A CFD-Aided Galerkin Method for Global Linear Instability Analysis

Global linear instability analysis is a powerful tool for the complex flow diagnosis. However, the methods used in the past would generally suffer from some disadvantages, either the excessive computational resources for the low-order methods orthe tedious mathematical derivations for the high-order methods. The present workproposed a CFD-aided Galerkin methodology which combines the merits from boththe low-order and high-order methods, where the expansion on proper basis functions is preserved to ensure a small matrix size, while the differentials, incompressibility constraints and boundary conditions are realized by applying the low-orderlinearized Navier-Stokes equation solvers on the basis functions on a fine grid. Several test cases have shown that the new method can get satisfactory results for one-dimensional, two-dimensional and three-dimensional flow problems and also for theproblems with complex geometries and boundary conditions.     

桡骨远端骨折伴腕关节不稳的临床分析

目的分析合并腕关节不稳的桡骨远端骨折不同治疗的功能影响。方法临床随访72例合并腕关节不稳的桡骨远端骨折,通过传统的手法复位石膏固定及手术治疗,根据X线片测量判断治疗前后腕关节的变化,按Frykman分型、汤锦波提出的腕关节不稳定的分型标准及Gartland和Werley评分评定腕关节功能恢复情况作分析。结果随访中发现有背侧偏移、掌侧偏移、背屈不稳(DISI)、掌屈不稳(VISI)和舟月分离5种腕关节不稳;腕关节不稳纠正率为75%;手术组为90.9%;非手术组为46.7%;手术组功能优良率为85.2%,非手术组为72.2%。结论桡骨远端骨折后常可合并不同类型的腕关节不稳定,手术治疗能提高腕关节不稳的纠正率,提高临床疗效。     

创伤性上颈椎不稳的早期诊断和治疗（附56例报告）

目的　回顾创伤性上颈椎不稳病例 5 6例 ,强调早期诊断的重要性及治疗原则。方法　对未合并横韧带断裂病例采用保守治疗 ;合并横韧带断裂者应早期外科干预。结果　 47例经治疗后上颈椎获满意稳定性 ,优良率达 86 8%。结论　全面体检 ,影像学检查早期可作出诊断。横韧带是否断裂是保守及手术治疗的重要依据之一     

Truncation Errors,Exact and Heuristic Stability Analysis of Two-Relaxation-Times Lattice Boltzmann Schemes for Anisotropic Advection-Diffusion Equation

This paper establishes relations between the stability and the high-order truncated corrections for modeling of the mass conservation equation with the two-relaxation-times (TRT) collision operator. First we propose a simple method to derive the truncation errors from the exact, central-difference type, recurrence equations of the TRT scheme. They also supply its equivalent three-time-level discretization form. Two different relationships of the two relaxation rates nullify the third (advection) and fourth (pure diffusion) truncation errors, for any linear equilibrium and any velocity set. However, the two relaxation times alone cannot remove the leading-order advection-diffusion error, because of the intrinsic fourth-order numerical diffusion. The truncation analysis is carefully verified for the evolution of concentration waves with the anisotropic diffusion tensors. The anisotropic equilibrium functions are presented in a simple but general form, suitable for the minimal velocity sets and the d2Q9, d3Q13, d3Q15 and d3Q19 velocity sets. All anisotropic schemes are complemented by their exact necessary von Neumann stability conditions and equivalent finite-difference stencils. The sufficient stability conditions are proposed for the most stable (OTRT) family, which enables modeling at any Peclet numbers with the same velocity amplitude. The heuristic stability analysis of the fourth-order truncated corrections extends the optimal stability to larger relationships of the two relaxation rates, in agreement with the exact (one-dimensional) and numerical (multi-dimensional) stability analysis. A special attention is put on the choice of the equilibrium weights. By combining accuracy and stability predictions, several strategies for selecting the relaxation and free-tunable equilibrium parameters are suggested and applied to the evolution of the Gaussian hill.     

