title: High loading rate during spinal manipulation produces unique facet joint capsule strain patterns compared with axial rotations.
abstract: OBJECTIVE
  Lumbar spinal manipulation (SM) is a popular, effective treatment for low back pain but the physiological mechanisms remain elusive. During SM, mechanoreceptors innervating the facet joint capsule (FJC) may receive a novel stimulus, contributing to the neurophysiological benefits of SM. The biomechanics of SM and physiological axial rotations were compared to determine whether speed or loading site affected FJC strain magnitudes or patterns.
  
  
  METHODS
  Human lumbar spine specimens were tested during physiological rotations and simulated SM while measuring applied torque, vertebral motion, and FJC strain. During physiological rotations, specimens were actuated at T12 to 20 degrees left and right axial rotation at 2 degrees to 125 degrees per second. During SM simulations, a 7-mm impulse displacement was applied to L3, L4, or L5 at 5 to 50 mm per second.
  
  
  RESULTS
  Physiological rotations. Increasing displacement rate resulted in significantly larger torque magnitudes (P < .001), whereas vertebral kinematics and FJC strain magnitudes were unchanged (P > .05). Physiological rotations vs SM. Applied torque and vertebral rotation magnitudes were similar across speed and vertebral level. Total vertebral translations were slightly larger during physiological rotations vs SM at a given loading rate (P < .05). Patterns of vertebral motions and FJC strain during SM and physiological rotations varied significantly with loading rate (P < .05) but not with actuation site (P > .15).
  
  
  CONCLUSIONS
  The similar patterns observed in vertebral motion and FJC strain across actuation sites during SM and physiological rotations suggest that site specificity of SM may have minimal clinical relevance. High loading rates during lumbar SM resulted in unique patterns in FJC strain, which may result in unique patterns of FJC mechanoreceptor response.
authors.affiliation: Department of Biomedical Engineering, Stony Brook University, HSC T18-030, Stony Brook, NY 11794-8181, USA
authors.forename: Allyson
authors.initials: A
authors.lastname: Ianuzzi
authors.forename: Partap S
authors.initials: PS
authors.lastname: Khalsa
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D026882:Manipulation, Chiropractic / Q000379:methods*; D008875:Middle Aged; D019415:Torque; D014102:Torsion Abnormality