References of "Maas, Stefan 50002241"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDesigning an early failure indicator channel for an in-tank hydrogen valve via a fatigue-based approach
Cao, Thanh Binh UL; Kedziora, Slawomir UL; Sellen, Stephan et al

in Journal of Computational Design and Engineering (2020)

This study introduced a fatigue-based approach to design and implement an indicator channel into an in-tank hydrogen valve. It was aimed at providing a mean to point out multiple early valve’s damages. To ... [more ▼]

This study introduced a fatigue-based approach to design and implement an indicator channel into an in-tank hydrogen valve. It was aimed at providing a mean to point out multiple early valve’s damages. To achieve the goal, the study was proposed to handle via three main phases. They included (i) the risk point determinations, (ii) the new valve design and the crack nucleation life estimations, as well as (iii) the simplified crack growth analyses. The obtained results firstly highlighted the construction of the test channel (TC), whose branches were located close to the predicted damage’s sites. The damages could be identified either when a crack reaches the TC (then forms a leakage) or indirectly via the crack propagations’ correlation. The results also pointed out that the TC-implemented valve could perform as similarly as the non-TC one in the non-treated condition. More importantly, this new structure was proved to have a capacity of satisfying the required minimal life of 1.5E5 cycles, depending on the combined uses of the specific material and the pre-treatment, among those considered. In addition, the results emphasized the complexity of the TC that could not be formed by the traditional manufacturing process. Hence, direct metal laser sintering was proposed for the associated prototype and the final TC was issued based on the fundamental requirements of the technique. Finally, it was suggested that practical experiments should essentially be carried out to yield more evidence to support the demonstrated results. [less ▲]

Detailed reference viewed: 91 (4 UL)
Full Text
Peer Reviewed
See detailMechanical strength of a new plate compared to six previously tested opening wedge high tibial osteotomy implants
Diffo Kaze, Arnaud; Maas, Stefan UL; Belsey, James et al

in Journal of Experimental Orthopaedics (2019)

Background This study aimed to assess the mechanical static and fatigue strength provided by the FlexitSystem plate in medial opening wedge high tibial osteotomies (MOWHTO), and to compare it to six ... [more ▼]

Background This study aimed to assess the mechanical static and fatigue strength provided by the FlexitSystem plate in medial opening wedge high tibial osteotomies (MOWHTO), and to compare it to six previously tested implants: the TomoFix small stature, the TomoFix standard, the ContourLock, the iBalance, the second generation PEEKPower and the size 2 Activmotion. Thus, this will provide surgeons with data that will help in the choice of the most appropriate implant for MOWHTO. Methods Six fourth-generation tibial bone composites underwent a MOWHTO and each was fixed using six FlexitSystem plates, according to standard techniques. The same testing procedure that has already been previously defined, used and published, was used to investigate the static and dynamic strength of the prepared bone-implant constructs. The test consisted of static loading and cyclical loading for fatigue testing. Results During static testing, the group constituted by the FlexitSystem showed a fracture load higher than the physiological loading of slow walking (3.7 kN > 2.4 kN). Although this fracture load was relatively small compared to the average values for the other Implants from our previous studies, except for the TomoFix small stature and the Contour Lock. During fatigue testing, FlexitSystem group showed the smallest stiffness and higher lifespan than the TomoFix and the PEEKPower groups. Conclusions The FlexitSystem plate showed sufficient strength for static loading, and average fatigue strength compared to the previously tested implants. Full body dynamic loading of the tibia after MOWHTO with the investigated implants should be avoided for at least three weeks. Implants with a wider T-shaped proximal end, positioned onto the anteromedial side of the tibia head, or inserted in the osteotomy opening in a closed-wedge construction, provided higher mechanical strength than implants with small a T-shaped proximal end, centred onto the medial side of the tibia head. [less ▲]

Detailed reference viewed: 39 (0 UL)
Full Text
Peer Reviewed
See detailEnergy efficiency and indoor aire quality os seminar rooms in older buildings with and without mechanical ventilation
Maas, Stefan UL; da Cruz Antunes, Joël UL; Steffgen, Georges UL

in Bauphysik (2019), 41(October 2019, Heft 5), 243-251

The present paper reports on an experimental study performed in a seminar room of the University of Luxembourg in a building of the 1970ies without a major renovation. This lecture room is typical for ... [more ▼]

