Experimental Study Of Treatment Of ANFH In Canine With Transplantation Of Noncelluar Tissue Engineered Bone Constructed By Nano-Nacre/PDLLA Artificial Bone

BackgroundsAvascular Necrosis of the Femoral Head(ANFH) is a common clinical orthopedic diseases,conservative treatment efficacy is usually poor,the progression in the disease results in collapse,hip dysfunction,which has a negative impact on the patients' normal life.We should pay much attention to the treatment of ANFH as the following describes:First,the blood supply and microcirculation of femoral head should be improved,so do the regeneration of bone and cartilage;Second,we should strengthen or replace the mechanical performance of subcartilaginous bone of the femoral head to prevent collapse.Bone tissue engineering progress expands the methods of treatment of ANFH. However,due to the difficulty of culturing seed cells in vitro,time-comsuming,easy to pollution,potential to trait change or canceration,those all restrict its clinical applications.Noncelluar Tissue Engineered Bone(NTEB) constructed by the scaffold compound growth factor and autologous bone marrow(ABM,containing a small amount of seed cells,without culture in vitro),which eliminates the steps and costs of culture in vitro,and avoids the pollution or canceration related to it,is more feasible at this stage of bone tissue engineering will be applied to clinical use as simplified methods.We design to use Nano-Nacre/PDLLA Artificial Bone(NNAB) as a carrier of bone morphogenetic protein-2(BMP-2) and autologous bone marrow(ABM) to construct Noncelluar Tissue Engineered Bone(NTEB),and we implant the NTEB into the necrosis zone of the femoral head through the tunnel of core decompression.We take the advantage of favourable quality of immunogenicity,biocompatibility,bone conduction of NNAB and bone induction of BMP and osteogenesis of ABM to promote bone repair;We take the advantage of favourable quality of biomechanical property of Nano-Nacre/PDLLA Artificial Bone as a supporting scaffold to prevent collapse of the femoral head.We hope that through mutual coordination of a variety of favorable factors,we can get a good result in the treatment of ANFH.Objectives:1.To investigate the feasibility of using Nano-Nacre/PDLLA artificial bone as a carrier to combinate bone morphogenetic protein and autologous bone marrow to construct Noncelluar Tissue Engineered Bone.2.To evaluate the ability to prevent collapse of femoral head using Noncelluar Tissue Engineered Bone constructed by Nano-Nacre/PDLLA artificial bone,bone morphogenetic protein and autologous bone marrow in the treatment of ANFH.Methods:Twelve healthy dogs(24 femoral heads) were used in this experiment.Ten dogs were selected to creat ANFH animal models using liquid nitrogen frozen method.At 4 weeks after liquid nitrogen frozen,the 10 animals were divided into 3 groups: NNAB group(group A,4 dogs),Core Decompression group(group B,4 dogs), necrosis control group(group C,2 dogs).The dogs in Group A were implanted Noncelluar Tissue Engineered Bone constructed by Nano-Nacre/PDLLA artificial bone combining ABM and BMP after core decompression,the dogs in Group B were treated with Core Decompression,the dogs in Group C were used to get primary information of necrosis of femoral head and as a test for animal models.The group in which the dogs haven't been useed to creat ANFH animal models is normal group(group D,2 dogs) The dogs in group A and group B were sacrificed respectively at 4,12th week after treatment,the dogs in group C and group D were sacrificed at 4th week after liquid nitrogen frozen.All dogs are subjected to radiograph,microscope and biomechanics examination.Factorial design ANOVA was used to compare the compressive strength in different times and in different groups,LSD method was usede for multiple comparison,so as to distinguish whether statistically significant difference exists or not.Statistical significance only exists when P＜0.05.Results:1.Imageology ObservationIn group A,we could see an stick-shape radiodense in 4th week's X-ray imagine, the boundary between it and its surrounding became blured in 12th week's X-ray imagine.We could see the radiodensity difference between implant and its surrounding became almost vanished in computed tomography image in 12 weeks.In group B,radioparent imagine caused by core decompression could only be found in the cortical bone under the big trochanter of the femur and the radioparent imagine gradually disappeared from 4th to 12th week's X-ray imagine.It is hard to distinguish the whole core decompression hole in X-ray.Computerized tomography image could show the core decompression hole,which is obviously radioparent in the test.2.Biomeehanies TestThere is no interaction between treatment methods and treatment times,the difference of the compressive strength of femoral head among the 4 groups is statistically significant(disconsidering the treatment time,F=146.291,P=0.000),all the compressive strength of the femoral head of different groups lined in order from lower to highter is of group C,group A,group B and group D(P=0.000).The mechanics compressive strength of the femoral head at 12th week is higher than that at 4th week(disconsidering the treatment methods,F=8.092,P=0.009).3.Histology ObservationIn group A,we can see several cells masses and matrix diffusedly distributed in the NNAB implant and its surface at 4th week.New bone formation can be found significantly at 12th week,and some new bone tissue get infiltrated to the pore of the NNAB transplant,the absorption of outer part of NNAB is significant and the degradation rate is about 20%-30%by radius,the space left behind by degradation of NNAB occupied by new bone formation which possessing an obvious appearance of enchondral ossification at 12th week.In group B,most of tissue in the drilled hole is fibrous tissue,new bone formation can hardly be found at both 4th and 12th week.Conclusions:1.It's feasible of using Nano-Nacre/PDLLA artificial bone as a carrier to combinate BMP and autologous bone marrow to construct Noncelluar Tissue Engineered Bone.2.The treatment of ANFH in canine with transplantation of Noncelluar Tissue Engineered Bone constructed by Nano-Nacre/PDLLA artificial bone after core decompression is effective,which can improve the anti-collapse biomechanical property of the femoral head,enhance the speed of new bone formation,necrosis reparation of the femoral head,and the degradation and absorption of NNAB is ideal.