Intramedullary fixation of cortical bone osteotomies with absorbable self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) rods in rabbits.

ABSTRACT

Osteotomies of the femoral diaphysis were fixed with absorbable self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) intramedullary rods (4.5 mm x 50-60 mm) in 43 adult rabbits. Follow-up times varied from 3 weeks to 3 yr. After sacrifice histological, oxytetracycline-fluorescence and microradiographic studies of the bones were performed. Strength characteristics and changes in crystallinity and molecular weight of the rods were also measured. All osteotomies were evaluated radiographically. Thirty-six osteotomies (84%) healed uneventfully. The implant disappeared almost totally within 3 yr and histology showed only a minor foreign body reaction. From 6 weeks on, the bending force needed to break the osteotomy was comparable to the bending force needed to break the control bone. The shear strength of the rods displayed only minor changes for the first 24 weeks. Subsequently, the rods rapidly lost their strength and at 48 weeks there was practically no shear strength left, which is ideal for healing of an osteotomy. The present investigation demonstrated, that absorbable. fibrillated SR-PLA96-rods can be used for the intramedullar fixation of simple cortical bone osteotomies in rabbits. These results have encouraged us to continue our studies with the fixation of experimental cortical bone osteotomies in larger species.