Background Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) may detect early cartilage pathology as it allows assessment of matrix proteoglycan content. It is not known whether changes in dGEMRIC indices are associated with changes in cartilage thickness over time.
Objectives To determine the association of changes in the dGEMRIC index with changes in cartilage thickness in the medial tibiofemoral compartment of knees in a sample of middle-aged women, over a 2-year period using 3.0T MRI.
Methods A total of 148 women (one knee per subject) aged ≥40 years were included. 3.0T MRI of the knee was performed at baseline (BL), 12 months, and 24 months follow-up (FU). Three-dimensional (3D) spoiled gradient recalled echo (SPGR) sequences were acquired for cartilage thickness measurements. 3D inversion recovery-prepared SPGR sequences were acquired 90 minutes after intravenous administration of gadolinium (Gd-DTPA2-) for dGEMRIC. Both segmentations (dGEMRIC and thickness) were performed at the central (weight-bearing) medial femur (cMF) and the medial tibia (MT). For each subregion, two groups were considered according to changes in the dGEMRIC indices: the increase group (the dGEMRIC index at 12 months FU was higher than the one at BL – improvement) and the decrease group (the dGEMRIC index at 12 months FU was lower than the one at BL – worsening). The association of changes in dGEMRIC indices between BL and 12 months FU with concomitant changes in cartilage thickness between baseline and 12 months follow-up, as well as cartilage thickness changes between 12 months and 24 months FU were assessed for each dGEMRIC group separately (increase and decrease), using linear regression models. Adjustments were performed for age, body mass index (BMI), knee malalignment, and Kellgren-Lawrence (KL) grade.
Results The mean age of participants was 56.8±8.7, mean BMI was 29.3±7.5, and 38% of knees had radiographic OA (KL grade ≥2). A total of 296 medial regions were included from 148 knees: 185 (62.5%) regions demonstrated an increase in dGEMRIC, whereas 107 (36.1%) regions showed a decrease in dGEMRIC over time. The remaining 4 (1.4%) subregions exhibited stable dGEMRIC indices. For the increase dGEMRIC group, no significant associations were found with changes in cartilage thickness over time. A decreased dGEMRIC over time (between BL and 12 months FU) at the cMF was significantly associated with an increase in cartilage thickness over time (between 12 months and 24 months FU) at both cMF (p=0.008) and MT (p=0.04).
Conclusions A decrease in dGEMRIC indices over 12 months significantly predicted an increase in cartilage thickness at 24 months in the medial tibiofemoral compartment. Researchers must be aware that an increase in cartilage thickness over time may be related not only to improvement of cartilage, but also with loss of proteoglycan content (degeneration) as demonstrated in our study. A combination of morphologic and compositional MRI techniques should be applied when monitoring the effects of different therapies.
Disclosure of Interest M. D. Crema Shareholder of: Boston Imaging Core Lab, D. J. Hunter: None Declared, D. Burstein: None Declared, L. Li: None Declared, N. Krishna: None Declared, F. W. Roemer Shareholder of: Boston Imaging Core Lab, F. Eckstein Shareholder of: Chondrometrics GmbH, M.-P. Hellio Le-Graverand Employee of: Pfizer Inc., A. Guermazi Shareholder of: Boston Imaging Core Lab, Consultant for: Novartis, Genzyme, AstraZeneca, Striker, Merck Serono
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