Modulation Techniques for Multi-Phase Converters and Control Strategies for Multi-Phase Electric Drives

The ever-increasing spread of automation in industry puts the electrical engineer in a central role as a promoter of technological development in a sector such as the use of electricity, which is the basis of all the machinery and productive processes. Moreover the spread of drives for motor control and static converters with structures ever more complex, places the electrical engineer to face new challenges whose solution has as critical elements in the implementation of digital control techniques with the requirements of inexpensiveness and efficiency of the final product. The successfully application of solutions using non-conventional static converters awake an increasing interest in science and industry due to the promising opportunities. However, in the same time, new problems emerge whose solution is still under study and debate in the scientific community During the Ph.D. course several themes have been developed that, while obtaining the recent and growing interest of scientific community, have much space for the development of research activity and for industrial applications. The first area of research is related to the control of three phase induction motors with high dynamic performance and the sensorless control in the high speed range. The management of the operation of induction machine without position or speed sensors awakes interest in the industrial world due to the increased reliability and robustness of this solution combined with a lower cost of production and purchase of this technology compared to the others available in the market. During this dissertation control techniques will be proposed which are able to exploit the total dc link voltage and at the same time capable to exploit the maximum torque capability in whole speed range with good dynamic performance. The proposed solution preserves the simplicity of tuning of the regulators. Furthermore, in order to validate the effectiveness of presented solution, it is assessed in terms of performance and complexity and compared to two other algorithm presented in literature. The feasibility of the proposed algorithm is also tested on induction motor drive fed by a matrix converter. Another important research area is connected to the development of technology for vehicular applications. In this field the dynamic performances and the low power consumption is one of most important goals for an effective algorithm. Towards this direction, a control scheme for induction motor that integrates within a coherent solution some of the features that are commonly required to an electric vehicle drive is presented. The main features of the proposed control scheme are the capability to exploit the maximum torque in the whole speed range, a weak dependence on the motor parameters, a good robustness against the variations of the dc-link voltage and, whenever possible, the maximum efficiency. The second part of this dissertation is dedicated to the multi-phase systems. This technology, in fact, is characterized by a number of issues worthy of investigation that make it competitive with other technologies already on the market. Multiphase systems, allow to redistribute power at a higher number of phases, thus making possible the construction of electronic converters which otherwise would be very difficult to achieve due to the limits of present power electronics. Multiphase drives have an intrinsic reliability given by the possibility that a fault of a phase, caused by the possible failure of a component of the converter, can be solved without inefficiency of the machine or application of a pulsating torque. The control of the magnetic field spatial harmonics in the air-gap with order higher than one allows to reduce torque noise and to obtain high torque density motor and multi-motor applications. In one of the next chapters a control scheme able to increase the motor torque by adding a third harmonic component to the air-gap magnetic field will be presented. Above the base speed the control system reduces the motor flux in such a way to ensure the maximum torque capability. The presented analysis considers the drive constrains and shows how these limits modify the motor performance. The multi-motor applications are described by a well-defined number of multiphase machines, having series connected stator windings, with an opportune permutation of the phases these machines can be independently controlled with a single multi-phase inverter. In this dissertation this solution will be presented and an electric drive consisting of two five-phase PM tubular actuators fed by a single five-phase inverter will be presented. Finally the modulation strategies for a multi-phase inverter will be illustrated. The problem of the space vector modulation of multiphase inverters with an odd number of phases is solved in different way. An algorithmic approach and a look-up table solution will be proposed. The inverter output voltage capability will be investigated, showing that the proposed modulation strategy is able to fully exploit the dc input voltage either in sinusoidal or non-sinusoidal operating conditions. All this aspects are considered in the next chapters. In particular, Chapter 1 summarizes the mathematical model of induction motor. The Chapter 2 is a brief state of art on three-phase inverter. Chapter 3 proposes a stator flux vector control for a three- phase induction machine and compares this solution with two other algorithms presented in literature. Furthermore, in the same chapter, a complete electric drive based on matrix converter is presented. In Chapter 4 a control strategy suitable for electric vehicles is illustrated. Chapter 5 describes the mathematical model of multi-phase induction machines whereas chapter 6 analyzes the multi-phase inverter and its modulation strategies. Chapter 7 discusses the minimization of the power losses in IGBT multi-phase inverters with carrier-based pulse width modulation. In Chapter 8 an extended stator flux vector control for a seven-phase induction motor is presented. Chapter 9 concerns the high torque density applications and in Chapter 10 different fault tolerant control strategies are analyzed. Finally, the last chapter presents a positioning multi-motor drive consisting of two PM tubular five-phase actuators fed by a single five-phase inverter.

