242 research outputs found
How to prevent dislocation after revision total hip arthroplasty: a systematic review of the risk factors and a focus on treatment options
Get PDFAbstract Background Dislocation represents the most common complication after revision total hip arthroplasty (rTHA). Understanding risk factors for dislocation has a great clinical relevance for every hip surgeon in order to consider all surgical options for effective planning. The aim of this systematic review was to answer two main questions—(1) what are the risk factors for instability after rTHA? and (2) what are the best preoperative assessments and surgical options to avoid dislocation after rTHA? Materials and methods Scientific databases were accessed to identify papers dealing with prevention and treatment of dislocation after rTHA. We performed a search using the keywords ‘revision hip arthroplasty’ and ‘dislocation’, ‘instability’, ‘outcome’, ‘failure’, ‘treatment’. After removal of duplicates and exclusion of works published in different languages, 33 articles were reviewed completely. Results Risk factors were analysed in order to establish the most relevant and evidence-based treatments available in the current literature. Conclusions The risk of dislocation after rTHA can be reduced using some precautions inferred from the literature. The use of a larger femoral and acetabular component, elevated rim liner and dual mobility implants can significantly reduce the risk of dislocation after rTHA. However, care must be taken regarding patient-related risk factors since these cannot be addressed and modified. Hence, a complete evaluation of risk factors should be performed for each patient and procedure before starting rTHA
Experimental study of blockage of random waves by counter currents
No full textFrom February to April 1999, wave-blocking experiments have been conducted at the Laboratory of Fluid Mechanics of the Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands as a part of the Ph.D. research of I.K. Suastika. Wave blocking is a special case of wave-current interaction. It can occur when waves are propagating against a counter of which the velocity is increasing in the wave propagation direction. Blocking occurs where the intrinsic wave group velocity (cg) is equal, but opposite in sign, to the mean velocity. The counter current velocity at the blocking point is called the blocking velocity. In this thesis the experiments are described and a part of the measurement data is analysed, especially the data concerning the blocking of irregular waves. The first objective of this research is to acquire quantitative data on partial and complete blocking. The second objective is to develop a model for wave blocking. The model should describe the wave field in a situation where blocking occurs. 80, for a given incoming (generated) wave field and counter current, the model should describe the wave field up to and at the blocking point. (And beyond, in cases of partial blocking.)Hydraulic EngineeringCivil Engineering and Geoscience
Validity and reliability of the Greek version of the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form
No full textBackground: The aim of our study is to prove the validity and reliability of the Greek translated version of the self-report section of the American Shoulder and Elbow Surgeons (ASES) questionnaire. Methods: A total of 108 patients with various shoulder disorders were evaluated at two different orthopedic centers. All patients answered the Greek ASES questionnaire as well as the previously validated Greek version of the Disability Arm Shoulder and Hand score. Three days after the first evaluation, a subgroup of 40 individuals was randomly selected to complete again the Greek ASES text to prove its reliability, after the test-retest procedure. Reliability was tested with Cronbach's alpha, stability by calculating the intraclass correlation coefficient and by Blant Altman plot and structural validity with the confirmatory factor analysis. Results: The internal consistency of the ASES functional score and the ASES total score was 0.925 and 0.750 respectively. The intraclass correlation coefficient between initial assessment and reassessment of the ASES functional and total score was 0.951 and 0.938 (P < .001), respectively. The correlation coefficients correlation between the ASES functional and total scores with DASH total score were −0.881 and −0.759 (P < .001), respectively. Conclusions: The Greek ASES version proved to be equivalent to the English original version in evaluating different shoulder disorders in the Greek population. © 2021 The Author
Experimental study of blockage of monochromatic waves by counter currents
No full textBlockage of waves by a current can occur if waves are propagating on a spatially varying opposing current in which the velocity is increasing in the wave propagation direction. The ongoing waves become shorter and steeper while they are propagating against the current. Blocking occurs at the location where the opposing current strength is the same as the effective wave energy transport velocity, the intrinsic wave group velocity. This implies that upstream of this location, the blocking point, there is no propagation of wave energy. A question that immediately arises is what happens with the ongoing wave energy. The theory suggests that the ongoing waves will break before reaching the blocking point due to steepening of the waves. However, other mechanisms than wave breaking may also play an important role in the wave energy dissipation such as energy dissipations due to wave interactions with the turbulence and due to viscous effects. Another possibility is that the ongoing wave energy may be partially reflected at the blocking point. Some earlier studies (e.g. Long et al [1993]) have reported some evidence of wave reflection in blocking situations. The present study aims to investigate experimentally the phenomena of wave breaking and/or wave reflection in blocking situations. For this purpose a novel experimental arrangement has been designed and implemented in a laboratory flume. Previous laboratory studies utilized a constant discharge (Q) and a varying cross section (A) to obtain a longitudinal velocity gradient. This has the disadvantage that the effects of non-uniform cross-section and non-uniform velocity are mixed. In the present study, it was decided to use a constant cross-section and a non-uniform discharge, to he obtained by withdrawal of water through a perforated false bottom. CONCLUSIONS The fitted model has shown to he capable to reproduce the wave field of monochromatic waves being blocked by a counter current reasonably well, allowing us to discriminate the reflected waves and the incoming waves. However, the model in its present form contains unknown calibration coefficients whose variation requires further study and most likely a reformulation of the dissipation model.Hydraulic EngineeringCivil Engineering and Geoscience
