Biological evaluation of biphasic calcium phosphate ceramic vertebral laminae

Abstract

An artificial vertebral lamina with a dense inside surface and porous outside part, fabricated with a biphasic calcium phosphate (70% hydroxyapatite/30% tricalcium phosphate) (HA-TCP) ceramic (abbr. CVL), was evaluated by animal experiments. The animal experiments showed that at half a month postoperation, no bone formation occurred on the macropore surfaces of the implants, however, fibrous connective tissues and blood vessels had grown into the macropores, contributing to the early fixation of the CVLs. The degradation of TCP phase was detected through X-ray diffraction (XRD); in the meanwhile, needle-like and plate-like crystals were found in the materials through scanning electron microscopy (SEM), and infrared spectroscopy (IR) observations showed that the carbonate apatites similar to bone apatites began to occur in the materials. At one month postoperation, the degradation of the TCP phase became moderate, new bone began to grow into the porous structures of the implants, and further degradation of the implants provided rich Ca and P ions for new bone formation. The newly formed bone in the macropores of the implants increased with implantation time. At one year postoperation, the implant was completely fused with natural bone on the interfaces between them, new bone had grown into most of the porous structures of the implants, and a natural bone tissue layer formed on the inside surface of the artificial vertebral lamina. The new bone tissue layer played a more effective role in protecting the spinal cord and improving the spinal stability in the later implantation time.