382 FRONTAL PLANE MALALIGNMENT AND CARTILAGE Tip AND T2 RELAXATION TIMES IN KNEE OSTEOARTHRITIS

Abstract

Purpose: Frontal plane malalignment is a known risk factor for development and progression of knee osteoarthritis (OA). In established disease, using standard MR imaging has shown that varus malalignment is associated with morphological changes like meniscal degeneration, bone attrition and cartilage loss. Using quantitative MRI, T1o and T2 relaxation times have emerged as promising markers of early cartilage changes. The purpose of this study was to examine the association of frontal plane malalignment with cartilage composition using quantitative MR imaging. Methods: 38 subjects with knee OA were stratified into varus (n =12, age: 61.2±10.3y, BMI: 28.6±5.1kg/m2; axis: 174.5±4.6°), neutral (n = 19, age: 56.8±7.2y, BMI: 27.1±5.9kg/m2 axis: 179.9±1.2°) or valgus (n = 7, age: 57.1±12.2y, BMI: 25.9±4.5 kg/m2; axis: 183.8±2.1°) groups based on the anatomical alignment from weight-bearing flexed PA radiographs. MRI was done using a 3T GE Excite Signa MR Scanner. Sequences used were (i) high-resolution fat suppressed spoiled-gradient-echo (SPGR) (for cartilage thickness), (ii) T2-weighted fat-saturated FSE (for clinical WORMS grading) sagittal 3D (iii) T1o and (iv) T2 maps. T1o and T2 relaxation times were quantified for the medial and lateral tibial and femoral condyles. Medio-lateral (M/L) ratio of T1o, T2 and thickness were calculated for tibia, femur. Pearson’s correlation was used to correlate alignment with T1o and T2 relaxation times of individual compartments and M/L ratios in subjects from varus and neutral groups pooled together. One way ANOVA was used for differences in M/L ratios between the 3 groups. Results: Greater varus angle was associated with a higher M/L T1o ratio at the tibia and higher M/L T2 ratio at the femur and tibia (Table 1).