The present paper reports on an experimental study performed in a seminar room of the University of Luxembourg in a building of the 1970ies without a major renovation. This lecture room is typical for this building period and has a capacity of 60 seats. It is equipped with a mechanical ventilation system that is normally in operation on workdays for 11 hours a day in semester periods (8:00-19:00h), while windows can be opened manually. A Blower-Door-Test revealed that the room is not airtight. During a year, the ventilation system was shut “on” and “off” in periods of some weeks and the consumed final-energy was measured, as well as the indoor climate assessed by physical and psychological measurements. For instance, the measured CO2 concentrations are marginally better with the ventilation system "on", which was not perceived in any way by the occupants during the investigations. It was not possible to properly identify the impact of ventilation on the consumed heat-energy, as the room could not be thermally separated from the rest of the building. But with the system “on” there was a clear increase in consumed primary energy due to the electric consumption of the fans. No relationship between the perceived percentage of dissatisfied and perceived climate could be observed. It is concluded that the typical normal operation modus is questionable for seminar rooms in older buildings with variable occupancy and that a simple shut down or semi-automatic user controlled modus by low-cost retrofit seems advantageous. [less ▲]

Detailed reference viewed: 52 (6 UL)
Full Text
See detailEvaluation von bauphysikalischen Vormessungen im Rahmen von komplexen Innendämmprojekten
Latz, Sebastian Joachim UL; Thewes, Andreas; Scholzen, Frank UL et al

in Vogel, Albert (Ed.) Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

The installation of internal insulation systems within the scope of refurbishment changes the hygrothermal behaviour of the existing masonry of a building in the long term. The internal insulation layer ... [more ▼]

The installation of internal insulation systems within the scope of refurbishment changes the hygrothermal behaviour of the existing masonry of a building in the long term. The internal insulation layer reduces the temperature of the masonry during the heating period and considerably reduces the drying potential. If the moisture content is too high due to the absorption of driving rain from the outside and moisture from the interior climate, the masonry may be permanently damaged and mould may form. The proof of function can be achieved by hygrothermal simulations. These simulations require the input of sensitive boundary conditions and different material parameters. In order to obtain precise simulation results, these input values should be validated by building physics measurements. In order to be able to better assess the simulation parameters, various physical measurements for the preparation of a field test for interior insulation systems in a conference room were carried out on behalf of the administration of the bâtiments publics at the University of Luxembourg as part of the research project "Possibilities and limitations of interior insulation in the renovation of public buildings in Luxembourg". [less ▲]

Detailed reference viewed: 119 (15 UL)
See detailAuswertung eines Großdemonstrators mit außenliegender Wandtemperierung, Wärmepumpe, Eisspeicher und PTV-Hybridkollektoren
Schmidt, Christoph Wilhelm UL; Altgeld, Horst; Groß, Bodo et al

in Völker, Conrad; Kornadt, Oliver; Jentsch, Mark (Eds.) et al Schriftenreihe der Professur Bauphysik, Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II ... [more ▼]

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der messtechnischen Auswertung des Großdemonstra-tors über die aktuelle Heizperiode (2018/19) und die anstehende Kühlperiode (2019). Der Fo-kus der Auswertung liegt auf der Feldtestfassade der außenliegenden Wandtemperierung und adressiert die folgenden Fragestellungen: - Konnten die theoretischen Ergebnisse aus Berechnung und Simulation reproduziert werden? - Welche Heizleistungen sind über die außenliegende Wandtemperierung übertragbar? - Welches Fazit kann nach dem Betrieb der Anlage/Feldtestfläche über ca. ein Jahr ge-zogen werden? Je nach aktuellem Stand der begleitenden Simulations- und Potentialstudien können auch hier erste Ergebnisse präsentiert werden. Inhaltlich baut der Beitrag auf dem Beitrag „Außen-liegende Wand- und Lufttemperierung: Umsetzung eines Großdemonstrators“ von den Bau-physiktagen 2017 in Kaiserslautern auf. Im Anschluss an die dort beschriebene Umsetzung soll nun ein Fazit bzgl. Umsetzung, Monitoring und Simulation gezogen werden. [less ▲]

Detailed reference viewed: 71 (1 UL)
See detailInbetriebnahme und Monitoring einer Feldtestfläche zur außenliegenden Lufttemperierung
Schmidt, Christoph Wilhelm UL; Altgeld, Horst; Groß, Bodo et al

in Völker, Conrad; Kornadt, Oliver; Jentsch, Mark (Eds.) et al Schriftenreihe der Professur Bauphysik, Bauphysiktage 2019 in Weimar - Bauphysik in Forschung und Praxis (2019, September 25)

