| Osteonecrosis of the femoral head(ONFH)is a persistently disease in orthopedics.The incidence of ONFH is increasing with high mortality and disability.When osteonecrosis progresses to middle and late stages,with micro-fracture of the subchondral bone,bone loss and collapse of the femoral head,hip osteoarthritis with pain and dysfunction is irreversible..Efforts are taken to repair and reconstruct the collapsed or pre-collapse necrotic femoral head.Widely accepted surgical techniques are iliac or fibular bone graft transfer with or without vascular supply.However,these techniques were reported unsatisfied clinical results because of insufficient biomechanical support to femoral head postoperatively.Nowadays,new techniques for hip-preserving therapy of ONFH could be expected with the progress of bio-tissue engineering technology and the development of new biomaterials research.Based on the three key elements of tissue engineering technology,the ideal bone graft scaffold material should have the following characteristics:Tissue engineering scaffolds should have stable chemical characteristics and good biocompatibility,and no metal ions react with tissue and body fluids.(2)The scaffolds should have similar mechanical properties to those of recipient bone structures,so as to avoid stress shielding.The elastic modulus of the scaffolds should be close to bone tissue(0.01-30 GPa)with sufficient biomechanical strength.(3)The scaffolds should have similar three-dimensional structure to bone tissue,which can provide favorable growth space and material exchange place for seed cells.At present,the commonly used biomedical metal materials are facing the problems of high modulus of elasticity,low porosity,low surface friction coefficient,stress shielding,thus resulting in corresponding fracture of host bone and failure of internal implants.Porous tantalum has a similar structure to bone trabecula.Its average pore size is between 400 and 600 microns,and its overall porosity is 75%-85%.Its modulus of elasticity is similar to that of human bone structure,which can reduce stress shielding after implantation and advantageous to bone remodeling and reconstruction.Porous tantalum products have been widely used in clinical field and achieved good clinical results.However,the preparation technology of porous tantalum materials is monopolized and the application price is high,so it is imperative to realize the importance of nationalization of porous tantalum metal.In this study,porous silicon carbide materials were used as scaffolds to prepare new porous tantalum materials by chemical vapor deposition,and preliminary biological evaluation was carried out.The experimental study of porous tantalum metal materials combined with bone marrow mesenchymal stromal cells(BMCS)to treat osteonecrosis was carried out,and the patients with ONFH were treated clinically.New porous tantalum metal with silicon carbide scaffold was evaluated comprehensively.The biological characteristics and clinical efficacy in the treatment of ONFH are evaluated as follows:1.Using porous silicon carbide as scaffold material and chemical vapor deposition(CVD)technology,tantalum metal was deposited on its surface to form neotype of domestic porous tantalum metal material.The surface morphology of the scaffold before and after coating was observed by ultra-depth of field three-dimensional digital microscopy system.The thickness of tantalum metal coating was determined by scanning electron microscopy and EDX energy spectrum analysis,and the preparation of the new porous tantalum metal was confirmed by energy spectrum analysis of tantalum element.A neotype porous tantalum metal made in China was successfully prepared by this process.The optimum hydrogen flow rate was 150 ml/min,the optimum matrix reaction temperature was 900 C,and the deposition time was 10 hours.The tantalum metal can be uniformly deposited on the porous surface of porous silicon carbide scaffolds by CVD method,and the adhesion between the coating and the silicon carbide matrix is good.Ta-coated porous silicon carbide scaffolds not only have ideal porosity structure and mechanical properties,but also have excellent biological properties of tantalum metal.2.Rabbit bone marrow stromal cells(BMSCs)were isolated and cultured.CD45,CD44 and CD34 proteins on the surface of cells were detected by flow cytometry,and cell types were identified.BMSCs were co-cultured with tantalum metal extract,normal medium and porous tantalum metal materials for 7 days.Growth and proliferation curves of cells were observed on 1,3,5 and 7 days respectively.No significant difference was found between the three groups on 1,3 and 5 days.At 7 days,tantalum metal co-culture group was higher than the other two groups,with statistical significance.MTT