Comparison of trabecular bone anisotropies based on fractal dimensions and mean intercept length

The mechanical quality of trabecular bone depends on both its stiffness and its strength characteristics. It can be predicted indirectly by the combination of bone volume fraction and architectural anisotropy. To analyze the directional anisotropy of the trabecular bone, we applied the fractal geometry technique to plain radiographs. The anisotropy of the bone was quantified from an ellipse, based on the directional fractal dimensions (FD), by the principal axes of inertia. The anisotropies based on the FD were compared with those determined using the common method of mean intercept length (MIL). The directional FD and MIL plots were highly correlated. The method using directional FDs as determined by the principal axis of inertia measures the anisotropy directly. This kind of method will be a useful tool to provide better estimates of bone quality in vim compared with the density measurements alone.