Ingrowth characteristics of the interface between hydroxyapatite coated intervertebral implant and vertebral cortex / 中华骨科杂志

ABSTRACT

Objective To observe the ingrowth characteristics of the interface between hydroxyapatite coated intervertebral implants and vertebral cortex loaded with physiological compressive stress. Methods Twelve titanium alloy intervertebral implants special for macaque were prepared, 4 of which were coated with corundum (control group) and 8 of which were coated with hydroxyapatite (HA, observed group). One control and two observed implants were randomly inserted into the intervertebral spaces of L2,3, L3,4 and L4,5 in each of 4 healthy homogenous adult macaques (2 males and 2 females). Roentgenology was performed at 3, 6, 12, 24 and 40 weeks postoperatively. Histomorphometry as well as histology were also evaluated at 40 weeks postoperatively. Results All the animals recovered well from the operation. Three days after operation all the animals began to stand and walk with normal gait. Gross anatomy showed excellent healing in the annulus fibrous involved, and no implant loosening or migration was found. On 40 weeks postoperatively, the interface of the observed group were filled with calcified mature bone and partly-mineralized osteoid tissue, the content of calcified bone as well as the amount of osteoblasts and osteocytes were significantly higher in observed group, and the differences were of statistical significance (t=5.001, P=0.000 and t=16.983, P=0.000). A tight connection was observed between the vertebral bones and HA coating. The thickness of coating decreased form 130-150 ?m to 100-130 ?m. And no evident breakage or debris was found on the implant coating. Conclusion HA coating was stable in vivo and had favorable biocompatibility with vertebral bone. It was more effective than corundum coating in inducing intervertebral cortical bone ingrowth under physical compressive loading.