[Histopathological degeneration score of fibrous cartilage. Low- and high-grade meniscal degeneration].

Although histopathology of meniscal degeneration plays an important role, no criteria to assess severity of the degeneration are available to date. Our aim was to create a histopathological scoring system for meniscal degeneration with good interobserver variability, taking matrix degradation and cellularity in meniscal tissue into consideration. Degeneration is classified as follows: grade 1 (low), grade 2 (intermediate), grade 3 (high). The pattern of NITEGE deposits (G1 fragment of aggrecan) was assessed immunohistochemically (n=38) and compared with the grades of degeneration. In 48% of the patients with grade 2 or 3 degeneration extracellular NITEGE deposits (specificity 100%) were found, whereas grade 1 patients showed no deposits. Extracellular NITEGE deposits correlated positively with the grade of degeneration. In all, 30 cases (10 per grade) were assessed by three pathologists (A, B, C). Grading conformity was 70% for grade 1, 66% for grade 2 and 100% for grade 3. Cohen's Kappa coefficient was 0.6--0.7 between pairs of observers. Combining grade 1 and 2 to low-grade degeneration, compared to a grade-3 high-grade degeneration achieved Kappa coefficients of between 0.93 and 1.0. This reproducible degeneration score for fibrous cartilage could form the basis for the standardized assessment of meniscal degeneration.