This article reviews the training model of orthopedic residents in the world's top orthopedic hospitals, such as Hospital for Special Surgery Affiliated to Cornell University and The Affiliated Hospital of Harvard University Medical School, and it is found that there are differences between China and the US in the training of orthopedic residents in the aspects of the admittance system of physicians, the setting of training contents , and the training model of orthopedic residents . The training of orthopedic residents in the US adheres to the concept of elite education and pays attention to the construction of tutors and learning atmosphere. The enlightenment to the training of orthopedic residents in China includes further clarification of the training objectives of orthopedic residents , improvement of the stage-based training system , integration of excellent medical teaching resources , and improvement of teaching methods and assessment systems.

Objective To investigate the mechanism of efflux pump AcrAB-TolC involved in the cross-resistance between quaternary ammonium compounds ( QAC) and fluoroquinolones ( FQ) in Escherich-ia coli. Methods Seventy-eight Escherichia coli strains were isolated from clinical samples and then tested for the sensitivity to benzalkonium bromide by ager dilution method. Six strains were randomly selected and induced with benzalkonium bromide. Changes in the sensitivity of these strains to benzalkonium bromide and ciprofloxacin were analyzed after induction. Expression of the efflux pump genes acrA, acrB and tolC at mRNA level in the induced strains and their parent strains were detected by quantitative real-time PCR. Re-sults Among the 78 strains, the minimum inhibitory concentrations ( MIC) ranged from 8 μg/ml to 64μg/ml and 47. 4％ of strains have higher MIC than the standard strain. Compared with the parent strains, the induced strains showed higher expression of acrA and tolC genes, and the differences between the two groups were statistically significant. The MIC values of ciprofloxacin to the six induced strains were 4-8 times higher than those to their parent strains. Conclusions It was speculated that the increased expression of acrA and tolC genes at transcription level in the induced strains were related to the cross-resistance between quaternary ammonium compounds and fluoroquinolone antibiotics.

Objective:To compare the clinical effect of percutaneous sacroiliac screw fixation assisted by O-arm navigation or C-arm X-ray fluoroscopy in the treatment of sacroiliac joint complex injury.Methods:A retrospective case-control study was conducted on 32 patients with sacroiliac joint complex injury admitted to Second Affiliated Hospital of Army Medical University from July 2016 to January 2019.There were 21 males and 11 females, aged from 20 to 59 years (mean, 41.3 years). According to Tile classification, there were 7 patients with type B1 fracturs, 13 with type B2, 5 with type B3, 5 with type C1, and 2 with type C1. Group A ( n=17) had percutaneous sacroiliac screw fixation assisted by O-arm navigation, while Group B ( n=15) had percutaneous sacroiliac screw fixation assisted by C-arm X-ray fluoroscopy. Time of single screw placement, time of intraoperative fluoroscopy, intraoperative bleeding volume and bone union time were measured. Reduction quality was evaluated by Matta standard score. Majeed function score was assessed 6 months at the latest follow-up. Complications were also observed. Results:All patients were followed up for 6-37 months (mean, 18.6 months). The time of sacroiliac joint screw placement [(27.3±5.1)minutes] and time of intraoperative fluoroscopy [(43.3±3.2)s] in Group A were significantly less than those in Group B [(52.3±5.9)minutes, (64.6±5.4)s] ( P<0.05). There were no significant differences between Group A and Group B in intraoperative bleeding [(17.8±2.6)ml vs. (20.7±3.1)ml] and bone union time [(13.4±1.4)weeks vs. (14.1±1.9)weeks] ( P>0.05). According to the reduction quality evaluated by Matta standard score, the good and excellent rate was 88% (15/17) in Group A and 87% (13/15) in Group B ( P>0.05). The good and excellent rate of the Majeed function score was 94% (16/17) in Group A and 87% (13/15) in Group B at the latest follow-up ( P>0.05). One patient in Group B demonstrated one screw slightly penetrating the anterior cortex of vertebral body. No neurovascular injury, wound infection, or screw loosening occurred. Conclusion:For sacroiliac joint complex injury, percutaneous sacroiliac screw fixation assisted by O-arm navigation has advantages in the duration of screw placement and intraoperative fluoroscopy over percutaneous sacroiliac screw fixation assisted by C-arm X-ray fluoroscopy.

Objective: To evaluate the efficacy of dynamic locking screw combined with plate internal fixation for tibial fractures. Methods: A retrospective case-control study was conducted to analyze the clinical data of 36 patients with tibial fractures (AO 4A-C) admitted to the Second Affiliated Hospital of Army Medical University from March 2017 to March 2018. There were 27 males and nine females, aged 26-71 years [(51.6±14.3)years]. A total of 18 patients were treated with dynamic locking screw combined with locking plate internal fixation (Group A), and another 18 patients received common locking screw combined with locking plate internal fixation (Group B). The operation time, intraoperative bleeding, hospital stay, visual analogue score (VAS), callus growth and fracture healing rate at 4, 8, 12 and 24 weeks after operation were compared between the two groups. At the same time, the complications of internal fixation were evaluated, including screw loosening, screw fracture and steel plate fracture. Results: All the patients were followed up for 8-18 months [(12.2±2.7)months]. There was no significant difference in operation time, intraoperative bleeding, postoperative hospital stay and postoperative VAS between the two groups (P>0.05). At 8 and 12 weeks after operation, the callus growth rate of Group A was 61% and 83% respectively, significantly higher than those of Group B (28% and 50%) (P<0.05). At 8, 12, and 24 weeks after operation, the fracture healing rate of Group A was 17%, 50% and 100% respectively, and those of Group B was 6%, 28% and 89%, showing no significant difference between the two groups (P>0.05). No complications or failure of internal fixation were found during the follow-up. Conclusion For tibial fractures, the locking plate internal fixation can achieve satisfactory clinical outcome, but the dynamic locking screw system can promote the growth of callus at early stage.