A histomorphological study on self-reinforced polyglycolide (SR-PGA) osteosynthesis implants coated with slowly absorbable polymers.

A total of 150 osteotomies of rabbits' distal femur were fixed with absorbable self-reinforced polyglycolide (SR-PGA) rods coated with slowly absorbable polymers. In order to reduce the degradation rate of the SR-PGA construction rods were coated with n-butyl-2-cyanoacrylate, polydioxanone (PDS), poly-beta-hydroxybutyrate (PHBA), or poly-l-lactide (PLLA). Biocompatibility and the rate of biodegradation were evaluated in histological, histomorphometric, microradiographic, and oxytetracycline labeling studies. PDS, PHBA, and PLLA coatings showed good biocompatibility although there were scattered fluid accumulations around the rod in each group. Cyanoacrylate coating seemed to inhibit cartilage regeneration and cause the formation of considerable amount of connective tissue around the implant. The PGA core of the rod had totally degraded in 24 to 36 weeks in each coating group. Cyanoacrylate and PDS coatings were not detectable after 6 weeks while PHBA and PLLA coatings were still observed after 48 weeks. There were five (14%) non-unions in the cyanoacrylate coating group, one (3%) in the PHBA coating group caused by a purulent infection and none in the PDS and PLLA coating groups.