BACKGROUND:Silicon carbide-carbon (C/C-SiC) composite materials are widely used, but no relevant experimental studies on medical prosthesis materials have been reported.
OBJECTIVE: To demonstrate the feasibility of C/C-SiC composite materials as a substitute for facet joint prosthesis based on the biomechanical research and three-dimensional finite element analysis.
METHODS:The predetermined size C/C-SiC composites and traditional carbon/carbon(C/C) composite materials were placed in an electronic universal testing machine, to measure and calculate material compressive elastic modulus, compressive strength, maximal anticompression force, flexural modulus, bending strength and maximal antibending force. Afterwards friction coefficient, wear volume and weight wear rate were measured. Using three-dimensional finite element analysis, finite element models of the third metacarpal bone were defined as C/C and C/C-SiC composite element types, respectively. 200 N axial force was applied to analyze the total displacement and node stress.
RESULTS AND CONCLUSION:Compressive elastic modulus, compressive strength,maximal anticompression force, flexural modulus, bending strength and maximal antibending force of C/C-SiC composites were significantly higher than those of the C/C materials (P < 0.05); friction coefficient, wear volume, weight wear rate, total displacement as wel as node stress of C/C-SiC composites were significantly lower than those of C/C materials (P < 0.05). These results prove that C/C-SiC composite has favorable mechanical properties, antiwear ability, compression resistance and stress resistance.

Objective To investigate the effects of interventticular septal thickness (IST) on postoperative trans-aonic valve pressure after aortic valve replacement (AVR).Methods 273 patients were divided into 3 groups with different mechanical valves and postoperative trans-aortic valve pressure (TAVP).Hemodynamic parameters including left ventricular end diastolic diameter,left ventricular end systolic diameter,ejection fraction and IST were analyzed.Results There was no significant difference in left ventricular diastolic diameter,left ventricular systolic diameter and ejection fraction in three groups with different mechanical valves ( P ＞ 0.05 ).In patients with St.Jude Regent valve,preoperative IST in severe TAVP group was significantly thicker than those of moderate and mild groups ( P ＜ 0.05 ).In patients with On-x valve,preoperative IST in severe and moderate TAVP groups were thicker than that of mild group ( P ＜0.05 ).In patients with other mechanical valve,preoperative IST in severe TAVP group is greater than those of moderate and mild groups ( P ＜ 0.05 ).Conclusion Interventricular septal thickness did have positive influence on postoperative trans-aortic valve pressure after AVR.When IST was more than 13.6mm,the postoperative trans-aortic valve pressure after aortic valve replacement was higher than the IST was less than 13.6mm.When IST was thicker than 15.3mm,partial ventticular septal resection or replacement of stentless valve should be considered.

Objective Univariate analysis and multivariate risk factors of early acute kidney injury on off-pump coronary artery bypass grafting are performed.Methods Analyzed retrospectively the clinical date of 261 patients who underwent off-pump coronary artery bypass surgery between Jan 2011 to Dec 2013.According to the clinical diagnostic ctriteria,261 patients were divided into AKI group (n =29) and NAKI group(n =232).There were 22 males and 7 females with an age of (68.74 ± 10.27) years in the AKI group,there were 179 males and 53 females with an age of (66.26 ± 9.82) years in the NAKI group.we summarize the clinical date,including blood pressure,left ventricular ejecting fraction,diameter of the left ventricle and serum creatinine before operation,and observed postoperative complications etc.Evaluated the factors for AKI Using Logistics regression analysis statistical methods.Results Among all the patients,the incidence of AKI was 11.11％ (29/261),1 patients died in all the patients for AKI.The statistical analysis revealed that the serum creatinine after operation,anesthesia time,and perioperative blood transfusion were the risk factors for acute injury after off-pump coronary artery bypass surgery.Conclusion AKI is the most common complication of off-pump coronary artery bypass surgery.we should carefully evaluate risk factors and enhance protection of the renal function and reduce the risk of AKI occurred.

Objective To evaluate the efficacy and safety of preoperative intra-aortic balloon pump(IABP) insertion in acute myocardial infarction(AMI) without cardiogenic shock(CS) patients receiving off-pump coronary artery bypass grafting ( OPCABG).Methods 444 consecutive AMI patients who underwent isolated OPCABG from January 2009 to December 2016 were enrolled.158 patients who underwent preoperative IABP placement(IABP group) and the other of 286 patients who did not have IABP placement(control group).The in-hospital mortality rate, postoperative complications, mechanical ventilation time, ICU stay and hospital length were compared between the two groups.Results The overall mortality was 5.0%.135 pairs of patients were matched.The preoperative IABP insertion showed benefits in postoperative survival rate compared with the control group(0 vs.5.9%, P＝0.004).However, patients with preoperative IABP were more likely to prolong duration of mechanical ventilation and ICU stay.The postoperative length of stay in hospital didn't show significant difference between the two groups.Conclusion Survival advantage was observed from preoperative IABP insertion in AMI patients without CS under-going OPCABG.

Objective:To investigate the safety and the efficacy of percutaneous and surgical approach in femoro-femoral veno-arterial extracorporeal membrane oxygenation (VA-ECMO) cannulation.Methods:All consecutive patients implanted with femoro-femoral VA-ECMO between January 2018 and December 2020 in Beijing Anzhen Hospital, Capital Medical University. Propensity score matching was used to compare outcomes of percutaneous and surgical groups while controlling for confounders.Results:Among the 276 patients who received femoro-femoral VA-ECMO (62 surgical and 214 percutaneous), propensity-score matching selected 52 pairs of patients with similar characteristics with mean age of(59.6±13.0)years old, in which 26 patients were female. There were a lower ECMO cannulation-associated complication (28.8% vs. 48.1%, P=0.044) and a lower hospital mortality (42.3% vs. 67.3%, P=0.010) in the percutaneous group. The circuit blood flow after ECMO initiation was similar in both groups[(3.3±0.8)L·min -1·kg -1 in percutaneous group vs. (3.2±0.7)L·min -1·kg -1 in surgical group, P=0.738]. The serum lactate was declined in both group after ECMO initiation[(5.4±5.8)mmol/L vs. (9.2±6.9)mmol/L, P<0.001 in percutaneous group; (6.3±6.2)mmol/L vs. (10.5±7.0)mmol/L, P=0.003 in surgical group]. Conclusion:Percutaneous approach is a safe and efficient technique in emoro-femoral VA-ECMO cannulation. Compared with surgical cannulation, percutaneous approach is associated with lower ECMO cannulation-associated complication and lower hospital mortality.