Macroscopic ICRS Poorly Correlates with O Driscoll Histological CartilageRepair Assessment in a Goat Model

Background: The purpose of this research was to evaluate whether the macroscopic assessment of repair cartilage quality of talar osteochondral defects in a goat model using the ICRS score is in correspondence with histological assessment using the O’Driscoll histology score. Methods: 32 caprine samples with six mm osteochondral defects treated with microfracture were analyzed six months postoperatively using high-resolution digital images. Two observers independently scored the defects using the ICRS (0-12 points). Histological analysis was performed by one expert histologist using the O’Driscoll Score (0-24 points) on 5 μm slices stained with Masson Goldner and Safranin O. Total ICRS and O’Driscoll scores as well as sub items were compared using a Spearman correlation coefficient (p<0.05). Results: The median ICRS for Observer 1 and 2 were 6.5 (range: 4-11) and 6.5 (range: 3-11). The median O’Driscoll score was 11.5 (range: 3-20). The correlation of the total ICRS scores and the O’Driscoll score was not significant, nor was the correlation of sub items (p>0.05). Conclusion: This animal study suggests that isolated macroscopic ICRS assessment of cartilage repair tissue does not correlate well with histological assessment. Possible explanations may be limitations of surface assessment compared to analysis deeper into the tissue and the necessity of more elaborate macroscopic assessment including hypertrophy, colour, lesion size, location and degenerative status of the joint. Techniques that are more accurate, precise and reliable, such as histology, dGEMERIC and T2 mapping MRI, contrast enhanced CT or optical coherence tomography (OCT), should be considered as alternatives or at least as complimentary methods.