Tissue response to polyglycolide and polylevolactide pins in osteotomized cancellous bone

A transcondylar osteotomy of the distal femur was fixed with a self-reinfor ced polyglycolide pin in one hind leg and with a self-reinforced polylevola ctide pin in the other hind leg of 49 rats. The intact femurs of eight rats that did not have surgical treatment were used as controls. The tissue rea ction to the implant and the consolidation of the osteotomy were examined r adiographically, histologically, histomorphometrically, microradiographical ly, and using oxytetracycline fluorescence studies. The followups were from 1 to 52 weeks. A vigorous osteostimulatory tissue response to self-reinfor ced polyglycolide pins and self-reinforced polylevolactide pins was observe d 1 week after fixation. This reaction reached its highest value 24 weeks a fter self-reinforced polyglycolide pin fixation and 6 weeks after self-rein forced polylevolactide pin fixation. The highest values of the mean trabecu lar bone area fraction, 27.9% for self-reinforced polyglycolide pins and 28 .1% for self-reinforced polylevolactide pins, were measured at 48 weeks. At 12 weeks there was a peak of phagocytizing macrophages in the specimens wi th self-reinforced polyglycolide pin fixation. During the followup, total p hagocytosis of self-reinforced polyglycolide pins was seen, but only a few signs of degradation of self-reinforced polylevolactide pins were observed. Both polymeric implants seemed to possess osteostimulatory properties, and the biocompatibility and clinical relevance proved to be acceptable.