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II ... [more ▼]

Der Beitrag ist inhaltlich dem Forschungsprojekt „Low Exergy Utilisation - Einsatz von außen-liegender Wandtemperierung bei der Gebäudesanierung - Feldtest, CO2- Wärmepumpe mit Eisspeicher“ (kurz LEXU II, Förderkennzeichen 0327370Y) zugeordnet. Im Rahmen des Pro-jektes wurde ein Großdemonstrator mit außenliegender Wand- und Lufttemperierung (kurz aWT & aLT) zusammen mit einem niederexergetischen Versorgungssystem, bestehend aus Eisspeicher, Wärmepumpe und PVT-Hybridkollektoren realisiert. Zur Heizperiode 2018/19 wurde die „Feldtestanlage“ in Betrieb genommen, sodass derzeit Messdaten generiert wer-den. In dem Forschungsprojekt wird der Demonstrator über eine Heizperiode und eine Kühl-periode messtechnisch begleitet und ausgewertet. Dabei wird der Großdemonstrator und alle Komponenten umfassend messtechnisch ausgewertet (~300 Messwerte). Ziel des Beitrags ist eine Darstellung der Grundlagen der außenliegenden Lufttemperierung, als niederexergetische und schnell regelbare Ergänzung zur außenliegenden Wandtemperie-rung. Bei der außenliegenden Lufttemperierung wird zwischen thermisch aktivierter Be-standswand und neuem Wärmedämm-Verbundsystem ein Luftspalt geschaffen, durch den Außenluft geführt und temperiert werden kann. Diese temperierte Außenluft wird dem dahin-terliegenden Raum (im Feldtest ein Büroraum mit rund 20 m² Grundfläche und zwei Arbeits-plätzen) als Frischluft zur Verfügung gestellt. Aufbauend auf den Grundlagen wird die Inbe-triebnahme der bereits umgesetzten Feldtestfläche mit möglichen Regelstrategien geschildert. Abschließend sollen erste Messergebnisse der Feldtestfläche dargestellt und diskutiert wer-den. Interessant sind hier vor allem (im Vergleich zur außenliegenden Wandtemperierung) die möglichen Zeitkonstanten und die erreichbaren Wärmeströme nach Innen (z.B. mögliche Wärmeübertragung als Kombination aus Konvektion im Luftspalt und Wärmeleitung durch die Bestandswand). Themengebiet: Energieeffiziente Gebäude & Bauphysik und Sanierung & Behaglichkeit und Raumklima [less ▲]

Detailed reference viewed: 57 (0 UL)
Full Text
Peer Reviewed
See detailGraft materials provide greater static strength to medial opening wedge high tibial osteotomy than when no graft is included
Belsey, James; Diffo Kaze, Arnaud UL; Jobson, Simon et al

in Journal of Experimental Orthopaedics (2019), 6(13),

Background The purpose of this study was to compare the stability of medial opening-wedge high tibial osteotomy (MOWHTO) with and without different graft materials. Good clinical and radiological outcomes ... [more ▼]

Background The purpose of this study was to compare the stability of medial opening-wedge high tibial osteotomy (MOWHTO) with and without different graft materials. Good clinical and radiological outcomes have been demonstrated when either using or not using graft materials during MOWHTO. Variations in the biomechanical properties of different graft types, regarding the stability they provide a MOWHTO, have not been previously investigated. Methods A 10 mm biplanar MOWHTO was performed on 15 artificial sawbone tibiae, which were fixed using the Activmotion 2 plate. Five bones had OSferion60 wedges (synthetic group), five had allograft bone wedges (allograft group), and five had no wedges (control group) inserted into the osteotomy gap. Static compression was applied axially to each specimen until failure of the osteotomy. Ultimate load, horizontal and vertical displacements were measured and used to calculate construct stiffness and valgus malrotation of the tibial head. Results The synthetic group failed at 6.3 kN, followed by the allograft group (6 kN), and the control group (4.5 kN). The most valgus malrotation of the tibial head was observed in the allograft group (2.6°). The synthetic group showed the highest stiffness at the medial side of the tibial head (9.54 kN·mm− 1), but the lowest stiffness at the lateral side (1.59 kN·mm-1). The allograft group showed high stiffness on the medial side of the tibial head (7.54 kN·mm− 1) as well as the highest stiffness on the lateral side (2.18 kN·mm− 1). Conclusions The use of graft materials in MOWHTO results in superior material properties compared to the use of no graft. The static strength of MOWHTO is highest when synthetic grafts are inserted into the osteotomy gap. Allograft wedges provide higher mechanical strength to a MOWHTO than when no graft used. In comparison to the synthetic grafts, allograft wedges result in the stiffness of the osteotomy being more similar at the medial and lateral cortices. [less ▲]

