By means of a new preparation technique which allows the combined 2- and 3-dimensional analysis of trabecular bone we analyzed the vertebral bodies of 22 autopsy cases. None of these cases had any skeletal disease.

With increasing age bone volume was decreased in all vertebral bodies (2nd cervical to 5th lumbar body) but this decrease was more pronounced in the lower vertebrae. In the upper cervical spine there was nearly no age-related loss of trabecular bone volume. 3-D analysis demonstrated that the loss of bone tissue is due to a loss of trabecular plates which are transformed to trabecular rods by perforations.

The number of plates and rods could be measured directly. In the 2nd lumbar vertebra at the age of 20 years the density of plates was 0,61mm, the density of rods was 0,2/mm. At the age of 80 years the density of plates was 0,2/mm. The density of rods remained constant at all ages. Perforations could be seen directly. They were located mainly in trabecular plates. At higher ages they occurred in rods either.

The number of vertically oriented trabeculae was about twice the number of horizontal ones. The rate of age-dependent reduction of trabeculae was the same in horizontal and vertical trabeculae.

It was possible to do real 3-dimensional measurements of the diameter of trabecular rods. These values were compared to the calculated values of trabecular plates. In mean trabecular plates are thinner than rods. It could be demonstrated that microcallus formation is a common feature in the human spine. It is our opinion that they are a physiological mechanism for bone turnover, especially in older humans. Microcallus formations were located at very special locations. These were not the thinnest parts of the trabeculae but rather they were close to intertrabecular connections.