based hypotheses regarding the mechanism of action of chiropractic and spinal manipulation. There is overlap between some of these theories, with research in several areas. However, the physiologic mechanism of spinal manipulation remains largely unknown.

• Traditional theories: The vertebral subluxation hypothesis proposes that alterations in normal anatomical/physiologic relationships between contiguous articular structures result in disease, and that chiropractic/manipulative methods can reduce these positional abnormalities (13-18). "Vitalism" is the concept that the body has the innate ability to heal itself if relieved of spinal irritations or subluxations (19). Correction of subluxations has been suggested to restore the flow of life force throughout the body, resulting in a brief convalescence and a return to optimum health (20;21). There is limited scientific evidence in these areas (22;23).

• The nerve compression hypothesis suggests that intervertebral subluxations can cause irritation or compression of spinal nerve roots and interfere with nerve transmission (14). The fixation hypothesis proposes that vertebral muscles become locked and lose range of motion, leading to the release of neurotoxic mediators and abnormal nerve conduction (24;25). The axoplasmic aberration hypothesis asserts that compression of spinal nerves or nerve roots may hinder axoplasmic transport and damage nerves.

• It has been proposed that chiropractic may reduce nerve impingement at intervertebral foramina (26), alter the distribution of loads between joints (27-30), create gaps between joints and break up fibrous adhesions that interfere with normal function (31), improve range of motion (32-35), improve immune function (36;37); and foster healing through the clinician-patient relationship (20;38-43).

• Scientific research: Animal experiments report that vertebral displacement may alter the function of nerves arising from intervertebral muscles and influence heart rate and blood pressure (44-46). Human studies report possible changes in patterns of nerve conduction and reflexes during spinal manipulation, although the evidence is not definitive (47-62). Reduced sensitivity to painful stimuli has been reported in some studies of spinal manipulation (63-68), but not in others (69). Some studies report elevated plasma levels of substance P (70;71) and endorphins (72-77) following spinal manipulation, although other research reports no effects (78-80).

• Problems in chiropractic research: Because spinal manipulation involves the hands-on application of a physical therapy, blinding in studies presents a challenge. Often, the effects of treatment are evaluated by those administering therapy. These individuals are not blinded to the type of treatment being administered (unlike assessors in pharmacologic studies in which active and placebo drugs are similar in appearance). This is a potential source of bias. Similarly, placebo control is difficult, and necessitates the use of "sham manipulation" (81). Existing studies are difficult to compare with each other, because methods of manipulation vary between trials, and definitions of medical conditions/diagnoses are inconsistent. Most research has used non-standardized, subjective outcome measures that cannot be pooled.

Scientific Evidence

Tradition/Theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.

• Acute respiratory distress syndrome (ARDS) (273), Addiction, anxiety, attention deficit hyperactivity disorder (ADHD), Cancer pain (274), closed head trauma (275), complex regional pain syndrome (276), constipation (277), glaucoma (278), hip pain, immune enhancement (279), Multiple sclerosis (280;281), optic nerve damage (282;283), optic nerve ischemia (282;284;285), osteoarthritis, pancreatitis (286), postoperative atelectasis (diminished lung volume) (287), Postoperative recovery (288;289), post-traumatic concussion syndrome (290), scoliosis (291), scotoma (292), spinal stenosis (293), thoracic spine pain (294), vision restoration after closed head trauma (295), visual perception deficit (262;265;296).

Safety

Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.

General:

• There are many reports of serious complications during and after spinal manipulation (particularly with cervical spine/neck manipulation). However, the frequency of these events remains controversial and unclear. The most common adverse effect is believed to be local discomfort in the area of treatment (297-299), although most concern centers around the less common but potentially life-threatening risks of stroke/vertebral artery dissection, and spinal cord/nerve damage. Deaths have been reported (300). Some researchers and practitioners blame poor technique, and others believe that the use of high-velocity forceful rotational (twisting) motions of the head increase the risk of serious complications, and suggest using lower-velocity/force non-rotational motion (301-305).

