Introduction: The validity of histopathological grading is a major problem in the assessment of articular cartilage. Calculating the cumulative strength of signal intensity of different stains gives information regarding the amount of proteoglycan, glycoproteins, etc. Using this system, we examined the medium-term effect of subchondral lesions on initially healthy articular cartilage.
Materials and methods: After cadaver studies, an animal model was created to produce pure subchondral damage without affecting the articular cartilage in 12 beagle dogs under MRI control. Quantification of the different stains was provided using a Photoshop-based image analysis (pixel analysis) with the histogram command 6 months after subchondral trauma.
Results: FLASH 3D sequences revealed intact cartilage after impact in all cases. The best detection of subchondral fractures was achieved with fat-suppressed TIRM sequences. Semiquantitative image analysis showed changes in proteoglycan and glycoprotein quantities in 9 of 12 samples that had not shown any evidence of damage during the initial examination. Correlation analysis showed a loss of the physiological distribution of proteoglycans and glycoproteins in the different zones of articular cartilage.
Conclusion: Currently available software programs can be applied for comparative analysis of histologic stains of hyaline cartilage. After subchondral fractures, significant changes in the cartilage itself occur after 6 months.