[The structure of the spongy bone in lumbar vertebrae and the neck of the femur. A comparative analysis of the age-dependent remodelling process (author's transl)].

In 114 autopsy cases of both sexes, aged between 31 and 97 years and without bone disease, the influence of mechanical forces on the age-dependent remodelling of the spongy bone was determined in the 3rd and 5th lumbar vertebrae and the neck of the femur. For this purpose contrasty X-ray images of 100 mu thick polished bone sections were analysed using the LEITZ texture analysis system. The volumetric density and the surface density are highest in the neck of the femur, lowest in the 3rd lumbar vertebra, and almost as low in the 5th lumbar vertebra. The volumetric density decreases with increasing age by about one-third in all three bones. Correspondingly, the surface density also decreases in the lumbar vertebrae by one-third, but only by 18% in the neck of the femur. The specific surface reveals no age differences in the lumbar vertebrae, but increases by 19% in the neck of the femur. The constancy of the specific surface in the lumbar vertebrae can be explained by the fact that compensatory hypertrophy of the remaining trabeculae takes place. This compensatory growth of bone does not occur in the neck of the femur. The age-dependent decrease in spongy bone manifests itself in a residual spongiosa structure that depends on compressive forces in the case of the lumbar vertebrae and bending forces in the neck of the femur.