Strength retention of self-reinforced drawn poly-L/DL-lactide 70/30 (SR-PLA70) rods and fixation properties of distal femoral osteotomies with these rods. An experimental study on rats.

Self-reinforced polylevo-dextro-lactic acid (SR-PLA) 70 composite rods, (2 mm x 26 mm) were implanted in the dorsal subcutaneus tissue of sixteen rats. Osteotomies of the distal femur were fixed with SR-PLA70 composite rods (2 mm x 15 mm) in 39 rats. The follow-up times varied from 1 week to 1 year. After sacrifice three-point bending and shear tests were performed for subcutaneously placed rods, and radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of osteotomized and intact control femora were performed. At 52 weeks the shear strength and flexural modulus of the rods were 41% of the initial value, and the flexural strength was 43% of the initial value. In the osteotomies seven specimens had to be excluded due to postoperative infection or dislocation of the fragment. Six of the thirty-two evaluated osteotomies showed signs of postoperative infection. Twenty-six osteotomies healed uneventfully. No signs of inflammatory or foreign-body reaction were observed. The present investigation demonstrated that the mechanical strength and fixation properties of the SR-PLA70 rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on successful application of SR-PLA70 rods for fixation of cancellous bone osteotomies studied.