Evaluation of bioactive bone cement in canine total hip arthroplasty

Total hip arthroplasties (THAs) were performed in beagle dogs using a bioactive bone cement (BABC) consisting of a silane-treated apatite- and wollastonite-containing glass-ceramic (AW glass-ceramic) powder and a silica glass powder as the filling particles and a bisphenol-A-glycidyl dimethacrylate-based resin (Bis-GMA-based resin) as the organic matrix. The outcomes were compared with the results of polymethylmethacrylate (PMMA) bone cement. The mechanical properties of the BABC were stronger than those of PMMA bone cement. The bonding strength of the BABC to bone in the dogs' femora increased with time and reached 3.7 MPa at 24 months after implantation whereas that of PMMA bone cement was 2.0 MPa (p < 0.05). Histological examination showed direct bonding between the BABC and the femoral bone for up to 24 months after implantation. However, with PMMA bone cement an intervening soft-tissue layer consistently was observed at the bone-cement interface. Direct bonding at the interface between the BABC and the bone through a calcium phosphorous layer 30 microm-thick was revealed by scanning electron microscopy. Femoral bone resorption was observed at 24 months after implantation in the BABC group, but it was not observed in the PMMA bone cement group. Direct bonding between BABC and the bone may have accelerated femoral bone resorption. Cement fractures of the BABC were observed on the acetabular side 24 months after implantation. Weak bonding between the BABC and an acetabular component made of ultrahigh molecular weight polyethylene (UHMWPE), relatively high elastic characteristics of BABC, and weakness of the calcium phosphorous layer formed on the surface of this cement seemed to lead to failure at 24 months on the acetabular side.