Background/Purpose: Osteoporosis screening is not systematic in sclerodermic patients but some studies demonstrated a similar risk between rheumatoid arthritis and systemic scleroderma [1,2,3]. Thoracic and/or TAP (thoraco–abdomino-pelvic) CT (Computed Tomography) scans are classically performed in the follow-up of scleroderma, mainly to evaluate lung involvement.

Objectives: To study vertebral fracture (VF) prevalence and the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) on CT scans in systemic scleroderma patients. Secondary objectives are to study specific risk factors of SBACL1 ≤ 145 Hounsfield Units (HU) and to evaluate SBAC-L1 measurements reliability.

Methods: This monocentric retrospective study included patients followed from 2000 to 2014 and fulfilling ACR/EULAR 2013 criteria for systemic scleroderma and who underwent a thoracic or TAP CT scan. Osteoporotic risk factors, Dual Energy X-ray Absorptiometry (DXA) measurements and clinical characteristics were collected. For CT scan, the VFs were determined according to Genant’s classification on sagittal sections. The SBAC-L1 was measured in Hounsfield Units (HU) on axial section of L1 in a Region of Interest drawed in trabecular bone. Intra- and inter-reader reliabilities for SBAC-L1 were calculated. An SBAC L1 ≤ 145 HU (fracture threshold) was used to define patients at risk of VF [4]. Predictive factors for VF or SBAC-L1 ≤ 145 HU were studied.

Results: A total of 70 patients were included (mean age: 62.3 (±15.6) years, women 88.5%, diffuse scleroderma 22.9% (n=16)) in the study. Sixty patients (85.7%) presented with at least one clinical risk factor for osteoporosis. Eighteen patients (25.7%) received vitaminocalcic supplementation and 10 (14.3%) received antiresorptive therapy. DXA was only performed on 30 patients (42.8%), and 5 (16.7%) of them presented a T-score ≤ -2.5 DS. 3 VFs were detected in 3 patients (4.3%). The mean SBAC-L1 was 157.26 HU (±52.1), and 35 patients (50%) presented a SBAC-L1 ≤ 145 HU. SBAC-L1 measurements were highly reliable (Kappa > 0.9 for both intra- and inter-reader reliability). For the univariate analysis, a SBAC-L1 ≤ 145 HU was significantly associated with age (OR=1.09, CI 95%: 1.04-1.13), calcinosis (OR=6.3, CI 95%: 1.61-24.75) and periarticular calcifications (OR=3.22, CI 95%: 1.06-9.77). For the multivariate analysis, age (especially patients older than 63 years), calcinosis and acro-osteolysis were independently associated with a SBAC-L1 ≤ 145 HU.

Conclusion: On a large sample of sclerodermic patients with clinical risks of osteoporosis, only 42.8% were screened for DXA and 16.7% of them were osteoporotic. The VF prevalence on CT scan was 4.3% and the SBAC-L1 measurement identified 50% of the population at the fracture threshold. The presence of calcinosis, periarticular calcifications or acro-osteolysis should lead to an osteoporosis screening, especially for patients under 63 years old.

References:

[1] Avouac J. Arthritis Care Res (Hoboken). déc 2012;64(12):1871-8.

[2] Yuen SY. J Rheumatol. juin 2008;35(6):1073-8.

[3] Kilic G. Int J Rheum Dis. 1 avr 2016;19(4):405-11.

[4] Pickhardt PJ. Ann Intern Med. 2013;158(8):588-95.