assay was used to determine the growth and proliferation of cells among the three groups,which indicated that porous tantalum metal had good cell compatibility.Scanning electron microscopy(SEM)was used to observe the adhesion and growth of stem cells on porous tantalum materials.On the 7th day of co-culture,the cells fused,connected and crawled into the porous tantalum pore.The cells completely covered the porous tantalum surface,forming a cluster overlap between cells,and secreting matrix covering the material surface.In addition,porous tantalum was Ccut into a circular disc with a diameter of 0.5 cm and a length of 0.7 cm.It was implanted into the fascia and muscle of rabbit back to observe the compatibility of porous tantalum with the surrounding connective tissue fibers.12 weeks later,it was found that porous tantalum was surrounded by connective tissue,and there were no inflammation and tumorigenesis,such as swelling,ulceration and purulence.Van Gieson staining showed that porous tantalum implanted subcutaneously was completely integrated into connective tissue without immunological rejection.It is confirmed that the new porous tantalum scaffold material has good biocompatibility in vivo and in vitro,which can provide a reliable theoretical basis for bone implantation in the next step.3.According to the characteristics and ability of bone marrow mesenchymal stem cells transforming into osteoblasts,bone marrow mesenchymal stem cells(BMSCs)were cultured in vitro and combined with porous tantalum to form a complex,which was implanted into the femoral necrosis area of rabbits to observe the improvement of osteogenesis and bone repair.Firstly,bone marrow mesenchymal stem cells were co-cultured with porous silicon carbide,porous titanium and self-made new porous tantalum metal in vitro.After 7 days of culture,the proliferation of cells in the porous tantalum scaffold group was higher than that in the Ti alloy and SiC scaffold group(P<0.05).The cultured cells were demonstrated by osteogenesis induction,alizarin red staining and alkaline phosphatase cobalt-calc;ium staining.Bone marrow mesenchymal stem cells were cultured with porous tantalum metal,and the number of cells increased with the increase of days,and the expression of osteocalcin and osteopontin increased in two-week culture group with tantalum metal,indicating that tantalum metal can promote osteogenesis.In vivo experiments,hormone-induced osteonecrosis models were prepared to implant more.Immunohistochemical staining of porous tantalum metal]and stem cells showed that BMP-2 and vascular endothelial growth factor were expressed in different degrees in bone tissues between the two groups,and yellowish-brown granules could be seen in bone marrow,microvascular and surrounding bone tissues.The expression of porous tantalum metal combined with BMSCs was deep-stained and strong at 12 weeks,and the expression of porous tantalum metal combined with BMSCs was obvious.Compared with the control group,the difference was significant(P<0.05).Hard tissue sections showed that after 12 weeks of porous tantalum implantation alone,almost all the porous tantalum pore was filled by new bone-like substances.In the co-culture group of porous tantalum and BMSCs,the regenerated bone trabeculae(red)could be seen inside porous tantalum.Through this experiment,it is proved that the new porous tantalum metal has good biocompatibility and meets the basic requirements of bone implant materials.Animal experiment results show that porous tantalum metal combined with bone marrow stromal cells has achieved good results in repairing osteonecrosis,which can provide some ideas and choices for the treatment of middle and late osteonecrosis.4.A neotype porous tantalum rod combined with bone marrow stromal cells and vascularized iliac bone flap transfer method was used to treat young and middle-aged patients with avascular necrosis of femoral head.Under the condition that bone marrow stromal cells can promote bone formation and porous tantalum metal band can induce bone growth and biomechanical support,the treatment of combined vascularized iliac bone flap transfer was studied.Treatment of femoral head necrosis has been carried out for young femoral head necrosis patients in the middle and late stages,and satisfactory results have been achieved.The results show that the neotype porous tantalum rod combined with bone marrow stromal cells combined with vascularized iliac bone flap transfer can effectively remove the necrotic bone in femoral head,promote the regeneration of new bone in femoral head,provide reliable blood supply and biomechanical support,and prevent collapse.It occurs one step without increasing the complications of the operation. |
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