Studying bone regeneration with the scanning electron microscope.

The interest in bone structure is very old. That is shown in a historical review with special regard to bone fractures and gap healing. The three-dimensional architecture of the supporting tissue corresponds to the strain acting on it. This can only be presented clearly in the SEM, especially by stereoscopical documentation. Three aspects of utmost importance when studying bone formation were taken into consideration: the three-dimensional presentation of the trabeculae, the processing of the vascular system together with the bony trabeculae, and the preservation of the cells and fibres in their natural state which is only guaranteed in a non-dehydrated frozen state. Reliable bone histology requires the preparation of non-decalcified specimens which are processed for light microscopy. Labeling newly formed bone with fluorochromes is a very common method to analyse sequences of bone formation. Studying the same specimens using both fluorescence microscopy and the SEM provides information not obtained using one method alone. Fresh specimens can be processed for the SEM following light microscopical documentation especially in incident fluorescent light; embedded blocks used for light microscopical investigations can also give valuable information in the SEM when the resin has been removed. The combination of the different methods is of special interest for orthopaedic basic research.