title: Low back related leg pain: an investigation of construct validity of a new classification system.
abstract: BACKGROUND
  Leg pain is associated with back pain in 25-65% of all cases and classified as somatic referred pain or radicular pain. However, distinction between the two may be difficult as different pathomechanisms may cause similar patterns of pain. Therefore a pathomechanism based classification system was proposed, with four distinct hierarchical and mutually exclusive categories: Neuropathic Sensitization (NS) comprising major features of neuropathic pain with sensory sensitization; Denervation (D) arising from significant axonal compromise; Peripheral Nerve Sensitization (PNS) with marked nerve trunk mechanosensitivity; and Musculoskeletal (M) with pain referred from musculoskeletal structures.
  
  
  OBJECTIVE
  To investigate construct validity of the classification system.
  
  
  METHODS
  Construct validity was investigated by determining the relationship of nerve functioning with subgroups of patients and asymptomatic controls. Thus somatosensory profiles of subgroups of patients with low back related leg pain (LBRLP) and healthy controls were determined by a comprehensive quantitative sensory test (QST) protocol. It was hypothesized that subgroups of patients and healthy controls would show differences in QST profiles relating to underlying pathomechanisms.
  
  
  RESULTS
  77 subjects with LBRLP were recruited and classified in one of the four groups. Additionally, 18 age and gender matched asymptomatic controls were measured. QST revealed signs of pain hypersensitivity in group NS and sensory deficits in group D whereas Groups PNS and M showed no significant differences when compared to the asymptomatic group.
  
  
  CONCLUSIONS
  These findings support construct validity for two of the categories of the new classification system, however further research is warranted to achieve construct validation of the classification system as a whole.
authors.affiliation: HAWK University of Applied Sciences and Arts, Hildesheim, Germany.
authors.forename: Axel G M
authors.initials: AG
authors.lastname: Schäfer
authors.affiliation: School of Physiotherapy, Curtin Innovation Health Research Institute, Curtin University of Technology Perth, Perth, Australia Manual Concepts, Perth, Australia.
authors.forename: Toby M
authors.initials: TM
authors.lastname: Hall
authors.affiliation: Universitätsklinikum Bonn, Bonn, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Rolke
authors.affiliation: Ruprecht-Karl University, Heidelberg, Germany.
authors.forename: Rolf-Detlef
authors.initials: RD
authors.lastname: Treede
authors.affiliation: Rückenzentrum am Michel, Hamburg, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Lüdtke
authors.affiliation: Rückenzentrum am Michel, Hamburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mallwitz
authors.affiliation: School of Physiotherapy, Curtin Innovation Health Research Institute, Curtin University of Technology Perth, Perth, Australia.
authors.forename: Kathryn N
authors.initials: KN
authors.lastname: Briffa
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002965:Classification / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007866:Leg; D017116:Low Back Pain / Q000150:complications*; D008297:Male; D008875:Middle Aged; D059352:Musculoskeletal Pain / Q000145:classification / Q000175:diagnosis / Q000209:etiology; D009437:Neuralgia / Q000145:classification / Q000175:diagnosis / Q000209:etiology; D010146:Pain / Q000145:classification* / Q000175:diagnosis / Q000209:etiology*; D017288:Pain Threshold; D012684:Sensory Thresholds
keywords: Low back pain; QST; classification system; leg pain; quantitative sensory testing; validity