title: In vivo stress measurement can predict pain on discography.
abstract: METHODS
  An in vivo experimental investigation of internal disc mechanics and discogenic pain.
  
  
  OBJECTIVE
  To test the hypotheses: 1) The pattern of internal loading of intervertebral discs in vivo is similar to that measured previously in vitro; 2) stress concentrations also are found in clinically degenerate discs in vivo; and stress concentrations are associated with discogenic pain.
  
  
  BACKGROUND
  Stress concentrations corresponding to potentially painful loading patterns of the intervertebral disc and endplate have been observed in vitro.
  
  
  METHODS
  The distribution of stress within the lumbar intervertebral discs of patients with chronic discogenic pain was measured using stress profilometry. The severity of their pain was assessed using provocative discography.
  
  
  RESULTS
  Discogenic pain was found to be associated with anomalous loading of the posterolateral anulus (P < 0.001) and nucleus (P < 0.01). Painful discs were found to have a 38% wider posterolateral anulus (P < 0.023) than painless discs and to have a 63% lower mean nuclear stress (P < 0.017).
  
  
  CONCLUSIONS
  Stress profilometry is an effective investigation of the mechanics of intervertebral discs in vivo. Discogenic pain is caused by changes in the pattern of loading of the posterolateral anulus or nucleus pulposus.
authors.affiliation: Department of Anatomy, University of Bristol, UK.
authors.forename: D S
authors.initials: DS
authors.lastname: McNally
authors.forename: I M
authors.initials: IM
authors.lastname: Shackleford
authors.forename: A E
authors.initials: AE
authors.lastname: Goodship
authors.forename: R C
authors.initials: RC
authors.lastname: Mulholland
mesh_terms: D000328:Adult; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010146:Pain / Q000473:pathology / Q000503:physiopathology*; D013122:Spinal Diseases / Q000473:pathology / Q000503:physiopathology*; D013314:Stress, Mechanical