Prediction of structural failure of tibial bone models under physiological loads: Effect of CT density–modulus relationships

Although finite element (FE) models can provide distinct benefits in understanding knee biomechanics, in particular the response of the knee to implants, their usefulness is limited by the modelling assumptions and input parameters. This study highlights the uncertainty of material input parameters derived from the literature and its limitation on the accuracy and usefulness of FE models of the tibia. An FE model of the intact human knee and a database of knee forces (muscles, ligaments and medial and lateral tibio-femoral contacts) were developed for walking and stair-descent activities. Ten models were constructed from ten different combinations of apparent bone density to elastic modulus material property relationships, published in the literature. Some of the published material property relationships led to predictions of bone strains in the proximal tibia which exceeded published failure criteria under loads imposed by normal activities. These relationships appear not to be applicable for the human tibia. There is a large discrepancy in proposed relationships that cover the cancellous bone density range. For FE models of the human tibia, the material relationship proposed by Morgan et al., which assumed species and anatomic site dependence, produced the most believable results for cancellous bone. In addition to casting doubt on the use of some of the published density–modulus relationships for analysis of the human proximal tibia, this study highlights the need for further experimental work to characterise the behaviour of bone with intermediate densities.     

多普勒超声评分体系在晚孕胎儿监护中的应用及意义

目的评价多普勒超声评分体系(DUPS)在晚孕胎儿监护中的应用价值。方法选择459例孕龄大于32周的孕妇行彩色多普勒超声检查,检测胎儿大脑中动脉搏动指数(MCAPI)、心脏大小、心功能、脐动脉搏动指数(UmAPI)、静脉导管搏动指数(DVPI)及脐静脉血流频谱(UV)。根据上述5项指标计算其DUPS评分,无异常时每项得2分,有异常时得1分或0分。将其评分结果与其围产期结局进行比较和分析。结果459例晚孕胎儿中有402例正常分娩(87.58%),48例因临床上需要而提早终止妊娠(10.46%),9例围产期死亡(1.96%)。正常分娩、提早终止妊娠、围产期死亡组间DUPS评分有显著性差异(P<0.001)。应用受试者工作特性曲线法确定预测围产期结局不良(包括提早终止妊娠和围产期死亡)DUPS评分的最佳诊断界点为8分(灵敏度78.95%,特异度95.52%),预测围产期死亡DUPS评分的最佳诊断界点为6分(灵敏度100.00%,特异度99.11%)。结论DUPS在预测晚孕胎儿的围产期结局不良中具有重要的临床价值,值得进一步研究与应用。     

Food or nutrient pattern assessment using the principal component analysis applied to food questionnaires. Pitfalls,tips and tricks

We considered the Blom’s transformation, a statistical method aimed to normalise and standardise food intakes before principal component analysis. A simulation study was performed to evaluate the eigenvalue distribution of a correlation matrix under common conditions in food questionnaire analysis. The scree plot visual inspection and the Guttman–Kaiser (GK) criterion were compared to Horn’s parallel analysis to evaluate their efficacy in food pattern identification. The scree plot results as a monotone continuous series when no food patterns are present. In this situation, about 50% of the eigenvalues assume a value higher than one, showing a first fallacy of the GK. When three food patterns are simulated a clear discontinuity appears after the third eigenvalue, showing that the scree-plot visual inspection is a suitable method to identify food patterns. Finally, according to the present work it appears that the GK generates a number of false-positive food patterns.     

What is the evidence status of Appropriate Use Criteria (AUC)? Insight from a matching exercise with the guidelines for echocardiography

There is interest in adapting the American Appropriate Use Criteria (AUC) for transthoracic echocardiography to Australian practice. We matched 90 of 98 AUC with the guidelines (53 appropriate, 12 sometimes appropriate, 25 rarely appropriate), but eight lacked any match. Among the matched criteria, 76 (82%) indications were concordant with the guidelines. A stronger evidence base would be desirable to settle these discrepancies before Australian adoption of AUC.     

Outcome in Dilated Cardiomyopathy Related to the Extent,Location, and Pattern of Late Gadolinium Enhancement

ObjectivesThis study sought to investigate the association between the extent, location, and pattern of late gadolinium enhancement (LGE) and outcome in a large dilated cardiomyopathy (DCM) cohort.BackgroundThe relationship between LGE and prognosis in DCM is incompletely understood.MethodsThe authors examined the association between LGE and all-cause mortality and a sudden cardiac death (SCD) composite based on the extent, location, and pattern of LGE in DCM.ResultsOf 874 patients (588 men, median age 52 years) followed for a median of 4.9 years, 300 (34.3%) had nonischemic LGE. Estimated adjusted hazard ratios for patients with an LGE extent of 0 to 2.55%, 2.55% to 5.10%, and >5.10%, respectively, were 1.59 (95% confidence interval [CI]: 0.99 to 2.55), 1.56 (95% CI: 0.96 to 2.54), and 2.31 (95% CI: 1.50 to 3.55) for all-cause mortality, and 2.79 (95% CI: 1.42 to 5.49), 3.86 (95% CI: 2.09 to 7.13), and 4.87 (95% CI: 2.78 to 8.53) for the SCD endpoint. There was a marked nonlinear relationship between LGE extent and outcome such that even small amounts of LGE predicted a substantial increase in risk. The presence of septal LGE was associated with increased mortality, but SCD was most associated with the combined presence of septal and free-wall LGE. Predictive models using LGE presence and location were superior to models based on LGE extent or pattern.ConclusionsIn DCM, the presence of septal LGE is associated with a large increase in the risk of death and SCD events, even when the extent is small. SCD risk is greatest with concomitant septal and free-wall LGE. The incremental value of LGE extent beyond small amounts and LGE pattern is limited.     

