Missing data represent a general problem in many scientific fields, especially in medical survival analysis. Dealing with censored data, interpolation method is one of important methods. However, most of the interpolation methods replace the censored data with the exact data, which will distort the real distribution of the censored data and reduce the probability of the real data falling into the interpolation data. In order to solve this problem, we in this paper propose a nonparametric method of estimating the survival function of right-censored and interval-censored data and compare its performance to SC (self-consistent) algorithm. Comparing to the average interpolation and the nearest neighbor interpolation method, the proposed method in this paper replaces the right-censored data with the interval-censored data, and greatly improves the probability of the real data falling into imputation interval. Then it bases on the empirical distribution theory to estimate the survival function of right-censored and interval-censored data. The results of numerical examples and a real breast cancer data set demonstrated that the proposed method had higher accuracy and better robustness for the different proportion of the censored data. This paper provides a good method to compare the clinical treatments performance with estimation of the survival data of the patients. This provides some help to the medical survival data analysis.
Abstract： The first generation scaffolds of bare metal stents （BMS） and the second generation of drug eluting stents （DES） have been widely used in the treatment of coronary heart diseases. However, long term incidences of major adverse cardiovascular events and revascularization treatments are still high because of in-stent re-stenosis and thrombosis. These may be caused by chronic inflammations and vascular wall damages due to persistent metal stents stimulation. What’s more, the eluting drugs within metal stents could also disturb normal growth of vascular endothelial cell, intima, tunica media, smooth muscle and epimysium. Therefore, in order to meet these demands several fully biodegradable scaffolds and drug carried stents have been manufactured using polymers polyester, polycarbonate and polyphosphate, etc. Among them, the security and histo-and hemo-compatibilities of coronary scaffolds made from poly-lactic acid （PLA）, poly-glycolic acid（PGA）, chitosan as coating, poly-caprolactone （PCL） and other copolymer like poly-lactic-co-glycolic acid （PLGA） have been testified to be sound. Nevertheless, there exist several different shortages for these stents such as tensile strength deficiency and slow degradation. PLA is hard and brittle with slow degradation, while PGA is soft with insufficient support force and fast degradation. Whether stents degrade too fast or too slow, they could not supply sufficient strength and effective support after implantation, and also they may cause target vascular injuries and elastic shrink inducing restenosis and thrombosis in long terms. Using optimized molar ratio component of PLA and PGA with chitosan coating, we can get sound composite materials with better biocompatibility, moderate degradation （approximately 3 - 6 months of completedegradation）, adequate mechanical strength, lower inflammatory response and good range of extension, and establish an experiment ground for fully biodegradable vascular scaffolds fabrication.
Objective To investigate the effect of axial stress stimulation on tibial and fibular open fractures healing after Taylor space stent fixation. Methods The data of 45 cases with tibial and fibular open fractures treated by Taylor space stent fixation who meet the selection criteria between January 2015 and June 2016 were retrospectively analysed. The patients were divided into trial group (23 cases) and control group (22 cases) according to whether the axial stress stimulation was performed after operation. There was no significant difference in gender, age, affected side, cause of injury, type of fracture, and interval time from injury to operation between 2 groups (P>0.05). The axial stress stimulation was performed in trial group after operation. The axial load sharing ratio was tested, and when the value was less than 10%, the external fixator was removed. The fracture healing time, full weight-bearing time, and external fixator removal time were recorded and compared. After 6 months of external fixator removal, the function of the limb was assessed by Johner-Wruhs criteria for evaluation of final effectiveness of treatment of tibial shaft fractures. Results There were 2 and 3 cases of needle foreign body reaction in trial group and control group, respectively, and healed after symptomatic anti allergic treatment. All the patients were followed up 8-12 months with an average of 10 months. All the fractures reached clinical healing, no complication such as delayed union, nonunion, or osteomyelitis occurred. The fracture healing time, full weight-bearing time, and external fixator removal time in trial group were significantly shorter than those in control group (P<0.05). After 6 months of external fixator removal, the function of the limb was excellent in 13 cases, good in 6 cases, fair in 3 cases, and poor in 1 case in trial group, with an excellent and good rate of 82.6%; and was excellent in 5 cases, good in 10 cases, fair in 4 cases, and poor in 3 cases in control group, with an excellent and good rate of 68.2%, showing significant difference between 2 groups (Z=–2.146, P=0.032). Conclusion The axial stress stimulation of Taylor space stent fixation can promote the healing of tibial and fibular open fractures and promote local bone formation at fracture site.
