Opportunistic screening for osteoporosis using the sagittal reconstruction from routine abdominal CT for combined assessment of vertebral fractures and density

Opportunistic osteoporosis screening using abdominal CT scans obtained for other purposes has the potential to increase detection of those at increased risk for fragility fractures. We sought to combine the tasks of density measurement and vertebral fracture assessment on the sagittal view. We confirm that this represents a robust approach and recommend its implementation in clinical practice.

Opportunistic osteoporosis screening at routine abdominal CT has been proposed by measuring axial (transverse) L1 trabecular attenuation and by sagittal reconstruction for vertebral fracture assessment. We sought to combine this dual evaluation on the sagittal reconstruction alone to improve efficiency.

Routine contrast-enhanced abdominal CT scans performed for any indication on 571 consecutive adults age 60 years or older (mean age 70.7 years) were retrospectively analyzed. These were performed at a single center over a 3-month period. L1 trabecular attenuation was measured using an ovoid region-of-interest on both the transverse and sagittal series. The sagittal reconstruction was also analyzed for moderate-to-severe vertebral compression fractures using the Genant visual semi-quantitative method. Likely osteoporosis was defined by a moderate-to-severe fracture and/or sagittal L1 trabecular attenuation of ≤110 Hounsfield units (HU) (previously found to be >90 % specific for osteoporosis on our calibrated GE CT scanners at 120 kV_p). Correlation was made with hip and spine dual X-ray absorptiometry (DXA).

Mean absolute difference in L1 trabecular attenuation between transverse and sagittal reconstructions was 6.7 HU (±5.7) or 6.2 %. The transverse and sagittal HU measurements were in agreement (i.e., both measurements above or below this threshold) in 94.5 % of cases at the 110-HU cutoff. A total of 243 (42.3 %) patients had likely osteoporosis by CT criteria, of which only 48 (19.8 %) had previous DXA screening.

Assessment of the sagittal view alone at routine abdominal CT for both vertebral fractures and trabecular bone mineral density provides a rapid and effective opportunistic screen for detecting individuals at increased risk for fragility fractures.