Acute Biocompatibility of X-ray Visible Bioabsorbable Bone Plate Coated with β-Tricalcium Phosphate and Poly(lactic-co-glycolic acid)

Abstract

To allow X-ray visibility, we coated a bioabsorbable bone plate in clinical use (PLT-1031, Inion, Finland) with a layer made of a composite of beta-tricalcium phosphate (β-TCP) and poly(lactic-co-glycolic acid) (PLGA) (i.e., β-TCP/PLGA plate) and assessed its in vivo acute biocompatibility for 4 months. For this, we fixed an intact Inion plate and β-TCP/PLGA plate on the left and right humeri of a New Zealand White rabbit, respectively. According to the X-ray imaging, the β-TCP/PLGA plate was observable for 2 weeks after the implantation while the intact plate was not visible during the whole tested period. To evaluate the biocompatibility of the plate, we performed a histological analysis with hematoxylin and eosin (H&E) staining on the tissues obtained at scheduled times. After being tested for 4 months, the overall biocompatibility of the β-TCP/PLGA plate was similar to that of the intact Inion plate and there was also no significant difference in bone repair process between the two plates. On the 5 day after the implantation, both plates exhibited a similar state of early reparative tissue reaction, showing tissue necrosis, abscess formation, and neutrophilic infiltration. In the 2 weeks, inflammation and granulation tissue formation around the plate extended to the skeletal muscle and fat tissue. This gradually decreased through the end of the experiment with only a few foreign body giant cells and macrophages remaining in the fibrotic tissue.