Reduced Mobility From Bone Bridge Formation Affects Low BMD in Ankylosing Spondylitis

For patients with ankylosing spondylitis (AS), the reduction in vertebrae mobility caused by bone bridge formation is associated with reduced bone mineral density (BMD), according to research results presented at the American Society of Bone and Mineral Research Annual Meeting 2019, held September 20 to 23, 2019, in Orlando, Florida.

Researchers used a chart review to retroactively analyze BMD and medical records of 52 patients with AS (78% men; mean age, 47.3 years; mean disease duration, 8.2 years). Quantitative computed tomography was used to assess the BMD of the lower thoracic and lumbar spine by scanning vertebrae from T11 to L4 in the supine position.

For BMD of the spinal trabecular bone, researchers used the International Society for Clinical Densitometry 2007 and American College of Radiology 2008 thresholds of 120 mg/cm³ for osteopenia and 80 mg/cm³ for osteoporosis. The near total or total bone bridge on x-rays at the thoracic and lumbar spine (T11-L5) was also analyzed; R software packages were used for statistical analysis.

Using quantitative computed tomography, the researchers found that trabecular BMD of the lower thoracic and lumbar spine ranged from 29.1 to 178.8 mg/cm³ (mean, 104.8±34.1 mg/cm³) and 22.5 to 177.7 mg/cm³ (mean, 102.7±35.5 mg/cm³), respectively.

According to lumbar BMD measurements, 28.8% of patients (n=15) had osteoporosis and 36.5% had osteopenia (n=19).

Researchers found a negative correlation between bone bridge formation and BMD. Low BMD was significantly associated with bone bridge of the lateral side in the vertebral body (P <.05), but not with bone bridge of the anterior side. The results of the study indicated that this correlation was higher in the lumbar spine compared with the lower thoracic spine (P <.05).

Reference

Lee S-Y, Song R, Yang H-I, Lee S. The correlation of bone bridge and low bone mineral density measured by quantitative computed tomography in patients with ankylosing spondylitis. Presented at: American Society of Bone and Mineral Research 2019 Annual Meeting; September 20-23, 2019; Orlando, Florida. Poster #1022.