| Backgrounds:Although considerable progresshas been made in recent years, repair and reconstruction of large bone defectscontinue tobea challengefororthopedic surgeons.The ultimate goal of bone reconstruction is to achieve healing of bone defects, while restoring limb function. At present, the most common therapies used in limb segmental defects are autogenous cancellous bone graft, bone transport technique as well as vascularized fibular grafting technique.These techniqueshave achieved great success in the treatment of bone defect. However, there are still limitations or shortagesin the existing techniques. Autogenous cancellous bone grafting generally applies to rebuild bone defects that no more than 4-6cm.Otherwise, the bone graft may be absorbed.Bone transport technique is restricted by its long treatment period.Vascularized fibular graft has certain advantages to large bone defects reconstruction, but it requires higher equipment and technical requirements, while it is also prone to bone nonunion and other complications [1-3]. Masquelet et al [4] has reported treatment of limb segmental bone defects with induced membrane technique.Since its high success rate, fewer complications as well as low technical requirements,this technique is gradually being more and more popular with orthopedic surgeons.During the first operation, polymethyl methacrylate(PMMA) bone cement spacer was implanted in the bone defects after debridement, PMMA then induceda biologically active membrane, which is known as the induced membrane. Next,induced membrane was filled with autologous cancellous bone to repair bone defect. Early studies showed that the success rate using induced membrane to treat bone defects is between 88% and 100%, and it was reported thatbone defects that up to 25 cm can be successfully repaired [5-7]. It was thought that the high success rate of induced membrane technical in the treatment of bone defects is due tothe biological membrane induced by bone cement. Induced membrane can not only prevent bone graft from absorbing by the surrounding tissue, but also provide necessary blood supply and growth factors for bone graft, such as bone morphogenetic protein-2(BMP-2), vascular endothelial growth factor(VEGF), etc.In this study, animal bone defect model was constructed and membrane was successfully induced after implantation of autologous bone or inactivated bone.The differences between autologous bone and inactivated bone was observed using imaging technologies and histological techniques.Finally, the differences of composition and function of membrane and the differences of osteogenesis induced by bone cement(PMMA) bone cement and calcium phosphate bone cement was compared.ObjectiveWe sought to 1)investigate the role of induced membrane on bone defect reconstructionby establishing bone defects models in rabbits, 2)determine whether induced membrane can promote osteogenesis of bone grafts, 3)compare the differences in membrane composition induced by bone cement(PMMA) bone cement and calcium phosphate bone cementas well asthe differences inosteogenic activitiesbetween these two bone cement.MethodsPart I32 healthy adult rabbits, average weight(2.35 ± 0.12) kg,male or female acquired from Third Military Medical University Experimental Animal Center.1.5cm bilateral radius bone defects were built, polymethyl methacrylate(PMMA) bone cement was implanted in the same time.Six weeks after surgery to remove PMMA bone cement was removed 6 weeks after surgery.Grouping(n=6/group): group a: PMMA bone induced membrane keepping + implantation of autologous bone;Groupb: PMMA bone induced membrane keepping + implanted inactivated autologous bone;Group c: PMMA bone induced membrane to remove + implantation of autologous bone;Group d: PMMA bone induced membrane to remove + implanted inactivated autologous bone.Closed the rabbit wound, limb don’t do any fixed, conventional breeding conditions for 12 weeks.Part II1. 1.5cm bilateral radius bone defect were built inrabbits, implanted with polymethyl methacrylate(PMMA) bone cement and Calcium phosphate bone cement, removed bone cement after 6 weeks, divided into three groups according to a random number table, experimental group, model group and control group were treated differently. Experimental group reservations induced membrane and implanted with inactivated autologous cancellous bone, model group reservations film, but not grafting, remove the membranes in control group and implanted with inactivation bone. New bone formation was detected by radiological and histological detection after 8 and 12 weeks.2. 32 healthy adult New Zealand white rabbits were divided into PMMA and calcium phosphate groups randomly. The 16 rabbits of each group were made 1.5cm bone defects on the bilateral radius, respectively, then the PMMA or calcium phosphate bone cement were transplanted in. 4 and 6 weeks later, induced membranes of two rabbits in each group were taken out to observe thefilm thickness and the density of blood vessels, while the bone cement was removed in 4 weeks and autogenous cancellous bone was implanted inside the membrane. 8 and 12 weeks later, the new bone formation was evaluated by radiological and histological observation.Results:Part I1. Bone defect repair radiology score wereevaluated using Lane-Sandhu X rayscore.Radiology results showed thatin the experimental group, there is a large amount of new bone that connecting both ends of the bone defectat8 weeks after bone reconstruction. In contrast, there is no obvious new bone formation observed in the model group and the control group.In the experimental group, bone defects completelyhealed in 12 weeks. The fracture line disappeared and marrow cavity partly recanalization.Rarely new bone callus formationand poor connection were observed in model group.2. H.E.stainingwas used to analyze new bone formation and angiogenesis.Woven bonestart to form at 8 weeks after the second stage bone reconstruction. There is only fibrous connection in the model group and the control group. Woven bone transformed into lamellar bone at postoperative weeks 12 in the experimental group. There is only fibrocartilage connection and fibrous connection in the model group and control group, respectively.Part II1. The comparison was made between membrane induced by PMMA or Calcium phosphate bone cement.The average membrane thickness at postoperative week 6 was(1108-26),(945-42)μm in PMMA group as well as(945 + 34),(778 + 22)μm in calcium phosphate bone cement group(P<0.05).Membrane and vascular densityinduced by PMMA bone cement and calcium phosphate bone cementwas 6,3/μm2and 2,2/μm2,respectively.2. ELISA test showed that BMP-2, VEGF levels in PMMA bone cement induced membrane were significantly higher than in calcium phosphate bone cement induced membrane(P < 0.05).3. At 8 and 12 weeks after the second stage procedure, new bone formation in the experimental group was superior to the model group and the control group(P <0.01). There was a little callus formation in the model group and hardly any bone formation in the control group.Osteocytes and chondrocytes were observed using H.E. staining in the experimental group. In contrast, there is no osteocytes and chondrocytes being observed in the control group.4. Woven bone formed at 8 weeks after graft in PMMA group, with osteocytes or chondrocyte are common. In contrast, there is only fibrous connection without any osteocytes or chondrocytes in calcium phosphategroup.Woven bone start to transform into lamellar bone at 12 weeks after graft in the PMMA group,the volume of bone callus decreased in the calcium phosphategroup.Compared to calcium phosphategroup, PMMA grouphas a better Bone defect repairing(P < 0.05).5. At 4 and 6 weeks after surgery, thickness of the induced membranes in PMMA bone cement group was(1108±26) and(945-42)μm, respectively.the thickness of the induced membranes in calcium phosphate bone cement group was(954+34) and(778+22) μm, respectively.Membrane and vascular density induced by PMMA bone cement and calcium phosphate bone cementwas 6/μm2and 2/μm2, respectively.The PMMA group was significant superior to the control group on bone formation at 8, 12 weeks after bone grafting(P<0.05), by either radiological examination or histological methods.Conclusions1. Induced membrane promotebone defects reconstruction by providing mesenchymal stem cells and elevated levels of osteogenic factors.2.Growth factors in induced membrane matured and reach the peak at 4-6 weeks.3. PMMA bone cement induced membrane is doing better than calcium phosphate bone cement induced membranein terms of vascularization capability and osteogenic activity. |
PDF Full Text Request