| OBJECTIVE : To study the radiology in the ability of bony generation by the way of the experiment of repairing bone defects with nano-hydroxyapatite and polyamide-66 composite, mean while with polymethylmethacrylate and calcium phosphate cement as matched controls. This research can theoretically guide us in applying the n-HA/PA66 composite in the clinic. METHODS:48 New Zealand rabbits were classified randomly into three groups: A ,B and C,every group had 16 rabbits. The Condyle of tibia was performed boring which was 3mm diameter and 5mm depth. In group A,B and C, n-HA/PA66 composite, PMMA and CPC were implanted dividedly by means of every two materials in every rabbit of one group. The specimens were taken respectively in different times: 2nd 4th 6th 8th 12th week after surgery, and were examined by the methods of plain roentgenography,hisology and magnetic resonance imaging. In 4th 8th and 12th week after the operation, all groups were undertaken the biomechanical test. Finally the collected data was analyzed using SAS 8.0 software. RESULTS:(1) In the 2nd week after operation, DR displayed that there was a round of nonopaqu line around the every area of bone transplant. The histology showed that was a layer of interface membrane forming. So MRI graph showed reinforcement around every area. (2) In the 4th week after operation, the interface membrane had been widest and revolved the n-HA/PA66 composite partly where the number of cells was increasing and some osteoid was formating. So there was some a little high density area in the range of material transplant on DR photographs, while there was some reinforcement at the edge of area on MRI graphs. At the same time, in the areas of PMMA and CPC, the photographs of DR and MRI showed little change from the 2nd week, which as the same thing on histology. (3) In the 6th week after operation, the range of high density among the area of n-HA/PA66 composite transplant was wide on DR graphs. While on MRI graphs the material had heterogeneous intensity, clouding border and reinforcement among the material. Histologically, there was intramembranous ossification appearance with more vessels in it. As to the area of PMMA transplant, histologically and on the DR MRI graphs, little change happended. On the side of CPC area, the density on the DR graph was decreasing and at the edge of transplanted area, a little reinforence appeared, which showed more material involved and someprimary trabecular bone and osteoblasts in the interface membrane formed. (4) In the 8th week after operation, on the DR graphs, among the area of n-HA/PA66 composite transplant, the range of high density was wider. n-HA/PA66 Composite was remarkable T1WI secondary high intensity and T2*WI secondary low signal intensity. The range of high intensity was wider after enhancement. Some primary trabecular bone and more osteoid in the interface membrane formed, the material was revolved widely. On the side of PMMA, MRI showed the signal intensity in the distal inter-medullary-cavity became higher and not so stepless, but inner material it was still low signal intensity. Histologically, the membrane was just at the boundary of material and only little inflammatory cells but no osteoblasts appeared. As to the CPC group, there was poor defined border on the DR graphs and some reinforcement among the area of material. Histologically, the material was separated into small areas and forming more primary trabecular bone. (5) In the 12th week after operation, there were some trabecular bone connected the area of material. While on the MRI showed obvious enhancement among the area of material and the intensity decreasing on the plain scan. Histologically, more bone trabecula was forming, and more osteoblasts and osteoclasts in the thicker interface membrane. In the area of PMMA transplant, there still no reinforcement, but the abnormal intensity in the distal inter-medullary-cavity became wide. On the DR graph showed little change as before. Histologically, theinterface membrane transformed into fibrous tissue. As t... |
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