Frequency of adverse effects:

• Because there is not a systematic surveillance system or a reliable large prospective study, the true prevalence of side effects due to spinal manipulation is not known (306). Estimates of the frequency of adverse effects range from 0.2-0.5% (307-310), with serious complications such as stroke occurring in 1-5 out of every 100,000 patients undergoing neck manipulation (311-318), or some estimates at fewer than 1 in a million (319-324). However, other authors believe that these events are much more common. Recent research suggests that the odds of experiencing a stroke/dissection after cervical spine manipulation may be more that six times greater than in people who do not undergo manipulation (325-327).

• Lower back manipulation is generally regarded as being safer than neck (cervical spine) manipulation (328). Some authors suggest that chiropractic manipulation is safer than treatment with non-steroidal anti-inflammatory drugs (329), spine surgery (330), or hospitalization (331), although these areas are not well studied.

• There are several possible causes of inaccuracies in estimates of prevalence. If people seek spinal manipulation for relief of symptoms related to underlying conditions that are the true causes of complications such as stroke, over-reporting of stroke due to manipulation would occur (324;332-340). In contrast, much higher rates of adverse effects have been proposed as being due to under-reporting (341-347). Collections of adverse event reports by professional organizations in the Unites States, Europe, and Australia have brought further attention to the serious risks associated with spinal manipulation (318;346;348-351).

Pre-treatment screening:

• It is unclear if there is an increased risk of adverse events in patients with preexisting abnormalities of blood vessels in the neck or brainstem, which potentially could be identified with pre-treatment questioning or imaging tests (352-354). Pre-treatment screening with cervical spine extension-rotation to assess for symptoms does not appear to be effective (355-358). Other attempts at pre-treatment testing to identify at-risk individuals have not been clearly successful (359-362).

Reported adverse effects:

• Stroke & vertebrobasilar/carotid artery dissection: There are many cases of stroke and arterial dissection following cervical manipulation reported in the medical and legal literature, often occurring in young individuals (20 to 60 years old) (315;333;363-393). Ischemic stroke may occur immediately during or after the procedure, with possible conversion to hemorrhagic stroke. Symptoms may not appear until several days or weeks later, based on reported cases. Various parts of the brain have been affected, including brainstem, cerebellum, occipital, parietal, and frontal lobes. Residual neurologic deficits may remain long-term (307;315;394-449).

• Reported symptoms include headache, vertigo, vomiting, neck pain, nausea, Horner's syndrome, double vision, blurred vision, vision loss, slurred speech (dysarthria), facial droop, hearing impairment, arm or leg weakness, ataxia, nystagmus, numbness, loss of consciousness, as well as reports of paralysis (315;384;385;450;451), coma, and death (300;333;383;387;433;452-459).

• These events are most often associated with vertebral artery dissection, a process that involves an expanding hematoma (blood collection or clot) within the wall of the blood vessel or blockage of the blood vessel by a small flap of vessel wall that develops due to trauma during neck manipulation movements. Carotid artery dissection and thrombosis have also been reported with neck manipulation (365;460-463). Involvement of the basilar and cerebral arteries is also reported (464-467).

• Spinal bleeding/blood clots: Bleeding and blood clots in the cervical (upper), thoracic (mid), and lumbar (lower) spine following manipulation have also been reported, including cervical spine epidural hematoma (468;469), thoracic spinal hemorrhage in a patient using the anticoagulant drug warfarin (Coumadin®) (470), thoracic or lumbar spine epidural hematoma (471) or aneurysm (472), and intraspinal bleeding (473).

• Spinal cord/nerve root compression & disc herniation: Spinal cord injury, cord compression/cauda equina syndrome, and nerve root compression have been reported with neck and back manipulation (474-477), due in some cases to vertebral body fracture (478-480), development of hematoma (481), or to disc herniation/rupture in the cervical, thoracic, or lumbar spine (482-492). Brachial plexus damage has been reported with cervical manipulation (493;494). Nerve root damage from lumbar disc herniation has been associated with cauda equina syndrome, including low back pain, sciatica, saddle sensory disturbances, bladder and bowel dysfunction, and lower extremity motor/sensory loss (490;495-497). Impaired diaphragmatic function can occur (498-500).

