Poly-L-lactic acid beta-tricalcium phosphate screws: a preliminary in vivo biocompatibility study

The aim of this study is to assess the biocompatibility of two types of Poly-L-lactic acid (PLLA) screws (with either hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP)) implanted in the left femur of four sheep euthanized at 42, 50, 57 and 84 days after surgery. Titanium screws were also implanted for comparison purposes. No signs of inflammation were seen in the 240 specimens. A rating of "+/-" for macrophages and "-" for neutrophils was assigned to all specimens. All specimens were assigned a rating which ranged from "+/-" to "+++" for fibroblasts and osteoblasts. The presence of macrophages, neutrophils and fibroblasts/osteoblasts was not statistically different for the four implantation periods. PLLA implants with beta-TCP have a biocompatibility comparable to PLLA implants with HA.