Viscous dissipation of monochromatic waves in still water of finite constant depth in a channel of finite width
No full textEnergy dissipation of water waves propagating in a smooth-walled channel of finite water depth and finite width is mainly due to viscous effects. Providing that the wave length is sufficiently large compared to the water depth and a finite channel width, wave energy is principally dissipated in the boundary layers on the bed and on the walls. Hunt [1952] studied the attenuation of periodic water waves travelling in shallow water in a channel of finite width. In the present study we investigate experimentally the wave attenuation of monochromatic waves travelling in still water of finite constant depth in a channel of finite width. In the experiments, we measured the water surface elevation at a number of locations along the flume. First, Fourier analysis is performed to the surface elevation data, in which the surface elevation is represented as a sum of many harmonic components. This analysis is performed to the surface elevation data obtained at each station, resulting in discrete values of wave amplitudes and phase shifts as function of wave travel distance. Next, the values of wave amplitudes and phase shifts so obtained are modelled by using a wave attenuation model in order to estimate the damping modulus K. Finally, the damping modulus K so determined is compared with that calculated using the formulation of Hunt. CONCLUSION The damping modulus representing the wave attenuation determined from the laboratory measurements of Auke - method gives on average slightly higher values of the damping modulus than the values from the theory by Hunt.Hydraulic EngineeringCivil Engineering and Geoscience
A pilot study to test a method to enhance the turbulence of a water flow in a laboratory flume
No full textIn this report we present some results of a laboratory pilot study which has been conducted to test a method to artificially enhance the turbulence of a water flow in a laboratory flume. The purpose of this test is to provide data which will be used to verify whether the method is suitable for the study of the dissipative effects of turbulence on surface waves. In order to study the dissipative effects of turbulence on the surface waves, it is essential to enhance the turbulent intensity of the flow. On the other hand, it is desirable to enhance the shear rates of mean flow, and to generate turbulence of relatively large length scales. A strong interaction between the turbulent motion and the surface waves might be expected in cases where the turbulent length scale is of the same order as the wave length of the surface waves. In this study, we investigate the feasibility of a method to intensify the turbulence of the flow and to establish larger structures ("turbulence") in the flow of length scale of order of the surface waves wave length. For this purpose, we disturb the flow in the flume of smooth walls by constructing a number of rectangular plates at the bottom of the flume. As first estimates, we use plates of height of about 20 percent of the water depth and width of about 20 percent of the flume width. The plates were fastened at the bottom on two rails by using T-shaped chords. It is possible to adjust the orientation of a particular plate by rotating it around the horizontal part of the T-chord and by rotating the T-chord itself on the rail around its vertical leg. Further, it is possible to adjust the distance between two subsequent plates on the rail. However, once the plates have been fastened on the rails, it is not possible to change their orientation and position during a particular test. In this series of experiments, we measured the flow velocity at a number of measurement points in a cross section of the flume. From the velocity measurement, a number of flow parameters are determined: mean velocity,standard deviation(r.m.s.-value of the velocity fluctuation),lateral shear stress and mean rate of shear. From the same measurement, we determine also the auto-correlation function of the flow velocity at each measurement point. In the analysis, these parameters and the plot of the auto-correlation function determined from the measurement in the presence of the plates are compared with those determined from a reference measurement, that is the measurement in the absence of the plates. CONCLUSIONS 1. The presence of the plates in the flume changes the mean longitudinal flow velocity; a decrease near the bottom and an increase at higher elevations. 2. The increase of turbulent intensity caused by the vertical plates is very much larger in the locations near the bottom, slightly smaller in the locations near the free surface and, over the whole cross section, very much larger than that caused by the tilted plates. 3. The increase of magnitude of the Reynolds stress caused by the vertical plates is larger than that caused by the tilted plates. 4. The increase of mean rates of shear caused by the vertical plates is smaller in the locations at higher elevations and larger in the locations near the bottom than that caused by the tilted plates. 5. The plates do not introduce turbulence of larger time scales.Hydraulic EngineeringCivil Engineering and Geoscience
Reconstruction of medial patellofemoral ligament (MPFL) for post-traumatic patellar instability
No full textLetter to the editor: "evaluation of bone mineral density using DXA and cQCT in postmenopausal patients under thyrotropin suppressive therapy"
No full textPractising critical architecture
No full textI see architecture not as a property of an object, but as a practise. For this project I have looked critically at the origins of an architect's instruments, methods and notions, and hypothesized how changing these could make them more equipped to deal with my personal understandings of contemporary conditions. Main topics include: Bottom-up, participation, logistics, architect as curator, cultivation and public expression.ExplorelabArchitectureArchitecture and The Built Environmen
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