矩形微缺损关节软骨在压缩载荷损伤演化的数值分析

目的 研究软骨在压缩载荷作用下的损伤扩展行为和演变机制。方法 采用有限元方法建立微缺损的纤维增强多孔弹性的软骨模型,对压缩载荷作用下损伤演化过程进行模拟和参数研究,获得不同损伤扩展阶段软骨基体和纤维的应力、应变分布规律。结果 软骨损伤表层和损伤前沿的应变随压缩量的增大而显著增大,两者呈明显的正相关性;在软骨演化过程中同时存在向深层和左右两侧扩展的趋势;软骨中的裂纹和损伤优先沿着纤维切线方向延伸,随着损伤的加剧,软骨横向扩展度明显快于纵向扩展速度。结论 软骨损伤演化过程与纤维的分布有着密切的关系,基质和纤维的损伤相互促进,骨演化速度和程度在不同层区和不同阶段存在变化。研究结果可为软骨创伤性退变的预测及修复提供定性的参考,为临床解释损伤退变病理现象和治疗提供理论依据。     

State selection in Markov models for panel data with application to psoriatic arthritis

Markov multistate models in continuous‐time are commonly used to understand the progression over time of disease or the effect of treatments and covariates on patient outcomes. The states in multistate models are related to categorisations of the disease status, but there is often uncertainty about the number of categories to use and how to define them. Many categorisations, and therefore multistate models with different states, may be possible. Different multistate models can show differences in the effects of covariates or in the time to events, such as death, hospitalisation, or disease progression. Furthermore, different categorisations contain different quantities of information, so that the corresponding likelihoods are on different scales, and standard, likelihood‐based model comparison is not applicable. We adapt a recently developed modification of Akaike's criterion, and a cross‐validatory criterion, to compare the predictive ability of multistate models on the information which they share. All the models we consider are fitted to data consisting of observations of the process at arbitrary times, often called ‘panel’ data. We develop an implementation of these criteria through Hidden Markov models and apply them to the comparison of multistate models for the Health Assessment Questionnaire score in psoriatic arthritis. This procedure is straightforward to implement in the R package ‘msm’. Copyright © 2015 John Wiley & Sons, Ltd.     

Laterality of central venous sampling: lack of effect on the accuracy of intraoperative parathyroid hormone monitoring

Background

The purpose of this study was to determine if laterality of internal jugular vein (IJV) sampling affects the accuracy of intraoperative parathyroid hormone (PTH) monitoring during parathyroidectomy for primary hyperparathyroidism.

Methods

In this study, 109 patients underwent parathyroidectomy (82 with unilateral disease, 27 with multigland disease). PTH samples were taken from both the left and the right IJV at these time points: preincision (baseline) and then at 5, 10, and, in selected patients, 20 minutes after excision. The Miami criterion was used to determine operative success.

Results

In all 109 patients combined, the mean decreases in intraoperative PTH levels were 73.8 ± 22.2% for the left IJV and 71.9 ± 23.0% for the right IJV (P = .22). The Miami criterion was met in 105 patients: in 100 (95%) left IJV samples and 99 (94%) right IJV samples (P = 1.00).

Conclusions

No difference was found in the accuracy of intraoperative PTH monitoring between patients' left and right IJV samples. Central venous laterality did not affect fulfillment of the Miami criterion.     

An evaluation of the proposed DSM-5 alcohol use disorder criteria using Australian national data

Aims To evaluate the proposed revisions to the DSM‐IV alcohol use disorder criteria using epidemiological data. Design, setting and participants Data came from the 1997 Australian National Survey of Mental Health and Well‐Being. The sample consisted of 10 641 participants aged 18 years and over. Measurements Alcohol use disorders were assessed using a revised version of the CIDI version 2.0. Alcohol use disorders were assessed in all respondents who indicated that they had used alcohol more than 12 times in the previous 12 months (n = 7746). Findings The proposed introduction of a single alcohol use disorder was supported by confirmatory factor analysis (CFA). DSM‐5 criteria were all indicators of a single underlying disorder. Under DSM‐5, the prevalence of alcohol use disorders would increase by 61.7% when compared with those diagnosed under DSM‐IV. When investigating the most appropriate diagnostic threshold, the 3+ threshold maximized agreement between DSM‐IV and DSM‐5 diagnoses, and produced similar prevalence estimates to those yielded by DSM‐IV. Item response theory (IRT) analyses supported the removal of the legal criterion while provided equivocal results for the craving criterion. Conclusions Under the proposed DSM‐IV revisions for alcohol use disorders, estimates of the prevalence in the general population would increase substantially. Whereas evidence supports some of the revisions such as a single underlying disorder, others such as the 2+ threshold for diagnosis of alcohol use disorder and the inclusion of a ‘craving’ criterion may be problematic.