Analysis of Evidence-Based Medicine for Shoulder Instability

Clinical research has become a major influencing factor in the determination of treatment choice in our society. Outcome data have been requested by third-party payers, patients, and administrators alike. Currently, there are over 10 different scoring systems that have been used to evaluate the efficacy of treatment for shoulder instability. Some of these scoring systems are based on the specific condition of shoulder instability; however, other systems are broadly based to incorporate a spectrum of shoulder conditions. This review summarizes the process of proper development and testing of the scoring systems, discusses their role in clinical research with respect to shoulder instability, and explains the dichotomy of postoperative recurrence of instability and high shoulder scores. The Shoulder Rating Questionnaire (SRQ), Melbourne Instability Shoulder Score (MISS), Western Ontario Shoulder Instability Index (WOSI), Oxford Instability Score (OIS), and Simple Shoulder Test were shown to be reliable for patients with instability. The SRQ, MISS, WOSI, OIS, and American Shoulder and Elbow Surgeons score have all been shown to be largely responsive. There are 2 shoulder scoring systems, the WOSI and the MISS, that we recommend be used to evaluate shoulder instability. The SRQ and OIS were found to be less responsive for patients with instability compared with patients with other shoulder dysfunctions. Other scoring systems lack inter-rater reliability, validity, and/or responsiveness for patients in the instability population. The optimal scoring system for patients with upper extremity problems other than those with shoulder instability has yet to be determined; however, the American Shoulder and Elbow Surgeons score may be considered, because this instrument has been proven to be valid, reliable, and responsive.     

Primary Total Knee Arthroplasty Revised for Instability: A Detailed Registry Analysis

BackgroundInstability after total knee arthroplasty is a common but poorly understood complication.MethodsData from a large national registry was used to study patient and prosthesis characteristics of 2605 total knee arthroplasty revisions for instability. The cumulative percent revision was calculated using Kaplan-Meier estimates, and Cox proportional models used to compare revision rates. The rate of further revision was analyzed with regard to prostheses used in the first revision.ResultsInstability increased from 6% of all first revision procedures in 2003 to 13% in 2019. The revision risk was lower for minimally stabilized prostheses, males, and patients aged ≥65 years. Polyethylene insert exchange was used for 55% of revision procedures, using a thicker insert in 93% and a change in insert conformity in 24% of cruciate-retaining knees. The increase in either thickness or conformity had no effect on the rate of further revision. After a revision for instability, 24% had a second revision by 14 years. Recurrent instability accounted for 32% of further revisions. A lower second revision rate was seen after revision of both femoral and tibial components, and where constrained components were used.ConclusionRevision for instability is increasing. Revising both femoral and tibial components led to a lower rate of second revision compared to a change in insert alone. Recurrent instability was common.     

Influence of Hemorrhagic Shock on Remifentanil: A Pharmacokinetic and Pharmacodynamic Analysis

Background: Hemorrhagic shock is known to alter significantly the pharmacokinetics of fentanyl, an opioid that requires delivery to the liver for metabolism. The authors hypothesized that the pharmacokinetics and pharmacodynamics of remifentanil, an esterase metabolized opioid that does not require delivery to a metabolic organ, would be altered less by hemorrhagic shock that those of fentanyl.

Methods: Sixteen pigs were assigned randomly to control and shock groups. The shock group was bled using an isobaric hemorrhage model. Remifentanil 10 [mu]g [middle dot] kg-1 [middle dot] min-1 was infused for 10 min to both groups. Arterial samples were collected for remifentanil concentration assay. Pharmacokinetic parameters were estimated using a three-compartment model. The electroencephalogram spectral edge was used as a measure of drug effect. The pharmacodynamics were characterized using a sigmoid inhibitory maximal effect model.

Results: Remifentanil blood levels were higher in the shocked group. The central clearance was slower and the central compartment was smaller in shocked animals. No difference between groups was observed in the magnitude or time course of the remifentanil-induced decrease in spectral edge.     

