BACKGROUND:Currently,pedicle screw fixation technology is recognized as the gold standard for lumbar posterior fusion surgery.However,this technique is associated with several complications such as suboptimal screw placement,loosening,and fracture.Addressing these issues,it requires a thorough investigation into the mechanical properties of screw reinsertion to optimize surgical procedures and enhance success rates and safety.OBJECTIVE:By combining finite element analysis with biomechanical experiments,this study aims to compare and analyze the mechanical performance of traditional trajectory pedicle screws during multiple extraction processes.The goal is to reveal patterns in screw extraction strength over repeated withdrawals,providing scientific insights into the safety and effectiveness of pedicle screw reinsertion for clinicians.METHODS:Based on CT scan data,a three-dimensional reconstruction of the L4 vertebra model was performed.Three-dimensional printing technology was used to create biological experimental samples.A pull-out experiment was conducted according to a screw placement plan.Utilizing CT data and standard pedicle screw parameters,a finite element model of the L4 vertebra and a pedicle screw model(diameter 6.0 mm,length 45 mm)were established.The model was divided into five operating conditions based on screw placement angle and cycles.A finite element model was developed to simulate axial pull-out testing,analyzing stress distribution in the vertebral body and maximum axial pull-out strength of the screw.Mechanics experimental results of three-dimensional printing were compared and analyzed against simulation outcomes.RESULTS AND CONCLUSION:(1)A dedicated experimental setup for pedicle screw extraction from single vertebrae was designed and constructed.(2)In the three-dimensional printing experiment,our groups of models were compared between correctly placed screws and once improperly placed screws.The correctly placed screws group exhibited a maximum pull-out force of(1 422.63±23.80)N.Furthermore,with increasing deviation angles in screw placement,the maximum pull-out forces of each group gradually decreased.(3)Comparing the condition of a single improper nail placement with repositioning the nail correctly,when the offset angle of the improper placement exceeded that of Model 3,correctly repositioning the nail helps to increase the screw's pull-out resistance.(4)Comparing the scenario of two consecutive improper nail placements with repositioning correctly after two improper placements,correctly repositioning the nail reduced the screw's pull-out resistance.Without replacing the screw,it was not advisable to attempt a third nail placement.(5)Experimental pull-out strength of three-dimensional printing correlates significantly with finite element simulation results,with a correlation coefficient of 0.98.There is no significant difference in the outcomes between the two methods(P＞0.05).

Objective·To investigate the reparative effects of photo-crosslinked gelatin methylacrylated(GelMA)hydrogel scaffolds loaded with tauroursodeoxycholic acid(TUDCA)on cartilage defects in rabbit knee joints.Methods·Photo-crosslinked GelMA hydrogel scaffolds loaded with TUDCA were prepared by the ultraviolet light irradiation method.The physicochemical properties of GelMA hydrogel scaffolds were characterized,and the cumulative release rate of TUDCA was determined.A rabbit knee cartilage defect model was established,and 18 rabbits were randomly assigned into three groups,with six rabbits in each group:the control group(no treatment was applied to the cartilage defect),the GelMA group(the cartilage defect was filled with GelMA hydrogel scaffold),and the GelMA+TUDCA group(the cartilage defect was filled with the GelMA hydrogel scaffold loaded with TUDCA).At 12 weeks postoperatively,the concentrations of two inflammatory factors in synovial fluid,tumor necrosis factor-α(TNF-α)and interleukin-1β(IL-1β),were detected by enzyme-linked immunosorbent assay(ELISA).After euthanasia,knee cartilage samples were harvested for gross observation,safranin O-fast green staining,and toluidine blue staining.The repair of the cartilage defects was evaluated according to the International Cartilage Repair Society(ICRS)and Modified O'Driscoll Score(MODS)systems.Immunohistochemical staining was performed to detect type Ⅱ collagen(COL-Ⅱ)protein in the cartilage tissue,and Western blotting was used to assess the protein levels of aggrecan(ACAN)and COL-Ⅱ.Results·GelMA hydrogel scaffolds exhibited a more compact microstructure after ultraviolet light irradiation,along with an suitable mass swelling ratio and compressive modulus.The TUDCA-loaded photo-crosslinked GelMA hydrogel scaffolds demonstrated effective and sustained TUDCA release,achieving a cumulative release rate of 90.2%±2.5%within 28 d.ELISA results showed that compared to the control and GelMA groups,the concentrations of TNF-α and IL-1β in the synovial fluid of the GelMA+TUDCA group were significantly reduced(P<0.001).In the GelMA+TUDCA group,the cartilage defects were nearly fully repaired,with a smooth surface and good integration with the surrounding tissue.The number of newly formed chondrocytes increased,displaying orderly alignment,and the neocartilage exhibited excellent formation.Both ICRS and MODS scores were significantly higher in the GelMA+TUDCA group than those in the control and GelMA groups(P<0.001).Additionally,the expression levels of ACAN and COL-Ⅱ proteins were significantly elevated in the GelMA+TUDCA group compared to the control and GelMA groups(P<0.001).Conclusion·Photo-crosslinked GelMA hydrogel scaffolds loaded with TUDCA can effectively promote the repair of cartilage defects in rabbit knee joints.

