BACKGROUND:Femoral neck fracture is mainly fixed by three inverted triangle cannulated screws. Scholars have proposed to add a cannulated screw to enhance the fixation strength of femoral neck fracture of Pauwels III type based on three cannulated screw fixation, but the stability is not verified. OBJECTIVE:To analyze the biomechanical stability and stress of the three and four cannulated screws for the treatment of the Pauwels III femoral neck fractures. METHODS:The CT imaging results of the fourth generation of artificial bone sawbones were imported into the Mimics software wherein a three-dimensional finite element model of the proximal femur was prepared and introduced in the 3-matic software. Models of middlesegment of femoral neck with Pauwels III fractures were established. Cannulated screw models were established with UG 8.0 software and introduced in the fractures models. Finally, finite element models of Pauwels III femoral neck fractures fixed with three and four screws were established. In the same condition, an axial load of 411 N was applied on the femoral head with Abaqus software. The displacement of two markers of the broken ends and internal fixation system Von Mises stress distribution were compared between the two models. RESULTS AND CONCLUSION:(1) The displacement was 0.42 mm in three screws model, and 0.17 mm in the four screws model. (2) Von Mises stress peak was 547 MPa and 27.8 MPa in both models. The peak value was lower in models of fourscrews than that of three screws. Stress concentration position was at the fracture site in both models. The stress range of models of four screws was more extensive and scattered. (3) Finite element analysis results demonstrated that four-screw implantation for Pauwels III femoral neck fractures had strong anti-shearing force and biomechanical stability. Clinical advantages need further clinical comparative study.

OBJECTIVE： To establish psoriasis animal model with a longer duration and more typical psoriatic characteristics by modifying psoriasis model induced by imiquimod. METHODS： Mice were randomly divided into normal group （treated with vaseline）， model group [treated with Imiquimod cream 60 mg/（2×3 cm2·d）] and modified group [treated with Imiquimod cream 60 mg/（2×3 cm2·d）+subcutaneous injection of rmIL-12 and LPS once a week]， for consecutive 21 d， with 10 mice in each group. The skin of the model site was observed daily from the first day of modeling. Psoriasis area and severity index （PASI） score was conducted for skin lesions such as erythema， scales and thickening. 21 d after modeling， mice were sacrificed， and histopathological examination of the skin lesions was performed. The spleen index was calculated， and the contents of IL-17A and IL-12 in the skin were detected by ELISA. RESULTS： From the third and second day of medication， erythema， scales and thickening were both observed in model group and modified group respectively. The PASI score reached peak on the 12th day. From the 11th day， erythema， scales and thickening of the modified group were more serious than that in model group. PASI scores of modified group was significantly higher than that of model group for 9 consecutive days （P＜0.05）. Histopathological observation showed that Munro microabscess， acanthosis and dermal inflammatory cell infiltration occurred in both model group and modified group. Compared with model group， spleen indexes of modified group were higher （P＜0.05）. Compared with normal group， the contents of IL-17A and IL-12 in mice skin of model group and modified group were both increased， and there was statistical significance in modified group （P＜0.05）. CONCLUSIONS： The estbalished modified model has the longer duration of typical characteristics of psoriasis.

Objective:To analysis the clinical characteristics of The clinical characteristics of using automated external defibrillation in the public place,To explore the feasibility and effectiveness of AED application in public places in China.Methods:From January 2014 to April 5, 2019, 54 cases of on-site emergency medical records of AED use in public places in China were analyzed retrospectively from three aspects: patient and AED user attributes, and AED clinical performance.Results:After field application of AED analysis, 54 patients did not have out of hospital cardiac arrest in 9 patients; cardiac arrest in 45 patients, cerebral resuscitation in 40 patients (88.9%), death in 5 patients (11.1%), one of them died in hospital. The accuracy of AED for defibrillation rhythm recognition and defibrillation recommendations was 100%. The success rate of shock to VF was 97.22%, and that of non pulse VT was 100%. The data shows that AEDs of different brands show clinical effectiveness in the core indicators of work. The operation level of the rescuer determines the critical time of AED shock, which is closely related to the prognosis of the patient ( P<0.05) . Conclusions:AED is reliable and effective in electric shock decision and performance.The overall efficiency of AED application can be improved by strengthening training, shortening the critical time of electric shock, rational configuration and effective management.

Under the leadership of the Beijing Winter Olympic Organizing Committee and the Beijing Municipal Health Commission, the Beijing Emergency Center, as the designated medical institution for the 2022 Beijing Winter Olympic Games, has completed the first aid support task of this Winter Olympic Games with other medical institutions. The author systematically analyzed the development of each link in the pre-hospital emergency support for the 2022 Beijing Winter Olympic Games, summarizes the key links of the entire Winter Olympics cycle, such as the construction of the organizational system, the formulation of support plans, and the training of support personnel, and analyzed the results of related work, so as to provide reference for the pre-hospital emergency support for China to host large-scale international events in the future.