Papers by Author: Yao Wu

Abstract: Fixation nail systems , such as DHS, DCS and the standard Gamma-nail, are widely applied for the 31-A2 intertrochanteric unstable fractures treatment, but which one would be of more curative effect is still remained as a disputed problem. In this work, precise femur model with 31-A2 fracture was rebuilt based on the CT data, and fixation nail models were built by CAD. By the means of finite element analysis (FEA), the biomechanical data of femur and nail systems were achieved under typical loading. The results show that under the same load, the maximal stresses on the fracture sections for DCS, DHS and Gamma nail systems are 48MPa, 24MPa and 19MPa, separately; and the directional deformation is the highest with DCS fixation systems, while lowest with Gamma nail fixation system. Considering the mechanical safety, Gamma nail is more suitable for 31-A2 intertrochanteric unstable fractures treatment.

Abstract: Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.

Abstract: The achievement of biological sealing is determined by the quality of the skin attachment on the surface of the percutaneous implant in the area where the implant penetrates the skin. It has been known that certain surface features of the implants can significantly influence the interactions between cells and substrate. In this study, titanium plates were bioactivated through anode-oxidization firstly, and then cultured with human epithelium cells for 72h. Untreated Ti plates were used as control. After the samples were dehydrated, the morphology of the cultured epithelium cells was tested with Scanning electron microscopy (SEM). The surfaces of control group did not enhance epithelium cell attachment and growth, while the bioactivated microporous surface of anode-oxidized group would be beneficial to induce the formation of the pseudopod of epithelium cell, and then interlock the human epithelium cells through the pseudopod, which imply that the surface modification method of anode oxidization may be one of the most effective methods to resolve the biological sealing.

Abstract: Dense HA/TCP bioceramics were immersed in pure bovine serum, rabbit serum and dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that some needle-like crystals formed on surface of sterilized HA/TCP, and needle crystals developed into sheet crystals and stick crystals after ceramics were immersed in bovine serum and rabbit serum respectively. The growth of crystals was maybe affected by the content of calcium, various kinds of albumen and alkaline phosphatase in different serums and the different pH of serum.

Abstract: Porous tricalcium phosphate ceramics were immersed in static and dynamic revised simulated body fluid (RSBF) at 37°C. Morphology, composition and phase of precipitates on TCP were identified by SEM, FTIR and TEM methods. FTIR and TEM results indicated the deposits on the inner pore walls of TCP were OCP, and SEM results implied that the deposited way of precipitates in static system was different from that in dynamic system.

Abstract: Porous HA/TCP bioceramics were immersed in pure dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that beamed sheet-like crystals formed on the surface of ceramics granules, and after postponement immersion time, crystals extended and became bigger. EDS and IR results suggested formed crystals were defect-calcium type carbonated hydroxyapatite. HRTEM photograph suggested formation process of new-formed crystals from non-crystal to crystal in serum. Directional organisms acted maybe as a template in process of crystals formation, so new crystals developed along certain direction.

Abstract: In this study, bovine serum albumin protein (BSA) was introduced to investigate the co-precipitation process of calcium phosphate and BSA on bioactivated Ti. Commercially pure titanium were bioactivated firstly, and then immersed in a highly supersaturated stable calcium phosphate (Ca-P) solution at three different conditions. The samples designated as Ti-C, Ti-C-CB, and Ti-C-B for control. The samples were evaluated by SEM with EDX, XRD and XPS. The co-precipitation of BSA protein and Ca-P influenced the morphology of the crystals of Ti-C-CB significantly. In terms of the immersion in the Ca-P solution containing BSA, the co-precipitation of Ca-P with BSA on the surface of Ti-C-CB was a chemical process rather than simple physical adsorption, which was most possibly achieved by the linkage of –COO− groups to Ca-P. Such coprecipitated interaction led to the formation of a tight, dense and uniform Ca-P coating.

Abstract: It is very necessary to develop a real biomimetic compound coating of CaP with organic component and investigate quantitatively the effects of different bovine serum albumin (BSA) concentration on the crystallite properties of the coprecipitated CaP layer. Bioactivated Ti was immersed in Ca-P solution with different BSA contents to obtain different biomimetic coating. The coatings were analyzed with scanning electron microscopy (SEM) and X-ray diffraction (XRD). With the increase of BSA, the crystals on the coating grew more slowly but packed more closely. The preferential crystallographic direction of 002 of hydroxyapatite became less distinguishable and the crystallinity of the deposited hydroxyapatite decreased gradually. The crystallite sizes reduced with the addition of BSA proteins. Accordingly, when a certain content of BSA protein was added to the Ca-P solution, Ti surface would form a real biomimetic coating with the crystal size and crystallinity similar to the natural bone.

Abstract: In this study, alkali-heat treatment in NaOH solution and heat treatment, which could form amorphous sodium titanate on nanophase titania ceramics surface by conditioning the process, was employed to modify the structure and bioactivity of biomedical titania ceramics. After the nanophase titania ceramics was subjected to alkali-heat treatment, thin film X-ray diffraction and scanning electron microscopy results showed the titania ceramics surfaces were covered by porous sodium titanate. In fast calacification solution (FCS), the alkali-heat treated titania ceramics could induce bonelike apatite formation on its surface. Our results showed that induction of apatite-forming ability on titania ceramics could be attained by alkali-heat treatment. So it was an effective way to prepare bioactive titania ceramics by combining sintering and alkali-heat treatment.

Abstract: In this study, the bioactivity of a new kind of anodic oxidized titanium metal was investigated in vitro and in vivo. After immersed in SBF solution for 7 days in vitro, apatite formed and covered almost all the surfaces of the anodic oxidized samples. In vivo animal experiment, the apatite was also tested precipitated on the interface of tissue/materials after 12 weeks post-operation, and there were no any fibrous capsule formed around the materials. The materials bonded with the bone very tightly and attached to the skin very closely, which would result in the achievement of the biological sealing for the bone-anchored percutaneous implants. These positive results might be contributed to the precipitated apatite layer formed on the surface of the bioactive oxidized titanium. Thus, Anodic oxidation treatment might be an effective way to prepare bioactive Ti both for bone replacement and percutaneous implant.