Les blessures tendineuses suscitent un intérêt relativement limité en recherche malgré leur impact personnel et socio-économique substantiel. L'usage des modalités thérapeutiques actuelles n'est pas soutenu par des preuves suffisantes, empêchant un traitement approprié. Cette thèse se veut donc un pas en avant dans la définition de traitements et la caractérisation du processus de réparation des blessures tendineuses. Premièrement, nous avons observé que l'imposition périodique d'un courant direct dans un modèle de blessure in vitro n'améliorait pas la migration cellulaire et la fermeture de la lésion. Au contraire, le champ électrique devenait délétère à forte amplitude. Deuxièmement, des rats débutaient un protocole de course volontaire immédiatement après avoir subi une lésion du tendon d'Achille causée par l'injection de collagenase. L'exercice hâtif accentuait la réaction inflammatoire mais favorisait la récupération du contenu en collagène dans les tendons blessés. Paradoxalement, les propriétés mécaniques semblaient alors réduites. Les rats qui commençaient l'exercice 7 jours après la blessure démontraient de meilleures propriétés mécaniques après 28 jours que les rats soumis au protocole hâtif. Troisièmement, nous avons induit un état thrombocytopénique ou neutropénique chez des souris afin de caractériser le rôle respectif des plaquettes et des neutrophiles dans la réparation tendineuse. Le tendon d'Achille était sectionné puis suturé pour permettre une mise en charge immédiate. La perte des plaquettes affectait légèrement la vascularisation et le contenu en collagène et diminuait le stress maximal supporté par les tendons blessés. Cependant, cette dernière différence disparaissait ultérieurement. La réduction du nombre de neutrophiles stimulait l'accumulation des macrophages et la prolifération cellulaire dans les tendons endommagés. Par contre, la replication cellulaire s'atténuait suivant une baisse des macrophages dans le tendon, suggérant une relation entre les deux phénomènes. Somme toute, ces travaux apportent de nouvelles connaissances sur le traitement et la réparation des blessures tendineuses et incitent à la poursuite des recherches. Entre autres, la définition de paramètres appropriés pour la stimulation électrique et les conséquences néfastes de l'exercice précoce sont des enjeux cliniques évidents. Le rôle limité que joueraient les plaquettes et les neutrophiles motive aussi l'analyse d'autres éléments, dont les macrophages, impliqués dans le processus de réparation tendineuse.

A literatura a respeito da capacidade da ressonância magnética em avaliar as afecções do tendão da cabeça longa do bíceps é escassa, a despeito da importância destas condições na gênese da dor e da disfunção do ombro. O objetivo primário deste estudo foi analisar o desempenho diagnóstico da ressonância magnética na detecção de roturas e de instabilidade na porção intra-articular deste tendão, comparando os achados de imagem com os dados de cirurgia artroscópica (padrão de referência). Foram objetivos secundários determinar as reprodutibilidades intraobservador e interobservador, avaliar a capacidade da ressonância magnética em classificar os tipos de rotura, avaliar a acurácia da associação entre alterações tendíneas e roturas do manguito rotador na instabilidade, além de pesquisar fatores preditores da acurácia da ressonância magnética. Foi realizado estudo transversal, com segmentos retrospectivo e prospectivo. Os critérios de inclusão foram indicação de cirurgia artroscópica do ombro para reparo do manguito rotador e exame de ressonância magnética préoperatória. Os critérios de exclusão foram: manipulação cirúrgica pregressa no ombro estudado; exames com imagens de má qualidade; intervalo entre exame pré-operatório e procedimento cirúrgico superior a um ano; indicação de técnica cirúrgica por via aberta. Foram estudados 100 ombros de 98 pacientes, operados consecutivamente de abril de 2013 a março de 2017 (47 meses). Todos os pacientes realizaram ressonância magnética de 1,5 Tesla em nossa instituição, sem utilização de contraste intra-articular. Todas as cirurgias foram realizadas pelos mesmos 3 cirurgiões, com 10 a 12 anos de experiência em cirurgia do ombro e cotovelo. Dois radiologistas, com 4 e 8 anos de experiência na área musculoesquelética, avaliaram as imagens de todos os exames, de forma independente e sem conhecimento prévio dos resultados intra-operatórios. Os mesmos casos foram revistos por um dos radiologistas, 4 meses após a primeira análise. Nossos resultados demostraram desempenho diagnóstico moderado da ressonância magnética para detecção de roturas do bíceps, com sensibilidades entre 71,1% a 73,3%, especificidades de 72,7% e acurácia entre 72 e 73%. A reprodutibilidade interobservador foi substancial (coeficiente Kappa de 0,62 a 0,69) e a reprodutibilidade intraobservador foi substancial ou quase perfeita na avaliação das roturas (coeficiente Kappa de 0,74 a 0,82). Houve correlação moderada entre os métodos para classificar o tipo de rotura (coeficiente Kappa de 0,38 a 0,47). Quando consideradas roturas completas, foram calculadas especificidades entre 75,0% e 95,7%, porém sensibilidades de 55,6% a 66,7%. Para o diagnóstico de instabilidade, observa-se sensibilidade de 52,4% a 59,1%, especificidade de 70,5% a 84% e acurácia de 64,4% a 69,5%. A avaliação