dGEMRIC T1 IS REDUCED IN HIP CARTILAGE OVERLYING BONE MARROW LESIONS

Bone marrow lesions are associated with pain and rapidly worsening osteoarthritis. Previous quantitative MRI research of knees with BMLs has found that the cartilage immediately overlying BMLs is less healthy than the adjacent non-overlying cartilage in patients with knee OA. It is not clear how BMLs affect overlying cartilage in the hip or in early OA. Determine whether dGEMRIC T1 (T1Gd) is reduced in hip cartilage overlying BMLs in a cross-sectional sample of adults aged 20-49. dGEMRIC and PD-weighted fat-suppressed (PDw-FS) images were acquired for 128 adults aged 20-49 recruited from a larger population-based study using a 3T MRI. Acetabular and femoral cartilage was segmented manually. BMLs were identified and segmented semi-automatically from the PDw-FS images and were identified as containing cysts or not. Cysts were defined as bright areas on the PDw-FS images within the BML with well-defined borders. Cartilage T1Gd maps and segmented BMLs were aligned using landmark-based registration. Age and sex-matched control subjects (without BMLs) were identified for each BML subject and were aligned using landmark-based registration. The overlying cartilage was defined as the projection of the BML shape onto the adjacent cartilage surface (ace/fem). The surrounding cartilage was defined as the cartilage not included in the overlying region. We compared characteristics between the BML and control group using a two-sample t-test or Wilcoxon sum rank test for continuous variables, and a χ2 or Fisher's exact test for categorical variables. We applied a linear mixed-effects model to compare the change score (mean T1Gd of overlying minus surrounding cartilage) between the BML and control group. The model was adjusted for BMI, physical activity (MET), FAI, hip pain, and location (ace/fem). Change scores were compared between cystic and non-cystic BML subjects. BML (n=32) and control (n=32) participants were similar on: mean BMI (27.1 vs 27.0), mean MET (10473 vs 10121), and presence of hip pain (53.1% vs 56.3%). The BML group had significantly higher rates of FAI (65.6% vs 37.5%, p=0.02). The change score was significantly larger for the BML subjects compared to controls: -80ms (95% CI: -158, -2), p=0.04. There was no significant difference between the change scores for cystic and non-cystic BML subjects: -32ms (95% CI: -154, 91), p=0.60. Change scores for each individual group are listed in Table 1. Hip cartilage overlying BMLs has reduced glycosaminoglycan (GAG) concentration, consistent with findings in knee OA. A strength of our approach is that we controlled for natural variations in T1Gd in the hip. This work demonstrates that BMLs are associated with osteoarthritis progression in the hip, even at early stages, and that progression is most pronounced overlying BMLs. Canadian Institutes of Health Research (PAF-107513). Arthritis Society (TGP-18-0229). BBF has an equity position in a private imaging clinic which includes MRI in Van BC. The IMPAKT-HiP participants and study team members. CORRESPONDENCE ADDRESS: [email protected].