BACKGROUND:Scholars have studied the three-dimensional finite element models of tibial plateau fractures with different fixation methods, but the research on three-dimensional finite element model of tibial plateau fracture fixation was not much. OBJECTIVE:To analyze the biomechanical characteristics of external fixator for tibial plateau fracture by using the three-dimensional finite element method. METHODS:The tibial plateau fracture models treated with locking plate fixation and external fixator were established. Three-dimensional finite element analysis was used to analyze the stress distribution and displacement of two kinds of models. RESULTS AND CONCLUSION:(1) The average displacement value and the maximum displacement value of tibial plateau fracture external fixator model group were smal er than that of tibial plateau fracture locking plate fixation model group, but no significant difference was found (P>0.05). (2) X axial displacement value and Y axial displacement value were smal er in the tibial plateau fracture external fixator model group than in the tibial plateau fracture locking plate fixation model group, but no significant difference was found (P>0.05). (3) The stress of tibial plateau fracture locking plate fixation model focused on the junction of the screw and bone tissue as wel as the junction of plates and screws. The maximum stress value of tibial plateau fracture locking plate fixation model (173 MPa) was greater than that of tibial plateau fracture external fixator model (86 MPa). The stress of tibial plateau fracture external fixator model was scattered. Obvious stress concentration did not occur. The stress at the junction of the clamp and the nail and the junction of the connecting rod and screw was higher than that at other regions, and was a weak link in the clinical mechanics. (4) Results showed that external fixation for tibial plateau fractures had better stability and fixing strength as compared with the internal fixation.

AlM:To investigate the effect of teaching mode of problem- based learning ( PBL ) in the teaching of medical students' clinical ophthalmology.
METHODS: Five classes ( total 148 students ) were randomly selected as experimental group, using PBL method, at the same time another 5 classes ( total 151 students) were also randomly selected as control group, using lecture-based learning ( LBL) mode in 2010 grade. The scores of the experimental group were compared with control at the end of term. ln addition, students and teachers were respectively interviewed using self -administered questionnaire to obtain their evaluation for PBL practice.
RESULTS:The mean scores of PBL group (78. 35±7. 63) were significantly higher than control group (71. 68±6. 37) (P<0. 001). Most of students thought that their ability of referring, synthesizing and analyzing information was enhanced by PBL, and their skills both in written and oral were also improved. PBL made it easier to understand the contexts of course. lt was the best way to improve the effect of teaching in ophthalmology based on the increase of quality in novitiate that gives more chance to students of contacting with practice, developing the ability of clinical thinking and verifying the theory in clinical novitiate. Lots of teachers considered that the classroom atmosphere was more active, students were becoming more and more proactive on their classes and the relationship between students and teachers were more harmonious when PBL was used.
CONCLUSlON:Using PBL teaching mode can highly improve the teaching effectiveness of clinical epidemiology, which is worth popularizing.

Objective To study the effects of injecting recombinant human granulocyte colony stimulating factor (rhG-CSF) and basic fibroblast growth factor (bFGF) alone or combined on actue myocardial infarction(AMI).Methods AMI models were induced by ligation of the left anterior descending artery.The survived rats were divided into four groups randomly:AMI group (MI),rhG-CSF group (G),bFGF group (B),combined group (GB).Respectively,saline,rhG-CSF,bFGF,and rhG-CSF plus bFGF were injected intraperitoneally 24 h after AMI.Also,sham-operated group (S) was established with only chest-opeaned,without ligation,and no drugs intervention. The white blood cells (WBC) and mononuclear cells (MNC) proportion in peripheral blood were counted 1 week before and 1 week after the intervention,and the number of CD34+ cells was observed with immunohistochemical staining 1 week after AMI in order to compare the situation of mobilization in peripheral blood;the capillary density was evaluated by HE staining both 1 and 4 weeks after AMI;their cardiac fuction was determined in vivo,the infarction size in each group was calculated,and the pathological changes in rat myocardium were observed by HE staining 4 weeks after AMI.Results Compared with MI group,the number of WBC and MNC% in peripheral blood 1 week after AMI in G,B and GB groups were higher(P