Climate change and the tourism sector: the clean development mechanism, a market instrument under the Kyoto Protocol to achieve multiple objectives

The main objective of this research is to demonstrate that the Clean Development Mechanism (CDM), an instrument created under a global international treaty, can achieve multiple objectives beyond those for which it has been established. As such, while being already a powerful tool to contribute to the global fight against climate change, the CDM can also be successful if applied to different sectors not contemplated before. In particular, this research aimed at demonstrating that a wider utilization of the CDM in the tourism sector can represent an innovative way to foster sustainable tourism and generate additional benefits. The CDM was created by Article 12 of the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) and represents an innovative tool to reduce greenhouse gases emissions through the implementation of mitigation activities in developing countries which generate certified emission reductions (CERs), each of them equivalent to one ton of CO2 not emitted in the atmosphere. These credits can be used for compliance reasons by industrialized countries in achieving their reduction targets. The logic path of this research begins with an analysis of the scientific evidences of climate change and its impacts on different economic sectors including tourism and it continues with a focus on the linkages between climate and the tourism sector. Then, it analyses the international responses to the issue of climate change and the peculiar activities in the international arena addressing climate change and the tourism sector. The concluding part of the work presents the objectives and achievements of the CDM and its links to the tourism sector by considering case studies of existing projects which demonstrate that the underlying question can be positively answered. New opportunities for the tourism sector are available.

Optimization of bioenergy solutions at different farm scales

RAF is a bio-energetic descriptive model integrates with MAD model to support Integrated Farm Management. RAF model aimed to enhancing economical, social and environmental sustainability of farm production in terms of energy via convert energy crops and animal manure to biogas and digestate (bio-fertilizers) by anaerobic digestion technologies, growing and breeding practices. The user defines farm structure in terms of present crops, livestock and market prices and RAF model investigates the possibilities of establish on-farm biogas system (different anaerobic digestion technologies proposed for different scales of farms in terms of energy requirements) according to budget and sustainability constraints to reduce the dependence on fossil fuels. The objective function of RAF (Z) is optimizing the total net income of farm (maximizing income and minimizing costs) for whole period which is considered by the analysis. The main results of this study refers to the possibility of enhancing the exploitation of the available Italian potentials of biogas production from on-farm production of energy crops and livestock manure feedstock by using the developed mathematical model RAF integrates with MAD to presents reliable reconcile between farm size, farm structure and on-farm biogas systems technologies applied to support selection, applying and operating of appropriate biogas technology at any farm under Italian conditions.

A farm-level programming model to compare the atmospheric impact of conventional and organic farming

A model is developed to represent the activity of a farm using the method of linear programming. Two are the main components of the model, the balance of soil fertility and the livestock nutrition. According to the first, the farm is supposed to have a total requirement of nitrogen, which is to be accomplished either through internal sources (manure) or through external sources (fertilisers). The second component describes the animal husbandry as having a nutritional requirement which must be satisfied through the internal production of arable crops or the acquisition of feed from the market. The farmer is supposed to maximise total net income from the agricultural and the zoo-technical activities by choosing one rotation among those available for climate and acclivity. The perspective of the analysis is one of a short period: the structure of the farm is supposed to be fixed without possibility to change the allocation of permanent crops and the amount of animal husbandry. The model is integrated with an environmental module that describes the role of the farm within the carbon-nitrogen cycle. On the one hand the farm allows storing carbon through the photosynthesis of the plants and the accumulation of carbon in the soil; on the other some activities of the farm emit greenhouse gases into the atmosphere. The model is tested for some representative farms of the Emilia-Romagna region, showing to be capable to give different results for conventional and organic farming and providing first results concerning the different atmospheric impact. Relevant data about the representative farms and the feasible rotations are extracted from the FADN database, with an integration of the coefficients from the literature.