The interventional therapy of vascular stent implantation is a popular treatment method for cardiovascular stenosis and blockage. However, traditional stent manufacturing methods such as laser cutting are complex and cannot easily manufacture complex structures such as bifurcated stents, while three-dimensional (3D) printing technology provides a new method for manufacturing stents with complex structure and personalized designs. In this paper, a cardiovascular stent was designed, and printed using selective laser melting technology and 316L stainless steel powder of 0?10 μm size. Electrolytic polishing was performed to improve the surface quality of the printed vascular stent, and the expansion behavior of the polished stent was assessed by balloon inflation. The results showed that the newly designed cardiovascular stent could be manufactured by 3D printing technology. Electrolytic polishing removed the attached powder and reduced the surface roughness Ra from 1.36 μm to 0.82 μm. The axial shortening rate of the polished bracket was 4.23% when the outside diameter was expanded from 2.42 mm to 3.63 mm under the pressure of the balloon, and the radial rebound rate was 2.48% after unloading. The radial force of polished stent was 8.32 N. The 3D printed vascular stent can remove the surface powder through electrolytic polishing to improve the surface quality, and show good dilatation performance and radial support performance, which provides a reference for the practical application of 3D printed vascular stent.
【Abstract】Objective To research relation of apoptosis muscular cell in 103Pd radioactive stent of dog biliary muscular formation and inhibition of biliary ductal stricture. Methods Twelve dogs were randomly divided into two groups, which were general stent group and 103Pd radioactive stent group. General stent and 103Pd radioactive stent were respectively put into extrahepatic biliary tract of two groups. After 30 days all dogs were killed, and biliary tract were taken out. Apoptotic cells were detected by immunohistochemical methodsand agar electrophoresis, and nucleus browyellow was positive cell. Dog biliary duct cross-sections were stained by hematoxylin-erosin; area and perimeter of lumen,thickness of inner membrane and stenosis degree in bile duct were analysed by image analysis software of computer.Results The apoptotic biliary duct smooth muscle cell ［(87.9±7.96)/cm2］ was more significantly increased in the 103Pd radioactive stent group than in the general stent group ［(5.6±0.51)/cm2］, P＜0.05; and comparing with the general stent group, the 103Pd radioactive stent significantly reduced biliary muscular formation thickness. Conclusion The result shows that 103Pd radioactive stent can inhibit proliferation of biliary ductal smooth muscle cell.
In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent’s original diameter.
Objective To systematically evaluate the efficacy and safety of sirolimus-eluting stents (SES) versus bare-metal stents (BMS) in treating patients with ST-segment elevation myocardial infarction. Methods The databases such as PubMed (1960 to Mar. 2011), EMbase (1980 to Mar. 2011), the Cochrane Central Register of Controlled Trials (1989 to Mar. 2011), CBM (1979 to Mar. 2011), VIP (1989 to Mar. 2011) and CNKI (1979 to Mar. 2011) were searched to collect all the randomized controlled trials (RCTs) on SES versus BMS in patients with ST-segment elevation myocardial infarction. After the data extraction and methodological quality evaluation, meta-analysis was conducted with RevMan 4.2 software. Results A total of 7 RCTs were included. Among 2 555 patients involved, 1 282 were in the SES group, while the other 1273 were in the BMS group. The results of meta-analyses showed that SES was superior to BMS in the target-lesion revascularization (OR=0.27, 95%CI 0.16 to 0.45, Plt;0.000 01) and target-vessel revascularization (OR=0.33, 95%CI 0.24 to 0.46, Plt;0.000 01). In contrast, there were no differences between SES and BMS in death, stent thrombosis and recurrence of myocardial infarction. Conclusion With the one-year clinical outcomes, SES is more effective than BMS in reducing the rate of target-vessel revascularization and target-lesion revascularization.
Objective To evaluate the feasibility of X-ray guided access to the extrahepatic segment of the main portal vein (PV) to create a transjugular extrahepatic portacaval shunt (TEPS). Methods 5F pigtail catheter was inserted into the main PV as target catheter by percutaneous transhepatic path under ultrasound guidance. The RUPS-100 puncture system was inserted into the inferior vena cava (IVC) by transjugular path under ultrasound guidance. Fluency covered stent was deployed to create the extrahepatic portacaval shunt after puncturing the target catheter from the IVC under the X-ray guidance, then shunt venography was performed. Enhanced CT of the abdomen helped identify and quantify the patency of the shunt and the presence of hemoperitoneum. Results The extrahepatic portacaval shunts were created successfully by only 1 puncture in 6 pigs. No extravasation was observed in shunt venography. One pig died of anesthesia on the day of operation. The extrahepatic portacaval shunts were failed in 2 pigs 3 days after the operation (one was occluded and the other one was narrowed by 80%). The extrahepatic portacaval shunts were occluded 2 weeks after the operation in the remaining 3 pigs. The shunts were out of the liver and no hemoperitoneum was identified at necropsy in the 6 pigs. Conclusion TEPS is technically safe and feasible under the X-ray guidance.
