Background/Purpose: Primary objective was to evaluate bone fragility prevalence on dual X-ray absorptiometry (DXA) and on computed tomography (CT), in patients with severe obesity. Secondary objective was to evaluate the risk factors for bone fragility.

Methods: This monocentric study was conducted in patients with grade 2 and 3 obesity, who performed a CT and/or a DXA within two years. Bone mineral density (BMD) and T-score were studied on DXA and scanographic bone attenuation coefficient of L1 (SBAC-L1) was measured on CT. Bone fragility was defined by T-score≤-2.5 standard deviation (SD) and an SBAC-L1≤145 Hounsfield units (HU). The diagnosis of osteoporosis was retained for a T-score ≤ − 2.5 SD and osteopenia for -2.5 SD < T-score ≤ -1 SD.

Results: Among 1386 patients included, 1013 had performed both DXA and CT within less than 2 years. Mean age was 48.4 years (±11.4), 77.6% were women and mean BMI was 45.6 kg/m² (±6.7). Eight patients (0.8%) had osteoporosis on at least one site and 119 (11.7%) had osteopenia. Mean SBAC-L1 was 192.3 HU (±52.4); 163 patients (16.1%) were under the fracture threshold of 145HU. Older age (OR[CI95]=1.1 [1.08-1.16]), lower BMD on femoral neck and spine (OR[CI95]=0.04[0.005-0.33] and OR[CI95]=0.001[0.0001-0.008], respectively), and higher lean mass (OR[CI95]=1.1[1.03-1.13]) were significantly associated with an SBAC-L1≤145HU in multivariate analysis. BMI was a protective factor (OR[CI95]=0.9[0.82-0.92].

Conclusion: About 16% of patients with grade 2 and 3 obesity were under the SBAC-L1 fracture threshold, when less than 1% were classified as osteoporotic on DXA. Risk factors for an SBAC-L1≤145HU were older age, lower BMI, lower BMD on femoral neck or spine and higher lean mass.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-bone-fragility-on-dxa-and-ct-in-patients-with-obesity/