Objective To evaluate the efficacy of combined anterior and posterior approaches in treatment of severely unstable lower lumbar burst fractures.Methods A retrospective case series study was made on clinical data of 14 patients with lower lumbar burst fractures collected from August 2009 to August 2014.There were 12 males and 2 females,with a mean age of 39 years.Seven fractures occurred at L3,five at L4,and two at L5.Nine patients were associated with injury to the posterior ligament complex (PLC).According to the American Spinal Injury Association (ASIA) classification,the spinal injuries were rated as grade B in two patients,grade C in four,grade D in five and grade E in three.All patients underwent posterior pedicle screw fixation combined with anterior spinal canal decompression and titanium mesh or iliac bone grafting.Lumbar lordosis angle,vertebral height,spinal canal decompression,ASIA grade and complications were evaluated after operation.Results Two patients experienced cerebrospinal fluid leakage postoperatively,which were healed after 2 weeks' local pressure treatment.Three patients experienced recurrent lumbar pain postoperatively,which were relieved after the removal of internal fixation 18 months after operation.All patients were followed up for 12-36 months (mean,18 months).Compared to the detection before operation,final follow-up showed improved lumbar lordosis [(30.2 ± 7.3) ° vs.(41.3 ± 6.5) °],decreased loss of the anterior vertebral height [(62.3 ± 21.5) ％ vs.(11.8 ± 7.8) ％] and reduced canal compromise [(65.7 ± 30.5) ％ vs.(21.9 ± 12.7)％] (all P ＜ 0.05).ASIA grade was significantly improved at the final follow-up,including grade C in one patient,grade D in three and grade E in ten (P ＜ 0.05).Follow-up showed no apparent graft loosening,pseudarthrosis,implant breakage and severe kyphosis.Conclusion Combined anterior and posterior approaches to treat severely unstable lower lumbar burst fractures can effectively reconstruct the height and stability of the vertebral body,restore the spinal canal volume,and attain satisfactory clinical outcome.

Objective To observe the research of the biologically performance,interface micro-structure and nano-indentation situation when polymethyl methacrylate bone cement-PMMA injected into rabbit in the near future and far future individually.Methods New Zealand white rabbits were used ovariectomy plus dcxamethasone intramuscular injection to establish osteoporosis animal model.All animal models were divided into 3 groups with 35 in each osteoporosis group,testing group,and normal group.Execute the lumbar centrum of New Zealand rabbit as osteoporosis bone defect model,injected bone cement,with the help of material dynamo experiment machine to do the axial compression tests,three point bending test,and torsion test in order to observe the biological dynamic changes.Optical microscope,fluorescence microscope and scanning electron microscope were used to observe the changes of micro bone cement and the changes of bone looseness.Nano-indentation testing was applied by the triboindenter to study the critical load.Results PMMA can rapidly establish the strong support with stable function in the near future.Biomechanical experiments showed that biomechanical properties of bone cement group was significantly higher than those in the other two groups.Biomechanical properties of bone cement group may decline with the time,but which were still better than those of OP in the control group.Histo-morphological observation result shows that under osteoporosis state the bone grows slower,bone's rebuilding time also extended.And in the later period,main bone's continuous osteoporosis had some impact on the interface.Nano-indentation testing showed that the young modulus and stiffness of the interface among bone,material and interface were significantly differences.Bone cement had showen the best nano indentation hardness,then was interface and bone tissue.Conclusion The polymethyl methacrylate bone cement llⅢ has a good effect in filling,on account of it has great plasticity and liquidity and can penetrate into the minuteness aperture between trabecula,then after solidifying,it will combine firmly with the host bone.PMMA can rapidly establish the strong support with stable function after operation.The performance is decreasing in the far future but still with satisfaction.

