Magnetic resonance imaging as a tool to predict reparability of longitudinal full-thickness meniscus lesions

Prediction of meniscus reparability is useful for surgeons to optimise surgical scheduling and to inform patients about postoperative management. This study was designed to determine the accuracy of MRI in predicting the reparability of longitudinal full-thickness meniscus lesions. We studied 100 MRIs of longitudinal full-thickness medial or lateral meniscus lesions located from the meniscosynovial junction to the axial part of the meniscus. The MRI criteria of reparability were a peripheral rim smaller than 4 mm and a lesion longer than 10 mm. At arthroscopy the menisci were considered as reparable when the lesion was located in red–red or red–white zones and when it was more than 1 cm in length. A heterogeneous or homogeneous aspect of the meniscus body was also considered. The length of the meniscus lesion averaged 17.6 mm and the thickness of the rim 3.4 mm. A heterogeneous signal of the axial fragment and of the rim was found in 11 cases and in 48 cases, respectively. In 90 cases, there was no difference between the MRI-predicted reparability and the arthroscopic findings. Global sensitivity of MRI to determine reparability of full-thickness meniscus lesions was 94%, increasing to 96% for the medial meniscus and dropping to 83% for the lateral meniscus. Global specificity was 81%, and was higher for the lateral meniscus (90%) than for the medial one (82%). Global positive predictive value was 0.94 and global negative predictive value was 0.82. A heterogeneous aspect of the rim did not compromise arthroscopic reparability whereas a heterogeneous aspect of the axial fragment indicated an irreparable meniscus. The described MRI criteria can predict meniscus reparability. Their accuracy is limited for lateral meniscus lesions close to the popliteal hiatus and for very young active patients in whom repair of white–white lesions can be attempted. Longitudinal full-thickness meniscus lesions are a good indication for repair in young active patients.