Beneficial effects of manually assisted chiropractic adjusting instrument in a rabbit model of osteoarthritis

Spine adjusting instrument (Impulse®) attenuates nociception and modulates oxidative stress markers in the spinal cord and sciatic nerve of a rat model of neuropathic pain

OBJECTIVE

Oxidative stress plays an important role in neuropathic pain. Spinal manipulative therapy (SMT) can exert beneficial effects in pain outcomes in humans and animal models. SMT can also modulate oxidative stress markers in both humans and animals. We aimed to determine the effect of Impulse®-assisted SMT (ISMT) on nociception and oxidative stress biomarkers in the spinal cord and sciatic nerve of rats with neuropathic pain (NP).

METHODS

NP was induced by chronic constriction injury (CCI) of the sciatic nerve. Animals were randomly assigned to naive, sham (rats with sciatic nerve exposure but without ligatures) and CCI, with and without ISMT. ISMT was applied onto the skin area corresponding to the spinous process of L4-L5, 3 times/week, for 2 weeks. Mechanical threshold, latency to paw withdrawal to thermal stimulus and oxidative stress biomarkers in spinal cord and sciatic nerve were the main outcomes evaluated.

RESULTS

ISMT significantly increased mechanical threshold and withdrawal latency after CCI. In the spinal cord, ISMT prevented the increase of pro-oxidative superoxide anion generation and hydrogen peroxide levels. Lipid hydroperoxide levels both in the spinal cord and in the sciatic nerve were attenuated by ISMT. Total antioxidant capacity increased in the spinal cord and sciatic nerve of CCI rats with and without ISMT. CCI and ISMT did not significantly change the total thiol content of the spinal cord.

CONCLUSIONS

Our findings suggest reduced oxidative stress in the spinal cord and/or nerve may be an important mechanism underlying a therapeutic effect of SMT to manage NP non-pharmacologically.

Neurophysiological mechanisms of chiropractic spinal manipulation for spine pain

Together, neck pain and back pain are the first cause of disability worldwide, accounting for more than 10% of the total years lived with disability. In this context, chiropractic care provides a safe and effective option for the management of a large proportion of these patients. Chiropractic is a healthcare profession mainly focused on the spine and the treatment of spinal disorders, including spine pain. Basic studies have examined the influence of chiropractic spinal manipulation (SM) on a variety of peripheral, spinal and supraspinal mechanisms involved in spine pain. While spinal cord mechanisms of pain inhibition contribute at least partly to the pain-relieving effects of chiropractic treatments, the evidence is weaker regarding peripheral and supraspinal mechanisms, which are important components of acute and chronic pain. This narrative review highlights the most relevant mechanisms of pain relief by SM and provides a perspective for future research on SM and spine pain, including the validation of placebo interventions that control for placebo effects and other non-specific effects that may be induced by SM. SIGNIFICANCE: Spinal manipulation inhibits back and neck pain partly through spinal segmental mechanisms and potentially through peripheral mechanisms regulating inflammatory responses. Other mechanisms remain to be clarified. Controls and placebo interventions need to be improved in order to clarify the contribution of specific and non-specific effects to pain relief by spinal manipulative therapy.