Prediction of Vertebral Strength Under Loading Conditions Occurring in Activities of Daily Living Using a Computed Tomography-Based Nonlinear Finite Element Method

Study Design. A clinical study on osteoporotic vertebral strength in daily living using a computed tomography (CT)-based nonlinear finite element (FE) model. Objective. To evaluate the differences in predicted fracture strength of osteoporotic vertebral bodies among the different loading conditions that are occurring in the activities of daily living. Summary of Background Data. FE model has been reported to predict vertebral strength in uniaxial loading, but forward bending load plays an important role in osteoporotic vertebral fractures. Methods. Strengths of the second lumbar vertebra in 41 female patients with postmenopausal osteoporosis were analyzed using a nonlinear CT-based FE method. Three different loading conditions were adopted uniaxial compression, forward bending, and erect standing. The same boundary condition was used for all loading conditions. Predicted strengths under forward bending and erect standing were compared with that under uniaxial compression and differences in strength were statistically analyzed. Results. The regression equation relating strength under uniaxial compression to that under erect standing was expressed as Y = 0.8912x + 19.332 (R = 0.9522), whereas the equation relating uniaxial compression to forward bending was Y = 0.7033x + 55.071 (R = 0.8342). Both relationships were significant, but the correlation between forward bending and uniaxial compression was not strong, while strength was lower under forward bending than under uniaxial compression according to the Friedman multiple comparison test (P = 0.00017). Conclusion. Strength under forward bending correlated significantly to that under uniaxial compression, but the correlation was not strong. Therefore, in osteoporotic patients, both uniaxial compression and forward bending should be assessed to evaluate fracture risk in daily living using a CT-based FE method.