Aim: This study compares the MRI scan with clinical diagnosis, and looks at the reliability of both these against the gold standard of arthroscopic diagnosis, in disorders of the knee.
Materials and methods: The patients were from the knee specialist unit of a tertiary referral centre seen and operated by the senior author , over a two year period. This is a retrospective study. The total number of patients in this study was 58(n=58) , with ages ranging from 18–63 years. The results were obtained using statistical formulae, which calculated the sensitivity , Specificity , accuracy and the positive and negative predictive values of the MRI scan and that of clinical diagnosis .
Results: The MRI scan was found to be significantly sensitive in diagnosis of medial meniscal lesions, 96% (95% Confidence interval 89–100), it was also found to be significantly specific in diagnosis of lateral meniscal, 90% ( 95% CI, 81–98) and ACL lesions 94% (95% CI,87–100). The MRI scan had poor sensitivity and specificity for articular cartilage lesions.
The sensitivity of clinical diagnosis for medial and lateral meniscus and ACL lesions was found to be less than 90%. Clinical impression was found to be significantly specific for lesions of ACL and the articular cartilage.
The negative predictive value of the MRI scan was found to be significantly high (>
95%), for lesions of the medial and lateral meniscus and the ACL.
Conclusion: The MRI had a poor diagnostic value in diagnosing and quantifying articular cartilage (chondral) lesions. Clinical diagnosis had a lower sensitivity as compared to MRI in diagnosis of medial meniscal lesions but was more specific in diagnosing cruciate and articular cartilage pathology. The reliability of a high negative predictive value for the MRI scan in ruling out medial meniscus, lateral meniscus and ACL lesion was demonstrated. Therefore, a ‘normal’ scan can be used to exclude lesions. thus sparing patients from expensive and unnecessary surgery and also freeing up valuable theatre time.
