[Objective]To analyze the biomechanics of different positions of femoral head-and-neck nail in fixation of proximal femoral fracture.[Method]Stable and unstable fracture models were made from 24 fresh femur specimens,and fixed with r-nail and DHS.Head-and-neck nails were placed in different positions to test their mechanical properties of anti-compression,anti-bending,anti-shearing and anti-torsion,and compared with each other.[Result]Mechanical properties of the femoral strength,stiffness,stability and loading capacity were tested and compared.To the stable fracture group,head-and-neck nail should be placed in middle-lower and posterior 1/3 of femoral neck,which leads to the best loading capacity.To the unstable fracture group,it should be placed between femoral head and neck,which lead to strong obliquity mechanics and valuable for bone union.[Conclusion]Confirm of the best position of femoral head-and-neck nail could improve the effect of fixation and enhance the surgical treatment of proximal femoral fracture.

Objective To evaluate the biomechanism of three kinds of internal fixations in treatment of complex tibial plateau fractures. Methods Eighteen human antiseptic cadaver tibial plateau specimens were used to make models of complex tibial plateau fracture (type Ⅵ fractures of Schatzker classification). The models were fixated with a lateral Golf-buttress plate (GP), modified dual plate (a lateral Golf-buttress plate plus a medial five-hole one-third tubular antiglide plate) (DP) or a lateral locking compression plate (LCP) respectively to compare strength, rigidity and stability of different fixation methods. Results The biomechanical strength, rigidity and stability in DP group and LCP group were better than those in GP group (P<0.05), while there was no statistical difference between LCP group and DP group (P>0.05). Conclusions Locking compression plate and modified dual plate are fairly ideal internal fixators for treatment of complex tibial plateau fractures. In the meantime, locking compression plate emphasizes conservation of soft tissues and blood supply, can better meet the requirement of the biological fixation of fracture and is the most ideal internal fixator at present.

BACKGROUND: Absorbable materials for internal fixation have some advantages such as simple surgery, rapid recovery and no need to second surgery, and have been accepted in the circle of orthopaedics, and had been applied in the clinic. However, the system experiment evidences are not reliable.OBJECTIVE: To investigate whether the absorbable material (the absorbable tension band, absorbable stick or screw) is an acceptable alternative to stainless steel wire with Kirschner wire by comparing their biomechanical properties in the fixation of patella transverse fractures.DESIGN, TIME AND SETTING: The randomized controlled study of biomechanical analysis was performed at the Laboratory of Institute of Biomechanics, Shanghai University from March 2007 to January 2008.MATERIALS: Eight fresh patellae specimens were collected, with the complete patella, articular capsule and patellar ligament (3.0-4.0 cm) and quadriceps femoris (4.0-5.0 cm), and then divided into two groups at random, AO steel wire group (n = 2) and absorbable tension band group (n = 6).METHODS: Eight fresh patellae specimens were divided into two groups at random, AO steel wire group (n = 2) and absorbable tension band group (n = 6) to create models of transverse fractures, which were separately fixed by absorbable tension band,steel wire tension band + Kirschner wire to measure their biomechanics function. If fracture gap reached 1.0 mm, the fixation failed.MAIN OUTCOME MEASURES: The changes in patellar ligament tensile force, quadriceps femoris tensile force, patellar displacement, quadriceps femoris displacement, patellar ligament displacement and patella tensile strain were measured under external load.RESULTS: Under external load, no significant difference was determined in total displacement between the absorbable tension band group and AO steel wire group (9%-10% difference). No significant difference was detected in patellar strain between absorbable tension band group and AO steel wire group (9%-10% difference). The patellofemoral joint force was similar between the absorbable tension band group and AO steel wire group. When internal fixation displaced 1 mm, the load was 587 N in the absorbable tension band group, and 650 N in the AO steel wire group (P > 0.05).CONCLUSION: The absorbable material is an acceptable alternative to stainless steel wire with Kirschner wire in the fixation of patella transverse fractures, with the advantages of good biological function and good stability at the broken ends of fractured bone.

