Distribution of trabecular and cortical bone related to geometry. A quantitative computed tomography study of the femoral neck.

METHODS

The relation between geometry and the distribution of trabecular and cortical bone mass and density in the human femoral neck was evaluated with quantitative computed tomography (QCT). Quantitative computed tomography data were obtained from 2-mm thick computed tomography slices of 20 human femur necks in vitro. A standardized scan position in each femur was used with the smallest cross-section as reference point.

RESULTS

When trabecular bone mass (TrBM) and cortical bone mass were presented as percentage of total bone mass (ToBM), it was found that, starting at the cranial (head) side, ToBM consists of 78% TrBM. About 21% of ToBM can be found as TrBM at the caudal (trochanter) side. At the smallest cross-sectional volume TrBM is 33% of ToBM. For every 2-mm slice, an average decrease of 5% TrBM can be seen.

CONCLUSIONS

These data show that geometry and bone mass distribution are related. Whereas total bone mass remains relatively stable, the cortical and trabecular bone mass changes extensively. This implies that QCT measurements in the femoral neck depend highly on midneck positioning.