A polarized light microscopy method for accurate and reliable grading of collagen organization in cartilage repair.
OBJECTIVE
Collagen organization, a feature that is critical for cartilage load bearing and durability, is not adequately assessed in cartilage repair tissue by present histological scoring systems. Our objectives were to develop a new polarized light microscopy (PLM) score for collagen organization and to test its reliability.


METHODS
This PLM score uses an ordinal scale of 0-5 to rate the extent that collagen network organization resembles that of young adult hyaline articular cartilage (score of 5) vs a totally disorganized tissue (score of 0). Inter-reader reliability was assessed using Intraclass Correlation Coefficients (ICC) for Agreement, calculated from scores of three trained readers who independently evaluated blinded sections obtained from normal (n=4), degraded (n=2) and repair (n=22) human cartilage biopsies.


RESULTS
The PLM score succeeded in distinguishing normal, degraded and repair cartilages, where the latter displayed greater complexity in collagen structure. Excellent inter-reader reproducibility was found with ICCs for Agreement of 0.90 [ICC(2,1)] (lower boundary of the 95% confidence interval is 0.83) and 0.96 [ICC(2,3)] (lower boundary of the 95% confidence interval is 0.94), indicating the reliability of a single reader's scores and the mean of all three readers' scores, respectively.


CONCLUSIONS
This PLM method offers a novel means for systematically evaluating collagen organization in repair cartilage. We propose that it be used to supplement current gold standard histological scoring systems for a more complete assessment of repair tissue quality.
Department of Chemical Engineering and Institute of Biomedical Engineering, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-Ville, Montreal, Québec H3C 3A7, Canada.
A
A
Changoor
N
N
Tran-Khanh
S
S
Méthot
M
M
Garon
M B
MB
Hurtig
M S
MS
Shive
M D
MD
Buschmann
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries / Q000648:ultrastructure*; D003094:Collagen / Q000648:ultrastructure*; D005260:Female; D006736:Horses; D006801:Humans; D007719:Knee Joint / Q000473:pathology; D008297:Male; D008859:Microscopy, Polarization / Q000295:instrumentation / Q000379:methods; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D055815:Young Adult
D003094:Collagen