Objective To investigate the regulative role of N-Acetyl-D-glucosamine(GlcNAc) on the stressed mice macrophages function.Methods The stressed mice model was established by electric footshock method.The mice were divided into 5 groups:normal control group,stressed mice model group,low dose Glc-NAc treatment group(0.25 ml 15% GlcNAc),medium-dose GlcNAc treatment group(0.5 ml 15% GlcNAc) and high-dose GlcNAc treatment group(1 ml 15% GlcNAc).GlcNAc was intragastrically injected to corresponding mice 2 h before the electrical stimulation.Peritoneal macrophage(PM?) phagocytosis capability was detected by phagocytosis saccharomycete assay,and PM? energy metabolism was detected by MTT assay.Results Compared with normal control group,stressed mice PM? phagocytosis capability was significantly lower(P

AIM: To investigate the influence of ischemic preconditioning on heart function, the activities of lactate dehydrogenase(LDH), malondialdehyde(MDA), and heme oxygenase-1(HO-1) after ischemia/reperfusion in isolated rat heart. METHODS: The model of Langendorff was used in isolated rat heart perfusion. Ischemic preconditioning protocol: stopping perfusion for 5 minutes and reperfusion for 5 minutes, repeating three times. Ischemia protocol: stopping perfusion for 40 minutes and reperfusion for 20 minutes. Indexes of heart function were recorded in control group, ischemia and reperfusion group(IR), and ischemic preconditioning group(IPC). The content of LDH of coronary effluent was measured. Moreover, the content of MDA and activity of HO-1 in myocardium were also measured. RESULTS: The recovery percentage of heart function in IPC group was significantly higher than that in IR group(P

Objective:To explore the value of diffusion tensor imaging (DTI) in evaluating the effects of hyperbaric oxygen therapy (HOT) in treating spinal cord injury.Methods:The modified Allen′s method was used to induce a traumatic spinal cord injury in 30 rats who were then divided randomly into an injured group and a treatment group, each of 15. The treatment group was given HOT twice a day for 3 days, then once a day for a total of 4 weeks. The injured group did not receive HOT. DTI was performed (along with Basso-Beattie-Bresnahan (BBB) evaluation) at 0h, 6h, 24h, as well as 3, 7, 14, 21 and 28 days after the operation. Two-factor repeated measures ANOVA was conducted to analyze any differences in the DTI results: the fractional anisotropy, mean apparent diffusivity, radial diffusivity and axial diffusivity, as well as the BBB scores. LSD t-tests were performed to analyze the significance of the differences at different time points.Results:At each time point after 24h the average FA value of the treatment group was significantly higher than the injured group′s average, while its average MD and RD values were significantly lower. Beyond 14 days the average AD value of the treatment group was significantly higher than that of the injured group. The treatment group′s average BBB score was also significantly higher at all the time points beyond 3 days.Conclusions:DTI results can evaluate spinal cord function and provide valuable information for the dynamic assessment of hyperbaric oxygen therapy after a traumatic spinal cord injury, and the therapy promotes the recovery of motor function, at least in rats.

Objective: To compare bioelectrical impedance analysis (BIA) and dual energy X ray absorptiometry (DXA) for measuring body mineral content (BMC) of children and adolescents, and to provide a basis for BIA to accurately measure BMC in children and adolescents. Methods: By using the convenience sampling method, among 1 469 children and adolescents aged 7-17 were recruited in Guangzhou from April to May 2019, the BMC was measured by DXA and BIA. The intraclass correlation coefficient ( ICC ) and Bland Altman analysis were used to evaluate the agreement between BIA and DXA. Bland Altman analysis was performed on log transformed data. The BMC was categorized into age and specific tertiles, and the agreement between methods was evaluated based on the kappa coefficients. Treating the BMC with DXA as the dependent variable, a prediction model was constructed for correcting the BIA measure. Results: The ICC s were 0.93 and 0.94 for boys and girls, respectively. In Bland Altman analysis, the limits of agreements for the BIA to DXA ratio were wide in boys and girls, ranging from 0.27-0.76 and 0.17-0.72, respectively. The kappa coefficients for categorized BMC levels were 0.57 and 0.45 for boys and girls, respectively, showing a fair to good degree of agreement. When sub grouped by BMI, the kappa coefficients for all BMI groups of boys and overweight girls were all >0.75 , with an excellent agreement. The prediction models for boys and girls were as follows: BMC DXA =-0.51+0.44× BMC BIA + 0.06× Age +0.02× BMI ; and BMC DXA =-0.55+0.43× BMC BIA +0.06× Age +0.02× BMI , respectively. The R 2 for models of boys and girls were 0.87 and 0.87, respectively. Conclusion The agreement between BIA and DXA was poor for measuring BMC, but acceptable when evaluating the categorized BMC levels, suggesting the BIA may be applied in assessment of the BMC levels when compared to the age and gender specific population. Additionally, the prediction model for correcting BMC by BIA fis well to the measurement by DXA.

