Relationship between spinal structural damage on radiography and bone fragility on CT in ankylosing spondylitis patients

Abstract

To evaluate whether the risk of bone fragility on computed tomography (CT) (scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1)) is associated with the severity of spine structural involvement (mSASSS) in patients with ankylosing spondylitis (AS). This retrospective study included AS patients, followed from 2009 to 2017, who fulfilled the New York criteria and who underwent thoraco-abdomino-pelvic CT and radiography (spine, pelvis). The structural involvement was retained for mSASSS ≥ 2. The SBAC-L1 was measured in Hounsfield units (HU). A SBAC-L1 ≤ 145 HU was used to define patients at risk of vertebral fracture (VF). A total of 73 AS patients were included (mean age: 60.3 (± 10.7) years, 8 women (11%), mean disease duration: 24.6 years (± 13.9)). Sixty patients (82.2%) had a mSASSS ≥ 2 (mean score 20.7 (± 21.2)). The mean SBAC-L1 was 141.1 HU (± 45), 138.1 HU (± 44.8) and 154.8 HU (± 44.9) in the total, mSASSS ≥ 2 and mSASSS < 2 populations, respectively. Patients with bone bridges had lower SBAC-L1 than mSASSS ≥ 2 patients without ankylosis (p = 0.02) and more often SBAC-L1 ≤ 145 HU (73% vs 41.9%, p = 0.006). A SBAC-L1 ≤ 145 HU was not associated with structural spine involvement, but patients with bone bridges had significantly decreased SBAC-L1 and an increased probability of being under the fracture threshold.

Prevalence and Factors of Osteoporosis and High Risk of Osteoporotic Fracture in Patients with Ankylosing Spondylitis: A Multicenter Comparative Study of Bone Mineral Density and the Fracture Risk Assessment Tool

“…In other words, we not only provided evidence that FRAX calculation has clinical value as a fracture risk prediction tool but also support the need to consider the FRAX calculation in decision making related to osteoporosis treatment. Another significant factor, the mSASSS, showed a positive association with fracture occurrence, consistent with several previous findings [ 51 ].…”

Low-dose CT hounsfield units: a reliable methodology for assessing vertebral bone density in radiographic axial spondyloarthritis

“…Whole spine ldCT scans from 50 patients with r-axSpA (mean (SD) age of 49 (10) years; 43 (86%) male and 42 (84%) HLA-B27 positive) were included -26 of them from Leiden, and 24 from Herne. Detailed information regarding demographic and clinical characteristics of the included patients is provided in online supplemental table S1.…”

“…Several studies opportunistically assessed vertebral HU in trauma patients, general population or patients with CT scans performed for other reasons, [11][12][13][14][15][16] including the lumbar spine in patients with r-axSpA. 10 Correlations between HU and BMD (as measured by DXA) have been established, and normative data have been defined throughout the spine. 11 14 However, the thorough assessment of HU from the cervical to the lumbar spine has never been made, mainly due to high radiation exposure issues.…”

“…However, QTC requires special settings for imaging acquisition, with high ionising radiation exposure 8. Therefore, studies included only a few vertebrae mainly at the lumbar spine 9 10. The use of ldCT to study bone loss in r-axSpA has not been evaluated in the literature.…”

Subchondral bone attenuation coefficient utility of the sacroiliac margins to differentiate spondyloarthritis and osteitis condensans ilii

“…The subchondral bone attenuation coefficient corresponded to the average bone mineral density, in Hounsfield units (HU), of a region of interest (ROI), drawn in the trabecular bone, avoiding cortical bone. Recent studies showed that subchondral bone attenuation coefficient of the first lumbar vertebra was useful for identifying osteoporosis 13 14. Ulano et al 15 demonstrated that CT attenuation measurements can be used to distinguish untreated osteoblastic metastases from enostoses 16…”