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Evaluierung und Charakterisierung von Instabilitäten im Kniegelenk bei Patienten mit einer vorderen Kreuzbandruptur
No full textOsteoarthrose ist eine degenerative Gelenkerkrankung, welche durch strukturelle als auch zelluläre Degeneration des Gelenkknorpels beschrieben wird. Es wird angenommen, dass Osteoarthrose im Kniegelenk durch pathologische Belastungsmuster und/oder Gelenkinstabilitäten hervorgerufen werden kann. Eine frühe Detektion von Osteoarthrose zu Beginn der Krankheit ist nach heutigem Stand der Wissenschaft bislang nicht möglich. Die Quantifizierung von Instabilität im Kniegelenk und Erkenntnisse über das Verhalten von Patienten mit einer Gelenkslaxizität während aktiver Bewegung, könnte jedoch in diesem Zusammenhang das Verständnis über den Einfluss von Instabilitäten auf eine Gelenksdegeneration erweitern. Da das vordere Kreuzband (VKB) primär dafür zuständig ist, die Verschiebung der Tibia nach vorne zu verhindern, ist es von besonders großem Interesse, die Kinematik von Knien mit VKB Ruptur mit physiologisch gesunden Knien zu vergleichen. Das Ziel dieser Dissertation ist es, den Einfluss von passiver Gelenkslaxizität, hervorgerufen durch einen VKB Riss, auf die aktive tibio-femorale Kinematik während des Gehens zu erklären. Innerhalb dieser Dissertation wurden eine Reihe von Studien durchgeführt, um neue Methoden zur Bestimmung funktioneller Bewegungen im Kniegelenk zu entwickeln. Außerdem wurde die Methode in ihrer Effizienz im Gebrauch und ihrer Bedeutung hinsichtlich mit Gelenkinstabilitäten assoziierter klinischer Probleme getestet.
Um die tibio-femorale Kinematik quantifizieren zu können, wurde ein nicht invasiver Ansatz entwickelt, der die tibio-femorale Bewegung dynamisch ermitteln kann. Dieser neue Ansatz erwies sich als reproduzierbar und wiederholbar. Er basiert auf der Bewegungsanalyse und ist mit fortgeschrittenen Techniken kombiniert, um die skelettale Kinematik im Kniezentrum zu bestimmen (inklusive SARA, SCoRE & OCST). Es wurden 13 Patienten untersucht, die an einer über das MRT bestätigte VKB Ruptur litten. Die verletzten Kniegelenke wurden sowohl mit ihrer gesunden Gegenseite als auch mit denen einer gesunden Kontrollgruppe verglichen. Hierbei wurden optische Messtechniken verwendet, um die Unterschiede in der Gelenkstabilität während Aktivitäten des täglichen Lebens zu ermitteln.
In einem weiteren Ansatz zur Bestimmung der Kinematik des Kniegelenks wurde zwischen einer medialen und einer lateralen Translation unterschieden, indem die Bewegung der jeweiligen Kondylen bestimmt wurde. Hierbei sollte die Rotation des Kniegelenkes in der transversalen Ebene näher untersucht werden. Diese Betrachtung lieferte die neue Erkenntnis, dass das Rotationszentrum beim Laufen in der transversalen Ebene auf der lateralen Seite zu liegen scheint. Außerdem zeigen die Ergebnisse eine erhöhte interne Rotation der Tibia in dem verletzten Kniegelenk im Vergleich zu der gesunden Kontrollgruppe während des Laufens. Ein wesentliches Ergebnis dieser Studien stellt zudem das gegensätzliche Verhalten der tibialen Vorwärtsbewegung während passiver und aktiver Situationen dar. Während der passiven Situation zeigt die Tibia des Kniegelenkes mit der VKB Ruptur eine signifikant erhöhte Vorwärtsbewegung im Vergleich zu dem kontralateralen gesunden Kniegelenk. Dahingegen ist das Femur des Kniegelenkes mit der VKB Ruptur im Vergleich zur Tibia während des Laufens über den gesamten Gangzyklus weiter hinten positioniert. Der Bereich von maximaler zu minimaler tibio-femoraler Translation (Range) in der transversalen Ebene ist überraschenderweise in den Kniegelenken mit VKB Ruptur im Vergleich zu den gesunden Kniegelenken über einen gesamten Gangzyklus signifikant geringer. Zwei mögliche Ansätze zur Erklärung der reduzierten Translation im verletzten Gelenk sind: a) eine aktive Stabilisierung von tibio-femoraler Kinematik oder b) eine Subluxation der Tibia nach vorne. Dies beinhaltet eine eventuelle muskuläre Überkompensation im Kniegelenk oder eine Limitierung der Bewegung, die durch sekundäre passive Stabilisatoren hervorgerufen wird. Beide Mechanismen haben einen reduzierten Range von aktiver Bewegung zur Folge, der von der physiologischen Stabilität abweicht. Unabhängig vom zutreffenden Mechanismus impliziert der reduzierte Range von tibio-femoraler Translation während aktiver Bewegung eine Überlastung der passiven Strukturen in passiv lockeren Kniegelenken. Obwohl der Fortschritt von Osteoarthrose in den Patientengruppen nicht nachzuweisen ist, wurde bewusst eine Patientengruppe gewählt, bei denen relevante Veränderungen bekannt sind und ein klinisches Problem darstellen.
