Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat

In this study the relationships of bone mineral density (BMD) and bone structure parameters calculated from 2D microtomography images to bone strength were investigated. Femurs from 21 male Sprague Dawley rats were subjected to dual-energy X-ray absorptiometry, computerized microtomography (CμT) and either three-point cantilever bending (femoral shaft) or two-point bending compression (femoral neck). Gastrectomy was performed on 12 animals and 9 were sham operated. From the tomograms bone structure analysis was performed using a software routine based on grey level run-length method. Correlations of BMD and bone structure parameters to mechanical parameters were investigated as were differences between the gastrectomized and the control samples. The reductions of BMD between the groups were 21 and 27% in the femoral neck and shaft, respectively. For the shaft, the correlations of BMD to all mechanical parameters were significant and BMD was a consistent predictor of bone strength for cortical bone. However, in the femoral neck where cancellous bone predominates, BMD was weakly correlated only to deflection. A significant correlation between trabecular thickness and neck bone strength was found. Hence, compared to trabecular thickness, BMD was of limited value in predicting bone strength in the femoral neck.