The value of MRI in the evaluation of the ACL deficient knee and in the post-operative evaluation after ACL reconstruction.

To evaluate the usefulness of magnetic resonance imaging (MRI) in the exploration of the anterior cruciate ligament (ACL) deficient-knee, a total of twenty-five patients with chronic instability of the knee joint and who underwent both MRI and arthroscopy were studied prospectively. Twenty-three of these patients underwent an intra-articular reconstruction of the ACL with bone-patellar tendon-bone autografts. For the ACL lesions MRI had a sensitivity of 95.8%, a specificity of 100% and a diagnostic accuracy of 97.7%. Associated bowing of the PCL was seen in 20 cases of the study group. For the associated meniscal lesions MRI had a sensitivity of 77.7%, a specificity of 94.7% and a diagnostic accuracy of 91.5%. In no case did MRI allow to detect the minimal cartilage irregularities observed in the arthroscopy. MRI had great accuracy for the evaluation of the anchoring points, direction of the tunnels and the state of the autografts at intra-articular level. It is concluded that MRI is a useful imaging diagnostic modality for evaluation of the ACL deficient-knee and the intra-articular reconstruction of the ACL, thereby MRI affords the surgeon better preoperative planning.