Die zusammengefassten Ergebnisse der innerhalb der Dissertation durchgeführten Studien demonstrieren außerdem, dass eine VKB Ruptur sich kritisch auf die Kinematik des Kniegelenkes während des normalen Laufens auswirkt. Eine durch Instabilität hervorgerufene zusätzliche oder auch veränderte Belastung im Gelenk kann einen Mechanismus hervorrufen, durch den sich posttraumatische Degeneration von Knorpel im Kniegelenk erklären lässt.Osteoarthritis is a degenerative joint disease that is characterized by structural and cellular degradation of the cartilage, which is thought to be induced by pathological loading patterns as well as joint instability. The disease naturally affects several joints of the human body; however, the incidence of osteoarthritis is known to be higher in the knee joint than in other joints. The early detection of osteoarthritic disease onset is not yet possible. However, the quantification of knee joint instability and further investigation into how subjects with joint laxity behave during active movement could provide the foundations for understanding the role of instability on joint degeneration. As the anterior cruciate ligament (ACL) is the primary restraint for stabilising anterior tibial translation, it is critical to understand the kinematics of ACL deficient knees compared to physiologically healthy joints. Therefore, this thesis aims to elucidate the role of passive joint laxity, primarily caused as a result of ACL rupture, on active tibio-femoral kinematics during walking. A series of studies have therefore been undertaken within this thesis to provide novel techniques for assessing the functional movement of the knee joint, testing and verifying the efficacy of its use and its application towards improving understanding of clinical problems related to joint instability. In order to quantify tibio-femoral kinematics, a non-invasive approach to evaluate dynamic tibio-femoral motion was developed and then demonstrated as both reproducible and repeatable. In addition, different calibration methods to assess the most suitable joint axes and centres at the lower limb have been tested. The approach was based on motion capture that was combined with advanced techniques for assessing skeletal kinematics (including SARA, SCoRE & OCST), initially determined at the centre of the knee joint. Detailed investigation into the influence of a changing marker placement or the use of different reference measurements to assess knee axes have been achieved to further develop the methodology and to better understand the functional determination of knee joint kinematics. Thirteen patients with MRI confirmed ACL rupture were then tested using the approach and compared against their healthy contralateral limb as well as against healthy control groups using optical measurement techniques to examine the difference in joint stability and kinematics during activities of daily living.In a further development, knee joint kinematics were determined by separating translations at the medial and lateral condyles of the knee in order to further investigate the rotation of the knee in the transverse plane. The consideration of assessing medial and lateral kinematics supplies the new insight that the centre of rotation in the transverse plane seems to be positioned on the lateral side during walking. The results further suggest an increased internal tibial rotation in the ACL ruptured knee joint compared to healthy controls during walking.An investigation in the influence of passive instability on knee joint kinematics during walking has shown passive tibial anterior translation to be significantly greater in the ACL ruptured knees than in the contralateral healthy controls. However, the femora of the ACL ruptured knees generally remained more posterior relative to the tibia within a gait cycle of walking compared to the healthy limbs. Surprisingly, the mean range of tibio-femoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL ruptured knees than in the healthy joints. The results suggest that either active stabilisation of tibio-femoral kinematics or anterior subluxation of the tibia reduces joint translation in lax knees. This implies that either a muscular overcompensation mechanism or a physical limitation due to secondary passive stabilisers occurs within the joint, and thus produces a situation that has a reduced range of active motion than in knees with physiological stability.
Whichever mechanism is appropriate, the reduced range of active tibio-femoral translation implies overloading of the passive structures in passively lax knees.
Although we were unable to follow the progression of Osteoarthritis degeneration in these cohorts we had selected a group that is known to develop relevant changes within the joint and therefore displays clinical problems.
The combined results of these studies further demonstrate that ACL rupture plays a critical role on the kinematics of the knee joint during normal walking, and that additional or altered joint loading due to joint instability could provide a plausible mechanism for explaining post-traumatic degeneration of cartilage in the joint
Anterior cruciate ligament-deficient patients with passive knee joint laxity have a decreased range of anterior-posterior motion during active movements
No full textThe reduced range of active tibiofemoral translation suggests overloading of the passive structures in passively lax knees, either through excessive muscular action or joint subluxation, and could provide a plausible mechanism for explaining posttraumatic degeneration of cartilage in the join
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Restoration of Passive Rotational Tibio-Femoral Laxity after Anterior Cruciate Ligament Reconstruction.
Full text linkWhile the anterior cruciate ligament (ACL) is considered one of the most important ligaments for providing knee joint stability, its influence on rotational laxity is not fully understood and its role in resisting rotation at different flexion angles in vivo remains unknown. In this prospective study, we investigated the relationship between in vivo passive axial rotational laxity and knee flexion angle, as well as how they were altered with ACL injury and reconstruction. A rotometer device was developed to assess knee joint rotational laxity under controlled passive testing. An axial torque of ±2.5Nm was applied to the knee while synchronised fluoroscopic images of the tibia and femur allowed axial rotation of the bones to be accurately determined. Passive rotational laxity tests were completed in 9 patients with an untreated ACL injury and compared to measurements at 3 and 12 months after anatomical single bundle ACL reconstruction, as well as to the contralateral controls. Significant differences in rotational laxity were found between the injured and the healthy contralateral knees with internal rotation values of 8.7°±4.0° and 3.7°±1.4° (p = 0.003) at 30° of flexion and 9.3°±2.6° and 4.0°±2.0° (p = 0.001) at 90° respectively. After 3 months, the rotational laxity remained similar to the injured condition, and significantly different to the healthy knees. However, after 12 months, a considerable reduction of rotational laxity was observed towards the levels of the contralateral controls. The significantly greater laxity observed at both knee flexion angles after 3 months (but not at 12 months), suggests an initial lack of post-operative rotational stability, possibly due to reduced mechanical properties or fixation stability of the graft tissue. After 12 months, reduced levels of rotational laxity compared with the injured and 3 month conditions, both internally and externally, suggests progressive rotational stability of the reconstruction with time
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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