The Influence of Hemorrhagic Shock on Propofol: A Pharmacokinetic and Pharmacodynamic Analysis

Background: Propofol is a common sedative hypnotic for the induction and maintenance of anesthesia. Clinicians typically moderate the dose of propofol or choose a different sedative hypnotic in the setting of severe intravascular volume depletion. Previous work has established that hemorrhagic shock influences both the pharmacokinetics and pharmacodynamics of propofol in the rat. To investigate this further, the authors studied the influence of hemorrhagic shock on the pharmacology of propofol in a swine isobaric hemorrhage model.

Methods: After approval from the Animal Care Committee, 16 swine were randomly assigned to control and shock groups. The shock group was bled to a mean arterial blood pressure of 50 mmHg over a 20-min period and held there by further blood removal until 30 ml/kg of blood was removed. Propofol 200 [mu]g [middle dot] kg-1 [middle dot] min-1 was infused for 10 min to both groups. Arterial samples (15 from each animal) were collected at frequent intervals until 180 min after the infusion began and analyzed to determine drug concentration. Pharmacokinetic parameters for each group were estimated using a three-compartment model. The electroencephalogram Bispectral Index Scale was used as a measure of drug effect. The pharmacodynamics were characterized using a sigmoid inhibitory maximal effect model.

Results: The raw data demonstrated higher plasma propofol levels in the shock group. The pharmacokinetic analysis revealed slower intercompartmental clearances in the shock group. Hemorrhagic shock shifted the concentration effect relationship to the left, demonstrating a 2.7-fold decrease in the effect site concentration required to achieve 50% of the maximal effect in the Bispectral Index Scale.     

On the Stability and CPU Time of the Implicit Runge-Kutta Schemes for Steady State Simulations

Implicit time integration schemes are popular because their relaxed stability constraints can result in better computational efficiency. For time-accurate unsteady simulations, it has been well recognized that the inherent dispersion and dissipation errors of implicit Runge-Kutta schemes will reduce the computational accuracy for large time steps. Yet for steady state simulations using the time-dependent governing equations, these errors are often overlooked because the intermediate solutions are of less interest. Based on the model equation dy/dt = (µ+iλ)y of scalar convection diffusion systems, this study examines the stability limits, dispersion and dissipation errors of four diagonally implicit Runge-Kutta-type schemes on the complex (µ+iλ)∆t plane. Through numerical experiments, it is shown that, as the time steps increase, the A-stable implicit schemes may not always have reduced CPU time and the computations may not always remain stable, due to the inherent dispersion and dissipation errors of the implicit Runge-Kutta schemes. The dissipation errors may decelerate the convergence rate, and the dispersion errors may cause large oscillations of the numerical solutions. These errors, especially those of high wavenumber components, grow at large time steps. They lead to difficulty in the convergence of the numerical computations, and result in increasing CPU time or even unstable computations as the time step increases. It is concluded that an optimal implicit time integration scheme for steady state simulations should have high dissipation and low dispersion.     

Anaphylactic Shock: A Form of Distributive Shock without Inhibition of Oxygen Consumption

Background: The pathophysiology of anaphylactic shock during anesthesia is incompletely characterized. It is described as distributive by analogy with septic shock (anaerobic metabolism, high tissue oxygen pressure [Ptio2] values). The Ptio2 profile and its metabolic consequences during anaphylaxis are not known.

Methods: Ovalbumin-sensitized anaphylactic shock rats (n = 11) were compared to nicardipine-induced hypotension rats (n = 12) for systemic hemodynamics, Ptio2, sympathetic nervous system activation, skeletal muscle blood flow, and interstitial lactate and pyruvate concentrations using combined microdialysis and polarographic Clark-type oxygen probes.