Development and application of an analytical method for the determination of total atmospheric biogenic non-methane organic carbon

Ein wesentlicher Anteil an organischem Kohlenstoff, der in der Atmosphäre vorhanden ist, wird als leichtflüchtige organische Verbindungen gefunden. Diese werden überwiegend durch die Biosphäre freigesetzt. Solche biogenen Emissionen haben einen großen Einfluss auf die chemischen und physikalischen Eigenschaften der Atmosphäre, indem sie zur Bildung von bodennahem Ozon und sekundären organischen Aerosolen beitragen. Um die Bildung von bodennahem Ozon und von sekundären organischen Aerosolen besser zu verstehen, ist die technische Fähigkeit zur genauen Messung der Summe dieser flüchtigen organischen Substanzen notwendig. Häufig verwendete Methoden sind nur auf den Nachweis von spezifischen Nicht-Methan-Kohlenwasserstoffverbindungen fokussiert. Die Summe dieser Einzelverbindungen könnte gegebenenfalls aber nur eine Untergrenze an atmosphärischen organischen Kohlenstoffkonzentrationen darstellen, da die verfügbaren Methoden nicht in der Lage sind, alle organischen Verbindungen in der Atmosphäre zu analysieren. Einige Studien sind bekannt, die sich mit der Gesamtkohlenstoffbestimmung von Nicht-Methan-Kohlenwasserstoffverbindung in Luft beschäftigt haben, aber Messungen des gesamten organischen Nicht-Methan-Verbindungsaustauschs zwischen Vegetation und Atmosphäre fehlen. Daher untersuchten wir die Gesamtkohlenstoffbestimmung organische Nicht-Methan-Verbindungen aus biogenen Quellen. Die Bestimmung des organischen Gesamtkohlenstoffs wurde durch Sammeln und Anreichern dieser Verbindungen auf einem festen Adsorptionsmaterial realisiert. Dieser erste Schritt war notwendig, um die stabilen Gase CO, CO2 und CH4 von der organischen Kohlenstofffraktion zu trennen. Die organischen Verbindungen wurden thermisch desorbiert und zu CO2 oxidiert. Das aus der Oxidation entstandene CO2 wurde auf einer weiteren Anreicherungseinheit gesammelt und durch thermische Desorption und anschließende Detektion mit einem Infrarot-Gasanalysator analysiert. Als große Schwierigkeiten identifizierten wir (i) die Abtrennung von CO2 aus der Umgebungsluft von der organischen Kohlenstoffverbindungsfaktion während der Anreicherung sowie (ii) die Widerfindungsraten der verschiedenen Nicht-Methan-Kohlenwasserstoff-verbindungen vom Adsorptionsmaterial, (iii) die Wahl des Katalysators sowie (iiii) auftretende Interferenzen am Detektor des Gesamtkohlenstoffanalysators. Die Wahl eines Pt-Rd Drahts als Katalysator führte zu einem bedeutenden Fortschritt in Bezug auf die korrekte Ermittlung des CO2-Hintergrund-Signals. Dies war notwendig, da CO2 auch in geringen Mengen auf der Adsorptionseinheit während der Anreicherung der leichtflüchtigen organischen Substanzen gesammelt wurde. Katalytische Materialien mit hohen Oberflächen stellten sich als unbrauchbar für diese Anwendung heraus, weil trotz hoher Temperaturen eine CO2-Aufnahme und eine spätere Abgabe durch das Katalysatormaterial beobachtet werden konnte. Die Methode wurde mit verschiedenen leichtflüchtigen organischen Einzelsubstanzen sowie in zwei Pflanzenkammer-Experimenten mit einer Auswahl an VOC-Spezies getestet, die von unterschiedlichen Pflanzen emittiert wurden. Die Pflanzenkammer-messungen wurden durch GC-MS und PTR-MS Messungen begleitet. Außerdem wurden Kalibrationstests mit verschiedenen Einzelsubstanzen aus Permeations-/Diffusionsquellen durchgeführt. Der Gesamtkohlenstoffanalysator konnte den tageszeitlichen Verlauf der Pflanzenemissionen bestätigen. Allerdings konnten Abweichungen für die Mischungsverhältnisse des organischen Gesamtkohlenstoffs von bis zu 50% im Vergleich zu den begleitenden Standardmethoden beobachtet werden.

