An in vivo study on the biocompatibility of a bioresorbable poly(L-lactide-co-glycolide) pin for bone fixation

The non-toxic and biodegradable natures of the PLA/PGA polymers provide themselves with a promising future in the application of bone fixation devices. The degradation behavior of the PLA/PGA polymers plays an important role in the decisive performance of its use. Because the degradation properties of a PLA/PGA specimen depend not only on the properties of a polymer used but also on its fabrication process, it is necessary to test the biocompatibility of the polyester specimens of the "as used" devices in the development of an orthopedic fixation device. This study assesses the biocompatibility of a bioresorbable PLGA pin used for bone fixation manufactured by the Industrial Technology Research Institute (ITRI). Two polymers, one purchased from PURAC and one synthesized by ITRI, were used as the raw materials for processing. These pins were placed in three regions, the interstices of dorsal muscle, the interstices of gluteal muscle and the bone marrow cavity of distal femur of adult New Zealand white rabbits, to compare the tissue responses of different implant sites. Tissue responses evaluated for 1 to 5 months reveal that both groups of PLGA pins are tissue tolerant and their inflammation reactions are quite mild. Morphology observations of the retrieved samples indicate that these PLGA pins degrade by surface erosion in vivo. It is different from the heterogeneously degradation pattern, which progresses from the interior to exterior of the implants, reported in the literatures for in vitro tests. This result suggests that the regular incubation conditions applied for in vitro study do not properly simulate the in vivo degradation behavior of the implants.