[Histocompatibility of porous hydroxyapatite coating NiTi shape memory alloy].
OBJECTIVE
To evaluate the histocompatibility of porous hydroxyapatite (HAP) coating NiTi shape memory alloy and to provide a theoretical basis for its clinical application in bone defect repair.


METHODS
Twenty-four Chinchilla rabbits weighing 2.0-2.5 kg were randomized into experimental group and control group (n=12). HAP coating NiTi shape memory alloy was implanted into the distal part of left femur of 12 rabbits in the experimental group, while holes without alloy implantation were performed on the control group. At 7, 14, 28 and 56 days after implantation, the animals were killed (3 rabbits in each group at a time). Gross observation, histology observation, BMP-2 immunohistochemistry observation and image grey scale analysis were performed. And the histology observation was evaluated by GB/T16886.6-1997 in terms of inflammation, capsule wall of fibrous tissue, materials degradation and the response of peripheral tissue.


RESULTS
All of the animals survived until being killed. The implants reached a peak embedded in bone tissue wholly, without loosening and bone absorption. The inflammatory cell infiltration and fibrous hyperplasia were at 7 days after implantation, with the formation of cyst wall of fibrous tissue and the implant wrapped by the cyst wall. The response of connective tissue proliferation was still obvious in partial samples of experimental group at 56 days after implantation, which was wrose than the control group but consistent with the in vivo implantation standard of GB/T16886.6-1997. Immunohistochemistry observation displayed the endogenous BMP-2 were in the cytoplasm of MSCs and osteoblast. The result of image analysis showed the expression of BMP-2 were staged in line with the repair of bone defect, two groups witnessed the peak expression of the BMP-2 at 14 days after implantation. There were no significant differences among different time points in the staining gray scale of BMP-2 (P > 0.05).


CONCLUSIONS
HAP coating NiTi shape memory alloy, as a biomedical material, has excellent histocompatibility with bone.
The Research Institute of Orthopaedics, the Second Hospital of Lanzhou University, Lanzhou Gansu, PR China.
Haijun
H
Zhang
Shuanke
S
Wang
Bin
B
Zhao
D000497:Alloys; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D018786:Bone Substitutes; D020099:Coated Materials, Biocompatible; D017886:Durapatite / Q000008:administration & dosage; D005260:Female; D020007:Implants, Experimental; D008297:Male; D008422:Materials Testing; D009532:Nickel; D011817:Rabbits; D014025:Titanium
D000497:Alloys; D055396:Bone Morphogenetic Protein 2; D018786:Bone Substitutes; D020099:Coated Materials, Biocompatible; D009532:Nickel; D017886:Durapatite; D014025:Titanium