Objective·To investigate the reparative effects of photo-crosslinked gelatin methylacrylated(GelMA)hydrogel scaffolds loaded with tauroursodeoxycholic acid(TUDCA)on cartilage defects in rabbit knee joints.Methods·Photo-crosslinked GelMA hydrogel scaffolds loaded with TUDCA were prepared by the ultraviolet light irradiation method.The physicochemical properties of GelMA hydrogel scaffolds were characterized,and the cumulative release rate of TUDCA was determined.A rabbit knee cartilage defect model was established,and 18 rabbits were randomly assigned into three groups,with six rabbits in each group:the control group(no treatment was applied to the cartilage defect),the GelMA group(the cartilage defect was filled with GelMA hydrogel scaffold),and the GelMA+TUDCA group(the cartilage defect was filled with the GelMA hydrogel scaffold loaded with TUDCA).At 12 weeks postoperatively,the concentrations of two inflammatory factors in synovial fluid,tumor necrosis factor-α(TNF-α)and interleukin-1β(IL-1β),were detected by enzyme-linked immunosorbent assay(ELISA).After euthanasia,knee cartilage samples were harvested for gross observation,safranin O-fast green staining,and toluidine blue staining.The repair of the cartilage defects was evaluated according to the International Cartilage Repair Society(ICRS)and Modified O'Driscoll Score(MODS)systems.Immunohistochemical staining was performed to detect type Ⅱ collagen(COL-Ⅱ)protein in the cartilage tissue,and Western blotting was used to assess the protein levels of aggrecan(ACAN)and COL-Ⅱ.Results·GelMA hydrogel scaffolds exhibited a more compact microstructure after ultraviolet light irradiation,along with an suitable mass swelling ratio and compressive modulus.The TUDCA-loaded photo-crosslinked GelMA hydrogel scaffolds demonstrated effective and sustained TUDCA release,achieving a cumulative release rate of 90.2%±2.5%within 28 d.ELISA results showed that compared to the control and GelMA groups,the concentrations of TNF-α and IL-1β in the synovial fluid of the GelMA+TUDCA group were significantly reduced(P<0.001).In the GelMA+TUDCA group,the cartilage defects were nearly fully repaired,with a smooth surface and good integration with the surrounding tissue.The number of newly formed chondrocytes increased,displaying orderly alignment,and the neocartilage exhibited excellent formation.Both ICRS and MODS scores were significantly higher in the GelMA+TUDCA group than those in the control and GelMA groups(P<0.001).Additionally,the expression levels of ACAN and COL-Ⅱ proteins were significantly elevated in the GelMA+TUDCA group compared to the control and GelMA groups(P<0.001).Conclusion·Photo-crosslinked GelMA hydrogel scaffolds loaded with TUDCA can effectively promote the repair of cartilage defects in rabbit knee joints.

