Intramedullary nailing of the cortical bone osteotomies in rabbits with self-reinforced poly-L-lactide rods manufactured by the fibrillation method.

Right femoral, cortical bone osteotomies of 42 rabbits were fixed with fibrillated, self-reinforced (SR) poly-L-lactide (PLLA) rods, 4.5 mm in diameter. Follow-up times were from 3 to 48 wk. None of the rods broke during this period. There was one non-union at three weeks and one non-union at 12 weeks. Radiographic, histologic, microradiographic and oxytetracyclic fluorescence studies showed normal healing. Shear load carrying capacity of the osteotomy plane was measured from 30 bone samples; the shear force at breaking increased during the follow-up time to 450 N, while the mean shear force of intact, left-side control femurs was 440 N. Before shear tests of the bones, the SR-PLLA rods were taken away from the medullary cavities of the femurs. The rods were also tested mechanically. About 25% of the initial 136 MPa shear-strength of the rods was left after 24 wk. The results show that fibrillated SR-PLLA rods are strong enough to be used in intramedullary nailing of femoral cortical bone osteotomies in rabbits.