Recurrent injury event-time analysis

Public health decision making based on data sources that are characterized by a lack of independence and other complicating factors requires the development of innovative statistical techniques. Studies of injuries in occupational cohorts require methods to account for recurrent injuries to workers over time and the temporary removal of workers from the 'risk set' while recuperating. In this study, the times until injury events are modelled in an occupational cohort of employees in a large power utility company where employees are susceptible to recurrent events. The injury history over a ten-year period is used to compare the hazards of specific jobs, adjusted for age when first hired, and race/ethnicity differences. Subject-specific random effects and multiple event-times are accommodated through the application of frailty models which characterize the dependence of recurrent events over time. The counting process formulation of the proportional hazards regression model is used to estimate the effects of covariates for subjects with discontinuous intervals of risk. In this application, subjects are not at risk of injury during recovery periods or other illness, changes in jobs, or other reasons. Previous applications of proportional hazards regression in frailty models have not needed to account for the changing composition of the risk set which is required to adequately model occupational injury data. Published in 1999 by John Wiley & Sons, Ltd. This article is a US Government work and is in the public domain in the United States.     

Median arcuate ligament syndrome: Predictor of ischemic complications?

Median arcuate ligament syndrome (MALS) is a pathologic entity that can affect the celiac axis. Due to the extensive collateral network of mesenteric circulation, stenosis of one mesenteric artery does not lead to significant symptoms. The purpose of this study was to describe multidetector computed tomography (MDCT) angiography findings of celiac artery entrapment by the median arcuate ligament and determine those patients with high risks of ischemic complications. From January 2012 to March 2016, 103 patients with celiac artery (CA) compression by median arcuate ligament were detected. In 23 patients collateral circulation was developed. In order to investigate the problem, we managed to estimate the correlation between range of stenosis of CA and presence of collateral circulation between the celiac artery (CA) and superior mesenteric artery (SMA). A statistically significant correlation was found between range of CA stenosis and collateral circulation presence (Spearman's correlation coefficient 0.339, P < 0.0001). In conclusions, based on our observations, we hypothesize that ischemia as a result of mesenteric vessel narrowing by the median arcuate ligament may occur more often than indicated by clinical symptoms and described in literature. Clin. Anat. 29:1025–1030, 2016. © 2016 Wiley Periodicals, Inc.     

Time efficiency of direct anterior hip arthroplasty compared to postero-lateral approach in elderly patients

IntroductionPrimary arthroplasty of the hip joint is currently one of the most commonly performed procedures in orthopedics. In Poland we are observing significant changes in the age structure. With the prolonged life more and more elderly patients require musculoskeletal surgery to maintain comfortable and painless mobility. Reducing the duration of the procedure reduces the costs of anesthesiology, surgical and instrument teams, as well as the operating room technical team. The aim of the study was to compare the time required to perform hip joint arthroplasty by the direct anterior approach (DAA) with the postero-lateral approach (PLA) in our hospital.Material and methodsA retrospective analysis of 559 total and bipolar cemented and cementless hip replacement procedures based on two operative approaches – the minimally invasive DAA over the course of 2 years, and the standard PLA over the course of 3 years – was performed.ResultsStatistically significant differences were observed between the approaches used for cementless total arthroplasty with regard to the mean treatment times: 51.9 min for the 272 DAA cases, and 78.3 min for the 190 PLA cases (p < 0.0001). For the cementless hemi-arthroplasty procedure, the mean treatment times were 46.9 min in 36 patients for DAA, and 48.2 min for 61 patients for PLA (p = 0.57).ConclusionsMinimally invasive DAA significantly shortens the time of the procedure in elderly patients compared to PLA. Further study is needed to analyze other aspects of those two approaches.     

Influence of MXene (Ti3C2) Phase Addition on the Microstructure and Mechanical Properties of Silicon Nitride Ceramics

This paper discusses the influence of Ti₃C₂ (MXene) addition on silicon nitride and its impact on the microstructure and mechanical properties of the latter. Composites were prepared through powder processing and sintered using the spark plasma sintering (SPS) technic. Relative density, hardness and fracture toughness, were analyzed. The highest fracture toughness at 5.3 MPa·m^1/2 and the highest hardness at HV5 2217 were achieved for 0.7 and 2 wt.% Ti₃C₂, respectively. Moreover, the formation of the Si₂N₂O phase was observed as a result of both the MXene addition and the preservation of the α-Si₃N₄→β-Si₃N₄ phase transformation during the sintering process.     

Cerebrovascular autoregulation in critically ill patients during continuous hemodialysis

Purpose

In chronic renal failure, intermittent hemodialysis decreases cerebral blood flow velocity (CBFV); however, in critically ill patients with acute renal failure, the effect of continuous venovenous hemodialysis (CVVHD) on CBFV and cerebrovascular autoregulation (AR) is unknown. Therefore, a study was undertaken to investigate the potential effect of CVVHD on CBFV and AR in patients with acute renal failure.

Methods

This cohort study investigated 20 patients with acute renal failure who required CVVHD. In these patients, the CBFV and index of AR (Mx) were measured using transcranial Doppler before and during CVVHD.

Results

The median Mx values at baseline were 0.33 [interquartile range (IQR): 0.02-0.55], and during CVVHD, they were 0.20 [0.07-0.40]. The differences in Mx (CVVHD – baseline) was (median [IQR]) ?0.015 [?0.19-0.05], 95% confidence interval (CI) ?0.16 to 0.05. The Mx was > 0.3 in 11/20 patients at baseline measurement. Six of these patients recovered to Mx < 0.3 during CVVHD. The CBFV was (median [IQR]) 47 [36-59] cm·sec^?1 at baseline and 49 [36-66] cm·sec^?1 during CVVHD. The difference of CBFV was 0.0 [?4 - 2.7], 95% CI ?2.5 to 4.2.

Conclusion

Compared with patients with intermittent hemodialysis, CVVHD did not influence CBFV and AR in critically ill patients with acute renal failure, possibly due to lower extracorporeal blood flow, slower change of plasma osmolarity, and a lower fluid extraction rate. In a subgroup of patients with sepsis, the AR was impaired at baseline in more than half of the patients, and this was reversed during CVVHD. The trial was registered at ClinicalTrials.gov ID: NCT01376531.