The purpose of this study is to create an accurate experimental database for the passive (in vitro)freedom-of-motion characteristics of the human knee joint on a subject to subject basis, suitable for the verification and enhancement of mathematical knee-joint models. Knee-joint specimens in a six degree-of-freedom motion rig are moved through flexion under several combinations of external loads, including tibial torques, axial forces and AP-forces. Euler rotation angles and translation vectors, describing the relative, spatial motions of the joint are measured using an accurate Roentgen Stereo Photogrammetric system. Conceptually the joint is considered as a two degrees-of-freedom of motion mechanism (flexion-tibial rotation), whereby the limits of internal and external tibial rotation are defined at torques of ± 3 Nm. The motion pathways along these limits are denned as the envelopes of passive knee joint motion. It is found that these envelope pathways are consistent and hardly influenced by additional axial forces up to 300 N and AP-forces of 30 N. Within the envelope of motion, however, the motion patterns are highly susceptible to small changes in the external load configuration. It is shown that the external tibial rotation during extension ('screw-home mechanism') is not an obligatory effect of the passive joint characteristics, but a direct result of the external loads. Anatomical differences notwithstanding, the inter-individual discrepancies in the motion patterns of the four specimens tested, showed to be relatively small in a qualitative sense. Quantitative differences can be explained by small differences in the alignment of the coordinate systems relative to the joint anatomy and by differences in rotatory laxity.
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In biomechanical joint-motion analyses, the continuous motion to be studied is often approximated by a sequence of finite displacements, and the Finite Helical Axis(FHA) or "screw axis" for each displacement is estimated from position measurements on a number of anatomical or artificial landmarks. When FHA parameters are directly determined from raw (noisy) displacement data, both the position and the direction of the FHA are ill-determined, in particular when the sequential displacement steps are small. This implies, that under certain conditions, the continuous pathways of joint motions cannot be adequately described. The purpose of the present experimental study is to investigate the applicability of smoothing (or filtering)techniques, in those cases where FHA parameters are ill-determined. Two different quintic-spline smoothing methods were used to analyze the motion data obtained with Roentgenstereophotogrammetry in two experiments. One concerning carpal motions in a wrist-joint specimen, and one relative to a kinematic laboratory model, in which the axis positions are a priori known. The smoothed and nonsmoothed FHA parameter errors were compared. The influences of the number of samples and the size of the sampling interval (displacement step) were investigated, as were the effects of equidistant and nonequidistant sampling conditions and noise invariance
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A great deal of attention has been paid to the performance of international joint ventures (IJVs) and trust has been recognised as a keyfactor influencing it. This paper examines the emergence of trust as a process and develops a process model of trust building in IJVs, which isused to analyse four case studies. The main conclusions are the following: Whereas competence-based trust starts from public information,promissory-based trust and goodwill-based trust are individually orientated and mainly develop through direct personal interaction. Suchinteraction may lead to bonds of friendship between delegates. Before these bonds evolve, trust is mainly based on the perceived self-interestof the partner in the joint venture. When the bonds of friendship dominate, the main source of trust shifts towards emotional commitments.Thus, in the early stages of an IJV, promissory-based trust predominates, and as the joint venture progresses, competence-based trust emerges.Goodwill-based trust is important throughout the process. A commitment to cooperate emerges from initial self-interest. The model is capableof further development and testing.
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The wrist allows the hand to combine dorsopalmar flexion and radioulnar deviation, a unique combination of functions that is made possible by a highly complex system of joints. The morphologic features of the carpal bones and of the radiocarpal and intercarpal contacts can be functionally interpreted by the mechanism that underlies the movements of the hand to the forearm. Displacements of the carpals take place in longitudinal articulation chains, with the proximal carpals having the position of an intercalated bone. The three articulation chains, radial, central, and ulnar, have interdependent movements at the radiocarpal and midcarpal levels. The linkage of movements in the longitudinal direction is associated to a transverse linkage by mutual joint contacts and by specific ligamentous interconnections. Kinematic analyses of the carpal joint motions have provided convincing evidence that each motion of the hand to the forearm demonstrates a specific motion pattern of the carpal bones. The stability of the carpus essentially depends on the integrity of the ligamentous system which consists of interwoven fiber bundles that differ in length, direction, and mechanical properties. Distinct separations into morphologic entities are difficult to make. From a functional point of view, the ligamentous interconnections can be regarded as a system that passively restricts movements of the carpals on one another and on the radius, but in a very differentiated way. The ligamentous system controls the linkage of the movements of the carpals, with the geometries of the bones and of the joint surfaces being, first of all, responsible for the kinematic behavior of the carpal joint.
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BACKGROUND: Instability of the knee joint during gait is frequently reported by patients with knee osteoarthritis or an anterior cruciate ligament rupture. The assessment of instability in clinical practice and clinical research studies mainly relies on self-reporting. Alternatively, parameters measured with gait analysis have been explored as suitable objective indicators of dynamic knee (in)stability.RESEARCH QUESTION: This literature review aimed to establish an inventory of objective parameters of knee stability during gait.METHODS: Five electronic databases (Pubmed, Embase, Cochrane, Cinahl and SPORTDiscuss) were systematically searched, with keywords concerning knee, stability and gait. Eligible studies used an objective parameter(s) to assess knee (in)stability during gait, being stated in the introduction or methods section. Out of 10717 studies, 89 studies were considered eligible.RESULTS: Fourteen different patient populations were investigated with kinematic, kinetic and/or electromyography measurements during (challenged) gait. Thirty-three possible objective parameters were identified for knee stability, of which the majority was based on kinematic (14 parameters) or electromyography (12 parameters) measurements. Thirty-nine studies used challenged gait (i.e. external perturbations, downhill walking) to provoke knee joint instability. Limited or conflicting results were reported on the validity of the 33 parameters.SIGNIFICANCE: In conclusion, a large number of different candidates for an objective knee stability gait parameter were found in literature, all without compelling evidence. A clear conceptual definition for dynamic knee joint stability is lacking, for which we suggest : "The capacity to respond to a challenge during gait within the natural boundaries of the knee". Furthermore biomechanical gait laboratory protocols should be harmonized, to enable future developments on clinically relevant measure(s) of knee stability during gait.
