BACKGROUND:From the point of view of human anatomy, the load of the spine is more. When the body moves, the range of activities, and activity are relatively large. After screws were implanted in the spine, if biomechanical properties and stability are not up to the standard, it easily leads to lack of grip force of screw and screw loosening so as to increase the incidence of complications after treatment.
OBJECTIVE:To compare biomechanical properties and stability of the spine after insertion of pedicle screw and cervical vertebral screw into the spine.
METHODS:100 vertebrae under human cervical spine specimens were analyzed and randomly divided into cervical vertebral screw fixation group and pedicle screw fixation group. Cervical vertebral screws and pedicle screws were implanted in lower cervical spine specimens. Electro Force 3510 material testing machine was used to test axial pul-out force, axial pul-out strength after the fatigue loading, and fixed stability. The biomechanical properties and stability were compared after two kinds of screws were implanted in the spine.
RESULTS AND CONCLUSION:(1) Instantaneous pul out force and immediate pul out stiffness were significantly higher in the pedicle screw fixation group than in the cervical vertebral screw fixation group (P<0.05). (2) Fatigue pul-out strength and fatigue pul-out stiffness did not have significant differences in both groups, but statistical analysis showed significant differences (P<0.05). Fatigue pul-out strength and fatigue pul-out stiffness were significantly higher in the pedicle screw fixation group than in the cervical vertebral screw fixation group. (3) These results suggested that pedicle screw fixation after implantation in the spine provides sufficient fixation stability, has better fatigue resistance, elevates instantaneous pul-out force and fatigue pul-out strength, and presents strong stability.

BACKGROUND:Currently, surgical implant fixation is mainly applied for spinal tuberculosis. How to choose implant materials, however, is stil under discussion.OBJECTIVE:To compare the biocompatibility and mechanical properties of titanium al oy and stainless steel for rabbit spinal tuberculosis. METHODS:Thirty rabbits were chosen to prepare spinal tuberculosis models. Then, the rabbits were equivalently randomized into two groups, which underwent implant fixation with stainless steel or titanium al oy, respectively. At 30 days after implantation, biocompatibility and biomechanical properties of the two materials in the repaired region of spine were observed and detected, respectively. RESULTS AND CONCLUSION:In view of the biocompatibility, infection and immunological rejection could not been found in the titanium al oy group;in contrast, infection appeared in three rabbits of the stainless steel group. Flexion, extension and lateral bending displacements under the spinal loading in the titanium al oy group were significantly less than those in the stainless steel group (P<0.05);axial pul-out strength in the titanium al oy group was significantly higher than that in the stainless steel group (P<0.05);flexion, extension, lateral bending and axial compression in the titanium al oy group were significantly greater than those in the stainless steel group (P<0.05). In conclusion, titanium al oy material has good biocompatibility that can be used to restore and maintain the spinal stability.

BACKGROUND: In recent years, ultrasound microbubble gene transfer system has been applied for gene transfection in many parts of the body, but it has been seldom reported to be used for gene transfection in bone parts. OBJECTIVE: To investigate the efficiency and feasibility of ultrasound-targeted microbubble destruction applied for transfection of enhanced green fluorescent protein plasmid into the femoral head of rabbits.METHODS: Japanese big-ear rabbits were randomly divided into five groups: bare transfection, pre-irradiation + bare transfection, ultrasound transfection, pre-irradiation+ultrasound transfection, and repeatable transfection. In the first two groups, ultrasound-targeted gene transfection and irradiation was not used, but in the latter three groups, ultrasound-targeted microbubble destruction was used to transfect enhanced green fluorescent protein (EGFP) plasmid into the femoral head of rabbits. At 1 week after transfection, EGFP expression in femoral head was observed under the fluorescence microscope. RESULTS AND CONCLUSION: EGFP expression appeared in the ultrasound transfection, pre-irradiation + ultrasound transfection and repeatable transfection. The transfection efficiency of EGFP plasmid was significantly higher in the repeatable transfection group than in the other groups (P < 0.01). Obvious injury loci were not observed in the soft tissue and bone tissue slices of ultrasonic irradiation parts in the ultrasound transfection, pre-irradiation + ultrasound transfection and repeatable transfection groups. These results confirm that ultrasound-targeted microbubble destruction is a safe and effective method to transfect EGFP plasmid into the femoral head of rabbits.

BACKGROUND:Adjustable piezoelectric effect can promote tissue regeneration and repair.Piezoelectric materials are widely used in weight-bearing tissue engineering. OBJECTIVE:To prepare a piezoelectric film material that can promote bone regeneration,and to explore its structural characterization,electrical output performance,biocompatibility,and effect of electrical output on osteogenic differentiation of rabbit bone marrow mesenchymal stem cells. METHODS:Using poly-3-hydroxybutyrateco/4-hydroxybutyrate(P34HB)as raw material,barium calcium stannate titanate powder(Ba0.94Ca0.06Sn0.08Ti0.92O3,BCST)was added according to mass ratios of 0%,5%,10%,15%,and 20%.Dichloromethane was added to solve P34HB,and the thickness of 150-200 μm BCST/P34HB piezoelectric film was prepared by vacuum drying method.After polarization in the oil bath,the surface morphology,crystal phase composition,piezoelectric coefficient and open circuit voltage were tested.The effect of BCST/P34HB electrical output at 110 Hz and 0.25 N force on the proliferation and osteogenic differentiation of rabbit bone marrow mesenchymal stem cells was tested. RESULTS AND CONCLUSION:(1)Scanning electron microscopy,X-ray diffraction,water contact angle,piezoelectric coefficient and electrical output performance tests showed that when the mass ratio of BCST increased to 20%,the BCST/P34HB piezoelectric film had good piezoelectric properties(d33=5.9 pC/N)and electrical output performance(180 mV),which was closer to the suitable range of 500 mV for electrical stimulation.(2)Live and dead staining showed that on the first day of co-culture,15%group and 20%group showed less red fluorescence.On the 5th day of culture,the number of green fluorescence in each group was significantly higher than that on the first day,and the red fluorescence was not observed in the 10%,15%and 20%groups,and only a small amount of red fluorescence was observed in the 0%and 5%groups.(3)On the 1st,3rd and 5th days of co-culture with rabbit bone marrow mesenchymal stem cells,Almar blue staining exhibited that the number of cells in each group showed an increasing trend with the increase of time.On the 5th day of culture,the number of cells in the 20%group was significantly more than that in the 0%group(P<0.05).(4)On day 10 of osteogenic induction,alkaline phosphatase staining results showed that the positive rate of the 20%group was significantly higher than that of the 0%group(P=0.000 1).On day 21,alizarin red staining and quantitative analysis of calcium nodules showed a similar trend to alkaline phosphatase staining.Compared with the 0%group,the 15%group and 20%group showed significant differences(P<0.01,P<0.000 1).(5)The results showed that 20%BCST/P34HB films had good piezoelectric properties,electrical output properties,biocompatibility and the ability of promoting osteogenic differentiation of bone marrow mesenchymal stem cells.