Detailed reference viewed: 79 (1 UL)
Full Text
Peer Reviewed
See detailComparison of different excitationand data sampling-methods in structural health monitoring
Maas, Stefan UL; Nguyen, Viet Ha UL; Kebig, Tanja UL et al

in Civil Engineering Design (2019), 1

Structural Health Monitoring with analysis of dynamic characteristics intends to detect stiffness changes caused by damage. It can be performed by vibrational tests resulting to modal parameters, that is ... [more ▼]

Structural Health Monitoring with analysis of dynamic characteristics intends to detect stiffness changes caused by damage. It can be performed by vibrational tests resulting to modal parameters, that is, eigenfrequencies, damping, modeshapes, or modal masses. Those parameters are themselves informational and even allow often deducing the stiffness matrix. Based on that, it is possible to identify and to localize changes in the stiffness matrix due to damage, that is, localization and quantification of damage. However, changing test conditions, like ambient temperature or excitation force or existing nonlinearities of concrete, show important influence on damage indicators and hence need compensation prior to damage detection. Considering this background, this article focuses on comparing ambient excitation to forced excitation including appropriate exciters. Furthermore, continuous monitoring is discussed vs discrete testing in distinct time-intervals. The intention of the comparison is to give an overview, that is, helpful for choosing appropriate measurement technique for the sake of correct damage detection subsequently. [less ▲]

Detailed reference viewed: 116 (15 UL)
Full Text
See detailMaterials, valves and sealing gaskets for high pressure applications
Repplinger, Christian UL; Sellen, Stephan; Kedziora, Slawomir UL et al

Poster (2019)

Detailed reference viewed: 56 (4 UL)
Full Text
Peer Reviewed
See detailBRIDGE MONITORING WITH HARMONIC EXCITATION AND PRINCIPAL COMPONENT ANALYSIS
Nguyen, Viet Ha UL; Golinval, Jean-Claude; Maas, Stefan UL

in The Baltic Journal of Road and Bridge Engineering (2019)

Principal Component Analysis is used for damage detection in structures excited by harmonic forces. Time responses are directly analysed by Singular Value Decomposition to deduct two dominant Proper ... [more ▼]

Principal Component Analysis is used for damage detection in structures excited by harmonic forces. Time responses are directly analysed by Singular Value Decomposition to deduct two dominant Proper Orthogonal Values corresponding to two Proper Orthogonal Modes. Damage index is defined by the concept of subspace angle that a subspace is built from the two Proper Orthogonal Modes. A subspace angle reflects the coherence between two different structural health states. An example is given through the application on a part of a real prestressed concrete bridge in Luxembourg where different damage states were created by cutting a number of prestressed tendons in four scenarios with increasing levels. Results are better by using excitation frequency close to an eigenfrequency of the structure. The technique is convenient for practical application in operational bridge structures. [less ▲]

Detailed reference viewed: 122 (14 UL)
Full Text
Peer Reviewed
See detailBiomechanical testing of osteotomy plates
Maas, Stefan UL; Diffo Kaze, Arnaud UL

Scientific Conference (2018, November 30)

Detailed reference viewed: 76 (3 UL)
Full Text
Peer Reviewed
See detailModellierung und Validierung von Simulationsansätzen für die aussenliegende Lufttemperierung
Schmidt, Christoph Wilhelm; Scholzen, Frank UL; Maas, Stefan UL et al

in Tagungsband BauSim 2018 (2018, September)

Detailed reference viewed: 45 (1 UL)
Full Text
Peer Reviewed
See detailFinite element analysis of the pelvis including gait muscle forces: an investigation into the effect of rami fractures on load transmission
Ricci, Pierre-Louis UL; Maas, Stefan UL; Kelm, Jens et al

in Journal of Experimental Orthopaedics (2018), 5(33), 1-9

Detailed reference viewed: 114 (18 UL)
Full Text
Peer Reviewed
See detailInfluence of pubic symphysis stiffness on pelvis stress distribution during single leg stance
Ricci, Pierre-Louis UL; Maas, Stefan UL; Gerich, Torsten et al

