Association between radiography-based subchondral bone structure and MRI-based cartilage composition in postmenopausal women with mild osteoarthritis

Objective: Our aim was to investigate the relation between radiograph-based subchondral bone structure and cartilage composition assessed with delayed gadolinium enhanced magnetic resonance imaging of cartilage (dGEMRIC) and T2 relaxation time. Design: Ninety-three postmenopausal women (KellgreneLawrence grade 0: n ¼ 13, 1: n ¼ 26, 2: n ¼ 54) were included. Radiograph-based bone structure was assessed using entropy of the Laplacian-based image (ELap) and local binary patterns (ELBP), homogeneity indices of the local angles (HIAngles,mean, HIAngles,Perp, HIAngles,Paral), and horizontal (FDHor) and vertical fractal dimensions (FDVer). Mean dGEMRIC index and T2 relaxation time of tibial cartilage were calculated to estimate cartilage composition. Results: HIAngles,mean (rs ¼ 0.22) and HIAngles,Paral (rs ¼ 0.24) in medial subchondral bone were related (P < 0.05) to dGEMRIC index of the medial tibial cartilage. ELap (rs ¼ 0.23), FDHor,0.34 mm (r ¼ 0.21) and FDVer,0.68 mm (r ¼ 0.24) in medial subchondral bone were related (P < 0.05) to T2 relaxation time values of the medial tibial cartilage. FDHor at different scales in lateral subchondral bone were related (P < 0.01) to dGEMRIC index (r ¼ 0.29e0.41) and T2 values of lateral tibial cartilage (r ¼ 0.28 to 0.36). FDVer at larger scales were related (P < 0.05) to dGEMRIC index (r ¼ 0.24e0.25) and T2 values of lateral tibial cartilage (r ¼ 0.21). HIAngles,Paral (r ¼ 0.25) and FDVer,0.68 mm (rs ¼ 0.22) in the lateral tibial trabecular bone were related (P < 0.05) to dGEMRIC index of the lateral tibial cartilage. Conclusion: Our results support the presumption that several tissues are affected in the early osteoarthritis (OA). Furthermore, they indicate that the detailed analysis of radiographs may serve as a complementary imaging tool for OA studies.