International survey of primary and revision total knee replacement

Purpose Total knee arthroplasty (TKA) is currently the international standard of care for treating degenerative and rheumatologic knee joint disease, as well as certain knee joint fractures. We sought to answer the following three research questions: (1) What is the international variance in primary and revision TKA rates around the world? (2) How do patient demographics (e.g., age, gender) vary internationally? (3) How have the rates of TKA utilization changed over time? Methods The survey included 18 countries with a total population of 755 million, and an estimated 1,324,000 annual primary and revision total knee procedures. Ten national inpatient databases were queried for this study from Canada, the United States, Finland, France, Germany, Italy, the Netherlands, Portugal, Spain, and Switzerland. Inpatient data were also compared with published registry data for eight countries with operating arthroplasty registers (Denmark, England & Wales, Norway, Romania, Scotland, Sweden, Australia, and New Zealand). Results The average and median rate of primary and revision (combined) total knee replacement was 175 and 149 procedures/100,000 population, respectively, and ranged between 8.8 and 234 procedures/100,000 population. We observed that the procedure rate significantly increased over time for the countries in which historical data were available. The compound annual growth in the incidence of TKA ranged by country from 5.3% (France) to 17% (Portugal). We observed a nearly 27-fold range of TKA utilization rates between the 18 different countries included in the survey. Conclusion It is apparent from the results of this study that the demand for TKA has risen substantially over the past decade in countries around the world.

Ankle arthrodesis versus total ankle replacement: how do I decide?

Taking into account numerous individual criteria, the correct indication substantially influences the outcome of patients with end-stage ankle arthritis treated by ankle arthrodesis or total ankle replacement. The purpose of this report is to assist the foot and ankle surgeon or orthopedic surgeon involved in choosing ankle arthrodesis or total ankle replacement in decision-making. Balancing the criteria that are discussed in consideration of the recent relevant literature and evidence available, the surgeon is directed to the correct individual decision.

The Permanent Income Hypothesis: A Test on Czech Privatisation

Since the late eighties, economists have been regarding the transition from command to market economies in Central and Eastern Europe with intense interest. In addition to studying the transition per se, they have begun using the region as a testing ground on which to investigate the validity of certain classic economic propositions. In his research, comprising three articles written in English and totalling 40 pages, Mr. Hanousek uses the so-called "Czech national experiment" (voucher privatisation scheme) to test the permanent income hypothesis (PIH). He took as his inspiration Kreinin's recommendation: "Since data concerning the behaviour of windfall income recipients is relatively scanty, and since such data can constitute an important test of the permanent income hypothesis, it is of interest to bring to bear on the hypothesis whatever information is available". Mr. Hanousek argues that, since the transfer of property to Czech citizens from 1992 to 1994 through the voucher scheme was not anticipated, it can be regarded as windfall income. The average size of the windfall was more than three month's salary and over 60 percent of the Czech population received this unexpected income. Furthermore, there are other reasons for conducting such an analysis in the Czech Republic. Firstly, the privatisation process took place quickly. Secondly, both the economy and consumer behaviour have been very stable. Thirdly, out of a total population of 10 million Czech citizens, an astonishing 6 million, that is, virtually every household, participated in the scheme. Thus Czech voucher privatisation provides a sample for testing the PIH almost equivalent to a full population, thus avoiding problems with the distribution of windfalls. Compare this, for instance with the fact that only 4% of the Israeli urban population received personal restitution from Germany, while the number of veterans who received the National Service Life Insurance Dividends amounted to less than 9% of the US population and were concentrated in certain age groups. But to begin with, Mr. Hanousek considers the question of whether the public percieves the transfer from the state to individual as an increase in net wealth. It can be argued that the state is only divesting itself of assets that would otherwise provide a future source of transfers. According to this argument, assigning these assets to individuals creates an offsetting change in the present value of potential future transfers so that individuals are no better off after the transfer. Mr. Hanousek disagrees with this approach. He points out that a change in the ownership of inefficient state-owned enterprises should lead to higher efficiency, which alone increases the value of enterprises and creates a windfall increase in citizens' portfolios. More importantly, the state and individuals had very different preferences during the transition. Despite government propaganda, it is doubtful that citizens of former communist countries viewed government-owned enterprises as being operated in the citizens' best interest. Moreover, it is unlikely that the public fully comprehended the sophisticated links between the state budget, state-owned enterprises, and transfers to individuals. Finally, the transfers were not equal across the population. Mr. Hanousek conducted a survey on 1263 individuals, dividing them into four monthly earnings categories. After determining whether the respondent had participated in the voucher process, he asked those who had how much of what they received from voucher privatisation had been (a) spent on goods and services, (b) invested elsewhere, (c) transferred to newly emerging pension funds, (d) given to a family member, and (e) retained in their original form as an investment. Both the mean and the variance of the windfall rise with income. He obtained similar results with respect to education, where the mean (median) windfall for those with a basic school education was 13,600 Czech Crowns (CZK), a figure that increased to 15,000 CZK for those with a high school education without exams, 19,900 CZK for high school graduates with exams, and 24,600 CZK for university graduates. Mr. Hanousek concludes that it can be argued that higher income (and better educated) groups allocated their vouchers or timed the disposition of their shares better. He turns next to an analysis of how respondents reported using their windfalls. The key result is that only a relatively small number of individuals reported spending on goods. Overall, the results provide strong support for the permanent income hypothesis, the only apparent deviation being the fact that both men and women aged 26 to 35 apparently consume more than they should if the windfall were annuitised. This finding is still fully consistent with the PIH, however, if this group is at a stage in their life-cycle where, without the windfall, they would be borrowing to finance consumption associated with family formation etc. Indeed, the PIH predicts that individuals who would otherwise borrow to finance consumption would consume the windfall up to the level equal to the annuitised fraction of the increase in lifetime income plus the full amount of the previously planned borrowing for consumption. Greater consumption would then be financed, not from investing the windfall, but from avoidance of future repayment obligations for debts that would have been incurred without the windfall.

