The usefulness of MRI in evaluating menisci after meniscus repair.

We reviewed magnetic resonance imaging (MRI) scans of 15 asymptomatic patients at 6 months to 1 year following meniscal repair procedures. All of the patients were found to have persistent MRI signals in the region of the repair. Nine of the 17 meniscal repairs in the 15 patients had persistent grade 3 signals. Arthrograms were performed on six patients (eight meniscal repairs). Seven of these postoperative menisci showed grade 3 signals on MRI. Only one meniscus was shown to have a complete tear by arthrogram. There were no false negative scans. The overall accuracy, defined as the percentage of postoperative menisci correctly diagnosed by MRI, was 38% (3/8). MRI is a useful preoperative diagnostic study following knee injury. This report demonstrates, however, that present MRI modalities are unable to distinguish between scar tissue of healed meniscal repairs and meniscal tears. Therefore, it is not a useful diagnostic tool in evaluating reinjury following successful meniscal repair.