Poster (2018, July 09)

Detailed reference viewed: 45 (10 UL)
Full Text
Peer Reviewed
See detailWas wissen wir über die Osteitis pubis bei Sporttreibenden?
Kelm, Jens; Ludwig, Oliver; André, Jan et al

in Sportverletzung Sportschaden : Organ der Gesellschaft für Orthopadisch-Traumatologische Sportmedizin (2018)

Hintergrund Die Osteitis pubis ist eine häufige Ursache chronischer Leistenbeschwerden. Aufgrund hoher klinischer Unsicherheit sowie dem unterschiedlichen Verlauf der Erkrankung wird die Diagnose nicht ... [more ▼]

Hintergrund Die Osteitis pubis ist eine häufige Ursache chronischer Leistenbeschwerden. Aufgrund hoher klinischer Unsicherheit sowie dem unterschiedlichen Verlauf der Erkrankung wird die Diagnose nicht selten erst spät gestellt. Das Krankheitsbild betrifft insbesondere Sportlerinnen und Sportler, wobei auch Patienten aus den Bereichen Orthopädie, Traumatologie, Neurologie, Urologie, Gynäkologie sowie der Rheumatologie betroffen sein können. Therapeutisch kommen sowohl konservative als auch operative Verfahren zum Einsatz. Material und Methoden Systematische Literaturrecherche, deskriptive Darstellung der Studienlage und Interpretation der Ergebnisse im Sinne der evidenzbasierten Medizin. Ergebnisse Das wissenschaftliche Niveau der Studien über die Osteitis pubis ist, wie die Anzahl der in Studien inkludierten Sporttreibenden, insgesamt niedrig. Aufgrund der Heterogenität der Publikationen ist ihr statistischer Vergleich methodisch schwierig. Klinisch führendes Symptom der Osteitis pubis ist die schmerzhafte Symphysis pubica, wobei ein klassisches pathognomonisches Zeichen fehlt. Die Diagnose basiert nach Ausschluss zahlreicher Differentialdiagnosen (z. B. „Sportlerleiste“, FA-Impingement, Adduktorenläsion) auf der Zusammenschau von Anamnese, klinischer Untersuchung sowie bildgebender Verfahren. Die Osteitis pubis ist eine durch Sportkarenz oftmals selbstlimitierende Erkrankung, die initial konservativ behandelt wird. Bei frustranem Verlauf sind operative Verfahren, in Abhängigkeit der Begleitpathologien, in Betracht zu ziehen. Schlussfolgerung Es existieren bis dato keine Leitlinien hinsichtlich Diagnostik und Therapie der Osteitis pubis, allerdings ein Konsens darüber, dass der operativen Behandlung eine konservative vorangehen muss. Das Evidenzniveau der Studien ist niedrig. Eine metaanalytische Auswertung ist mit den derzeitig vorhandenen Publikationen nicht möglich. Die Anzahl der untersuchten Sporttreibenden ist in Relation zu den sozioökonomischen Folgen der Erkrankung, insbesondere im Profisport, niedrig. [less ▲]

Detailed reference viewed: 168 (4 UL)
Full Text
See detailDetermination of the optimum autofrettage pressure for a complex aluminum valve body
Repplinger, Christian UL; Sellen, Stephan; Kedziora, Slawomir UL et al

Scientific Conference (2018)

Detailed reference viewed: 32 (1 UL)
Full Text
See detailModeling of a prestressed concrete bridge with 3D finite elements for structural health monitoring using model updating techniques
Schommer, Sebastian UL; Kebig, Tanja UL; Nguyen, Viet Ha UL et al

in ISMA2018 International Conference on Noise and Vibration Engineering (2018)

This paper presents a linear finite element model for a prestressed concrete beam, which was part of a real bridge. Static and dynamic tests were carried out and compared to the numerical simulation ... [more ▼]

This paper presents a linear finite element model for a prestressed concrete beam, which was part of a real bridge. Static and dynamic tests were carried out and compared to the numerical simulation responses. A solid finite element model was created including the prestressed concrete beam, permanent dead load, two additional live loads and a shaker. A well planned finite element model is very important for later detection and localization of damage. Therefore, a mapped mesh was used to define so-called ‘slices’, which enables describing stiffness changes, e.g. damage. The model validation was performed by comparing simulated results to measured responses in the healthy state of the beam. After validation of the reference model, it is possible to modify the bending stiffness along the longitudinal axis of the beam by modifying Young’s moduli of different slices to adapt for the effect of damage. [less ▲]

