Postoperative medial meniscal shift in the knee-flexed position following meniscal repair associated with anterior cruciate ligament reconstruction

Abstract

Purpose: The anterior cruciate ligament (ACL) is an important restraint against anterior tibial translation and internal rotation. The ACL injury has a high risk of meniscal injury and cartilage damage that progresses to osteoarthritis of the knee. The medial meniscus (MM) acts as a secondary stabilizer of the anterior tibial translation. Therefore, the MM posterior segment is more susceptible to injury in knees with chronic ACL failure. Compared with the extended position, in the knee-flexed position, the contact area of the tibiofemoral joint is reduced and the contact pressure between the meniscus and the femoral condyle seems to be increased. However, relationships between MM repair concomitant with ACL reconstruction and the postoperative MM translation in the knee-flexed position remains unclear. The aim of this study was to evaluate the positional shift of MM posterior segment at 90° of knee flexion in patients who underwent MM repair associated with ACL reconstruction. Methods: The subjects were 24 patients who had open magnetic resonance imaging (MRI) scans before and after arthroscopic surgery from August 2014 to June 2017. This study included 12 patients who underwent ACL reconstruction without MM tears (no tear group) and 12 patients who underwent ACL reconstruction with MM repair (MM repair group). The shape of MM posterior segment was evaluated using open MRI at 90° of knee flexion before surgery and 3 months postoperatively. MM length (MML), MM posterior body width (MMPBW), MM height (MMH), and MM posterior extrusion (MMPE) were investigated. Differences between groups were assessed using the Mann–Whitney U test. Power and statistical analyses were performed using EZR-WIN software. Significance was set at P < 0.05. Results: In MM repair group, MML decreased from 46.8 ± 3.9 mm to 43.6 ± 3.6 mm (P = 0.01). MMH, MMPBW, and MMPE decreased from 7.2 ± 1.3 mm to 6.8 ± 1.2 mm (P = 0.3), from 14.1 ± 1.6 mm to 11.2 ± 1.6 mm (P < 0.01), and from 4.4 ± 1.6 mm to 1.8 ± 1.1 mm (P < 0.01) after concurrent MM repair with ACL reconstruction, respectively. Compared with no tear group, there were no significant differences in preoperative MML, MMH, and MMPBW. However, preoperative MMPE was significantly higher in MM repair group than in no tear group. On the other hand, no significant differences between two groups were observed in postoperative four parameters. Conclusions: This study demonstrated that the MM posterior segment was compressed and extruded posteriorly by an abnormal anterior tibial translation at 90° of knee flexion in ACL-deficient knees, especially with concomitant MM posterior segment tears. Concurrent MM repair with ACL reconstruction improved an abnormal posterior extrusion of the MM. Our results suggest that simultaneous meniscal repair with ACL reconstruction can decrease excessive posterior shift of the torn MM at the knee-flexed position. The clinical relevance of our study is that the procedure can restore posterior shift of the torn MM and eventually prevent osteoarthritis of the knee.TableNo tear group (n=12)MM tear group (n=12)P value< pre-operation >MML (mm)45.0 ±3.246.8 ±3.90.25MMPW (mm)13.3 ±1.914.1 ±1.70.19MMH (mm)7.5 ±1.17.2 ±1.30.43MMPE (mm)2.0 ± 1.84.4± 1.60.007*< post-operation >MML (mm)43.9 ±3.143.6 ±3.60.62MMPW (mm)12.4 ±2.011.3 ± 1.70.16MMH (mm)7.2 ±1.16.8 ± 1.20.43MMPE (mm)1.4 ±1.31.8 ± 1.10.14*P < 0.05 Open table in a new tab *P < 0.05