Vertebral strength prediction under anterior compressive force using a finite element model for osteoporosis assessment

Abstract

Vertebral fractures are one of the most common clinical manifestations with the major adverse consequences of osteoporosis as they usually occur under non-traumatic loading conditions. Height loss, back pain and func-tional disability are the most encountered consequences of vertebral fractures with repetitive fracture experience more likely occurring within a year after the first fracture. Early diagnosis of osteoporosis is therefore important for vertebral fracture prevention as drug treatments are more effective before perforation of the trabeculae (Mc Donnell et al. 2007). Bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) is the most clinically used method to diagnose osteopo-rosis. However this technique can only predict 40–70% of vertebral fractures as it only measures areal BMD which does not account for three dimensional (3D) geometry and BMD distribution (Sornay-Rendu et al. 2005). The combination of patient-specific 3D geometry and 3D BMD distribution is necessary to predict vertebral strength. Finite element models (FEM) derived from quantitative computed tomography (qCT) images are used to predict failure strength of vertebral bodies (Crawford et al. 2003; Imai et al. 2006; Buckley et al. 2007). Most of these models were validated under axial compressive forces to the vertebral body while vertebral fractures are more associated with eccentric compres-sion (Lunt et al. 2003). The purpose of this study was to compare the performance of the aBMD from DXA and qCT-based FEM in predicting experimen-tal vertebral strength. The experimental set up allowed for anterior compression testing on isolated vertebral bodies to ensure repeatable loading condition simulat-ing an anterior wedge-shape fracture.