Associations between bone attenuation and prevalent vertebral fractures on chest CT scans differ with vertebral fracture locations

SUMMARY: Vertebral fracture (VF) locations are bimodally distributed in the spine. The association between VF and bone attenuation (BA) measured on chest CT scans varied according to the location of VFs, indicating that other factors than only BA play a role in the bimodal distribution of VFs. INTRODUCTION: Vertebral fractures (VFs) are associated with low bone mineral density but are not equally distributed throughout the spine and occur most commonly at T7–T8 and T11–T12 (“cVFs”) and less commonly at T4–T6 and T9–T10 (“lcVF”). We aimed to determine whether associations between bone attenuation (BA) and VFs vary between subjects with cVFs only, with lcVFs only and with both cVFs and lcVFs. METHODS: Chest CT images of T4–T12 in 1237 smokers with and without COPD were analysed for prevalent VFs according to the method described by Genant (11,133 vertebrae). BA (expressed in Hounsfield units) was measured in all non-fractured vertebrae (available for 10,489 vertebrae). Linear regression was used to compare mean BA, and logistic regression was used to estimate the association of BA with prevalent VFs (adjusted for age and sex). RESULTS: On vertebral level, the proportion of cVFs was significantly higher than of lcVF (5.6% vs 2.0%). Compared to subjects without VFs, BA was 15% lower in subjects with cVFs (p < 0.0001), 25% lower in subjects with lcVFs (p < 0.0001) and lowest in subjects with cVFs and lcVFs (− 32%, p < 0.0001). The highest ORs for presence of VFs per − 1SD BA per vertebra were found in subjects with both cVFs and lcVFs (3.8 to 4.6). CONCLUSIONS: The association between VFs and BA differed according to VF location. ORs increased from subjects with cVFs to subjects with lcVFs and were highest in subjects with cVFs and lcVFs, indicating that other factors than only BA play a role in the bimodal VF distribution. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT00292552