BACKGROUND:Currently,pedicle screw fixation technology is recognized as the gold standard for lumbar posterior fusion surgery.However,this technique is associated with several complications such as suboptimal screw placement,loosening,and fracture.Addressing these issues,it requires a thorough investigation into the mechanical properties of screw reinsertion to optimize surgical procedures and enhance success rates and safety.OBJECTIVE:By combining finite element analysis with biomechanical experiments,this study aims to compare and analyze the mechanical performance of traditional trajectory pedicle screws during multiple extraction processes.The goal is to reveal patterns in screw extraction strength over repeated withdrawals,providing scientific insights into the safety and effectiveness of pedicle screw reinsertion for clinicians.METHODS:Based on CT scan data,a three-dimensional reconstruction of the L4 vertebra model was performed.Three-dimensional printing technology was used to create biological experimental samples.A pull-out experiment was conducted according to a screw placement plan.Utilizing CT data and standard pedicle screw parameters,a finite element model of the L4 vertebra and a pedicle screw model(diameter 6.0 mm,length 45 mm)were established.The model was divided into five operating conditions based on screw placement angle and cycles.A finite element model was developed to simulate axial pull-out testing,analyzing stress distribution in the vertebral body and maximum axial pull-out strength of the screw.Mechanics experimental results of three-dimensional printing were compared and analyzed against simulation outcomes.RESULTS AND CONCLUSION:(1)A dedicated experimental setup for pedicle screw extraction from single vertebrae was designed and constructed.(2)In the three-dimensional printing experiment,our groups of models were compared between correctly placed screws and once improperly placed screws.The correctly placed screws group exhibited a maximum pull-out force of(1 422.63±23.80)N.Furthermore,with increasing deviation angles in screw placement,the maximum pull-out forces of each group gradually decreased.(3)Comparing the condition of a single improper nail placement with repositioning the nail correctly,when the offset angle of the improper placement exceeded that of Model 3,correctly repositioning the nail helps to increase the screw's pull-out resistance.(4)Comparing the scenario of two consecutive improper nail placements with repositioning correctly after two improper placements,correctly repositioning the nail reduced the screw's pull-out resistance.Without replacing the screw,it was not advisable to attempt a third nail placement.(5)Experimental pull-out strength of three-dimensional printing correlates significantly with finite element simulation results,with a correlation coefficient of 0.98.There is no significant difference in the outcomes between the two methods(P＞0.05).

Objective To investigate the hydrophilic chemical constituents from Thesium Chinensis Turcz.Methods The water extract of Thesium Chinensis Turcz.was adsorbed onto AB-8 resin column and eluted with 50% ethanol to give the hydrophilic portion TT50.TT50 was further separated and purified by repeated column chromatography on silica gel,Sephadex LH-20.The structures of these purified compounds were identified by NMR spectral analysis and comparison with the reported data.Results Six compounds were isolated and identified as kaempferol(1),kaempferol-3-O-glucoside(2),kaepmferol-3,7-di-O-β-D-glucopyranoside(3),kaempferol-3-O-L-rhamnopyranosyl(1 → 2)-β-D-glucopyranoside(4),kaemperol-3-O-α-L-rham-nopyranosyl(1→2)-[6-O-acetyl]-β-D-glucopyranoside(5),rutinoside(6).Conclusion The main constituents of TT50 were kaempferol glycosides.Compounds 4 and 5 were isolated from this plant for the first time.

Objective To evaluate the effectiveness and safety of recombinant human endostatin combined with concurrent chemoradiotherapy versus concurrent chemoradiotherapy for advanced non small cell lung cancer ( NSCLC) . Methods Electronic databases including the Cochrane library, PubMed, the Chinese biomedical literature database, China national knowledge internet(,EMbase,VIP and Wanfang database system were searched,until August,2013. The inclusion criteria was efficacy and safety studies of randomized controlled clinical studies in which recombinant human endostatin combined with concurrent chemoradiotherapy was compared with concurrent chemoradiotherapy alone for patients with advanced NSCLC. Cochrane handbook 5. 1. 0 was applied in evaluating the quality of included trials and RevMan 5. 1. 0 software was used for data analysis.Results Five studies including 217 cases of advanced NSCLC were included. The results of the meta-analysis exhibited that compared with concurrent chemoradiotherapy alone, recombinant human endostatin combined with concurrent chemoradiotherapy could increase effective rate [OR=2. 62,95%CI(1. 41,4. 86),P=0. 002]. But there were no significant differences in clinical benefit rate [OR=2. 08,95%CI(0. 92,4. 73),P=0. 08],one year survival rate [OR=1. 18,95%CI(0. 53,2. 66),P=0. 68], improvement in quality of life [OR=1. 57,95%CI(0. 40,6. 07),P=0. 52],rate of leucopenia [OR=1. 25,95%CI(0. 72,2. 17), P=0.43],radioactive esophagitis [OR=1. 16,95%CI(0. 42,3. 21),P=0. 77] and radiation pneumonitis [OR=2. 47,95%CI (0. 34,17. 68),P=0. 37]. Conclusion Compared with concurrent chemoradiotherapy alone,recombinant human endostatin combined with concurrent chemoradiotherapy may be more effective for advanced NSCLC,whereas improvement of life quality and toxicities are similar. For the quality restriction and possible publication bias of the included studies,more high quality randomized controlled trials are required to further verify this conclusion.