BACKGROUND:Epidural scar after laminectomy is one important reason for the secondary spinal stenosis, and local application ofSanqi sodium hyaluronate gel can prevent epidural scar adhesion after laminectomy. OBJECTIVE: To study the effects ofSanqisodium hyaluronate gel on α-smooth muscle actin expression in the process of rabbit's epidural scar formation. METHODS: In this study, there were ninety-six rabbits which were randomized into four groups and given 0.5 mL normal saline, 0.5 mLSanqi concentrated solution, 0.5 mL sodium hyaluronate and 0.5 mLSanqisodium hyaluronate gel around the dura. At 1, 2, 4, 8 weeks after treatment, immunohistochemistry staining was employed for analysis of α-smooth muscle actin expression. RESULTS AND CONCLUSION:At the end of weeks 1 and 2, the expression of α-smooth muscle actin antibody in the normal saline group was significantly higher than that in the other three groups (P < 0.01 orP < 0.05), but there were no significant differences among the Sanqi, sodium hyaluronate andSanqisodium hyaluronate gel groups (P> 0.05). At weeks 4 and 8, the expression of α-smooth muscle actin antibody in theSanqi sodium hyaluronate gel group was significantly lower than that in the other three groups (P < 0.01 orP < 0.05), and there was no significant difference among the latter three groups (P > 0.05). These findings suggest thatSanqi sodium hyaluronate gel can inhibit the expression of α-smooth muscle actin, and thus ease scar contracture.

Objective To assess the reliability and validity of the Tree-Drawing Test in medical college students.Methods The study randomly selected 312 aged 19 to 23-year-old medical students to take part in TreeDrawing Test.In addition,a total of 275 college students were selected to receive re-test,30 days late and Pearson correlation coefficient of two tests were calculated.The three raters were invited to assess 30 trees painting score,analyzing the Kendall coefficient of concordance between the scores to verify raters' reliability; parts of students also participated in the 16PF test,SAS,SDS test,analyzing the correlation coefficient between the various test results,in order to assess the effectiveness of the Tree-Drawing Test.Results The re-test reliability in different time was 0.570-0.733 and 0.341-0.713 (P＜0.05),the raters' reliability was 0.491 ～ 0.626(P＜0.05),there are some correlations between Tree-Drawing Test and 16PF,SAS,SDS.Conclusion The Tree-Drawing Test has good reliability and validity; it can be applied to the detection of college students' psychological assessment and psychological problems.

Objective To develop and validate a novel method of atlantoaxial pedicle screw placement by using three-dimensional reconstruction software Mimics and rapid prototyping. Methods Three-dimensional reconstruction of 20 CT scanned cadaver atlantoaxial specimens was performed by using Mimics and the parameters of the pedicles were measured. Then, physical model of the pedicles was manufactured by using rapid prototyping and the parameters of the cadaver pedicles were measured. The parameters of the atlantoaxial pedicle were directly measured. All the data were analyzed statistically to verify the accuracy of the reconstructed images and physical models. The optimal pedicle channel was found to design individual fixation parameters, based on which fixation of cadaver specimens was performed under direct guidance of physical model. The accuracy of fixation was assessed by CT scanning. Results There was no statistical difference in parameters of the reconstructed images, the physical model and the specimens, which could reflect accurate atlantoaxial anatomy. Postoperative CT scanning showed that the pedicle screws were inserted successfully in 16 sides of four specimens, except for one screw wearing medial bone cortex of the atlas artery. Conclusions Three-dimensional reconstruction of the atlantoaxial specimens by using Mimics and physical models made by rapid prototyping technology facilitate atlantoaxial pedicle screw placement and can enhance the accuracy of screw fixation.

Objective To investigate the indication, feasibility and technique of minimally invasive nuss procedure with thoracoscope by using double braces in the treatment of wide-scope pectus excavatum repairing in adolescence. Methods 31 patients including 24 boys and 7 girls, suffered from pectus excavtum were corrected by nuss procedure under thoracoscope.The average age was (15.32 ± 3.89)years (ranged, 14 years and 18 years). All cases were moderate to severe degree according to Hallar index with depression scope of 4 ribs or more. A couple of braces of two-point or multipoint fixation for thoracoscopic-assisted nuss procedure were used. Results The procedure was successfully completed under thoracoscopy in all patients. Double braces were utilized in 27 cases, double are bars were required in 4 cases, and multipoint fixations were in 6 patients. The postoperative hospital stay was 5-11 days [average, ( 7.48 ± 1.95 ) days]. The duration of following up was one month to three years. The perioperative complications included intraoperative hemorrhage in 2 patients, bar invertion with displacement in 1, and interrupted pain for two months in 1. All patients recovered after expectant treatment. Conclusion Nuss procedure with double braces for the correction of a large area of asymmetric pectus excavatum under thoracoscopy is safe and effective technique for adolescence.

