The role of the patellar tendon angle and patellar flexion angle in the interpretation of sagittal plane kinematics of the knee after knee arthroplasty: A modelling analysis

BACKGROUND: Many different measures have been used to describe knee kinematics. This study investigated the changes of two measures, the patellar tendon angle and the patellar flexion angle, in response to variations in the geometry of the knee due to surgical technique or implant design. METHODS: A mathematical model was developed to calculate the equilibrium position of the extensor mechanism for a particular tibiofemoral position. Calculating the position of the extensor mechanism allowed for the determination of the patellar tendon angle and patellar flexion angle relationships to the knee flexion angle. The model was used to investigate the effect of anterior-posterior position of the femur, change in joint line, patellar thickness (overstuffing, understuffing), and patellar tendon length; these parameters were varied to determine the effect on the patellar tendon angle/knee flexion angle and patellar flexion angle/knee flexion angle relationships. RESULTS: The patellar tendon angle was a good indicator of anterior-posterior femoral position and change in patellar thickness, and the patellar flexion angle a good indicator of change in joint line, and patellar tendon length. CONCLUSIONS: The patellar tendon angle/knee flexion angle relationship was found to be an effective means of identifying abnormal kinematics post-knee arthroplasty. However, the use of both the patellar tendon angle and patellar flexion angle together provided a more informative overview of the sagittal plane kinematics of the knee

Le modèle TELEMAC-3D pour les écoulements tridimensionnels : De nouvelles perspectives pour les études d'environnement

Le modèle numérique est un outil qui a trouvé sa place en complément des modèles réduits et des mesures in-situ; il permet à l'ingénieur de mieux comprendre le fonctionnement d'un site et de prédire son évolution, en simulant éventuellement différents scénarios d'interventions humaines. Un nouveau pas vient d'être franchi grâce aux progrès informatiques et numériques. II est maintenant envisageable de simuler sur le long terme des phénomènes couplant l'écosystème et l'hydrodynamique. Le modèle tridimensionnel TELEMAC-3D est aujourd'hui opérationnel, d'un coût d'utilisation admissible pour des études courantes. Après une brève description de ses fonctionnalités, quelques applications sont évoquées

The role of the patellar tendon angle and patellar flexion angle in the interpretation of sagittal plane kinematics of the knee after knee arthroplasty: A modelling analysis

Background: Many different measures have been used to describe knee kinematics. This study investigated the changes of two measures, the patellar tendon angle and the patellar flexion angle, in response to variations in the geometry of the knee due to surgical technique or implant design. Methods: A mathematical model was developed to calculate the equilibrium position of the extensor mechanism for a particular tibiofemoral position. Calculating the position of the extensor mechanism allowed for the determination of the patellar tendon angle and patellar flexion angle relationships to the knee flexion angle. The model was used to investigate the effect of anterior–posterior position of the femur, change in joint line, patellar thickness (overstuffing, understuffing), and patellar tendon length; these parameters were varied to determine the effect on the patellar tendon angle/knee flexion angle and patellar flexion angle/knee flexion angle relationships. Results: The patellar tendon angle was a good indicator of anterior–posterior femoral position and change in patellar thickness, and the patellar flexion angle a good indicator of change in joint line, and patellar tendon length. Conclusions: The patellar tendon angle/knee flexion angle relationship was found to be an effective means of identifying abnormal kinematics post-knee arthroplasty. However, the use of both the patellar tendon angle and patellar flexion angle together provided a more informative overview of the sagittal plane kinematics of the knee

Medium-term 2DH coastal area modelling

The state-of-the-art in depth-averaged mathematical modelling of 3-D coastal morphology is described for the medium-term morphodynamic model type, in which constituent models of waves, currents and sediment transport based on first physical principles are linked together to describe the time-evolution of the bed topography. Various aspects of the combined system of equations are discussed, such as its mathematical character, its inherent stability and its equilibrium state. The results of an intercomparison of different models are shown for two test cases and the potentials and limitations of the model concept are discussed

Acoustic emission technology can warn of impending iatrogenic femur fracture during femoral canal preparation for uncemented hip replacement. A cadaveric animal bone study

During uncemented hip arthroplasty the femoral prosthesis can be fitted too tightly into the femoral canal, causing a hoop-stress fracture of the proximal femur. The research undertaken evaluated Acoustic Emission (AE) technology as a potential method of detecting a fracture forming in this manner, in an attempt to assess whether this technology may be used as a means of early warning of impending fracture during surgery. Deer femora were prepared in a manner similar to surgery and uncemented hip arthroplasty broaches were inserted until fracture occurred. AE sensors were mounted on the femoral cortex and also on the broach. Five femora were fractured manually by hammering the broaches in a manner similar to surgery. Four femora were fractured using a hydraulic loading machine to insert the broach. Stepwise increases in the AE signals coincided with stepwise increases in surface strain of the femoral cortex, crack mouth growth and fracture. Both sensors recorded similar signal profiles. The sensor on the femur registered greater magnitude signals than the sensor on the broach, suggesting that there is signal impedance across the bone-broach interface. AE signals from sensors mounted on the femur and on the broach can detect damage processes happening within the femur during insertion of the broach in the time period of approximately 100 s prior to fracture. These damage processes may represent micro cracking, and ultimately fracture. This supports the possibility of the use of AE signals as a means to monitor internal damage within the femur and possibly predict impending fracture. It is clear that AE signals change significantly prior to fracture however in order to attempt to develop a warning system, further understanding of the significance of the signals and limitations of these methods must be gained

Modelisation numerique des ecoulements dans les digues : revue bibliographique et developpement d'un modele bidimensionnel horizontal

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 26165 C, issue : a.1997 n.18 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Molecular mechanisms involved in vasoactive intestinal peptide receptor activation and regulation: current knowledge, similarities to and differences from the A family of G-protein-coupled receptors.

An actual paradigm for activation and regulation of the GPCR (G-protein-coupled receptors)/seven-transmembrane helix family of receptors essentially emerges from extensive studies of the largest family of receptors, the GPCR-A/rhodopsin family. The mechanisms regulating the GPCR-B family signal transduction are less precisely understood due in part to the lack of the conserved signatures of the GPCR-A family (E/DRY, NPXXY) and in part to the absence of a reliable receptor modelling, although some studies suggest that both families share similar features. Here, we try to highlight the current knowledge of the activation and the regulation of the VIP (vasoactive intestinal peptide) receptors, namely VPAC (VIP/pituitary adenylate cyclase-activating peptide receptor) 1 and 2. This includes search for amino acids involved in the stabilization of the receptor active conformation and in coupling to G-proteins, signalling pathways activated in response to VIP, agonist-dependent receptor down-regulation, phosphorylation and internalization as well as pharmacological consequences of receptor hetero-dimerization.Comparative StudyJournal ArticleReviewinfo:eu-repo/semantics/publishe