| [Backgrounds] The number of patients receiving total hip arthroplasty increasesannually, even in younger adult patients, because of excellent intermediate andlong-term clinical results without the use of bone cement. Recently, earlyweight-bearing has been recommended to shorten hospital stay despite thepotential risk of early migration or loosening of the cementless femoralcomponent. A number of femoral component surface textures, such as porousplasma-sprayed titanium with or without a hydroxyapatite coating, have beenintroduced to enhance fixation of the cementless prosthesis by bone ingrowth.however, the migration or loosening of articular prosthesis still remains achallenge problem. Bone morphogenetic proteins (BMPs) belong to thetransforming growth factor superfamily. Among the BMP family, BMP-2showsthe most powerful and rapid bone induction. Clinically, however, BMP-2promotion of bone formation is markedly limited due to its rapid diffusion and absorptionwhen it is injected into the body. To maximise BMP-2-induced bone formation, itis necessary to find an ideal sustained delivery method. It is reported thatsustained growth factor delivery can be established through different non-covalentretention mechanisms, including physical entrapment, absorption andcomplexation. Apart from entrapping it in a gelatine sponge, BMP-2is usuallyencapsulated in poly(lactic-co-glycolic acid)(PLGA) microspheres. Thesemicrospheres can prolong the sustained release of BMP-2, maximising its abilityto induce bone information. Ti6Al4V alloy, because of its excellent combinationof mechanical toughness, corrosion resistance, chemical stability andbiocompatibility, is one of the mostly used titanium alloys in aeronautical andbiomedical application. Surface roughness has been shown to be an influencingparameter for osteoblast cell response. Coating of implants with locally actinggrowth factors may influence the remodeling process at the tissue–implantinterface and therefore the integration of implants into healing bone. [Aims] The aim of this study was to demonstrate a biomaterial that can promotebone ingrowth into the surface of the implant. Therefore, it can provide essentialexperimental data for designing biological femoral component.[Materials and Method] Ti6Al4V cylinders,3mm in diameter and12mm inlength, were manufactured and provided to us by Baimtec Material CO.,LTD.The surface of the implants was sandblasted (with the parameter,60orders,5Papressure,45o). Then, the test samples were ultrasound washed in acetone,alcohol and deionized water for20minutes respectively. Finally, they were boiledin the compound solution (3%HCl+48%H2SO4+49%deionized water) for2minutes. The surface of Ti6Al4V cylinders were observed with environmentalscanning electron microscope (SEM, FEI QUANTA600, FEI, USA) and theporosity was measured. The rhBMP-2microspheres were fabricated using awater-in-oil-in-water (W/O/W) double-emulsion-solvent-extraction technique.Then, α-Butyl–cyanoacrylate was used to control the burst release of rhBMP-2microspheres, pour and adhere more particles into the pores of Ti6Al4V. Theencapsulation efficiency and sustained release in vitro of rhBMP-2was measuredby ELISA kit. Finally, the Ti6Al4V was implanted into the femoral condyle.Push-out testing and energy dispersion spectroscopy were performed to determineshear strength and bone ingrowth of the bone-implant. In addition, histology ofthe bone-implant interface was carried out with Giemsa and toluidine blue stain.[Result] Honeycomb porus with different diameter were presented on thesurface of the Ti6Al4V, which was boiled in acid compound solution. Small poreswere inlayed in the large ones. The diameter of the biggest pore is about60um,while the smallest is approximately2-5um. The size distribution demonstratedthat the microspheres fabricated with the water-in-oil-in water (W/O/W) doubleemulsion-solvent-extraction technique were well distributed in size, with morethan98%of particles having a diameter of approximately1μm and theencapsulation efficiency was as high as98.86%. The α-Butyl–cyanoacrylatecould control the burst release of rhBMP-2(about24%) and sustainedly release for a month. In vivo, push-out testing showed the Ti6Al4V coated with rhBMP-2has larger shear strength than the pore group and the control group. Furthermore,the SEM and energy dispersion spectroscopy demonstrated more bone ingrowth inexperimental group than the other groups. Finally, the histology showed that boneingrowth at the adjacent of the bone-implant, while the new tissues on the surfaceof the Ti6Al4V were mostly fibrous in the control group.[Conclusion] Ti6AlV coated with rhBMP-2microspheres/α-Butyl–cyanoacrylate implanted into the rabbit femoral condyle could promote boneingrowth at the early stage and has more bone ingrowth than in the pore group andin the control group. Thus, it may be a good biomaterial for designing femoralcomponent. |
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