Long-term follow-up study of bioactive bone cement for repairing a segmental defect in a canine femur.

We report on a 7-year long-term follow-up study of a bioactive bone cement (BA cement) that was used to repair a segmental defect in a canine femur. Bilateral femoral segmental defects were repaired with metallic implants that were fixed to the femur using two kinds of bone cement. The BA cement used in this study consists of an apatite- and wollastonite-containing glass ceramic (AW-GC) with a bis-phenol-alpha-glycidyl methacrylate (bis-GMA)-based resin. The bone-cement interface was examined histologically. Previous short-term studies have shown that using BA cement for segmental replacement of the canine femur produced excellent biomechanical and histological results. The BA cement maintained the fixation of a metallic implant to the femur very well. In contrast, the PMMA cement did not maintain alignment under long-term weight-bearing conditions. The results of histological examinations showed direct bonding between the BA cement and bone, while an intervening soft tissue layer was observed at the bone-cement interface with the PMMA cement. The BA cement bonded to the bone through a Ca-P-rich reactive layer, which was twice as thick after 7 years than it was at 26 weeks. No adverse effects of BA cement were observed during the 7-year observation period.