title: A validated new histological classification for intervertebral disc degeneration.
abstract: Histology is an important outcome variable in basic science and pre-clinical studies regarding intervertebral disc degeneration (IVD). Nevertheless, an adequately validated histological classification for IVD degeneration is still lacking and the existing classifications are difficult to use for inexperienced observers.
  
  
  OBJECTIVE
  Therefore the aim of this study was to develop and to validate a new histological classification for IVD degeneration. Moreover, the new classification was compared to the frequently used non-validated classification.
  
  
  METHODS
  The new classification was applied to human IVD sections. The sections were scored twice by two independent inexperienced observers, twice by two experienced IVD researchers and once by a pathologist. For comparison, the sections were also scored according to the classification described by Boos et al. by two experienced IVD researchers. Macroscopic grading according Thompson et al., glycosaminoglycan (GAG) content and age were used for validation.
  
  
  RESULTS
  The new classification had an excellent intra- and a good inter-observer reliability. Intraclass Correlation Coefficients (ICC) were 0.83 and 0.74, respectively. Intra- and inter-observer reliability were comparable for experienced and inexperienced observers. Statistically significant correlations were found between the new classification, macroscopic score, GAG content in the nucleus pulposus (NP) and age; Correlation coefficient (CC) 0.79, -0.62 and 0.68, respectively. The CCs of the Boos classification were all lower compared to the new classification.
  
  
  CONCLUSIONS
  the new histological classification for IVD degeneration is a valid instrument for evaluating IVD degeneration in human IVD sections and is suitable for inexperienced and experienced researchers.
authors.affiliation: Dept. of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: j.rutges@umcutrecht.nl.
authors.forename: J P H J
authors.initials: JP
authors.lastname: Rutges
authors.forename: R A
authors.initials: RA
authors.lastname: Duit
authors.forename: J A
authors.initials: JA
authors.lastname: Kummer
authors.forename: J E J
authors.initials: JE
authors.lastname: Bekkers
authors.forename: F C
authors.initials: FC
authors.lastname: Oner
authors.forename: R M
authors.initials: RM
authors.lastname: Castelein
authors.forename: W J A
authors.initials: WJ
authors.lastname: Dhert
authors.forename: L B
authors.initials: LB
authors.lastname: Creemers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000145:classification / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Classification; Degeneration; Histology; Intervertebral disc