SHEAR-STRENGTH OF A DISTAL RABBIT FEMUR DURING CONSOLIDATION OF AN OSTEOTOMY FIXED WITH A POLYLACTIDE EXPANSION PLUG

The consolidation of a transverse transcondylar osteotomy of the dista l rabbit femur, fixed with a self-reinforced polylactide expansion plu g, was studied radiographically and mechanically. The peak shear force was assessed by stressing the osteotomy site to failure. The intact c ontralateral femur of the same rabbit served as a control. Fifteen rab bits were tested in groups of five animals with follow-up times of 6, 12 or 24 wk after fixation of the osteotomy. The absorbable plug, meas uring 4.5 mm in diameter and 30 mm in length, had an expandable distal locking blade system. Thirteen osteotomies showed a radiographically solid bony union. The mean shear strength of the specimens was 3.5 MPa at 6 wk, 3.5 MPa at 12 wk and 4.3 MPa at 24 wk. The mean shear streng th of the control distal femora was 3.6 MPa. In conclusion, the fixati on properties of the newly developed absorbable expansion plug were de emed satisfactory in this experimental fracture model.