Background/Purpose: Bariatric surgery could impact bone metabolism and induce significant changes, leading to increased bone resorption and an increased risk of fractures.

The primary objective was to study the bone fragility prevalence 3 years (±6 months) after bariatric surgery, on dual X-ray absorptiometry (DXA) and computed tomography (CT) in patients with obesity. The secondary objectives were to identify the risk factors for the development of bone fragility (BMD ≤ -2 SD on any site or a scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) ≤145 Hounsfield units (HU)) and to compare CT and DXA methods.

Methods: This descriptive study included patients with obesity who underwent bariatric surgery and performed DXA or CT before and 3 years (±6 months) after bariatric surgery. The BMD, T-score, and data on lean and fat mass distribution were assessed on DXA. SBAC-L1 was measured on CT with a threshold at 145 HU.

Results: Among the 44 included patients, 84.1% were women, with a mean age of 53.9 years (±10.7). In this paired study before surgery vs 3 years (+/- 6 months) after surgery:  the mean body mass index (BMI) was 46.9 kg/m² (±8.8) before and 31.4 kg/m² (±9.2) after; after 3 years, there was more osteoporosis on at least one site (p=0.002) and T-score were significantly lower on all sites (p< 0.001) on DXA than at baseline. On CT, SBAC-L1 was significantly lower after vs before surgery (p=0.008). In multivariate analysis, no risk factor was significantly associated with the development of bone fragility at 3 years. The correlation between CT and DXA was positive, moderate to strong (0.53 to 0.63).

Conclusion: There was a significantly higher prevalence of osteoporosis and lower SBAC-L1 3 years after bariatric surgery than before with a moderate to strong correlation between the 2 exams modalities.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ct-and-dxa-bone-fragility-evaluation-after-bariatric-surgery/