LAUSR

STUDY DESIGN Four-year, longitudinal cohort study. OBJECTIVE To investigate the effect of original spinal shape on incidental vertebral fractures and to identify the influence of changes in pre- and post-fracture geometrical spinal shape. SUMMARY OF BACKGROUND DATA Clinical evidence demonstrates that vertebral fractures cause spinal kyphosis, morbidities, and deteriorating quality of life in elderly people. However, knowledge of geometrical spinal shapes that affect incidental vertebral fractures is limited. METHODS Three hundred and seventeen volunteers underwent whole spine radiography as part of a health screening in both 2012 and 2016. We extracted volunteers with incidental vertebral fracture in 2016. Sex- and age-matched volunteers without vertebral fracture were enrolled as controls. Baseline demographic variables, geometrical spinal shape, and spinopelvic parameters were compared between the two groups. In volunteers with incidental vertebral fracture, we investigated the association between baseline spinal shape and post-fracture shape. RESULTS Twenty-seven volunteers (12 men; mean age 75.4 ± 5.4 and 15 women; mean age 71.6 ± 7.9) with vertebral fracture were enrolled, and 175 volunteers (48 men, 127 women) without vertebral fracture were selected as controls. In men with vertebral fracture, the thoracic kyphosis apex was located significantly more posteriorly and caudally than in those without vertebral fracture. In women with vertebral fracture, the lordosis apex was located significantly more posteriorly and caudally than in those without vertebral fracture. After fractures occurring above the inflexion vertebra, the low anterior apex spine (L5) changed its geometrical shape in that the posterior apex and the inflexion vertebra shifted significantly more posteriorly compared to the high anterior apex spine (L4/5). CONCLUSIONS Original geometrical spinal shape affected the occurrence of vertebral fracture, and post-fracture spinal shape depended on the positional relationship between the inflexion vertebra and fractured vertebra. Our study helps to understand the influence of geometrical spinal shape on the risks of vertebral fracture. LEVEL OF EVIDENCE 3.