A new histology scoring system for the assessment of the quality of human cartilage repair: ICRS II.
BACKGROUND
A reliable and reproducible method is needed to assess cartilage repair.


OBJECTIVE
This study was undertaken to test the reproducibility of 2 established histological scoring systems, the Modified O'Driscoll Scale (MODS) and International Cartilage Research Society (ICRS) Visual Assessment Scale (ICRS I), and subsequently to develop and evaluate a new grading system for cartilage repair.


METHODS
Cohort study; Level of evidence, 2.


METHODS
A total of 107 cartilage biopsy specimens were graded using MODS and ICRS I, and the reader variability was measured. The new grading system, ICRS II, was developed and the inter- and intrareader variability determined by 3 independent readers. Collagen type II deposition was assessed immunohistochemically.


RESULTS
The MODS and ICRS I demonstrated high interreader variability, with MODS also showing high intrareader variability. A new histological scoring system, ICRS II, was developed comprising 14 criteria to assess parameters related to chondrocyte phenotype and tissue structure. The ICRS II demonstrated lower inter- and intrareader variability compared with MODS or ICRS I. The overall assessment and matrix staining scores had the best correlation coefficients for inter- and intrareader variability (r = .81 and .82, respectively). The extent of collagen type II in cartilage, considered a marker of differentiation toward hyaline cartilage, could represent a measure of good cartilage repair. A correlation coefficient of .56 was obtained between the extent of collagen type II staining and the overall assessment score.


CONCLUSIONS
The ICRS II represents an improvement over current histological cartilage repair grading systems in terms of reader reproducibility. The clinical relevance and its ability to predict long-term repair durability will be assessed once long-term clinical data become available.
Mainil-Varlet
Pierre
P
Institute of Pathology, University of Bern, Bern, Switzerland.
Van Damme
Boudewijn
B
Nesic
Dobrila
D
Knutsen
Gunnar
G
Kandel
Rita
R
Roberts
Sally
S
D000328:Adult; D002358:Cartilage, Articular / Q000166:cytology* / Q000293:injuries / Q000601:surgery*; D015331:Cohort Studies; D006652:Histological Techniques; D006801:Humans; D019637:Orthopedic Procedures; D019651:Plastic Surgery Procedures; D012038:Regeneration; D015203:Reproducibility of Results; D016896:Treatment Outcome