A Reliable, Ultrasound-Based Method for the Diagnosis of Discoid Lateral Meniscus.

Purpose: To explore the feasibility and validity of ultrasound in the diagnosis of discoid lateral meniscus (DLM) by comparing quantitatively the morphologic difference between DLM and normal lateral meniscus.

Methods: This study was designed to develop and validate the ultrasound diagnostic criterion for DLM. In the development stage (July 2018 to June 2019), data from 180 subjects were used to derive the ultrasound diagnostic criterion, including 90 patients diagnosed as DLM by magnetic resonance imaging (DLM group) and 90 matched controls diagnosed as normal lateral meniscus diagnosed by magnetic resonance imaging (control group). Twelve distinct parameters of meniscus thickness, width, 0.5∗thickness/width, and angle were obtained through anterior, lateral, and posterior views with the probe oriented perpendicular to the lateral tibiofemoral joint line. In the validation stage (July 2019 to December 2019), data from 324 additional participants were used to validate the criterion derived from the development stage. Differences of the continuous variables and categorical variables between the 2 groups were analyzed by an independent t test and χ test, respectively. The diagnostic value of parameters was analyzed by the receiver operating characteristic curve.

Results: In the development stage, significant differences were found in the above 12 parameters between the 2 groups (P < .05 for all). Cut-off values of anterior meniscus angle, meniscus body angle, and posterior meniscus angle were 28.45°, 27.85°, and 29.15°, respectively. The area under the curve, sensitivity, and specificity of anterior meniscus angle (0.953, 95.6%, 91.1%), meniscus body angle (0.980, 95.6%, 95.6%), and posterior meniscus angle (0.942, 80.0%, 97.8%) were greater than other parameters. In the validation stage, the sensitivity, specificity, and accuracy of anterior meniscus angle, meniscus body angle, and posterior meniscus angle in diagnosing DLM were as high as 91.3%, 88.6%, and 89.2%; 94.2%, 93.3%, and 93.5%; and 76.8%, 95.7%, and 91.7%.

Conclusions: DLM can be reliably diagnosed by ultrasound measurements of anterior meniscus angle, meniscal body angle, and posterior meniscus angle.

Level Of Evidence: Level III, case-control study.