Vertebral fracture prevalence and measurement of the scanographic bone attenuation coefficient on CT-scan in patients with systemic sclerosis

Abstract

To study vertebral fracture (VF) prevalence and the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) on computed tomography scans (CT-scans) in systemic sclerosis patients. This monocentric retrospective study included patients followed from 2000 to 2014 and fulfilling ACR/EULAR 2013 criteria for systemic sclerosis and who underwent a thoracic or thoraco-abdomino-pelvic CT-scan during their follow-up. Clinical characteristics for sclerosis and osteoporosis risk factors were collected. For CT-scan, the VFs were determined according to Genant's classification, the SBAC-L1 was measured in Hounsfield Units (HU), and a SBAC-L1 ≤ 145 HU (fracture threshold) defined patients at VF risk. Predictive factors for SBAC-L1 ≤ 145 HU were studied. A total of 70 patients were included [mean age, 62.3 (± 15.6) years, women 88.5%, diffuse sclerosis 22.9% (n = 16)]. On CT-scans, three VFs were detected in three patients (4.3%). The mean SBAC-L1 was 157.26 HU (± 52.1), and 35 patients (50%) presented a SBAC-L1 ≤ 145 HU. In multivariate analysis, only age (especially patients older than 63 years, OR = 1.08, CI 95% 1.04-1.13, p = 0.001) and calcinosis (OR = 6.04, CI 95% 1.27-28.70, p = 0.02) were independently associated with a SBAC-L1 ≤ 145 HU. On a large sample of patients with systemic sclerosis, the VF prevalence on CT-scan was low (4.3%) while 50% of the patients presented a SBAC-L1 ≤ 145 HU. Interestingly, the presence of calcinosis, periarticular calcifications or acro-osteolysis was linked with low SBAC-L1 and should lead to an osteoporosis screening, especially for patients under 63 years old.

Consequences of spinal ankylosis on bone trabecular fragility assessed on CT scans in patients with ankylosing spondylitis. A retrospective study

“…The use of SBAC is interesting in AS patients because this technique permits direct evaluation of the trabecular bone density, avoiding cortical artifacts, such as osteophytes and syndesmophytes, as well as other artifacts (vascular calcifications) frequently observed in elderly AS patients. Furthermore, the SBAC measure is very reproducible [23,40] and easy to perform. This method could be used in daily practice to consider initial opportunistic bone screening on CT scans already performed during AS patients' follow-up (treatment side effects, comorbidity evaluation, emergency, etc.).…”

“…The largest elliptical region of interest (ROI) was drawn in the trabecular bone and provided the average bone mineral density (in HU). This evaluation was performed by only a reader (MF) because we have previously shown the excellent intra-and interreader reliability of the SBAC-L1 (kappa > 0.9) [23]. Pickardt et al showed that CT scans performed similarly from T12 to L5 for the SBAC measure [21].…”

“…Recent studies reported that an SBAC-L1 ≤ 145 Hounsfield units (HU) was more reliable than a T-score ≤ -2.5 SD for identifying patients at risk of VF in rheumatoid arthritis (RA) and the general population [21,22]. Furthermore, SBAC-L1 allowed us to identify 50% of sclerodermic patients with bone fragility and was statistically significantly associated with severity criteria of the disease [23]. CT scans offer an opportunity to explore the trabecular bone density in the AS population and to study the effect of vertebral ankylosis on trabecular bone density.…”

Study of vertebral fracture and Scanographic Bone Attenuation Coefficient in rheumatoid arthritis and ankylosing spondylitis vs. controls

“…If there was a VF in the L1 vertebra, the measurement was performed on the adjacent vertebrae (CT-scan performed similarly from T12 to L5) 16 . This evaluation was performed by a single lector (MF) because we had previously demonstrated the excellent reliability on this measure in an earlier study (for intra and inter-reader, kappa >0.9) 17 .…”

Osteoporosis in Rheumatic Diseases

“…Finally, data on fractures are limited to vertebral fractures and are quite variable, with a prevalence ranging between less than 15% [174,190] and up to 24–25% [191,192]. Interestingly, the majority of fractures involve the thoracic spine, but no effect on lung function was found [174].…”