Tissue reactions to bioabsorbable ciprofloxacin-releasing polylactide-polyglycolide 80/20 screws in rabbits’ cranial bone

The aim of this study was to assess tissue reactions to bioabsorbable self-reinforced ciprofloxacin-releasing polylactide/polyglycolide (SR-PLGA) 80/20 screws in rabbits’ cranial bone. Two screws were implanted in each rabbit, one screw on either side of the sagittal suture (n = 28 rabbits). Animals were sacrificed after 2, 4, 8, 16, 24, 54 and 72 weeks, four animals per group. On histological examination the number of macrophages, giant cells, active osteoblasts and fibrous tissue layers were assessed and degradation of the screws was evaluated. At 2 weeks, the highest number of macrophages and giant cells were seen near the heads of the screws. After 4 and 8 weeks, the number of giant cells decreased but that of macrophages decreased from 16 weeks and on. Screws were surrounded by fibrous tissue capsule that progressively was growing in thickness by time. Active osteoblasts were seen around the shaft of the screws with the highest number seen at 4 weeks postoperatively. At 16 weeks, compact fragmentation of the screw heads was seen with macrophages seen inside the screw matrices. After 24 weeks, no polarization of the screws was seen. After one year, PLGA screws had been replaced by adipose tissue, fibrous tissue and “foamy macrophages” which had PLGA particles inside them. After 1½ years, the amount of biomaterial remaining had decreased remarkably. The particles of biomaterial were inside “foamy macrophages.” Ciprofloxacin-releasing SR-PLGA 80/20 screws elicited a mild inflammatory reaction but did not interfere with osteoblast activity. No complications were seen when implanted in cranial bone of rabbit.