Do the radiographic findings of symptomatic discoid lateral meniscus in children differ from normal control subjects?

The aim of this study was to quantitatively compare radiographic findings of symptomatic discoid lateral meniscus in children with those of matched controls. Seventy-eight consecutive children (91 knees) who underwent arthroscopic surgery for a symptomatic discoid lateral meniscus (discoid group) were included. Another 91 age- and sex-matched controls with normal medial and lateral menisci on the basis of magnetic resonance imaging findings were included in this study (control group). Each plain radiograph was evaluated from the anteroposterior view for the following variables: height of the lateral tibial spine, lateral joint space distance, height of the fibular head, squaring of the lateral femoral condyle, obliquity of the lateral tibial plateau and cupping of the lateral tibial plateau. Lateral femoral condylar notch was evaluated in lateral view. Statistical analyses were used to determine the differences between the two groups. A significant difference in the mean height of the lateral tibial spine, lateral joint space distance, height of the fibular head, and obliquity of the lateral tibial plateau distinguished the two groups (p < 0.0001). However, there was no statistical difference in the condylar off sign, squaring of the lateral femoral condyle, cupping of the lateral tibial plateau and lateral femoral condylar notch between groups (n.s.). The cut-off values for the height of the lateral tibial spine (6 mm), lateral joint space distance (8 mm), height of the fibular head (14.9 mm) and obliquity of the lateral tibial plateau (17.6A degrees) were determined. With these cut-off values in diagnosing discoid lateral meniscus, the sensitivity and accuracy of height of the fibular head were 78 and 70 %, respectively. Several plain radiographic findings in symptomatic discoid lateral meniscus in children were significantly different from those in normal control. These findings would be helpful in screening tool of discoid lateral meniscus for children.