Relation of lateral lumbar spine DXA to age-related bone loss, aortic calcification, scoliosis and vertebral degeneration: Analysis of over 10,000 patients

Dual-energy X-ray absorptiometry (DXA) is a valuable tool for measuring bone mineral density (BMD). Conventional skeletal projection images for BMD assessment include the hip and the posterior-anterior (PA) lumbar spine DXA scans. However, the PA view suffers from the pileup of anatomical structures which are not present in the lateral view. This study aimed to evaluate the significance of lateral projection in measuring BMD. We acquired a dataset covering over 10,000 patients with the lateral projection included in the routine clinical DXA examination together with PA lumbar spine and femur projections. Age-related BMD decrease was more pronounced in the lateral lumbar spine and femur than in the PA lumbar spine. To elaborate on this difference, we estimated aortic calcification score from lateral spine DXA images and detected degeneration and scoliosis from PA lumbar spine images using neural networks. Multivariate linear regression analysis suggested that aortic calcification increased BMD in PA spine, but in lateral spine and femur, the expected decline in BMD was observed. The spinal degeneration was related to higher BMD in all sites, with the largest effect on PA spine BMD. Scoliosis increased BMD on lateral spine but was associated with decreased BMD in PA spine and at femur. Lateral lumbar spine DXA helped to reveal sources for the artificially elevated BMD and provided better insight into age-related decrease in vertebral bone mineral density than the PA scan. Lateral projection should therefore be considered more in clinical practice, as it enhances the reliability of lumbar spine BMD measurement.