Anatomical knee variables result in worse outcomes of lateral meniscal allograft transplantation with discoid lateral menisci than with nondiscoid lateral menisci

Purpose To compare the clinical results of meniscal allograft transplantation (MAT) between patients with discoid lateral meniscus (DLM) and non-DLM (NDLM) and to analyse whether anatomical deformities cause worse clinical results in DLM patients. Methods Patients who underwent unilateral MAT from 2005 to 2017, including 115 patients with DLMs or NDLMs, were included in this study. Clinical outcomes [International Knee Documentation Committee (IKDC) scores, Lysholm scores, Tegner scores, and visual analogue scale (VAS) scores] and radiographic and MRI data were assessed. Clinical outcomes and anatomical knee variables were analysed by multivariate stepwise regression. Results After more than 2 years of follow-up, 9 patients were lost to follow-up, and 59 patients with DLM and 47 patients with NDLM were included. The mean postoperative results were significantly better than the preoperative data ( P < 0.05) in both the DLM and NDLM groups. In addition, postoperative IKDC, Lysholm, and VAS scores but not Tegner scores were better in the NDLM group than in the DLM group. Several anatomical knee variables differed significantly between the NDLM and DLM groups and were associated with MAT outcomes. The condylar prominence ratio of the lateral and medial femoral condyles adjacent to the intercondylar notch and squaring of the lateral femoral condyle (the distance of the straight articular condylar surface) were independent factors significantly correlated with the Lysholm scores for MAT at last follow-up. Conclusion MAT improved knee function in both patients with DLM and patients with NDLM, but patients NDLM had better clinical outcomes than patients with DLM. The condylar prominence ratio and squaring of the lateral femoral condyle may underlie this result. Level of evidence III.