Accuracy considerations in navigated cup placement for total hip arthroplasty

Computer assisted orthopaedic surgery (CAOS) technology has recently been introduced to overcome problems resulting from acetabular component malpositioning in total hip arthroplasty. Available navigation modules can conceptually be categorized as computer tomography (CT) based, fluoroscopy based, or image-free. The current study presents a comprehensive accuracy analysis on the computer assisted placement accuracy of acetabular cups. It combines analyses using mathematical approaches, in vitro testing environments, and an in vivo clinical trial. A hybrid navigation approach combining image-free with fluoroscopic technology was chosen as the best compromise to CT-based systems. It introduces pointer-based digitization for easily assessable points and bi-planar fluoroscopy for deep-seated landmarks. From the in vitro data maximum deviations were found to be 3.6 degrees for inclination and 3.8 degrees for anteversion relative to a pre-defined test position. The maximum difference between intraoperatively calculated cup inclination and anteversion with the postoperatively measured position was 4 degrees and 5 degrees, respectively. These data coincide with worst cases scenario predictions applying a statistical simulation model. The proper use of navigation technology can reduce variability of cup placement well within the surgical safe zone. Surgeons have to concentrate on a variety of error sources during the procedure, which may explain the reported strong learning curves for CAOS technologies.

Clinical decision support capabilities of commercially-available clinical information systems.

BACKGROUND: The most effective decision support systems are integrated with clinical information systems, such as inpatient and outpatient electronic health records (EHRs) and computerized provider order entry (CPOE) systems. Purpose The goal of this project was to describe and quantify the results of a study of decision support capabilities in Certification Commission for Health Information Technology (CCHIT) certified electronic health record systems. METHODS: The authors conducted a series of interviews with representatives of nine commercially available clinical information systems, evaluating their capabilities against 42 different clinical decision support features. RESULTS: Six of the nine reviewed systems offered all the applicable event-driven, action-oriented, real-time clinical decision support triggers required for initiating clinical decision support interventions. Five of the nine systems could access all the patient-specific data items identified as necessary. Six of the nine systems supported all the intervention types identified as necessary to allow clinical information systems to tailor their interventions based on the severity of the clinical situation and the user's workflow. Only one system supported all the offered choices identified as key to allowing physicians to take action directly from within the alert. Discussion The principal finding relates to system-by-system variability. The best system in our analysis had only a single missing feature (from 42 total) while the worst had eighteen.This dramatic variability in CDS capability among commercially available systems was unexpected and is a cause for concern. CONCLUSIONS: These findings have implications for four distinct constituencies: purchasers of clinical information systems, developers of clinical decision support, vendors of clinical information systems and certification bodies.

