The association between hip bone marrow lesions and bone mineral density: a cross-sectional and longitudinal population-based study

OBJECTIVE: To describe the cross-sectional and longitudinal association between hip Bone marrow lesions (BMLs) and bone density. DESIGN: 198 subjects with a right hip MRI and dual-energy X-ray absorptiometry (DXA) scans conducted at two time points, approximately 2.6 years apart were included. MR images were used to assess hip BML presence and size (cm2) while DXA scans were used to determine bone mineral density (BMD) of the total hip, spine and femoral neck. RESULTS: Fifty-five subjects (28%) had either a femoral and/or acetabular BML. Cross-sectionally, acetabular BMLs were associated with 5-6% lower total hip [P = 0.01] and femoral neck BMD [P < 0.001]. Resolving acetabular BMLs were associated with a 1-2% increase in BMD at hip [P = 0.05] and femoral neck [P = 0.01]. In contrast, resolving femoral BMLs were associated with a 4% lower and incident femoral BMLs with 3% higher femoral neck BMD [P = 0.04, P < 0.001 resp.]. Finally, each 1 cm2 change femoral BMLs was associated with increase in femoral neck BMD: +0.03 g/cm2, 95% CI: +0.00, +0.05, and enlarging acetabular BMLs was associated with decrease in hip: -0.01 g/cm2, 95% CI: -0.03, -0.00 and femoral neck BMD: -0.01 g/cm2, 95% CI: -0.03, -0.001. CONCLUSION: Hip BMLs were associated with local BMD (hip and femoral neck) but not with spine BMD and these associations vary according to site. BML prevalence and change was low in this study, hence these findings need confirmation. However, we hypothesize that these associations represent a combination of changes related directly to the BML pathology or changes adjacent to the disease process.