Effects of gas produced by degradation of Mg–Zn–Zr Alloy on cancellous bone tissue

Mg–Zn–Zr alloy cylinders were implanted into the femoral condyles of Japanese big-ear white rabbits. X-ray showed that by 12weeks following implantation the implant became obscure, around which the low-density area appeared and enlarged. By 24weeks, the implant was more obscure and the density of the surrounding cancellous bone increased. Scanning electron microscopy examination showed bone tissue on the surface of the alloy attached by living fibers at 12weeks. Micro-CT confirmed that new bone tissue on the surface of the residual alloy implant increased from 12weeks to 24weeks. By 12weeks, many cavities in the cancellous bone tissue around the implant were noted with a CT value, similar to gas value, and increasing by 24weeks (P<0.01). Histological examination of hard tissue slices showed that bone tissue was visibly attached to the alloy in the femoral condyle at 12weeks. The trabecular bone tissues became more intact and dense, and the cavities were filled with soft tissue at 24weeks. In general, gas produced by the degradation of the Mg–Zn–Zr alloy can cause cavitation within cancellous bone, which does not affect osteogenesis of Mg alloy.