Meniscal tears after anterior cruciate ligament reconstruction.

The aim of this study was to follow patients in whom preoperative MRI demonstrated grade-3 lesions in the medial meniscus but no visible tears at arthroscopic ACL reconstruction, and to ascertain whether these meniscal lesions would progress to definite tears after reconstruction. The Study population consisted of 19 patients with a mean age of 23.2 years. Intraoperative arthroscopy showed normal appearance in 16 of 19 menisci and mild degree superficial legions in 3 menisci. None of the patients had any special treatment for the menisci at surgery. As controls, 39 patients who showed no tears on MRI and arthroscopy were studied. All MR studies were performed on a 0.5 T MR unit with field echo pulse sequences. A slice thickness of 1.5 mm was used with no interslice gap. Grade-3 legions progressed to definite tears in 8 of the 19 studied patients (42.1%) 12 to 33 months after ACL reconstruction. The Remaining 11 patients showed only symptoms or signs suggesting meniscal tears during a mean follow-up of 26.1 months. In the controls, medial meniscal tears occurred in 2 of the 39 patients (5.1%) 15 to 18 months after reconstruction. The studied patients were divided into a tear group (n=8) and a no-tear group (n=11). When the number of slices with grade-3 lesions was compared between the 2 groups, the mean slice number in the tear group (5.8 slices) was significantly greater than that in the no-tear group (3.1 slices) (P<0.05). These results suggest that even if no visible tear is found at surgery, patients in whom grade-3 lesions are identified in many slices have a high risk of developing definite tears after ACL reconstruction.