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Knee joint instability is frequently reported by patients with knee osteoarthritis (KOA). Objective metrics to assess knee joint instability are lacking, making it difficult to target therapies aiming to improve stability. Therefore, the aim of this study was to compare responses in neuromechanics to perturbations during gait in patients with self-reported knee joint instability (KOA-I) versus patients reporting stable knees (KOA-S) and healthy control subjects.Forty patients (20 KOA-I and 20 KOA-S) and 20 healthy controls were measured during perturbed treadmill walking. Knee joint angles and muscle activation patterns were compared using statistical parametric mapping and discrete gait parameters. Furthermore, subgroups (moderate versus severe KOA) based on Kellgren and Lawrence classification were evaluated.Patients with KOA-I generally had greater knee flexion angles compared to controls during terminal stance and during swing of perturbed gait. In response to deceleration perturbations the patients with moderate KOA-I increased their knee flexion angles during terminal stance and pre-swing. Knee muscle activation patterns were overall similar between the groups. In response to sway medial perturbations the patients with severe KOA-I increased the co-contraction of the quadriceps versus hamstrings muscles during terminal stance.Patients with KOA-I respond to different gait perturbations by increasing knee flexion angles, co-contraction of muscles or both during terminal stance. These alterations in neuromechanics could assist in the assessment of knee joint instability in patients, to provide treatment options accordingly. Furthermore, longitudinal studies are needed to investigate the consequences of altered neuromechanics due to knee joint instability on the development of KOA.
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Study Type – Aetiology (individual cohort)Level of Evidence 2bWhat's known on the subject? and What does the study add?Recent studies have already shown associations between generalized joint hypermobility (GJH) and voiding and defecation dysfunction and/or slow transit constipation. Changes in extracellular matrix composition in vesico‐ureteric junction of vesico‐ureteral reflux (VUR) patients were also observed previously.This study is the first to assess joint mobility as a parameter for connective tissue composition in vesico‐ureteral reflux. We convincingly demonstrate that VUR patients have significantly more hypermobile joints compared to controls and this provides a new angle to the intriguing subjects of development of VUR and susceptibility to VUR.OBJECTIVE•To assess whether there is an increased prevalence of joint hypermobility in patients with vesico‐ureteric reflux (VUR).MATERIALS AND METHODS•We studied 50 patients with primary VUR and matched controls drawn from a reference population.•Joint mobility was assessed using the Bulbena hypermobility score.RESULTS•We identified significantly more patients with VUR with generalized joint hypermobility than controls (24% vs 6.7%, P= 0.007).CONCLUSION•Our findings confirm our clinical observation of an increased rate of joint hypermobility in patients with VUR. We speculate that an altered composition of the connective tissue may contribute to the severity of the (pre‐existing) VUR phenotype.
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The Refined Core and Balance Model of Family Leisure Functioning was used to guide our study of the link between vacation experiences of romantic couples and satisfaction with their relationship life. Results revealed that romantic couples who had more shared or joint experiences during their vacations in the previous year reported higher levels of satisfaction with their relationship life at the end of the year. This association was mediated by relationship functioning (i.e., couple cohesion and flexibility). The number of vacations was not a significant predictor of romantic couples’ satisfaction with relationship life; what mattered most was the extent to which partners were engaged in joint experiences during their vacations such as having fun together, mindful conversations, physical intimacy, and trying new things together. These findings demonstrate the need to continue to study less frequent, extraordinary leisure vacation experiences that may help maintain the love within romantic relationships. Theoretical and practical implications are discussed
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PURPOSE: To compare the responses in knee joint muscle activation patterns to different perturbations during gait in healthy subjects.SCOPE: Nine healthy participants were subjected to perturbed walking on a split-belt treadmill. Four perturbation types were applied, each at five intensities. The activations of seven muscles surrounding the knee were measured using surface EMG. The responses in muscle activation were expressed by calculating mean, peak, co-contraction (CCI) and perturbation responses (PR) values. PR captures the responses relative to unperturbed gait. Statistical parametric mapping analysis was used to compare the muscle activation patterns between conditions.RESULTS: Perturbations evoked only small responses in muscle activation, though higher perturbation intensities yielded a higher mean activation in five muscles, as well as higher PR. Different types of perturbation led to different responses in the rectus femoris, medial gastrocnemius and lateral gastrocnemius. The participants had lower CCI just before perturbation compared to the same phase of unperturbed gait.CONCLUSIONS: Healthy participants respond to different perturbations during gait with small adaptations in their knee joint muscle activation patterns. This study provides insights in how the muscles are activated to stabilize the knee when challenged. Furthermore it could guide future studies in determining aberrant muscle activation in patients with knee disorders.
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Aan de performance van internationale joint ventures (IJV’s) is veel aandacht besteed. Voor een goede performance is wederzijds, persoonlijk vertrouwen tussen de partners van de alliantie als één van de belangrijkste factoren onderkend. In dit artikel wordt de ontwikkeling van persoonlijk vertrouwen tussen managers van IJV-partners over de tijd bestudeerd. Op basis van de resultaten van vier casestudies presenteren we een procesmodel van persoonlijk vertrouwen. De inzichten die aan dit model ontleend kunnen worden, dienen als leidraad voor de ontwikkeling van succesvolle allianties.
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