P-Values and Power in Orthopedic Research: Myths and Reality

The results of statistical tests in orthopedic studies are typically reported using P-values. If a P-value is smaller than the pre-determined level of significance (eg, < .05), the null hypothesis is rejected in support of the alternative. This automaticity in interpreting statistical results without consideration of the power of the study has been denounced over the years by statisticians, since it can potentially lead to misinterpretation of the study conclusions. In this paper, we review fundamental misconceptions and misinterpretations of P-values and power, along with their connection with confidence intervals, and we provide guidelines to orthopedic researchers for evaluating and reporting study results. We provide real-world orthopedic examples to illustrate the main concepts. Please visit the following https://youtu.be/bdPU4luYmF0 for videos that explain the highlights of the paper in practical terms.     

Anatomically contoured large femoral heads can reduce iliopsoas impingement: A cadaver verification study

While use of large heads in total hip arthroplasty (THA) continues to grow, concerns have been raised regarding anterior hip pain resulting from impingement of the prosthetic head against soft-tissues like the iliopsoas. To address these concerns, a new anatomically contoured head (ACH) was developed. In this study cadaver tests were utilized to show that iliopsoas impingement/tenting caused by conventional heads is significantly relieved with the more rounded and reduced distal profile of the ACH. Thus, the ACH implant may be able to decrease the risk of soft-tissue impingement with conventional heads, particularly in the smaller hip.     

Sample size re-estimation for clinical trials with longitudinal negative binomial counts including time trends

In some diseases, such as multiple sclerosis, lesion counts obtained from magnetic resonance imaging (MRI) are used as markers of disease progression. This leads to longitudinal, and typically overdispersed, count data outcomes in clinical trials. Models for such data invariably include a number of nuisance parameters, which can be difficult to specify at the planning stage, leading to considerable uncertainty in sample size specification. Consequently, blinded sample size re-estimation procedures are used, allowing for an adjustment of the sample size within an ongoing trial by estimating relevant nuisance parameters at an interim point, without compromising trial integrity. To date, the methods available for re-estimation have required an assumption that the mean count is time-constant within patients. We propose a new modeling approach that maintains the advantages of established procedures but allows for general underlying and treatment-specific time trends in the mean response. A simulation study is conducted to assess the effectiveness of blinded sample size re-estimation methods over fixed designs. Sample sizes attained through blinded sample size re-estimation procedures are shown to maintain the desired study power without inflating the Type I error rate and the procedure is demonstrated on MRI data from a recent study in multiple sclerosis.     

Impact of sampling rate on statistical significance for single subject fMRI connectivity analysis

A typical time series in functional magnetic resonance imaging (fMRI) exhibits autocorrelation, that is, the samples of the time series are dependent. In addition, temporal filtering, one of the crucial steps in preprocessing of functional magnetic resonance images, induces its own autocorrelation. While performing connectivity analysis in fMRI, the impact of the autocorrelation is largely ignored. Recently, autocorrelation has been addressed by variance correction approaches, which are sensitive to the sampling rate. In this article, we aim to investigate the impact of the sampling rate on the variance correction approaches. Toward this end, we first derived a generalized expression for the variance of the sample Pearson correlation coefficient (SPCC) in terms of the sampling rate and the filter cutoff frequency, in addition to the autocorrelation and cross‐covariance functions of the time series. Through simulations, we illustrated the importance of the variance correction for a fixed sampling rate. Using the real resting state fMRI data sets, we demonstrated that the data sets with higher sampling rates were more prone to false positives, in agreement with the existing empirical reports. We further demonstrated with single subject results that for the data sets with higher sampling rates, the variance correction strategy restored the integrity of true connectivity.     

SWIM技术治疗后循环大血管闭塞所致急性缺血性卒中的有效性和安全性观察

目的 观察SWIM技术治疗后循环大血管闭塞所致急性缺血性卒中的有效性及安全性。 方法 回顾性分析2017年2月-2018年11月于大连市中心医院采用SWIM技术治疗的后循环大血管闭 塞所致急性缺血性卒中患者的临床资料，评价该技术的疗效和安全性，并分析影响患者预后的因素。 观察指标为术后即刻成功再通（mTICI≥2b）、90 d良好预后（mRS评分≤2分），以及术后24 h任何颅内 出血、90 d全因死亡。 结果 共纳入35例患者，平均年龄66.1±12.1岁，男性26例（74.3%），基线NIHSS评分22（15～34）分。 术后即刻成功再通率为94.3%（33/35），90 d良好预后率为45.7%（16/35），24 h颅内出血率为17.1% （6/35），90 d全因死亡率为37.1%（13/35）。单因素分析显示，基线NIHSS评分较低（P =0.001）、基 线后循环ASPECTS评分较高（P =0.016）、发病至到院时间较短（P =0.039）、发病至再通时间较短 （P =0.047）、血管成功再通率较高（P =0.036）以及饮酒比例较低（P =0.042）与良好预后相关。 结论 使用SWIM技术治疗后循环急性缺血性卒中相对安全、有效。     

大肠癌术后早期肠梗阻的临床特点和治疗

目的探讨大肠癌术后早期肠梗阻的诊断与治疗.方法回顾性分析大肠癌手术424例术后早期肠梗阻32例的临床资料.结果22例经手术探查发现以机械性梗阻占多数(20/22),手术治愈20例,死亡2例,死亡原因均为延误手术时机造成;非手术治愈10例.结论大肠癌手术后早期肠梗阻虽有梗阻症状,但由于术后诸多因素的影响,大多缺乏典型机械性肠梗阻的临床表现,处理应先进行适当时间的非手术治疗,无缓解者再手术.     

存样食物在追查食物中毒源头中的作用

[目的]针对食物中毒事件追查源头的困难局面,探索1种新的食物中毒追查方法。[方法]通过分析各种常见类型食物中毒的潜伏期,结合各种实际情况,探讨存样食物保存的时间和方法。[结果]存样食物至少要保存24h。[结论]这种存样待检方法有其先进性,但仍存在不少问题,需进一步改进。     

新生儿出生信息样本分析

目的:了解和探讨新生儿出生信息的分布态势及规律。方法:对本院2006年1~6月间所有新生儿出生信息进行样本分析。结果:半年间分娩的新生儿共1075例,其中死亡19例,双胞胎15例,以1028例单胎活产新生儿的出生体重、胎龄及产妇年龄作为研究样本进行分析,统计数据与传统意义上的正常胎龄和新生儿体重基本相符,胎龄、体重均值均有所提高。结论:孕产妇的健康状况和新生儿的体质均有所改善,随胎龄的增加,新生儿出生体重亦随之增加,并且,目前新生儿的整体统计体重要大于现有的临床指标,因此,应对现有的临床指标进行适当调整,重新确定低出生体重儿和巨大儿的临床指标。     

急性大血管闭塞性轻型卒中血管内治疗的疗效及安全性观察

目的 观察急性大血管闭塞性轻型卒中患者血管内治疗的疗效及安全性。
方法 回顾性分析2018年1月-2019年5月行血管内治疗的急性大血管闭塞性轻型卒中（NIHSS评分
≤5分）患者的临床资料。观察术后血管成功再通率（mTICI≥2b级）、围手术期并发症、90 d良好预后率
（mRS评分≤2分）等。
结果 共纳入13例患者，平均年龄58.7±14.5岁，男性11例（84.6%）。术后血管成功再通率100%；围
手术期并发症2例，假性动脉瘤1例、无症状性颅内出血1例；90 d良好预后率100%。
结论 急性大血管闭塞性轻型卒中行血管内治疗可能是安全、有效的。