Thoracic kyphosis on chest CT scans is associated with incident vertebral fractures in smokers.

Greater kyphosis angles lead to increased loading on vertebral bodies in computational models. However, results about the relationship between severity of kyphosis and incident vertebral fracture (VF) risk have been conflicting. Therefore, the aim of this study was to evaluate associations between a) prevalent VFs and severity of kyphosis, and b) severity of kyphosis and incident VF risk, in smokers with or without COPD. Former and current smokers with or without COPD were included. CT scans were made at baseline, one-year and three-year follow-up. VFs were evaluated on superposed sagittal CT reconstructions. Kyphosis was measured as the angle between the lines above T4 and below T9 or T12 . We included 1239 subjects (mean age 61.3 ± 8.0, 61.1% male, 80.6% with COPD), of whom 253 (20.4%) had a prevalent VF and 294 (23.7%) an incident VF within three years. Presence, number and severity of prevalent VFs were associated with a greater kyphosis angle. The mean increase in kyphosis angle within three years was small, but significantly greater in subjects with incident VFs compared to those without (2.2 ± 4.1 vs. 1.2 ± 3.9 degrees, respectively, for T4 -T12 angle, p < 0.001). After adjustment for bone attenuation (BA) and prevalent VFs, baseline kyphosis angle was associated with incident VFs within one and three years (angle T4 -T12 per +1SD HR: 1.34 [1.12-1.61] and HR: 1.29 [1.15-1.45], respectively). Our data showed that a greater kyphosis angle at baseline was independently associated with increased risk of incident VFs within one and three years, supporting the theory that greater kyphosis angle contributes to higher biomechanical loads in the spine. This article is protected by copyright. All rights reserved.