Low Bone Mass Linked to Radiographic Progression in axSpA

November 8, 2018

A look at the relationship between disease activity, progression, and low bone mineral density in axial spondyloarthritis.

Korean researchers have discovered that low bone mineral density (BMD) and the presence of existing syndesmophytes predict the development of new syndesmophytes in young patients with axial spondyloarthritis (axSpA).

Axial spondyloarthritis and syndesmophytes
Patients with axSpA suffer from a combination of inflammation and structural bone damage that mostly affects the sacroiliac joints and the spine. The development of syndesmophytes in these patients leads to bridging of the intervertebral spaces, which causes disability and loss of function.

The progression of axSpA is highly variable, with bone mass changes reflecting the severity of persistent inflammation. Kim and colleagues1 at The Catholic University of Korea in Seoul, South Korea, sought to determine the association between low bone mass and new syndesmophyte formation, as well as the impact of low bone mass on radiographic progression in axSpA.

The study
Patients who met the imaging arm of the Assessment of SpondyloArthritis International Society axSpA criteria were enrolled in this longitudinal observational study. The modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) was assessed by two trained readers blinded to the patients’ data. BMD (lumbar spine, femoral neck, or total hip) at baseline was assessed using dual-energy absorptiometry (DXA).

Logistic regression analyses were performed to identify predictors associated with the development of new syndesmophytes and spinal radiographic progression. Ultimately, 119 patients were included in the analysis

Next: the results and take-home points for clinicians

The results
• 29% of patients had syndesmophytes at baseline.

• 76% of patients had radiographic sacroiliitis fulfilling the modified New York criteria for the classification of ankylosing spondylitis.

• 16% of patients had low BMD.

• New syndesmophytes had developed in 21% of patients at the 2-year follow-up.

• Patients with new syndesmophytes had a higher frequency of syndesmophytes at baseline and a higher baseline mSASSS score than those who did not develop new syndesmophytes (P = .001 and P = .015, respectively).

• Low BMD was associated with the development of new syndesmophytes (P = .047).

• Syndesmophytes and low BMD at baseline were independently associated with significant spinal progression.

Take-home points
• Consider the presence of baseline syndesmophytes in axSpA a predictor of further formation.

• Patients with axSpA should be monitored for bone loss, which further predicts formation of new syndesmophytes.

• It appears that bone mass changes driven by inflammation are responsible for the relationship between disease activity, progression, and low BMD in axSpA.

• Aggressive treatment aimed at suppressing bony inflammation should be considered, especially in young axSpA patients with baseline syndesmophytes.

References:

1. Kim HR, Hong YS, Park SH, Ju JH, Kang KY. Low bone mineral density predicts the formation of new syndesmophytes in patients with axial spondyloarthritis. Arthritis Res Ther. 2018;20:231. doi: 10.1186/s13075-018-1731-8.