T2 Relaxation Time Changes in the Distal Femoral Condylar Cartilage of Children and Young Adults with Discoid Meniscus

Abstract

Objective: To investigate compositional changes in the distal femoral condylar cartilage (FCC) of children and young adults with and without discoid meniscus by T2 relaxation time mapping.

Design: We retrospectively reviewed knee magnetic resonance images including sagittal T2 maps of distal FCC performed in patients with or without discoid meniscus. Combined meniscal pathology such as degeneration or tears was also reviewed. Regions of interest were selected, and T2 relaxation time profiles were generated according to medial and lateral and FCC and according to weight-bearing and non-weight-bearing FCC. Nonparametric comparison tests using median values were performed.

Results: Seventy-nine knees from 73 patients (2-20 years) including 45 knees with lateral discoid meniscus (discoid group) were studied. T2 values of FCC showed negative correlation with age in both the discoid and nondiscoid groups (P < 0.01), except for medial weight-bearing FCC. In the discoid group, T2 relaxation times of lateral weight-bearing FCC (median, 46.5 ms) were lower than those of lateral non-weight-bearing (median, 53.2 ms; P < 0.001) and medial weight-bearing (median, 50.5 ms; P = 0.012) FCC. Lateral weight-bearing FCC also showed lower T2 values than other areas in patients with meniscal pathology in the discoid group. However, T2 relaxation times did not differ between the discoid and nondiscoid groups in patients without meniscal pathology.

Conclusions: Children and young adults with discoid meniscus have lower T2 relaxation times in lateral weight-bearing FCC compared with non-weight-bearing or medial FCC, suggesting compositional changes have occurred in these patients.

Keywords: T2 mapping; children; discoid meniscus.

Figure 1.

Representative images of T2 mapping in weight-bearing and non-weight-bearing portions of the medial and lateral femoral condyles. The maximum area of the distal femoral condylar cartilage for T2 mapping is drawn in the (A) medial non-weight-bearing (yellow box), (B) medial weight-bearing (orange box), (C) lateral non-weight-bearing (blue box), and (D) lateral weight-bearing (green box) portions.

Figure 2.

A scatter plot correlating age and T2 values of the femoral condylar cartilage. The discoid and nondiscoid group both showed negative correlation between age and T2 values of the femoral condylar cartilage. This graph only shows the T2 values of lateral non-weight-bearing femoral condylar cartilage (ρ = −0.607, P < 0.001 in the nondiscoid group and ρ = −0.467, P = 0.001 in the discoid group).

Figure 3.

Box plots to compare T2 values. The graphs show T2 values of femoral condylar cartilage in the medial weight-bearing, lateral weight-bearing, medial non-weight-bearing medial, and lateral non-weight-bearing areas. (A) When comparing the discoid and nondiscoid group, only the discoid group had lower T2 values in the lateral weight-bearing portion compared with other areas (P < 0.02). (B) When comparing the discoid group with and without meniscal pathology, the T2 value of the lateral weight-bearing portion was lower than the other portions, but only in patients with meniscal pathology (P < 0.02).