title: Mechanisms and effects of spinal high-velocity, low-amplitude thrust manipulation: previous theories.
abstract: OBJECTIVE
  When the clinical efficacy of spinal manipulative treatment for spinal pain has been assessed, high-velocity low-amplitude thrust (HVLAT) manipulation and mobilization have been regarded as clinical interventions giving identical and equivalent biologic effects. The objective of this review is to critically discuss previous theories and research of spinal HVLAT manipulation, highlighting reported neurophysiologic effects that seem to be uniquely associated with cavitation of synovial fluid.
  
  
  METHODS
  The biomedical literature was searched for research and reviews on spinal manipulation. MEDLINE and EMBASE databases were used to help find relevant articles.
  
  
  METHODS
  All articles relevant to the objectives were selected.
  
  
  METHODS
  All available data were used.
  
  
  RESULTS
  The main hypotheses for lesions that respond to HVLAT manipulation were critically discussed: (1) release of entrapped synovial folds or plica, (2) relaxation of hypertonic muscle by sudden stretching, (3) disruption of articular or periarticular adhesions, and (4) unbuckling of motion segments that have undergone disproportionate displacements.
  
  
  RESULTS
  There appear to be 2 separate modes of action from zygapophyseal HVLAT manipulation. Intra-articular "mechanical" effects of zygapophyseal HVLAT manipulation seem to be absolutely separate from and irrelevant to the occurrence of reported "neurophysiologic" effects. Cavitation should not be an absolute requirement for the mechanical effects to occur but may be a reliable indicator for successful joint gapping.
  
  
  CONCLUSIONS
  It is hoped that identification of these unique neurophysiologic effects will provide enough theoretical reason for HVLAT manipulation and mobilization to be assessed independently as individual clinical interventions.
authors.affiliation: British School of Osteopathy, London, United Kingdom.
authors.forename: David W
authors.initials: DW
authors.lastname: Evans
mesh_terms: D002574:Cervical Vertebrae / Q000503:physiopathology*; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology; D017116:Low Back Pain / Q000628:therapy*; D020393:Manipulation, Spinal / Q000379:methods* / Q000592:standards*; D010147:Pain Measurement; D016896:Treatment Outcome; D021801:Zygapophyseal Joint / Q000503:physiopathology