ObjectiveTo evaluate safety and effectiveness of stent placement and emergency surgery in treatment of proximal colon cancer obstruction.MethodsThe PubMed, Embase, Cochrane Library, ClinicalTrials, CNKI, CBM, Wanfang Data, etc. were searched comprehensively. The literatures of Chinese and English randomized controlled trial and retrospective comparative study of stent placement and emergency surgery for the proximal colon cancer obstruction were retrieved. The RevMan 5.3 and Stata 12.0 softwares were used. The meta-analysis was made on the safety and effectiveness of these two treatments.ResultsA total of 9 literatures involving 636 patients were included, all of them were the retrospective studies, 4 of them only reported the clinical success rate and technical success rate. The technical success rate of stent placement was 0.94 [95% CI (0.91, 0.96)]. The clinical success rate was 0.90 [95% CI (0.87, 0.93)]. Compared with the emergency surgery group, the total complication rate and the temporary stoma rate were lower [OR=0.32, 95% CI (0.11, 0.94), P=0.04; OR=0.18, 95% CI (0.05, 0.65), P=0.009] and the hospital stay was shorter [MD=–2.97, 95% CI (–4.52, –1.41), P=0.000 2] in the stent placement group. The perioperative mortality rate, laparoscopic surgery rate, 5-year disease-free survival rate, and 5-year overall survival rate had no significant differences between these two groups (P>0.05).ConclusionCompared with emergency surgery, endoscopic stent placement for treatment of proximal colon cancer obstruction has a lower incidence of complications, temporary colostomy rate, shorter hospital stay, and it has no significant differences in mortality, laparoscopic surgery rate, and survival rate.
ObjectivesTo evaluate the efficacy and safety of four antiplatelet regimens after coronary drug-eluting stents by network meta-analysis.MethodsPubMed, The Cochrane Library, EMbase and Web of Science databases were electronically searched to collect randomized controlled trials (RCTs) of the comparison of different antiplatelet regimens after coronary drug-eluting stenting from inception to December 31st, 2019. Two reviewers independently screened literature, extracted data and assessed risk bias of included studies. Network meta-analysis was then performed by using Gemtc14.3 software, Stata16.0 software and RevMan5.3 software.ResultsA total of 23 RCTs involving 45 837 patients were included. The results of network meta-analysis showed that: in terms of prevention of myocardial infarction (MI) recurrence, the aspirin monotherapy after short-term dual antiplatelet therapy was inferior to the triple antiplatelet therapy (OR=2.13, 95%CI 1.08 to 4.03). In terms of reducing the incidence of ischemic compound events, the triple antiplatelet therapy was superior to the standard dual antiplatelet therapy (OR=0.53, 95%CI 0.39 to 0.72), the aspirin monotherapy after short-term dual antiplatelet therapy (OR=0.49, 95%CI 0.35 to 0.69) and the P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy (OR=0.51, 95%CI 0.35 to 0.73). There was no statistically significant difference among the four interventions in reducing the rate of in-stent thrombosis and all-cause mortality (P>0.05). In terms of safety, the bleeding rate of aspirin monotherapy after short-term dual antiplatelet therapy was lower than that of standard dual antiplatelet therapy (OR=0.70, 95%CI 0.55 to 0.86) and triple antiplatelet therapy (OR=0.58, 95%CI 0.36 to 0.90), and the bleeding rate of P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy was also lower than that of standard dual antiplatelet therapy (OR=0.51, 95%CI 0.39 to 0.65) and triple antiplatelet therapy (OR=0.43, 95%CI 0.26 to 0.67). The probability ranking diagram showed that: in terms of the recurrence rate of MI, the rate of in-stent thrombosis and the incidence of ischemic compound events, triple antiplatelet therapy was the lowest and aspirin monotherapy after short-term dual antiplatelet therapy was the highest. However, in terms of all-cause mortality and bleeding rate, aspirin or P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy was the lowest and triple antiplatelet therapy was the highest.ConclusionsThe available evidence suggests that when the risk of ischemia is low, we should choose aspirin or P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy, and P2Y12 inhibitor monotherapy may have a lower risk of ischemia and bleeding. When the risk of ischemia is high and bleeding is low, the triple or standard dual antiplatelet therapy should be selected, and the efficacy of triple antiplatelet therapy is superior, while the safety may be inferior.