Short-term Functional and Patient Outcome of the Bi-cruciate Stabilized Total Knee Replacement: Prospective Consecutive Case-series

Background: Total knee replacement is the gold standard treatment for patients suffering from advanced symptomatic knee osteoarthritis. The main goals of knee prosthetics are pain reduction and restoration of knee motion. The new prostheses on the market such as the bi-cruciate stabilized Journey knee implant, promise a reconstruction of total physiological function of the knee with physiological range of motion and therefore high patient satisfaction. Purpose: The aim of this study was to analyze the patient-based Knee Injury and Osteoarthritis Outcome Score (KOOS) outcome after total knee replacement with new physiological bi-cruciate stabilized Journey knee prosthesis. Study Design: Prospective, consecutive case-series. Patients: Ninety nine patients, who received bi-cruciate stabilized Journey total knee prosthesis between January 1st 2006 and May 31st 2012, were included in the study. A single surgeon operated all patients. There were 61.1% females and the overall average age was 68 years (range 41-83 years). Left knee was replaced in 55.6%. Methods: The patients filled in KOO’s questionnaire pre- and 1 year postoperative. Range of motion (ROM) was studied preoperatively and at 1-year follow-ups. The pre- and postoperative KOOS subscores and ROM were compared using the Wilcoxon signed rank test. Results: There are significant improvements of all KOOS subscores. Ninety percent of patients have reached the minimum clinically relevant 10 points in symptoms, 94.5% in pain, 94.5% in activities of daily living, 84.9% in sport and recreation, and 90% in knee related quality of life. Postoperative, the average passive ROM was 131° (range 110-145°) and the average active ROM 122° (range 105-135°). The highest correlation coefficients ROM and the KOOS were observed for the activity and pain subscores. Very low or no correlation was seen for the sport subscore. Conclusions: Bi-cruciate stabilized knee prosthetic offers a solid outcome 1 year postoperative based on the results measured with the KOOS evaluation questionnaire. The Patients showed a generalized improvement in all domains measured in the KOOS of minimally 35, and up to over 52 points, what can be described as statistically significant. Patients described the level of functionality close to double compared to the preoperative status.

Cystatin C is independently associated with total and cardiovascular mortality in individuals undergoing coronary angiography. The Ludwigshafen Risk and Cardiovascular Health (LURIC) study.

AIMS Cystatin C is a well established marker of kidney function. There is evidence that cystatin C concentrations are also associated with mortality. The present analysis prospectively evaluated the associations of cystatin C with all-cause and cardiovascular (CV) mortality in a well-characterized cohort of persons undergoing angiography, but without overt renal insufficiency. METHODS Cystatin C was available in 2998 persons (mean age: 62.7 ± 10.5 years; 30.3% women). Of those 2346 suffered from coronary artery disease (CAD) and 652 (controls) did not. Creatinine (mean ± SD: 83.1 ± 47.8 vs. 74.1 ± 24.7 μmol/L, p = 0.036) but not Cystatin C (mean ± SD: 1.02 ± 0.44 vs. 0.92 ± 0.26 mg/L, p = 0.065) was significantly higher in patients with CAD. After a median follow-up of 9.9 years, in total 898 (30%) deaths occurred, 554 (18.5%) due to CV disease and 326 (10.9%) due to non-CV causes. Multivariable-adjusted Cox analysis (adjusting for eGFR and established cardiovascular risk factors, lipid lowering therapy, angiographic coronary artery disease, and C-reactive protein) revealed that patients in the highest cystatin C quartile were at an increased risk for all-cause (hazard ratio (HR) 1.93, 95% CI 1.50-2.48) and CV mortality (HR 2.05 95% CI 1.48-2.84) compared to those in the lowest quartile. The addition of cystatin C to a model consisting of established cardiovascular risk factors increased the area under the receiver-operating characteristic curve for CV and all-cause mortality, but the difference was statistically not significant. However, reclassification analysis revealed significant improvement by addition of cystatin C for CV and all-cause mortality (p < 0.001), respectively. CONCLUSION The concentration of cystatin C is strongly associated with long-term all-cause and cardiovascular mortality in patients referred to coronary angiography, irrespective of creatinine-based renal function.

German Total Ankle Replacement Register of the German Foot and Ankle Society (D. A. F.) - presentation of design and reliability of the data as well as first results

