TISSUE-IMPLANT INTERFACE AT AN ABSORBABLE FRACTURE FIXATION PLUG MADEOF POLYLACTIDE IN CANCELLOUS BONE OF DISTAL RABBIT FEMUR

The tissue-implant interface at a self-reinforced poly-L-lactide (SR-P LLA) expansion plug implanted in distal rabbit femoral cancellous bone was studied histologically, histomorphometrically, and microradiograp hically in 35 rabbits during consolidation of a transverse transcondyl ar osteotomy fixed with the SR-PLLA expansion plug. The absorbable plu g for internal fixation of fractures and osteotomies measured 4.5 mm i n diameter and 30 mm in length and had an expandable distal locking bl ade system. The femoral specimens were harvested in groups of 5-10 rab bits after a follow-up time of 3, 6, 12, and 24 weeks. The intact cont rolateral femur served as a control. Vigorous osteogenic response to t he implant was already observed at 3 weeks postoperatively, and the os teoid surface fraction at 24 weeks was still significantly higher than in the unoperated contralateral femur. Incomplete union of the osteot omy seemed to result in increased fibrous tissue formation at the tiss ue-implant boundary. No signs of degradation of the SR-PLLA was observ ed within the entire follow-up period. The number of inflammatory cell s at the tissue-implant interface was low. Consequently, the short-ter m biocompatibility of the implant was deemed acceptable. Clinical appl ication of the expansion plug is being planned.