Isolated medial meniscus allograft transplant intraoperatively restores anteroposterior knee stability as effectively as isolated anterior cruciate ligament reconstruction.

Abstract

To compare the capacity of isolated medial or lateral meniscus allograft transplantation (MAT) and isolated anterior cruciate ligament (ACL) reconstruction (ACLR) to reduce pre-operative knee laxity in vivo. Isolated MAT was hypothesized to restore knee stability comparably to isolated ACLR. All surgical procedures performed with intraoperative navigation were retrospectively analyzed. Patients with post-meniscectomy syndrome and intact ACL undergoing medial or lateral MAT (MAT-M and MAT-L groups) were matched 1:1 by age and sex to patients with intact menisci undergoing ACLR (ACLR-M and ACLR-L groups, respectively). Intraoperative anteroposterior (AP), internal/external rotation, varus/valgus and pivot-shift (PS) laxity were quantified using the navigation system before and after surgery. Repeated-measures ANOVA was used to compare laxity between groups across pre- and post-operative states. Statistical significance was set at p < 0.05. From a total of 232 patients, 36 were selected: 8 in the MAT-M group, 8 in the ACLR-M group, 10 in the MAT-L group and 10 in the ACLR-L group. MAT-M reduced pre-operative AP laxity with no statistically significant difference compared to ACLR, across all measured parameters, including AP translation at 30° and 90° of flexion, internal/external rotation and varus-valgus. Conversely, ACLR was a significantly more effective stabilizer compared to MAT-L, demonstrating a greater reduction in AP laxity at 30° (43.2% vs. 37.2%, p = 0.045) and 90° of flexion (62.6% vs. 36.3%, p = 0.007), and PS area (62.5% vs. 32.5%, p = 0.002). In patients with chronic post-meniscectomy syndrome, isolated MAT-M restored AP knee stability comparably to isolated ACLR, suggesting that the medial meniscus acts as a primary stabilizer in this population. In contrast, isolated MAT-L was significantly less effective than ACLR in controlling AP and PS laxity, despite significantly reducing it. These findings highlight the critical, compartment-specific biomechanical role of the menisci. Level III.