Bone marrow lesions and cartilage health in the hip: quantitative imaging and indentation testing

Abstract

Objective:

Changes in the bone, like bone marrow lesions (BMLs) and residual bony deformity from healed Legg-Calve-Perthes disease (LCPD), play an important role in osteoarthritis (OA) progression. BMLs are associated with less-healthy cartilage in the knee but we don’t know how they affect the hip. People with healed LCPD are at a high risk of developing OA but we don’t know when cartilage degeneration begins. Quantitative MRI sequences (e.g. dGEMRIC, T1ρ, T2 mapping) are important tools for studying cartilage health in vivo. We do not know how well T1ρ maps intra-subject stiffness variations. Overall goal: learn more about how bone changes are linked to changes in hip cartilage. Specific objectives: determine if hip BMLs are associated with poorer cartilage health; determine how healed LCPD affects cartilage health in teenagers; and determine how intra-subject cartilage stiffness is related to T1ρ in the acetabulum.

Methods:

We compared cartilage T1Gd values in hips with BMLs to hips without BMLs (overall and in BML overlying cartilage) in a group of young adults imaged at 3T. We compared cartilage T1ρ and T2 values in hips with healed LCPD deformity to a control group of teenagers imaged at 3T. We compared local

stiffness to local T1ρ in human acetabula imaged at 9.4T.

Results:

Mean T1Gd was 75ms lower (95% CI [-150, -1]) in hips with BMLs, and the effect was localized to the BML overlying acetabular cartilage (-105ms; 95% CI [-175, -35]). T1ρ and T2 were significantly higher in the severe LCPD group, and T1ρ was significantly higher in the mild LCPD group. IM and T1ρ were

negatively correlated in acetabular cartilage (r_rm = -0.18, 95% CI [-0.245, -0.117]).

Conclusions:

Cartilage is more degenerated in hips with BMLs than hips without BMLs and the degeneration is found immediately over the acetabular BMLs, which suggests a local effect. Hip cartilage degeneration begins in adolescence in severe LCPD. T1ρ appears to be the most promising qMRI method for following cartilage health in longitudinal studies of LCPD. T1ρ may be useful to study stiffness distribution noninvasively in the hip.