Tissue response to bioabsorbable self-reinforced polylevolactide and polyglycolide pins implanted intra-articularly and directly into the bone on different levels - An experimental study on rats

Self-reinforced poly-L-lactide (SR-PLLA) and self-reinforced polyglycolide (SR-PGA) pins were implanted intra-articularly and directly into the bone of the distal femur of rats at three levels: above, on the same level, and under the surface. For the controls only channels were drilled, or the controls were not operated at all. The follow-up times were 3, 6, and 12 weeks for SR-PGA and 3, 6, 12, and 24 weeks for SR-PLLA. The macroscopic appearance and histologically the villus reaction, the mononuclear phagocytosis and giant cells, the neutrophils, the lymphocytes, the plasma cells, the eosinophils, and the mast cells were analyzed. In the histologic analysis, the most favorable implantation depth was found to be under the surface where the contact between the implants and bone was best, and the orifice was covered with new trabecular bone at 3 weeks. This was especially seen in intra-articular implantation. In general, the tissue responses were mild, and could also be explained in the statistical analysis by a normal postoperative tissue response and faster biodegradation of PGA.