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Abstract Presented at the 26th Annual Meeting of the Arthroscopy Association of North America| Volume 23, ISSUE 6, SUPPLEMENT , e8-e9, June 2007

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Accuracy of Knee MRI to Evaluate Osteochondral Lesions (SS-15)

      Purpose

      Determine the MRI diagnostic precision for assessment of osteochondral knee defects, and the concordance between the grading of such lesions by arthroscopy with the Density Prototonic Fat Sat (DP Fat Sat) MRI.

      Type of study

      Transversal with prospective data.

      Material and methods

      Fifty knees of 49 patients (divided into 6 regions) were studied. Relationship between surface of the lesions in mm2 using a coefficient of variation ±2mm2, and the grading of the lesion according to Outerbridge modify system, using arthroscopy as a standard pattern. The Wilcoxon test was used for comparison between medians with the significance of 95% confidence. To evaluate grading concordance was used, the kappa coefficient.

      Results

      Osteochondral lesions were found in 48% of the cases (24/50). Comparing such data with the arthroscopic findings, we found: sensibility 79.4%, specificity 99.3% and accuracy of 97%. Concerning the lesion size, the 53% of the small ones (0-20mm2), 92% of the moderate (20-100mm2) and the 100% of the large lesion (>100mm2) were underestimated by MRI. The average of underestimation was 37,2% (p < 0,0004). Concordance of 70% with kappa coefficient (0.80) was obtained in relationship with grading of the lesions. Grade IV lesions presented the largest percentage of coincidence (77%).

      Conclusions

      The DP Fat Sat MRI possesses a sensibility and specificity similar to those reported with specific cartilage sequences and high concordance in the grading of osteochondral lesions. MRI presents poor precision to evaluate the surface of osteochondral lesions.