INTRODUCTION Even though arthroplasty of the ankle joint is considered to be an established procedure, only about 1,300 endoprostheses are implanted in Germany annually. Arthrodeses of the ankle joint are performed almost three times more often. This may be due to the availability of the procedure - more than twice as many providers perform arthrodesis - as well as the postulated high frequency of revision procedures of arthroplasties in the literature. In those publications, however, there is often no clear differentiation between revision surgery with exchange of components, subsequent interventions due to complications and subsequent surgery not associated with complications. The German Orthopaedic Foot and Ankle Association's (D. A. F.) registry for total ankle replacement collects data pertaining to perioperative complications as well as cause, nature and extent of the subsequent interventions, and postoperative patient satisfaction. MATERIAL AND METHODS The D. A. F.'s total ankle replacement register is a nation-wide, voluntary registry. After giving written informed consent, the patients can be added to the database by participating providers. Data are collected during hospital stay for surgical treatment, during routine follow-up inspections and in the context of revision surgery. The information can be submitted in paper-based or online formats. The survey instruments are available as minimum data sets or scientific questionnaires which include patient-reported outcome measures (PROMs). The pseudonymous clinical data are collected and evaluated at the Institute for Evaluative Research in Medicine, University of Bern/Switzerland (IEFM). The patient-related data remain on the register's module server in North Rhine-Westphalia, Germany. The registry's methodology as well as the results of the revisions and patient satisfaction for 115 patients with a two year follow-up period are presented. Statistical analyses are performed with SAS™ (Version 9.4, SAS Institute, Inc., Cary, NC, USA). RESULTS About 2½ years after the register was launched there are 621 datasets on primary implantations, 1,427 on follow-ups and 121 records on re-operation available. 49 % of the patients received their implants due to post-traumatic osteoarthritis, 27 % because of a primary osteoarthritis and 15 % of patients suffered from a rheumatic disease. More than 90 % of the primary interventions proceeded without complications. Subsequent interventions were recorded for 84 patients, which corresponds to a rate of 13.5 % with respect to the primary implantations. It should be noted that these secondary procedures also include two-stage procedures not due to a complication. "True revisions" are interventions with exchange of components due to mechanical complications and/or infection and were present in 7.6 % of patients. 415 of the patients commented on their satisfaction with the operative result during the last follow-up: 89.9 % of patients evaluate their outcome as excellent or good, 9.4 % as moderate and only 0.7 % (3 patients) as poor. In these three cases a component loosening or symptomatic USG osteoarthritis was present. Two-year follow-up data using the American Orthopedic Foot and Ankle Society Ankle and Hindfoot Scale (AOFAS-AHS) are already available for 115 patients. The median AOFAS-AHS score increased from 33 points preoperatively to more than 80 points three to six months postoperatively. This increase remained nearly constant over the entire two-year follow-up period. CONCLUSION Covering less than 10 % of the approximately 240 providers in Germany and approximately 12 % of the annually implanted total ankle-replacements, the D. A. F.-register is still far from being seen as a national registry. Nevertheless, geographical coverage and inclusion of "high-" (more than 100 total ankle replacements a year) and "low-volume surgeons" (less than 5 total ankle replacements a year) make the register representative for Germany. The registry data show that the number of subsequent interventions and in particular the "true revision" procedures are markedly lower than the 20 % often postulated in the literature. In addition, a high level of patient satisfaction over the short and medium term is recorded. From the perspective of the authors, these results indicate that total ankle arthroplasty - given a correct indication and appropriate selection of patients - is not inferior to an ankle arthrodesis concerning patients' satisfaction and function. First valid survival rates can be expected about 10 years after the register's start.

Labour Market Prospects of Swiss Career Entrants after Completion of Vocational Education and Training

This study seeks to find the reasons for the rising risk of unemployment for people who have completed basic vocational education and training (VET) in Switzerland. We focus on the long-term structural shift on the demand side of the labour market and its consequences for new entrants? chances of employment in the labour force. A detailed analysis of the development of vacancies for such ?career entrants? in the time period 2001 to 2011 suggests that neither a growing occupational mismatch nor a general shift in the level of education to the disadvantage of workers with vocational education can be made responsible for the rising unemployment of labour market entrants. Instead, the available evidence indicates that a diminishing part of the vacancies suited for VET graduates remains open to entrants because of the increasing job requirements with regard to work experience and further education. Basic vocational education and training alone is increasingly less a guarantee for a smooth entry into the working world.

Management of pelvic discontinuity in revision total hip arthroplasty: a review of the literature

Pelvic discontinuity is a complex problem in revision total hip arthroplasty. Although rare, the incidence is likely to increase due to the ageing population and the increasing number of total hip arthroplasties being performed. The various surgical options available to solve this problem include plating, massive allografts, reconstruction rings, custom triflanged components and tantalum implants. However, the optimal solution remains controversial. None of the known methods completely solves the major obstacles associated with this problem, such as restoration of massive bone loss, implant failure in the short- and long-term and high complication rates. This review discusses the diagnosis, decision making, and treatment options of pelvic discontinuity in revision total hip arthroplasty.