Detailed reference viewed: 83 (8 UL)
Full Text
Peer Reviewed
See detailStatic and fatigue strength of a novel anatomically contoured implant compared to five current open-wedge high tibial osteotomy plates
Diffo Kaze, Arnaud UL; Maas, Stefan UL; Belsey, James et al

in Journal of Experimental Orthopaedics (2017), 4(39),

Abstract Background The purpose of the present study was to compare the mechanical static and fatigue strength of the size 2 osteotomy plate “Activmotion” with the following five other common implants for ... [more ▼]

Abstract Background The purpose of the present study was to compare the mechanical static and fatigue strength of the size 2 osteotomy plate “Activmotion” with the following five other common implants for the treatment of medial knee joint osteoarthritis: the TomoFix small stature, the TomoFix standard, the Contour Lock, the iBalance and the second generation PEEKPower. Methods Six fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy (HTO), according to standard techniques, using size 2 Activmotion osteotomy plates. All bone-implant constructs were subjected to static compression load to failure and load-controlled cyclic fatigue failure testing, according to a previously defined testing protocol. The mechanical stability was investigated by considering different criteria and parameters: maximum forces, the maximum number of loading cycles, stiffness, the permanent plastic deformation of the specimens during the cyclic fatigue tests, and the maximum displacement range in the hysteresis loops of the cyclic loading responses. Results In each test, all bone-implant constructs with the size 2 Activmotion plate failed with a fracture of the lateral cortex, like with the other five previously tested implants. For the static compression tests the failure occurred in each tested implant above the physiological loading of slow walking (> 2400 N). The load at failure for the Activmotion group was the highest (8200 N). In terms of maximum load and number of cycles performed prior to failure, the size 2 Activmotion plate showed higher results than all the other tested implants except the ContourLock plate. The iBalance implant offered the highest stiffness (3.1 kN/mm) for static loading on the lateral side, while the size 2 Activmotion showed the highest stiffness (4.8 kN/mm) in cyclic loading. Conclusions Overall, regarding all of the analysed strength parameters, the size 2 Activmotion plate provided equivalent or higher mechanical stability compared to the previously tested implant. Implants with a metaphyseal slope adapted to the tibia anatomy, and positioned more anteriorly on the proximal medial side of the tibia, should provide good mechanical stability. [less ▲]

Detailed reference viewed: 138 (19 UL)
Full Text
Peer Reviewed
See detailA finite element model of the lower limb during stance phase of gait cycle including the muscle forces
Diffo Kaze, Arnaud UL; Maas, Stefan UL; Arnoux, Pierre-Jean et al

in BioMedical Engineering OnLine (2017), 16(138),

Abstract Background Results of finite element (FE) analyses can give insight into musculoskeletal diseases if physiological boundary conditions, which include the muscle forces during specific activities ... [more ▼]

Abstract Background Results of finite element (FE) analyses can give insight into musculoskeletal diseases if physiological boundary conditions, which include the muscle forces during specific activities of daily life, are considered in the finite element modelling. So far, many simplifications of the boundary conditions are currently made. This study presents an approach for FE modelling of the lower limb for which muscle forces were included. Method The stance phase of normal gait was simulated. Muscle forces were calculated using a musculoskeletal rigid body (RB) model of the human body, and were subsequently applied to a FE model of the lower limb. It was shown that the inertial forces are negligible during the stance phase of normal gait. The contact surfaces between the parts within the knee were modelled as bonded. Weak springs were attached to the distal tibia for numerical reasons. Results Hip joint reaction forces from the RB model and those from the FE model were similar in magnitude with relative differences less than 16%. The forces of the weak spring were negligible compared to the applied muscle forces. The maximal strain was 0.23% in the proximal region of the femoral diaphysis and 1.7% in the contact zone between the tibia and the fibula. Conclusions The presented approach based on FE modelling by including muscle forces from inverse dynamic analysis of musculoskeletal RB model can be used to perform analyses of the lower limb with very realistic boundary conditions. In the present form, this model can be used to better understand the loading, stresses and strains of bones in the knee area and hence to analyse osteotomy fixation devices. [less ▲]

Detailed reference viewed: 147 (22 UL)