BACKGROUND:Porous gradient hydroxyapatite/zirconia composite, which can adhere to a variety of cel s, such as osteoblasts, bone marrow mesenchymal stem cel s and chondrocytes, can induce and promote fracture healing or replace bone defects. OBJECTIVE:To review the development and application of porous gradient hydroxyapatite/zirconia composite in bone tissue engineering. METHODS:Articles related to porous gradient hydroxyapatite/zirconia composite in bone tissue engineering were retrieved in CNKI and PubMed databases (1971-01/2014-12). The key words were“porous bioceramic, bone tissue engineering, bone morphogenetic protein-2, induced pluripotent stem cel s”in Chinese and English, respectively. A total of 54 articles based on inclusion criteria and exclusion criteria were obtained for the review. RESULTS AND CONCLUSION:Porous gradient hydroxyapatite/zirconia composite can provide a scaffold to induce natural y forming bone growing to fil the three-dimensional pores, thus realizing the perfect integration of tissue-engineered bone material and host-bone tissue. As zirconia functions as an enhancer of hydroxyapatite, high-quality artificial bone materials, which have elastic modulus, fracture toughness and structure similar to human bone, can be prepared by adjusting the proportion and porosity of materials. Additional y, the new hydroxyapatite/zirconia foamed ceramics as tissue-engineered bone carrying bone morphogenetic protein-2/chitosan gel sustained release system and bone marrow mesenchymal stem cel s derived from induced pluripotent stem cel s wil be expected to increase bone formation and bone fusion rates significantly in the future.

Objective To investigate the effect of hydroxyapatite/zirconia (HA/ZrO2) scaffold by three-dimensional printing compounded with vascular endothelial growth factor (VEGF) 165 calcium alginate microsphere slow-release system on repairing femoral shaft defects in dogs.Methods The HA/ZrO2 artificial prosthesis was prepared by three-dimensional printing,and the co-culture system of slow-release system of composite VEGF 165 calcium alginate microspheres was constructed.Sixteen beagle dogs were divided into four groups according to the extent of femoral shaft interception,with four dogs in each group.Group A:no biomaterials were implanted into the middle femur of dogs after 15 mm of femur interception as blank control group;Group B:HA/ZrO2 scaffolds composite with VEGF165 calcium alginate microspheres were implanted into the middle femur of dogs after 15 mm of femur interception;Group C:the same method as Group B was adopted after 25 mm of femur interception;Group D:the same method as Group B was adopted after 35 mm of femur interception.General examination and X-ray imaging observation were taken after operation.The ability of new HA/ZrO2 gradient biocomposites to repair bone defects was evaluated by micro CT scanning,biomechanical testing,ink staining and toluidine blue staining 12 weeks after operation.Results The drug loading capacity of calcium alginate microspheres reached (23.6 ± 2.9) ng/mg,and the entrapment efficiency reached (62.4 ± 3.6) ％,showing a slow rate of release.Gross examination showed surgical incision was healed in all four groups.Postoperative X-ray imaging of experimental animals showed that nonunion was formed in Group A over time;in Group B,the artificial prosthesis was gradually filled with new bone and the boundary was blurred;in Group C,the early reaction was slower than that in Group A,and the callus passed continuously 12 weeks after operation;in Group D,new bone formation was slow,only surrounding the broken end.At 12 weeks after operation,the neonatal bone mass was (238.6 ± 19.1)mm3 in Group B,(223.3 ± 13.4) mm3 in Group C,and (110.8 ± 6.5) mm3 in Group D.There were significant differences among the three groups (P ＜ 0.05),but no significant difference was found between Group B and Group C (P ＞ 0.05).The results limit compression test at 12 weeks after operation showed no significant differences among Groups B [(49.7 ± 2.3) MPa],C [(49.81 ± 2.4) MPa] and D [(46.9 ± 3.6) MPa](P ＞ 0.05).At 12 weeks after operation,the histological sections showed that the blood vessels in Groups B and C were thickened,with obvious branches,and the surrounding new bone increased.During the period,the blood vessels were filled with vascular network.There were no obvious differences in the number and shape of blood vessels between groups.However,Group B had more new bones and blood vessel networks.New bone and small vascular networks were seen in Group D.Conclusion The hydroxyapatite/zirconia scaffold by three-dimensional printing compounded with vascular endothelial growth factor 165 calcium alginate microsphere slow-release system can repair dogs' femoral bone defect within 35 mm.