Inflammation on spinal magnetic resonance imaging is associated with poor bone quality in patients with ankylosing spondylitis.

Objective

To determine the association between inflammatory lesions on spinal magnetic resonance imaging (MRI) and trabecular bone score (TBS) in patients with ankylosing spondylitis (AS).

Methods

Ninety-seven patients with AS underwent spine MRI and dual energy X-ray absorptiometry of the lumbar spine to measure TBS and bone mineral density (BMD). Bone marrow edema (BME) on MRI was considered an inflammatory lesion. The presence, depth (>1 cm), and intensity of BME on MRI were scored for the 1st-4th lumbar spine segments. Inflammatory markers and spinal structural damage scores at the time of MRI examination were recorded. The association between inflammatory activity score on MRI and TBS was evaluated.

Results

Among the 97 patients, 52 had BME on spinal MRI (L1-L4). The mean TBS values were 1.38 ± 0.11 and 1.43 ± 0.11 for patients with and without BME, respectively (p = .022). Total inflammatory activity scores on spinal MRI correlated negatively with TBS, but not with BMD. Patients with a TBS value representing a high fracture risk had more deep BME (>1 cm) (p = .048) on MRI. After adjustment for age, symptom duration, and lumbar spinal structural damage, the TBS decreased as inflammation severity on MRI increased (p = .026). Discussion: In AS patients, inflammation on spinal MRI was negatively correlated with TBS. The severity of local bone inflammation in the spine was associated with poor bone quality. These findings suggest that the control of active bone inflammation may be effective for preventing osteoporosis in AS patients.