Femoral strength is better predicted by finite element models than QCT andDXA

Clinicians and patients would benefit if accurate methods of predicting and monitoring bone strength in-vivo were available. A group of 51 human femur s (age range 21-93; 23 females, 28 males) were evaluated for bone density a nd geometry using quantitative computed tomography (QCT) and dual energy X- ray absorptiometry (DXA). Regional bone density and dimensions obtained fro m QCT and DXA were used to develop statistical models to predict femoral st rength ex vivo. The QCT data also formed the basis of a three-dimensional f inite element (FE) models to predict structural stiffness. The femurs were separated into two groups; a model training set (n = 25) was used to develo p statistical models to predict ultimate load, and a test set (n = 26) was used to validate these models. The main goal of this study was to test the ability of DXA, QCT and FE techniques to predict fracture load non-invasive ly, in a simple load configuration which produces predominantly femoral nec k fractures. The load configuration simulated the single stance phase porti on of normal gait; in 87% of the specimens, clinical appearing sub-capital fractures were produced. The training/test study design provided a tool to validate that the predictive models were reliable when used on specimens wi th "unknown" strength characteristics. The FE method explained at least 20% more of the variance in strength than the DXA models. Planned refinements of the FE technique are expected to further improve these results. Three-di mensional FE models are a promising method for predicting fracture load, an d may be useful in monitoring strength changes in vivo. (C) 1999 Elsevier S cience Ltd. All rights reserved.