Objective analysis of gait coordination for total knee arthroplasty outcome

Introduction: Coordination is a strategy chosen by the central nervous system to control the movements and maintain stability during gait. Coordinated multi-joint movements require a complex interaction between nervous outputs, biomechanical constraints, and pro-prioception. Quantitatively understanding and modeling gait coordination still remain a challenge. Surgeons lack a way to model and appreciate the coordination of patients before and after surgery of the lower limbs. Patients alter their gait patterns and their kinematic synergies when they walk faster or slower than normal speed to maintain their stability and minimize the energy cost of locomotion. The goal of this study was to provide a dynamical system approach to quantitatively describe human gait coordination and apply it to patients before and after total knee arthroplasty. Methods: A new method of quantitative analysis of interjoint coordination during gait was designed, providing a general model to capture the whole dynamics and showing the kinematic synergies at various walking speeds. The proposed model imposed a relationship among lower limb joint angles (hips and knees) to parameterize the dynamics of locomotion of each individual. An integration of different analysis tools such as Harmonic analysis, Principal Component Analysis, and Artificial Neural Network helped overcome high-dimensionality, temporal dependence, and non-linear relationships of the gait patterns. Ten patients were studied using an ambulatory gait device (Physilog®). Each participant was asked to perform two walking trials of 30m long at 3 different speeds and to complete an EQ-5D questionnaire, a WOMAC and Knee Society Score. Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh. The outcomes of the eight patients undergoing total knee arthroplasty, recorded pre-operatively and post-operatively at 6 weeks, 3 months, 6 months and 1 year were compared to 2 age-matched healthy subjects. Results: The new method provided coordination scores at various walking speeds, ranged between 0 and 10. It determined the overall coordination of the lower limbs as well as the contribution of each joint to the total coordination. The difference between the pre-operative and post-operative coordination values were correlated with the improvements of the subjective outcome scores. Although the study group was small, the results showed a new way to objectively quantify gait coordination of patients undergoing total knee arthroplasty, using only portable body-fixed sensors. Conclusion: A new method for objective gait coordination analysis has been developed with very encouraging results regarding the objective outcome of lower limb surgery.

Validation of the IMPACT-III quality of life questionnaire in Swiss children with inflammatory bowel disease.

BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) frequently manifests during childhood and adolescence. For providing and understanding a comprehensive picture of a patients' health status, health-related quality of life (HRQoL) instruments are an essential complement to clinical symptoms and functional limitations. Currently, the IMPACT-III questionnaire is one of the most frequently used disease-specific HRQoL instrument among patients with IBD. However, there is a lack of studies examining the validation and reliability of this instrument. METHODS: 146 paediatric IBD patients from the multicenter Swiss IBD paediatric cohort study database were included in the study. Medical and laboratory data were extracted from the hospital records. HRQoL data were assessed by means of standardized questionnaires filled out by the patients in a face-to-face interview. RESULTS: The original six IMPACT-III domain scales could not be replicated in the current sample. A principal component analysis with the extraction of four factor scores revealed the most robust solution. The four factors indicated good internal reliability (Cronbach's alpha=.64-.86), good concurrent validity measured by correlations with the generic KIDSCREEN-27 scales and excellent discriminant validity for the dimension of physical functioning measured by HRQoL differences for active and inactive severity groups (p<.001, d=1.04). CONCLUSIONS: This study with Swiss children with IBD indicates good validity and reliability for the IMPACT-III questionnaire. However, our findings suggest a slightly different factor structure than originally proposed. The IMPACT-III questionnaire can be recommended for its use in clinical practice. The factor structure should be further examined in other samples.

Genes mirror geography within Europe.

Understanding the genetic structure of human populations is of fundamental interest to medical, forensic and anthropological sciences. Advances in high-throughput genotyping technology have markedly improved our understanding of global patterns of human genetic variation and suggest the potential to use large samples to uncover variation among closely spaced populations. Here we characterize genetic variation in a sample of 3,000 European individuals genotyped at over half a million variable DNA sites in the human genome. Despite low average levels of genetic differentiation among Europeans, we find a close correspondence between genetic and geographic distances; indeed, a geographical map of Europe arises naturally as an efficient two-dimensional summary of genetic variation in Europeans. The results emphasize that when mapping the genetic basis of a disease phenotype, spurious associations can arise if genetic structure is not properly accounted for. In addition, the results are relevant to the prospects of genetic ancestry testing; an individual's DNA can be used to infer their geographic origin with surprising accuracy-often to within a few hundred kilometres.

Social trust : a public good?

Combining theories on social trust and social capital with sociopsychological approaches and applying contextual analyses to Swiss and European survey data, this thesis examines under what circumstances generalised trust, often understood as public good, may not benefit everyone, but instead amplify inequality. The empirical investigation focuses on the Swiss context, but considers different scales of analysis. Two broader questions are addressed. First, might generalised trust imply more or less narrow visions of community and solidarity in different contexts? Applying nonlinear principal component analysis to aggregate indicators, Study 1 explores inclusive and exclusive types of social capital in Europe, measured as regional configurations of generalised trust, civic participation and attitudes towards diversity. Study 2 employs multilevel models to examine how generalised trust, as an individual predisposition and an aggregate climate at the level of Swiss cantons, is linked to equality- directed collective action intention versus radical right support. Second, might high-trust climates impact negatively on disadvantaged members of society, precisely because they reflect a normative discourse of social harmony that impedes recognition of inequality? Study 3 compares how climates of generalised trust at the level of Swiss micro-regions and subjective perceptions of neighbourhood cohesion moderate the negative relationship between socio-economic disadvantage and mental health. Overall, demonstrating beneficial, as well as counterintuitive effects of social trust, this thesis proposes a critical and contextualised approach to the sources and dynamics of social cohesion in democratic societies. -- Cette thèse combine des théories sur le capital social et la confiance sociale avec des approches psychosociales et s'appuie sur des analyses contextuelles de données d'enquêtes suisses et européennes, afin d'étudier dans quelles circonstances la confiance généralisée, souvent présentée comme un bien public, pourrait ne pas bénéficier à tout le monde, mais amplifier les inégalités. Les études empiriques, centrées sur le contexte suisse, intègrent différentes échelles d'analyse et investiguent deux questions principales. Premièrement, la confiance généralisée implique-t-elle des visions plus ou moins restrictives de la communauté et de la solidarité selon le contexte? Dans l'étude 1, une analyse à composantes principales non-linéaire sur des indicateurs agrégés permet d'explorer des types de capital social inclusif et exclusif en Europe, mesurés par des configurations régionales de confiance généralisée, de participation civique, et d'attitudes envers la diversité. L'étude 2 utilise des modèles multiniveaux afin d'analyser comment la confiance généralisée, en tant que prédisposition individuelle et climat agrégé au niveau des cantons suisses, est associée à l'intention de participer à des actions collectives en faveur de l'égalité ou, au contraire, à l'intention de voter pour la droite radicale. Deuxièmement, des climats de haute confiance peuvent-ils avoir un impact négatif sur des membres désavantagés de la société, précisément parce qu'ils reflètent un discours normatif d'harmonie sociale qui empêche la reconnaissance des inégalités? L'étude 3 analyse comment des climats de confiance au niveau des micro-régions suisses et la perception subjective de faire partie d'un environnement cohésif modèrent la relation négative entre le désavantage socio-économique et la santé mentale. En démontrant des effets bénéfiques mais aussi contre-intuitifs de la confiance sociale, cette thèse propose une approche critique et contextualisée des sources et dynamiques de la cohésion sociale dans les sociétés démocratiques.