Factors associated with bilateral discoid lateral meniscus tear in patients with symptomatic discoid lateral meniscus tear using MRI and X-ray.

Background: The incidence of bilateral discoid lateral meniscus (DLM) is as high as 73 to 85%, and associated contralateral meniscus tears ranged from 4 to 33% in symptomatic surgical DLM. The goal of the study was analyzing the factors that predict contralateral presence and tearing of DLM in patients who underwent surgery for symptomatic DLM. Our hypothesis was that there is a significant correlation between operative DLM properties and the incidence of bilateral DLM with associated contralateral meniscus tears. These properties include tear patterns, younger patient age, and characteristic X-ray findings.

Patients And Methods: This prospective study included 76 patients who underwent arthroscopic surgery for symptomatic DLM. The contralateral knees were evaluated with X-ray and MRI. Based on the MRI findings, DLM was categorized into three types, and tear patterns were analyzed. The characteristic X-ray findings were evaluated as follows: (1) high fibular head, (2) squared-off appearance of the lateral femoral condyle, (3) cupping of the lateral tibial plateau, (4) widened femorotibial joint space, (5) hypoplasia of the lateral intercondylar spine, (6) notching of the LFC. The number of characteristic X-ray findings (0/1/more than 2) was noted. Binary logistic analysis was performed to find the factors that predict the presence and tear of contralateral DLM.

Results: MRI of contralateral knees revealed 43 cases (57%) of complete DLM, 25 cases (33%) of incomplete DLM, and 8 cases (11%) of normal meniscus. Meniscus tears were found in 29 cases (38%) in the contralateral knee. X-ray of the contralateral knee revealed that 27 patients (36%) had one and 24 patients (32%) had two or more characteristic X-ray findings. On logistic regression analysis, the associations between contralateral knee meniscal tear and the presence of one or more than two characteristic X-ray findings were statistically significant (OR: 16.5, p=0.028; OR: 264.0, p=0.000, respectively).

Discussion: The number of characteristic X-ray findings in the contralateral knee is a significant predictive factor for contralateral DLM type and/or tear. Symptomatic DLM patients with characteristic X-ray findings should be carefully evaluated for contralateral DLM and meniscal tears.

Level Of Evidence: III, prospective diagnostic study of consecutive patients.