I am often asked by patients and doctors alike what research exists regarding chiropractic care, and how chiropractic works. Below is a short overview of research on chiropractic and low back pain, as well as information on the mechanisms by which chiropractic works. The second part is written in medical-ese, so the lay reader may want to skip it. If your medical doctor is a "non-believer", tell him not to worry--belief is no longer required, we have research and mechanisms! Have him give this article a read!
1) The British Medical Journal published a 1990 study comparing chiropractic to hospital outpatient treatment in the treatment of mechanical low back pain (involving physical therapy and medication). The results were that “Chiropractic was more effective than hospital management, mainly for patients with chronic or severe low back pain.”--BMJ 1990 Jun 2;300(6737):1431-7.
2) BMJ published another study in 1992. The objective stated was “to compare the effectiveness of manipulative therapy, physiotherapy, treatment by a general practitioner, and placebo therapy in patients with persistent non-specific low back and neck complaints.” The authors stated that “Improvement in the main complaint was larger with manipulative therapy.”
--BMJ 1992 Mar 7;304(6827):601-5.
3) Another BMJ study reported results of an extended follow-up—3 years after the initial study. The results were “improvement in all patients at three years was about 29% more in those treated by chiropractors than in those treated by the hospitals. The beneficial effect of chiropractic on pain was particularly clear.”
--BMJ 1995 Aug 5;311:349-351.
4) An excellent study reported in the world’s premier orthopedic journal, Spine, in 2003 compared medication, acupuncture, and chiropractic in the treatment of chronic spinal pain. Chiropractic treatment was more than 5 times more effective than medication, and three times more effective than acupuncture.--Spine 2003 Jul 15;28(14):1490-502.
5) A follow-up to the previous article was published in 2005 in JMPT. This follow-up was performed more than a year after the initial study. The authors conclude that “In patients with chronic spinal pain syndromes, spinal manipulation, if not contraindicated, may be the only treatment modality of the assessed treatment regimens that provides broad and significant long-term benefit.”--JMPT 2005;28:3-11.
6) A study in the European Spine Journal evaluated the effects of a chiropractic treatment called “flexion-distraction” compared to physical therapy. This is a technique that I use in my office. The authors found that “Subjects randomly allocated to the flexion-distraction group had significantly greater relief from pain than those allocated to the exercise program.” They also noted that patients with radiculopathy did significantly better with flexion distraction.--European Spine Journal 2005 Dec 8;1-13
7) Researchers sought to determine if chiropractic manipulation was safe for patients with injured discs. The reviewers concluded, “An estimate of the risk of spinal manipulation causing a clinically worsened disc herniation or cauda equina syndrome in a patient presenting with lumbar disc herniation is calculated form the published data to be less than 1 in 3.7 million.”
--JMPT 2004 March 27;3:179-210.
8) Another recent study published in the journal Spine reported on a dose dependent response for chiropractic care in patients with chronic low back pain. They found patients reported the best relief with care 3-4 times per week for 3 weeks. This study demonstrates that spinal changes and changes in the nervous system require both time and consistency of treatment..--Spine Sept-Oct 2004;4(5):574-83.
9) Lastly, the Manga Report is an independent study funded by the Ontario Ministry of Health to evaluate the cost effectiveness of all types of treatment for low back pain, including medical treatment, physical therapy, and chiropractic. Here are some of the findings (you can read the entire report online, as it represents the most comprehensive study on the subject to date): “On the evidence, particularly the most scientifically valid clinical studies, spinal manipulation applied by chiropractors is shown to be more effective than alternative treatments for LBP. Many medical therapies are of questionable validity or are clearly inadequate.”
“There is no clinical or case-control study that demonstrates or even implies that chiropractic spinal manipulation is unsafe in the treatment of low-back pain. Some medical treatments are equally safe, but others are unsafe and generate iatrogenic complications for LBP patients. Our reading of the literature suggests that chiropractic manipulation is safer than medical management of low-back pain.”
These researchers additionally found that injured workers returned to work earlier and care was considerably less expensive with chiropractic care.
The mechanisms for improvements in spinal pain with chiropractic care are many, but they fall into 2 main categories, neurological and mechanical.
The rapid speed of the high velocity, low amplitude thrust sets off a barrage of high-threshold mechanoreceptors. According to the gate theory of pain (whose owner received the Nobel Prize in physiology), the activation of high threshold mechanoreceptors is necessary for the inhibition of pain. Low speed mobilization does not activate these receptors. The cavitation created during an adjustment has been shown in numerous studies to stimulate these receptors.
Individuals with chronic pain undergo a process called synaptogenesis that results in long-term potentiation of spinal pain. Several studies have indicated that stimulation from chiropractic adjustments affect mechanoreceptive afferents, which proceed to the cerebellum, then the thalamus, the cortex, the hypothalamus, the peri-aqueductal grey, then the raphe magnus nucleus, wherefrom serotonergic neurons project to the dorsal root ganglion. There, at the “gateway” of nociceptive input, serotonin actually has the ability to degenerate maladaptive synapses that perpetuate spinal pain. To my knowledge, chiropractic adjustments are the only treatment modality that produces this effect. For more information, see JMPT June 2004;27(5):314-26—the article title is “Central neuronal plasticity, low back pain and spinal manipulative therapy.”—authored by renowned neurophysiologist Richard Gillette.
The rapid speed associated with the chiropractic adjustment also creates a reflex in the golgi tendon organ within muscle tissue resulting in reduction in spasm and increases in control and coordination (proprioception). A 2006 in the German medical journal Manual Therapy, found that a single chiropractic adjustment led to improved contractability of the transverses abdominis (a "core" muscle associated with spinal stability). This is especially significant since Vladimir Janda, MD, demonstrated that the transverses abdominis becomes inhibited in individuals with low back pain.
2) Mechanical Mechanisms:
There are 3 phases to healing injured tissue. Inflammatory, regenerative, and remodeling. We know that the regenerative and remodeling phases are guided by joint motion. We know that immobilization during healing leads to contracted, disorganized scar tissue that is less elastic and more sensitive to pain. Ultimately, tissue cannot heal where motion is not complete.
There are 3 types of motion; active, passive, and motion into the paraphyisiologic space. If, by using your finger muscles alone, you attempt to extend your forefinger as far as possible, that is termed active range of motion If you use your other hand to push your finger back further, it will move a great deal more—this is passive motion. Lastly, if a well-trained individual (chiropractor) applies a short thrust to the joint into extension, the finger will move even further. This motion is still within the anatomical limits of motion, and does not injure capsular ligaments when performed by a chiropractor (this is movement into the paraphysiologic space). This adjustment is capable, however, of breaking down capsular adhesions and fibrosis to restore normal motion in an impaired joint. Therein lies the magic of chiropractic—no other healing system trains is practitioners to be so adept at palpating segmental joint movement, diagnosing joint dysfunction, and lastly restoring normal, full range of motion to a joint. Obviously restoring movement to a joint produces optimal healing. Less obviously, normal movement leads to normal afferent firing patterns and normal motor organization in the brain. With normal movement patients achieve both normal optimal biomechanics and proprioceptive activity--this optimizes healing and decreases chronic pain.