Is MRI Essential Prior to Arthroscopic Management of Internal Derangement of the Knee?

Abstract

Background:  Magnetic Resonance imaging (MRI) is a frequently used, non-invasive investigation for the diagnosis of knee meniscal and anterior cruciate ligament (ACL) injuries. This investigation is not available at our institution and is fairly expensive costing about seven thousand rupees. Patients have to be outsourced to get this investigation causing significant delay and expense. This study was designed to compare the accuracy of clinical examination and MRI by arthroscopic exami-nation in patients with knee meniscal and ACL injuries.If clinical diagnosis could be as accurate as MRI, the need for this expensive and time consuming investigation could be avoided.

Patients and Methods:  This study had prospective observational design. Thirty patients who were diagnosed clinically and by MRI to have meniscal or ACL injury and needed arthroscopic intervention, were included in the study on the basis of intention to treat. Accuracy of clinical and MRI diagnosis as had been made earlier were compared after arthroscopic exami-nation.4 by 4 statistical table was used to determine the sensitivity, specificity, positive predictive value(PPV), negative pre-dictive value (NPV) and accuracy of clinical  and MRI diagnosis for meniscal and ACL injuries.

Results:  In case of meniscal injuries, clinical examination had sensitivity of 91%, specificity of 22%, positive predictive value of 73%, negative predictive value of 50% and accuracy of 70% and MRI had sensitivity of 94%, specificity of 9%, positive predictive value of 64%, negative predictive value of 50% and accuracy of 63%. Similarly in case of ACL injuries, Clinical examination had sensitivity of 84%, specificity of 100%, positive predictive value of 100%, negative predictive value of 78% and accuracy of 90% and MRI had sensitivity of 94%, specificity of 58%, positive predictive value of 77%, negative predictive value of 87% and accuracy of 80%.

Conclusion:  The accuracy of diagnosis of meniscal and ACL injuries by clinical examination and MRI were arthroscopi-cally compared and found to be fairly matched .It is suggested that routine use of MRI just to confirm the clinical diagnosis of these injuries should be reconsidered.