Results: In both groups, the time course and the magnitude of arterial hypotension were similar. The ovalbumin group but not the nicardipine group displayed decreased skeletal muscle blood flow (from 45 +/- 6.2 ml [middle dot] 100 g-1[middle dot]min-1 to 24.3 +/- 5 ml[middle dot]100 g-1[middle dot]min-1; P < 0.0001) and Ptio2 values (from 42 +/- 5 to 5 +/- 2; P < 0.0001). The ovalbumin group had more intense sympathetic nervous system activation with higher plasma epinephrine and interstitial norepinephrine concentrations. For the ovalbumin group, there was skeletal muscle anaerobic metabolism (lactate concentration increased from 0.446 +/- 0.105 to 1.741 +/- 0.459 mm; P < 0.05) and substrate depletion (pyruvate concentration decreased from 0.034 +/- 0.01 mm to 0.006 +/- 0.002 mm; P < 0.05) leading to increased interstitial lactate/pyruvate ratios (from 17 +/- 6 to 311 +/- 115; P < 0.05).     

Os Odontoideum: A Cause of Atlanto-Axial Instability

Os odontoideum is a rare condition in which instability may damage the upper cervical cord. A delay in diagnosis is not uncommon. This paper describes a series of 11 patients with os odontoideum. The presenting symptoms were divided into three groups: posttraumatic neck-pain, gradually appearing signs of medullary compression and an asymptomatic group. Eight patients had atlanto-axial instability. Six had interlaminar fusion between atlas and axis. No serious complications were seen. Stability was obtained in all patients postoperatively. In case of significant instability, fusion is indicated. In patients with cerebral palsy a closer examination of the upper cervical cord is recommended.     

A Comparison of Prognostic Schemes for Perihilar Cholangiocarcinoma

Introduction

Although widely used, the 7th edition American Joint Committee on Cancer (AJCC) staging system for perihilar cholangiocarcinoma (PHC) may be limited. Disease-specific nomograms have been proposed as a better means to predict long-term survival for individual patients. We sought to externally validate a recently proposed nomogram by Memorial Sloan Kettering Cancer Center (MSKCC) for PHC, as well as identify factors to improve the prediction of prognosis for patients with PHC.

Methods

Four hundred seven patients who underwent surgery for PHC between 1988 and 2014 were identified using an international, multi-center database. Standard clinicopathologic and outcome data were collected. The predictive power of the AJCC staging system and nomogram were assessed.

Results

Median survival was 24.4 months; 3- and 5-year survival was 37.2 and 20.8 %, respectively. The AJCC 7th edition staging system (C-index 0.570) and the recently proposed PHC nomogram (C-index 0.587) both performed poorly. A revised nomogram based on age, lymphovascular invasion, perineural invasion, and lymph node metastases performed better (C-index 0.682). The calibration plot of the revised PHC nomogram demonstrated good calibration.

Conclusion

The 7th edition AJCC staging system and the MSKCC nomogram had a poor ability to predict long-term survival for individual patients with PHC. A revised nomogram provided more accurate prediction of survival, but will need to be externally validated.

     

前臂纵向不稳定的生物力学研究

目的研究前臂纵向不稳定的生物力学机制,为临床诊断及治疗提供可靠的理论依据。方法12具新鲜冷冻尸体上肢标本制成生物力学模型,固定于MTS858型生物材料实验机上加载恒定100N的轴向负荷,测试不同解剖状态对桡骨纵向位移及前臂纵向稳定性的影响。结果单纯切断骨间膜对前臂的纵向稳定性影响甚微。切除桡骨头,前臂的纵向稳定性降低,桡骨向近端移位明显,再切断骨间膜,将使上述改变加重。结论桡骨是维持前臂纵向稳定的主要结构,前臂骨问膜是次要稳定结构。桡骨头切除后骨间膜损伤是前臂纵向不稳定产生并发症的主要原因。     

A Dimensional Splitting of ETD Schemes for Reaction-Diffusion Systems

Novel dimensional splitting techniques are developed for ETD Schemes which are second-order convergent and highly efficient. By using the ETD-Crank-Nicolson scheme we show that the proposed techniques can reduce the computational time for nonlinear reaction-diffusion systems by up to 70%. Numerical tests are performed to empirically validate the superior performance of the splitting methods.