Stability behavior of human tibias after bone removal--comparative examination in 15 cadaver tibia pairs.

PURPOSE

To obtain scientific information on the loss of stability of tibias after removal of bone grafts, we performed a comparative study of 15 freshly preserved adult cadavers to determine the axial breaking loads of the operated and nonoperated tibial heads.

MATERIALS AND METHODS

From all cadavers, 1 tibia was randomly selected from which the maximum possible amount of cancellous bone was harvested. The respective contralateral side remained untouched. After maceration, the proximal tibias of each cadaver were removed bilaterally and adjusted to precisely equal lengths. Using a Zwick universal testing machine, the tibial heads were loaded by an axial force until fracture. As the final breaking load, the force value was recorded when the first distinct decrease in the feed-force curve was observed. To compare the mean breaking loads of the operated and nonoperated control tibias, a t test for related samples at P = .05 was used.

RESULTS

The mean breaking load for the donor tibias was 3,767 N and was significantly lower than that of the control side with an average of 5,126 N. This finding was independent of age and gender.

CONCLUSIONS

Bone removal from the proximal tibia leads to a significant reduction of the axial load capacity. Therefore, we recommend partial loading of up to one half of the body weight during the first postoperative week. For an additional 5 weeks, patients should bear their full body weight on the affected leg only when walking normally and on flat ground.