| [Objective] 1. To make artificial femoral stem of the no-cement prostheses and animal models of artificial joint replacement; 2. To plasma spray pure Ti on the artificial femoral stem prostheses under vacuum, then graded coat HA-Ti compound in order to understand the structural properties of these compound coating materials, their mechanical strengths and feasibility of artificial joint prostheses and to find the best technological process of graded coating this compound material; 3. To implant artificial femoral stem prostheses in dogs to observe the biological structures and property changes of bone, coating and prostheses.[Method] 1 Making artificial femoral stem prostheses made in no-cement, replacing artificial femoral stem prostheses in dogs, Joint function tests, X ray films, bone-coating interface bond strength were tested and interface structure of the coatings were observed; 2 Pure HA coatings were plasma sprayed under different power and distances. Shear strengths and structural properties were tested; 3. primary pure Ti, HA coating and graded Ti-HA coating were made under vacuum and air, their shear strength, microstructure and structure were tested and compared, histologic studies of bone biopsy and observe the structure between bone and coatings under microscopy.[Results] 1. Position and function of artificial prostheses in 3 groups were all good after replacement. No loose prostheses were found; Shear strength in pull-out testing was 16.04±0.95MPa in HA+Ti+A group,20.08±1.95MPa in HA+Ti+V group, and 23.43±0.37MPa in Ti+HAG+Ti+V group. Statistic differences were significant(p<0.05); SEM illustrated that bones bonded tightly with interfaces in Ti+HAG+Ti+V group, which was better than those in HA+Ti+V group and HA+Ti+A group. Bone bond rate in Ti+HAG+Ti+V group was much higher than that in HA+Ti+V group and HA+Ti+A group. 35kW spraying power and 80mm spraying distance can make both the structures of coating intact and bond strength strong.; The shear strengths between Ti coatings and substrates were 46.52±3.43MPa in Vacuum group, while they were 35.15±2.43 Mpa in air group. There were significant differences in these two groups; Average shear strength was 23.36±1.61 Mpa in Ti+HAG+Ti+V group,18.52±1.63MPa in HA+Ti+V group, and 15.52±1.58MPa in HA+Ti+A group; Statistic differences were significant(p<0.05); Regarding the analysis results of microstruction and structure:(1) In Vacuum group, there were continuous layer structure and low porosity on coatings, no big cracks were found under scanning electron microscope; In Ti+HAG+Ti+V group, there were continuous layer structure on the coatings, there were dense bond within the particles in HA surface layers of graded coatings, no big cracks were found. There were low porosity on coatings, even layer, no deep cracks, purely ladder like tissue distributors from the substrate to coating surface. (2) XRD results of Ti-coating showed that spraying Ti under vacuum had more intact crystallizations and denser structure; pure Ti substrate bond with HA was better in Ti+HAG+Ti+V group; (3) Analysis of the FTIR results showed that plasma spraying primary Ti was adapt to HA coating attachment. Crystallizations in Ti+HAG+Ti+V group were better; 3 In the respect of histological results:(1) there were no bone defects under the Large tuberosities, The femoral stems were fixed firmly.(2) under microscopy, the majorities of new bones on the coating-bone interfaces had been mineralized, and connected with femurs through Lamellar bones; From the Tetracycline marked bone tissues, we found that new bones had grown into coatings. There were averagely 28.9±3.5 osteoblasts and oesteocytes per view under microscopy in Ti+HAG+Ti+V group, which was more than those in HA+Ti+V group (19.4±2.4), and HA+Ti+A group (14.9±2.1).The statistical difference was significant.(p<0.05). (3) The SEM results of interface in the femoral medullary cavity illustrated good bond between interfaces in Ti+HAG+Ti+V group, broken layers were in the bone tissues after pulling out the prostheses, while broken interfaces were within the coatings in Ti+HA+A group and HA+Ti+V group.[Conclusion] 1. The technology of plasma spraying pure-Ti on the substrate of artificial femoral stems under vacuum and graded coating HA-Ti can improve bonding strengths between medullary and coatings, enhance stability of prostheses.2. Plasma spraying primary Ti under vacuum and graded coating HA-Ti,35kw spray power and 80mm spray distance in this trial can make density of the substrate high, the porosity appropriate, their bond strength and crystallizations with HA is high 3. The technology in this study can improve fixation ability of joints through better bone growing in.
|
PDF Full Text Request