title: Do participants with low back pain who respond to spinal manipulative therapy differ biomechanically from nonresponders, untreated controls or asymptomatic controls?
abstract: METHODS
  Nonrandomized controlled study.
  
  
  OBJECTIVE
  To determine whether patients with low back pain (LBP) who respond to spinal manipulative therapy (SMT) differ biomechanically from nonresponders, untreated controls or asymptomatic controls.
  
  
  BACKGROUND
  Some but not all patients with LBP report improvement in function after SMT. When compared with nonresponders, studies suggest that SMT responders demonstrate significant changes in spinal stiffness, muscle contraction, and disc diffusion. Unfortunately, the significance of these observations remains uncertain given methodological differences between studies including a lack of controls.
  
  
  METHODS
  Participants with LBP and asymptomatic controls attended 3 sessions for 7 days. On sessions 1 and 2, participants with LBP received SMT (+LBP/+SMT, n = 32) whereas asymptomatic controls did not (-LBP/-SMT, n = 57). In these sessions, spinal stiffness and multifidus thickness ratios were obtained before and after SMT and on day 7. Apparent diffusion coefficients from lumbar discs were obtained from +LBP/+SMT participants before and after SMT on session 1 and from an LBP control group that did not receive SMT (+LBP/-SMT, n = 16). +LBP/+SMT participants were dichotomized as responders/nonresponders on the basis of self-reported disability on day 7. A repeated measures analysis of covariance was used to compare apparent diffusion coefficients among responders, nonresponders, and +LBP/-SMT subjects, as well as spinal stiffness or multifidus thickness ratio among responders, nonresponders, and -LBP/-SMT subjects.
  
  
  RESULTS
  After the first SMT, SMT responders displayed statistically significant decreases in spinal stiffness and increases in multifidus thickness ratio sustained for more than 7 days; these findings were not observed in other groups. Similarly, only SMT responders displayed significant post-SMT improvement in apparent diffusion coefficients.
  
  
  CONCLUSIONS
  Those reporting post-SMT improvement in disability demonstrated simultaneous changes between self-reported and objective measures of spinal function. This coherence did not exist for asymptomatic controls or no-treatment controls. These data imply that SMT impacts biomechanical characteristics within SMT responders not present in all patients with LBP. This work provides a foundation to investigate the heterogeneous nature of LBP, mechanisms underlying differential therapeutic response, and the biomechanical and imaging characteristics defining responders at baseline.
  
  
  METHODS
  3.
authors.affiliation: *Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong †Department of Physical Therapy, University of Alberta, Alberta, Canada ‡Department of Radiology and Diagnostic Imaging, University of Alberta, Alberta, Canada §University of Alberta Hospital, Alberta, Canada; and ¶Department of Mathematical and Statistical Sciences, University of Alberta, Alberta, Canada.
authors.forename: Arnold Y L
authors.initials: AY
authors.lastname: Wong
authors.forename: Eric C
authors.initials: EC
authors.lastname: Parent
authors.forename: Sukhvinder S
authors.initials: SS
authors.lastname: Dhillon
authors.forename: Narasimha
authors.initials: N
authors.lastname: Prasad
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Kawchuk
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D020393:Manipulation, Spinal / Q000379:methods; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology / Q000601:surgery*; D010147:Pain Measurement; D016896:Treatment Outcome; D055815:Young Adult