Objective:To evaluate the diagnostic value of multiparametric cardiac magnetic resonance(CMR)or detecting the occurrence of acute rejection(AR)after heart transplantation(HT).Methods:From 2019 to 2021, 44 HT recipients are prospectively recruited from Guangdong Provincial People's Hospital.Another 51 healthy volunteers are recruited from a local community as healthy controls.CMR studies are performed for obtaining baseline parameters.According to the clinicopathological diagnostic criteria of AR by the consensus of International Society for Heart and Lung Transplantation, 81 CMR studies of 44 HT recipients are further divided into two groups of AR (18 cases)and non-AR(71 cases). CMR parameters includ global ventricular structure/function, T2, T1, extracellular volume(ECV)and late gadolinium enhancement(LGE). A combined model is established by binary Logistic regression and receiver operator characteristic curve(ROC)constructed.Results:The age range is(41.8±16.8)years in 44 HT recipients and(41.8±9.7)years in 51 healthy controls.T1 mapping indicated that myocardial global ECV of left ventricle is significantly higher in AR patients than non-AR controls(32.4%±6.0% vs 28.5%±2.4%; P<0.001 9). Global native T1 is higher in AR group than that in non-AR group(49.8±3.1 vs 47.5±2.8 ms, P=0.009)and the difference is statistically significant.The cutoff value of global ECV is 30.62% with a sensitivity of 61% and a specificity of 86% for detecting AR.And T2 mapping reveale that T2 value of global left ventricle is significantly higher in AR group than that in non-AR group(49.8±3.1 vs 47.5±2.8 ms, P=0.009). LGE extent is significantly higher in AR group than those in non-AR group( P=0.004). Through including global native T1 and ECV into a logistic regression model, multiparametric CMR can yield an area under curve(AUC)of 0.794.It hints at the potential of CMR for detecting AR. Conclusions:Multiparametric cardiac magnetic resonance offers an excellent predictive capacity for a noninvasive detection of AR.

Epidemiologic, clinical and imaging data were collected from 14 children with confirmed coronavirus disease 2019 (COVID-19) admitted in Beijing Ditan Hospital from January 27, 2020 to February 12, 2020. There were 6 boys and 8 girls with a median age of 3.5 years (6 months-9.4 years). Four patients had a history of travel to Wuhan City or Hubei Province and 2 patients had contacted with people from Wuhan; 13 patients were familial cluster of infection. The incubation period was 4 to 16 days. The clinical manifestations were fever in 8 cases, cough in 5 cases, diarrhea in 1 case; and 2 cases were asymptomatic. Four patients had abnormal peripheral blood routine, including 1 had lymphocytosis, 3 had lymphocytopenia; 3 patients had a slightly elevated CRP, and 3 patients had hepatic dysfunction. Thirteen patients underwent chest CT; and 1 case showed bilateral lung glass exudation, 1 case showed multiple patchy high density shadows of bilateral lung. One patient underwent chest X-ray examination, which was showed no abnormal findings. The pediatric patients with COVID-19 in this series generally have a traceable epidemiological history. The clinical manifestations are fever, cough and diarrhea. Peripheral white blood cell counts were most normal. Chest CT reveals less severe changes than those in adults, most child patients show no manifestation of pneumonia.

Objective:To analyze the current status of body composition and development patterns of children and adolescents aged 6-17 years in Guangzhou.Methods:This was a cross-sectional study involving 8 169 school students from 3 elementary schools and 3 middle schools in Guangzhou from March to December 2019.The fat-free mass (FFM) and fat mass (FM) were measured by the bioelectrical impedance analysis.The fat-free mass index (FFMI) and fat mass index (FMI) were calculated via the height standardization. T test was used to compare quantitative variables between groups.The growth pattern of body composition was described using the Hattori chart. Results:A total of 4 431 boys (54.24%) and 3 738 girls (45.76%) were involved in this study.FFM and FM both increased with age between boys and girls.Except for boys aged 11 years, FFM in boys were significantly higher than that in girls with the same age (all P<0.05). In the age of 7-10 years, FM in boys were significantly higher than that in girls with the same age, while it was significantly higher in girls aged 12 years and older than that of boys at the same age (all P<0.05). The Hattori chart showed that the difference in body composition between genders occurred after 11 years old.In contrast to girls, increases in the weight and body mass index (BMI) in boys were mainly attributed to the FFM development. Conclusions:The development of FFM and FM in children and adolescents varies with age, accompanied with the gender-specific features.FFM in boys is higher than that of girls at the same age.The weight gain in boys is mainly attributed to the development of fat-free tissues, and thus the utility of BMI may lead to the overestimation of obesity.