ObjectiveTo explore the degradation of AZ31 magnesium alloy and poly (lactic-co-glycolic acid) (PLGA) in the femoral condyle, and then evaluate the laws of degradation of AZ31 magnesium alloy by Micro-CT images and data. MethodsForty 3-month-old male New Zealand white rabbits (weighing, 2.5 kg) were randomly divided into 4 groups, 10 rabbits each group. Forty micro-arc-oxidized AZ31 magnesium alloy pins and 40 PLGA pins were implanted into the right and left femoral condyle, respectively. Micro-CT images and data analysis were used to evaluate the degradation at 4, 8, 12, and 16 weeks after operation (n=10). Degradation was evaluated by weight difference between pre-and post-implantation. The inflammatory response was observed around the implants by HE staining. The weight loss of magnesium alloy and Micro-CT results were compared. ResultsThe Micro-CT images showed that PLGA pins had gray low signal, which was similar to the soft tissue around. At 4 weeks after operation, no signs of degradation were observed, and there were little corrosion pitting on the magnesium alloy. At 8 weeks, corrosion pitting gradually expanded, the boundary between the longitudinal axis and the cross section became blurred; at 16 weeks, corrosion pitting became bigger, and the boundary was discontinuous. Micro-CT quantitative analysis showed that the volume fraction of magnesium pins decreased slowly at 4 and 8 weeks; it was significantly lower at 12 and 16 weeks than 4 and 8 weeks (P < 0.05). The magnesium cylinder mineral density continuously decreased during the study period, it had a rapidly speed from 12 to 16 weeks (P < 0.05). However, the magnesium CT image density showed a slight change (P>0.05). The surface-to-volume ratio of the pins constantly increased, and the ratio was significantly larger at 12 and 16 weeks than 4 and 8 weeks, and at 16 weeks than 12 weeks (P < 0.05). There was more and more corrosion pitting on the surface with time, which resulted in a decrease in the radius that mean trabecular thickness gradually decreased, showing significant difference between different time points after 8 weeks (P < 0.05). The weight loss detection showed that the degradation of magnesium pin and PLGA gradually increased with time (P < 0.05), and the degradation rate of magnesium pin was significantly lower than that of PLGA at 8-12 weeks (P < 0.05), but the degradation rate of magnesium pin was higher than that of PLGA at 16 weeks. At each time point, the weight loss of magnesium alloy was similar to that by Micro-CT, but mass fraction was lower than volume fraction and had significant differences at 8, 12, and 16 weeks (P < 0.05). HE staining revealed that slight inflammatory response was observed around the magnesium pins at 4 weeks, and inflammatory reaction gradually reduced with time and disappeared at 16 weeks, but no inflammatory reaction was seen around PLGA. ConclusionMicro-CT has the advantages of non-trauma, in vivo detection, quantitative analysis, and precise data in evaluating the degradation of AZ31 magnesium alloy. Regarding the degradation of the magnesium alloy and PLGA in vivo, the degradation rate is slow in the early stage, and then increases with time. The degradation of PLGA is faster and earlier but it is then overtaken by AZ31 magnesium alloy at 16 weeks. During the degradation, the density of the magnesium has almost no change. The biomaterials can not firmly attach to the surrounding tissues due to inadequate holding forces.
ObjectiveTo systematically review the efficacy of mobile health (mHealth) apps on weight loss.MethodsWeb of Science, PubMed, CNKI, WanFang Data and CBM databases were electronically searched to collect randomized controlled trials (RCTs) on the efficacy of mHealth APPs on weight loss from inception to October 18, 2019. Two reviewers independently screened literature, extracted data and assessed risk of bias of included studies. Meta-analysis was then performed using RevMan 5.3 software.ResultsA total of 12 RCTs involving 1 074 patients were included. The results of meta-analysis showed that the apps group was superior to the control group in body weight (MD=−1.88, 95%CI −3.23 to −0.53, P=0.006). There was a decreasing trend of body mass index (BMI) in apps group (MD=−0.55, 95%CI −1.09 to 0.00, P=0.05).ConclusionsCurrent evidence shows that mHealth app can increase the efficacy of weight loss. Due to limited quality and quantity of the included studies, more highquality studies are required to verify above conclusions.