| Repairing bone defects caused by all kinds of reasons is a difficult problem in clinic, especially reconstruction of long segment weight-bearing bone defects is more difficult. The nano-hydroya-patite and polyamide66 (n-HA/PA66) is a new type of inorganic-organic biomimetic component. Results of the test and analytical studies indicated that the distribution of n-HA homogeneously in polyamide matrix, nanograde needle-shape apatite crystals of n-HA was similar to bone apatite. Dor Mengchunyang had completed"Experimental study on the biological capability of the nano-hydroxyapatite/polyamide66 composite and repairing bone defect with the porous composite". And the results indicated n-HA/PA66 have good cellular compatibility,biocompatibility,bioactivity and osteoacusis. Pycnotic n-HA/PA66 used in our experiment was a kind of new bone repairing and reconstruction material. The mechanical and chemical property of it was similar with natural bone, It had big intensity compared with porous composite and was more fit to repair weight-bearing bone defects. But vascularize and osteocyte adhereing were difficult because of it,s solid and pycnotic texture. So we constructed single weight-bearing bone defect model and used MGBR in order to solve that bone formation and revascularization were difficult in pycnotic composite at early stage and to verify feasibility of pycnotic n-HA/PA66 and PLGA complex repairing weight-bearing bone defect compared with porous composite.OBJECTIVE Initial empirical study of pycnotic n-HA/PA66 repairing weight-bearing bone defect was did. Observing the feature and mechanism of pycnotic n-HA/PA66 and PLGA complex repairing bone defec. Solving that bone formation and revascularization were difficult in pycnotic composite at early stage. Testing incorporate stability of pycnotic n-HA/PA66 and autogenous bone. Verifying feasibility of pycnotic n-HA/PA66 and PLGA complex repairing weight-bearing bone defect.METHODS 1.0cm defect was produced on the rabbit,s left femoral bone. The pycnotic n-HA/PA66 composite (hollow, inner diameter was 0.2cm) was implanted in experimental group A, and the composite was enveloped with absorbent PLGA membrane. The pycnotic n-HA/PA66 composite and porous n-HA/PA66 composite without membrane was implanted in control group B and C. Then these composites were fixed with plates and wire. X-ray,histology,morphology were applied at 12W, 16W,20W,24W and biomechanics,SEM were applied at 24W after operation.RESULTS Obvious rejection was not observed in operating field.(1) X-ray: Composite had been combined fast with rabbit,s autogenous bone in 3 groups at 12W. And implant was enwrapped by much neoformative callus, fracture line had became indefinite. Callus had been moulded(rebuilded), and been stretched with cortical bone, but the shape of them was irregular at 16W in group A. The shape of the callus became to regular in group A. And the callus came to be rebuilded , but the shape of them was irregular in groupB,C at 20W. The plant had been coalesced fast with autogenous bone, and the callus had been continuous with autogenous os integumentale. The shape of the callus was natural,laevis and rebuilded as autogenous bone. The callus had became to regular and been stretched with autogenous cortical bone in group B,C at 24W. Osteoconductivable of group A were superior to group B, and there was not statistically significant difference between group A and group C ( p<0.05) from 12W by Lane,s radiology score.(2) Histology: Many osteoblasts and neoformative bone trabeculas could be observed around composite in group A, which was more than that of it in group B. Neoformative chondrocytes could be observed around the composite, and there was collagen tissue and osteoblast in mesh of the composite in group C at 12W. Many neoformative bone trabeculas,some lamellar bone around the composite, and degradation at the edge of the composite induced by osteoclast could be observed in group A. There were many osteoblasts and neoformative bone trabeculas around the composite in group B. Neoformative chondrocytes and some lamellar bone could be observed around the composite in group C at 16W. Many neoformative lamellar bone could be observed in group A. There were many neoformative bone trabeculas and lamellar bone around the composite in group B. Chondrocytes came to reduce and lamellar bone came to increase. Neoformative bone trabeculas could be onserved in the mesh of group C at 20W. Neoformative lamellar bone increased and became compact in group A. Many neoformative lamellar bone could be observed in group B too. And chondrocytes were replaced gradually by lamellar bone in group C at 24W. Os-integrate rate of composite in group A was higher than that of it in group B, and the difference was significant between them ( p<0.05 ) by image analysis. But the difference between group A and group C was not significant ( p>0.05 ).(3) SEM: New osteotylus could be seen on the surfaces and interfaces of three groups. And the composite was fused with bone. Bone collagen extended to composite as feet of the crab.There was new bone in the mesh of group C. Bone matrix vesicles could be seen on the surfaces of group A and B, and the vesicles were distributed aequalis and were similar with autogeneic bone matrix. Hydroxyapatite was corpuscular and calcium salts were deposited on the surface of three groups.(4) Biomechanics: Intensity,ductility,elasticcity of the composite were compared within three groups and with normal group .No statistically significant difference was noted between group A and normal bone ( p>0.05 ). But the difference was significant between group A and group B ( p<0.05 ). And no statistically significant difference was noted between group A and group C ( p>0.05 ).CONCLUSIONS Pycnotic n-HA/PA66 and PLGA complex has better biocompatibility,bone guided capability and biomechanics, which can be applided to repair weight-bearing bone defection. |
