The minimalinvasive direct anterior approach in aseptic cup revision hip arthroplasty: a mid-term follow-up.

INTRODUCTION: The minimally invasive direct anterior approach (DAA) is an established approach for primary total hip arthroplasty (THA). The complication rates in hip revision arthroplasty are much higher in comparison with primary THA. A right positioning of the implants and a soft tissue, especially the abductors spearing approach, is important to get good functional results and low complication rates. The aim of this study was to show the clinical and radiological outcome of isolated revision hip arthroplasty of the cup by using the DAA. MATERIALS AND METHODS: Aseptic cup revisions were carried out in 48 patients using the DAA. A decision to exchange the stem was made intraoperatively in seven cases. Complications, radiological and functional outcome were assessed. All of the data were collected retrospectively. The mean follow-up period was 65 months. RESULTS: In most of the cases the standard DAA was used. A proximal extension was nescessary in 15 patients (31%). The mean cup inclination angle after revision was 44° (min. 25°, max. 62°). Six implants (12.5%) were located outside of the Lewinnek safe zone. The centers of rotation of the revision implants were a mean of 0.6 cm superior (min. 0, max. 2.2 cm) and 0.5 cm lateral (min. 0.2 cm, max 1.2 cm) in comparison with the center of rotation in the healthy hip on the contralateral side. Harris Hip Score improved significantly from 50 to 91 (P = 0.03). Complications noted consisted of two periprosthetic infections (4.2%), one aseptic cup loosening (2.1%), two hematomas requiring revision (4.2%), and one case each of femoral nerve injury, lower-leg venous thrombosis, and pneumonia. No dislocations were observed and there were no cases of heterotopic ossification based on the Brooker classification. No persistent damage of the nervus cutaneus femoris lateralis was found at the follow-up examinations. CONCLUSIONS: The DAA represents a feasible option in hip revision arthroplasty. Anatomic reconstruction of the cup is reproducibly possible. Good medium-term results can also be achieved. Particularly in relation to dislocation, the complication rates are low. Due to the learning curve, the DAA should only be used in hip revision arthroplasty by those with sufficient experience in primary THA. Adequate data regarding stem revisions through the DAA are not available at the moment.

DNA methylation profiling of human chromosomes 6, 20 and 22.

DNA methylation is the most stable type of epigenetic modification modulating the transcriptional plasticity of mammalian genomes. Using bisulfite DNA sequencing, we report high-resolution methylation profiles of human chromosomes 6, 20 and 22, providing a resource of about 1.9 million CpG methylation values derived from 12 different tissues. Analysis of six annotation categories showed that evolutionarily conserved regions are the predominant sites for differential DNA methylation and that a core region surrounding the transcriptional start site is an informative surrogate for promoter methylation. We find that 17% of the 873 analyzed genes are differentially methylated in their 5' UTRs and that about one-third of the differentially methylated 5' UTRs are inversely correlated with transcription. Despite the fact that our study controlled for factors reported to affect DNA methylation such as sex and age, we did not find any significant attributable effects. Our data suggest DNA methylation to be ontogenetically more stable than previously thought.

Bayesian hierarchical response time modelling-A tutorial.

Response time modelling is developing rapidly in the field of psychometrics, and its use is growing in psychology. In most applications, component models for response times are modelled jointly with component models for responses, thereby stabilizing estimation of item response theory model parameters and enabling research on a variety of novel substantive research questions. Bayesian estimation techniques facilitate estimation of response time models. Implementations of these models in standard statistical software, however, are still sparse. In this accessible tutorial, we discuss one of the most common response time models-the lognormal response time model-embedded in the hierarchical framework by van der Linden (2007). We provide detailed guidance on how to specify and estimate this model in a Bayesian hierarchical context. One of the strengths of the presented model is its flexibility, which makes it possible to adapt and extend the model according to researchers' needs and hypotheses on response behaviour. We illustrate this based on three recent model extensions: (a) application to non-cognitive data incorporating the distance-difficulty hypothesis, (b) modelling conditional dependencies between response times and responses, and (c) identifying differences in response behaviour via mixture modelling. This tutorial aims to provide a better understanding of the use and utility of response time models, showcases how these models can easily be adapted and extended, and contributes to a growing need for these models to answer novel substantive research questions in both non-cognitive and cognitive contexts.