Objective To analysis the biomechanical properties of four-rod fixation system for lumbosacral reconstruction after sacrectomy.Methods Two finite element models of lumbosacral area were established according to pelvic CT images:a subtotal saerectomy model and a total sacrectomy model.The range of motion of L3 vertebral body and max yon Mise stress of instruments of a novel four-rod fixation system were evaluated and compared with those of modified Galveston technique(MGT)under conditions of veaebral body and max von Mise stress of instruments of the four-rod fixation system were evaluated and compared with those of MGT under vertical compression.Results In subtotal sacreetomy model,the range of motion of L3 vertebral body in the four-rod fixation system were 4.2 mm,0.49°,0.49°,0.24°and 0.26°compared to 5.5 mm.0.74°,0.74°,0.27°and 0.30°in the MGT.The max von Mise stress of instruments in the four-rod fixation system were 810.7,148.0,148.0,134.6 and 14.4 MPa,compared to 655.0,109.9,109.9,119.1 and 11.4 MPa in the MGT.In total sacrectomy model under veaical compression,the range of motion of L3 vertebral body and max van Mise stress of instruments in the four-rod fixation system were 10.9mm and 2172 MPa compared to 49.1 mm and 4325 MPa in the MGT.Conclnsion Comparing with the MGT.the four-rod fixation system was stiffer and showed a significant increase in the stability of lumbosacral area.When total sacrectomy without bone graft were performed,the max stress of the four-rod fixation system was much lower than that of the MGT,which means smaller risk of instrument failure.When subtotal sacrectomy or bone graft were performed,despite better stability,the higher stress shielding-effect of the four-rod fixation svstem might be unfavorable for bone fusion,which still need to be evaluated by clinical trials.

Objective To explore the clinical features of sentinel polyps (rectal polyps with proximal colon carcinoma) and its correlation with proximal colon carcinoma.Methods From January 2003 to December 2013,the clinical features of 963 hospitalized patients with rectal polyps were retrospectively analyzed.According to whether the patient with colon carcinoma,the clinical data of rectal polyps patients were divided into pure polyps group (n=855) and sentinel polyps group (n 108).The characteristics under endoscopy,clinical pathological features,treatment and prognosis of the two groups were observed.Chi square test was performed for differences comparison between groups.Results The length of stay in hospital of 963 patients was from four to 33 days,the average age was (49.7 ± 9.4) years,and the majority of the patients were male (n=610,63.3％).A total of 785 patients (81.5％) had non-specific abdominal symptoms,such as frequency or habit change of defecation,hematochezia,abdominal pain,abdominal distension.The relatives within three generation of 78 patients (8.1 ％) were diagnosed with tumor and some relatives of the patients diagnosed with familial adenomatous polyposis (2.2％,21/963).The positive rate of tumor marker of sentinel polyps group was higher (69.4％,75/ 108) than that of pure polyps group (6.8％,58/855; x2 =316.285,P＜0.01).The proximal colon carcinoma of patients with sentinel polyps appeared as neoplasma with circumferential growth,there was no specific appearance between distal rectal polyps and proximal colon carcinoma.When compared with pure polyps group,most polyps of sentinel polyps group were in maximum diameter over 1 cm (61.1％ (66/108) vs 46.9％ (401/855)),multi polyps (n＞5,38.9％ (42/108) vs 11.8％ (101/855)) and adenomatous polyp (83.3％ (90/108) vs 35.6％(304/855),x2=7.752,55.595 and 90.544,all P＜ 0.01).Majority of the proximal colon carcinoma with rectal polyps was papillary adenocarcinoma and tubular adenocarcinoma which was account for 75.9％ (82/108).Some were mucinous carcinoma and signet ring cell carcinoma.Most of the proximal colon carcinoma with rectal polys did not penetrate the serosa layer (Duk A-+Duk B,59.3％,64/108) and with little distant metastasis (Duke D,17.6％,19/ 108).Ninty-five point six percent (817/855) of patients with pure polyps underwent endoscopic treatment and all of them were cured and discharged.Forty-one point seven percent (45/108) of patients of sentinel polyps group accepted the radical operation and 19.4％ (21/108) received endoscopic submucosal dissection.Conclusions If multiple,maximum diameter over 1 cm and adenomatous rectal polyps were detected under colon endoscope,the possibility of carcinogenesis of the polyps or the proximal colon should be awared.If the endoscope is difficult to go further or the patient can not tolerate the whole colon examination,the patient should be followed up in short-term and complete the whole colon examination.

Objective To find the way of inducing the bone marrow mesynchymal stem cells(MSCs)into cardiac cells with pacemaking function in vitro.Methods Dissociate the rat MSCs and induce them with 5AZA,bFGF+EGF,HGF,SCF and lysate of the sinoatrial cells respectively.The morphological changes were observed,and the expressing of protein cTnT,connexin 43 and HCN2/4 were analyse by immunohistologic and flowcytometry techniques.The pacmaking current If were evaluted by patch clamp techniques.Results All the methods can induce the bone marrow MSCs to differentiate into cardiac cells,which expressing cardiac cell specific protein and HCN2.Cells induced by 5AZA,bFGF+EGF and SAN CMs show higher rate of HCN2 expressing(22.9%,22.3%,11%).The cells of these groups have the pacmaking current If.Conclusion Lysate of the sinoatrial cells are ideal methods of inducing the bone marrow MSCs to differentiate into cardiac cells with pacemaking function in vitro.HCN is a promising marker protein to select pacmaking cells out of the differentiated cells.