BIOLOGICAL EFFECTS OF SPINAL MANIPULATION IN CHRONIC NON-SPECIFIC LOW BACK PAIN PATIENTS

Low back pain (LBP) affects up to 85% of the adult population imposing an economic burden of $86 billion annually or 1% of the US gross domestic product. Traditionally, acute spinal pain has been considered as self-resolving with chronic low back pain (pain 3 months duration) only accounting for 5% of those individuals with low back pain. Though, more recent literature has contested this view point by citing that between one-third and two-thirds of those patients with acute spinal pain do not improve, but instead transition to chronic pain. Thus, determining and using efficacious interventions for low back pain may prevent or improve the disability associated with chronic low back disorders. One viable treatment option for low back pain is spinal manipulative therapy (SMT). However, insufficient evidence exists to explain the mechanisms of pain reduction and improved function associated with SMT, although SMT appears to be an advocated intervention for managing low back pain patients. If the biological mechanisms of SMT were understood, clinicians could determine a priori which patients may respond to SMT, perhaps improving clinical outcomes and reducing health care costs. Thus, our study sought to improve the understanding of the biological mechanisms associated with spinal manipulation. This pilot project involved a prospective, randomized, single-blinded clinical trial of 3-week spinal manipulative therapy in individuals with chronic non-specific low back pain (CNSLBP). We enrolled and randomly assigned 29 subjects (n = 29) to spinal manipulation (SMT) or sham spinal manipulation (sham SMT) groups. After group allocation, we conducted testing including pressure pain threshold (PPT) and kinematic analyses (angular displacement and velocity), along with clinical outcomes (Numeric Pain Rating Scale and Oswestry Disability Index). This is the first study that demonstrates the effect of SMT on PPT at local, regional, and remote testing sites in chronic low back patients. Furthermore, the results demonstrate that SMT and sham SMT can lead to significant improvements in pain and patient-reported disability along with trunk kinematics in CNSLBP patients. Though not significant, the SMT group showed more favorable improvements in trunk angular displacement in the SMT group than the sham SMT group at 3-weeks post-intervention. It is therefore recommended to use the standard SMT in the clinical setting, even though some technique variations may influence trunk kinematics. Lastly, our results indicated that the relationship between SMT-induced changes in biological outcome measures appears limited. Results of this study support the use of SMT or its variation in patients with CNSLBP. Furthermore, the specific technique of how spinal manipulation is conducted may be less important, as long as a mechanical load is applied to the spine. Overall, the presented work stipulates acquiescent evidence that SMT is an effective intervention in patients with CNSLBP. Nevertheless, further study with a larger sample size and longer-term outcome is required to better appreciate the biological mechanisms associated with SMT