Bone structure as revealed by microtomography

The appearance of cancellous bone architecture is different for various skeletal sites and various disease states. In the iliac crest it is more plate-like, whereas in the spine rods dominate. During aging and disease plates are perforated and connecting rods are dissolved. There is a continuous shift from one structural type to the other. So traditional histomorphometric procedures, which are based on a fixed model type, will lead to questionable results. 3-D microtomography allows to assess model independent structural parameters so that trabecular thickness, for example, can be determined directly. Not only mean thicknesses are available but also thickness histograms which are helpful to identify pathologic states. Other features such as trabecular separation, degree of anisotropy and structural type index can be extracted from the 3-D images and allow to characterize cancellous bone and its changes due to aging, disease and treatment. To fully exploit the significance of bone structure on bone strength large scale Finite Element (FE) analyses are performed. Hence microtomography, performed with a sufficiently fine isotropic spatial resolution, reveals information on the structural features of cancellous bone which were not available so far and which will, hopefully, lead to a better understanding of the pathogenesis of bone diseases and subsequently to improved treatment regimes.