• Bone/vertebral fracture: Individuals with osteomyelitis (bone infection) (501), cancer involving bone (502), vertebral fractures, severe degenerative joint disease (osteoarthritis), osteoporosis, and ankylosing spondylitis may be at increased risk of fracture or spinal damage leading to nerve disorders or spinal cord damage (503-505). Fracture of the temporal bone complicated by subdural hematoma has been reported with chiropractic manipulation (506).

• Anticoagulant (blood-thinning) therapy: Thoracic spinal hemorrhage after manipulation has been reported with the use of the anticoagulant ("blood thinning") drug warfarin (Coumadin®) (507). Patients with blood clotting disorders or taking anticoagulant therapies may be at increased risk of adverse effects such as spinal bleeding following manipulative therapy.

• Musculoskeletal: There are reports of muscle strains, sprains, and spasm following chiropractic manipulation, although it is not clear if these problems were actually related to the therapy, or were preexisting conditions (508;509). Osteomyelitis (bone infection) in the spine has been reported, although chiropractic was likely not the cause, but rather was sought as a therapy due to pain related to infection (510).

• Blood pressure effects: The effects of spinal manipulative techniques on blood pressure remain controversial. It has been hypothesized that nervous system effects of spinal manipulation can lower both systolic and diastolic pressure. Numerous trials, reviews, and commentaries have been published in this area (209;217;218;511-521). Although some studies are suggestive, overall the existing evidence remains indeterminate due to methodologic weaknesses and variability between studies. Better research is necessary before a firm conclusion can be drawn.

• Radiation exposure: Some authors suggest that exposure to radiation during x-rays ordered by chiropractors may pose a health risk, since approximately 96% of new U.S. patients and 80% of follow-up patients undergo x-rays (72% in Europe) (522). Although the amount of radiation from plain x-rays is generally considered to be small, regular use of x-rays may increase the risk of some types of cancer.

• Tracheal damage: Prior surgery of the trachea ("windpipe") or tracheostomy may increase the risk of tracheal rupture during neck manipulation (523).

• Cardiovascular complications: There is a report of a heart attack which occurred in a 38-year-old man during cervical spine manipulation (524). It is not clear if manipulation played a causative role in this event.

Underlying conditions that may increase risk:

• Patients with existing blood vessel aneurysms (such as abnormalities in brain blood vessels or aortic aneurysms), atherosclerotic disease ("hardening" of the arteries, including carotid artery disease), collagen disorders, vasculitis, other underlying blood vessel abnormalities, or collagen vascular diseases (such as systemic lupus erythematosus) may be at increased risk of stroke or blood vessel dissection (525;526). Individuals with osteomyelitis (bone infection) (527), cancer involving bone (502), vertebral fractures, severe degenerative joint disease (osteoarthritis), osteoporosis, and ankylosing spondylitis may be at increased risk of fracture or spinal damage leading to nerve disorders or spinal cord damage (528-530). Prior surgery of the trachea or tracheostomy may increase the risk of tracheal rupture (531). Underlying tumors of the brain or near the spinal cord may result in adverse outcomes such as tumor rupture or delayed diagnosis (532-537). Patients with blood clotting disorders or taking anticoagulant ("blood thinning") therapies such as warfarin (Coumadin®) may be at increased risk of adverse effects such as spinal bleeding following manipulative therapy (538). Caution should be used in patients with low blood pressure or taking medications that may lower blood pressure further due to inconclusive reports of lowered blood pressure with the use of manipulative techniques (209;217;218;539-549). Neck pain following cervical manipulation may be a warning sign for stroke (550;551).

