In vivo evaluation of nano-crystal hydroxyapatite intervertebral fusion cage

As the main inorganic component of natural bone, hydroxyapatite has good biocompatibility and osteoconductivity. Conventional sintered hydroxyapatite ceramics are too brittle and have low fatigue strength, thereby limiting their clinical applications. Nano-crystal hydroxyapatite (NHA) ceramic could be prepared by a two-step sintering process and overcomes the disadvantages of brittleness and low fatigue strength. The NHA ceramic provides good mechanical properties that meet the load-bearing requirement of human spine. In this study, animal experiments were performed to evaluate osteointegration and repair effect of the NHA ceramic spinal fusion cage. NHA ceramics intervertebral fusion cages were prepared and implanted into L6-L7 and L7-S1 intervertebral spaces of beagle dogs. The spinal fusion efficacy was evaluated by X-ray imaging and histological observations 2 months and 6 months post-operation. The results showed that the cages and the endplates of the vertebral bodies fused very well 6 months post-operation. Disc space heights were enlarged by the implantation and were not lost post-operation. Histological observations indicated obvious osteointegrations between the implants and the host bone. With good biocompatibility, bioactivity and mechanical strength, NHA is a promising bone substitution material and has a broad application prospect in the field of spinal intervertebral fusion cage.