VASCULAR AND STRUCTURAL-CHANGES IN RAT FEMORA FOLLOWING NAILING AND INTRAMEDULLARY OCCLUSION

The purpose of this study was to evaluate biomechanical, structural, a nd blood now changes of the femoral canal in rats 12 weeks after intra medullary reaming, nailing, or occlusion. In one group, reaming alone was performed. In a second group, reaming was followed by use of a tig ht-fit steel nail. In a third group, reaming was followed by use of in ert silicone that totally plugged the medullary cavity. A fourth group served as the control. The acute mechanical and vascular effects caus ed by reaming and nailing were determined in a separate group. Reaming and nail insertion reduced blood flow in femoral bone to about one-th ird. Reaming reduced bending moment by approximately 40%, whereas bend ing rigidity was unchanged. After 12 weeks, the cortical bone blood no w was significantly increased in both the nailed and the silicone-plug ged bones compared with the reamed and control groups. The bending mom ent and energy absorption in the silicone group were inferior to those of the other groups. There were no differences in either the external or internal diameter or the medullary and net bone areas. In the sili cone group, both the number and the area of large pores (larger than 1 0 mu m) significantly increased in comparison with the other groups; h ence, bone porosity was increased. This increment was confined to larg e pores. It is concluded that medullary occlusion contributes to struc tural and blood flow changes in bone.