Delayed diagnosis/additional care:

• Use of spinal manipulation for symptoms/conditions should not delay the time to diagnosis or treatment with more proven methods. Individuals who experience persistent symptoms or develop neck pain after manipulation should seek further medical attention without delay, as this may be a warning sign for stroke (532;552-557). Patients are advised to discuss spinal manipulation/chiropractic with a primary healthcare provider before starting treatment.

Author Information

• This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

1. Aker, P. D., Gross, A. R., Goldsmith, C. H., and Peloso, P. Conservative management of mechanical neck pain: systematic overview and meta-analysis. BMJ 11-23-1996;313(7068):1291-1296. View Abstract

2. Beneliyahu, D. J. Magnetic resonance imaging and clinical follow-up: study of 27 patients receiving chiropractic care for cervical and lumbar disc herniations. J Manipulative Physiol Ther 1996;19(9):597-606. View Abstract

3. Bronfort, G., Evans, R. L., Kubic, P., and Filkin, P. Chronic pediatric asthma and chiropractic spinal manipulation: A prospective clinical series and randomized clinical pilot study. J Manipulative Physiol Ther 2001;24(6):369-377. View Abstract

4. Deyle, G. D., Henderson, N. E., Matekel, R. L., Ryder, M. G., Garber, M. B., and Allison, S. C. Effectiveness of manual physical therapy and exercise in osteoarthritis of the knee. A randomized, controlled trial. Ann.Intern.Med 2-1-2000;132(3):173-181. View Abstract

5. Froehle, R. M. Ear infection: a retrospective study examining improvement from chiropractic care and analyzing for influencing factors. J Manipulative Physiol Ther 1996;19(3):169-177. View Abstract

6. Hawk, C., Long, C., and Azad, A. Chiropractic care for women with chronic pelvic pain: a prospective single-group intervention study. J Manipulative Physiol Ther 1997;20(2):73-79. View Abstract

7. Hondras, M. A., Linde, K., and Jones, A. P. Manual therapy for asthma. Cochrane.Database.Syst.Rev 2005;(2):CD001002. View Abstract

8. Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com

9. Pistolese, R. A. Epilepsy and seizure disorders: a review of literature relative to chiropractic care of children. J Manipulative Physiol Ther 2001;24(3):199-205. View Abstract

10. Plaugher, G., Long, C. R., Alcantara, J., Silveus, A. D., Wood, H., Lotun, K., Menke, J. M., Meeker, W. C., and Rowe, S. H. Practice-based randomized controlled-comparison clinical trial of chiropractic adjustments and brief massage treatment at sites of subluxation in subjects with essential hypertension: pilot study. J Manipulative Physiol Ther 2002;25(4):221-239. View Abstract

11. Schiller, L. Effectiveness of spinal manipulative therapy in the treatment of mechanical thoracic spine pain: a pilot randomized clinical trial. J Manipulative Physiol Ther 2001;24(6):394-401. View Abstract

12. Winters, J. C., Jorritsma, W., Groenier, K. H., Sobel, J. S., Meyboom-de Jong, B., and Arendzen, H. J. Treatment of shoulder complaints in general practice: long term results of a randomised, single blind study comparing physiotherapy, manipulation, and corticosteroid injection. BMJ 5-22-1999;318(7195):1395-1396. View Abstract

13. Winters, J. C., Sobel, J. S., Groenier, K. H., Arendzen, H. J., and Meyboom-de Jong, B. Comparison of physiotherapy, manipulation, and corticosteroid injection for treating shoulder complaints in general practice: randomised, single blind study. BMJ 5-3-1997;314(7090):1320-1325. View Abstract

14. Wreje, U., Nordgren, B., and Aberg, H. Treatment of pelvic joint dysfunction in primary care--a controlled study. Scand J Prim Health Care 1992;10(4):310-315. View Abstract

15. Yates, R. G., Lamping, D. L., Abram, N. L., and Wright, C. Effects of chiropractic treatment on blood pressure and anxiety: a randomized, controlled trial. J Manipulative Physiol Ther 1988;11(6):484-488. View Abstract