combinada do deslocamento tendíneo e das roturas do manguito rotador resultou em sensibilidades de 17,5% a 47,7% e especificidades de 72,7% a 90,7%. A reprodutibilidade interobservador foi substancial (coeficiente Kappa de 0,59 a 0,7) e a reprodutibilidade intraobservador foi substancial ou quase perfeita (coeficiente Kappa de 0,76 a 0,80) para avaliação de instabilidade. Não identificamos fatores preditores para acurácia da ressonância magnética na pesquisa dessas afecções / There is paucity of literature regarding the performance of magnetic resonance imaging to assess long head of the biceps tendon disorders, despite the importance of such disorders in the genesis of pain and shoulder dysfunction. The primary objective of this study was to analyze the diagnostic performance of magnetic resonance imaging in the detection of tears and instability of the intra-articular portion of this tendon, comparing imaging findings with data from arthroscopic surgery (reference standard). Secondary objectives were to determine intraobserver and interobserver reproducibility; to evaluate the capability of MRI to classify types of tears; to evaluate the accuracy of the association between tendon displacement and rotator cuff tears to predict instability; to investigate predictive factors of magnetic resonance accuracy. A cross-sectional study was carried out, with retrospective and prospective segments. Inclusion criteria were indication of arthroscopic shoulder surgery for rotator cuff repair and preoperative magnetic resonance imaging. Exclusion criteria were: previous surgical manipulation in the studied shoulder; poor quality images; interval between preoperative examination and surgical procedure above one year; and indication of open surgical technique. We studied 100 shoulders of 98 consecutively operated patients from April 2013 to March 2017 (47 months). All patients underwent magnetic resonance imaging at our institution, using a 1.5 Tesla scanner, without use of intra-articular contrast. All surgeries were performed by the same 3 surgeons, with 10 to 12 years of experience in shoulder and elbow surgery. Two radiologists, with 4 and 8 years of experience in musculoskeletal radiology, evaluated the images independently and without previous knowledge of the intraoperative results. The same cases were reviewed by one of the radiologists, 4 months after the first analysis. Our results demonstrated a moderate diagnostic performance of MRI to detect biceps tears, with sensitivities between 71.1% and 73.3%, specificities of 72.7% and accuracy between 72 and 73%. Interobserver reproducibility was substantial (Kappa coefficient ranged from 0.62 to 0.69), and intraobserver reproducibility was substantial or almost perfect (Kappa coefficient ranged from 0.74 to 0.82). There was moderate correlation between the methods when classifying the type of tear (Kappa coefficient ranged from 0.38 to 0.47). Regarding full-thickness tears, specificities were calculated between 75.0% and 95.7%, but sensitivities from 55.6% to 66.7%. For the diagnosis of instability, sensitivity was from 52.4% to 59.1%, specificity was from 70.5% to 84% and accuracy was from 64,4% to 69,5%. The combined evaluation of tendon displacement and rotator cuff tears resulted in sensitivities from 17.5% to 47.7% and specificities from 72.7% to 90.7%. Interobserver reproducibility was substantial (Kappa coefficient ranged from 0.59 to 0.7), and intraobserver reproducibility was substantial or almost perfect (Kappa coefficient ranged from 0.76 to 0.80) for instability assessment. We did not identify predictive factors for magnetic resonance imaging accuracy in the assessment of these conditions

Einleitung: Die Verwendung der Hamstringsehnen als Transplantate in der rekonstruktiven Chirurgie des vorderen Kreuzbandes stellt eine wenig invasive Alternative zur herkömmlichen Verwendung des mittleren Patellarsehnendrittels dar. Hier ist jedoch die Transplantatverankerung, die bisher meist extrakortikal, also weit entfernt der nativen Kreuzbandinsertion angelegt wurde problematisch. Hierdurch zeigt das Transplantat-Verankerungs-Konstrukt ein unbefriedigendes elastisches und plastisches Dehnungsverhalten, welches u.A. für eine geringere Kniestabilität und eine gestörte ossäre Transplantatintegration verantwortlich gemacht wird. Eine anatomiegerechte Transplantatverankerung auf Gelenkniveau könnte die mechanischen und biologischen Rahmenbedingungen verbessern, um so die Hamstringsehnen als Alternativtransplantat mit verbesserter klinischer Prognose einsetzten zu können. Eine direkte Verankerung mit Interferenzschrauben erlaubt eine solche anatomische Transplantatverankerung, so dass wir dieses neue Operationsverfahren biomechanisch und tierexperimentell untersucht haben. Methoden: In sechs biomechanischen Teilprojekten und in zwei tierexperimentellen Untersuchungen wurde die Eignung der direkten Verankerung mit biodegradierbaren Interferenzschrauben der Hamstringsehnen im Vergleich zu konventionellen Patellar- und Hamstringsehnen-Techniken untersucht. Ergebnisse: Wir konnten demonstrieren, dass die initiale femorale Verankerungsfestigkeit, auch in Sinne der sog. Hybridfixation ausreichend ist. Die tibiale Verankerung unterliegt jedoch verschiedenen Variablen und bedarf einer differenzierten klinischen Anwendung. Im Vergleich zu konventionellen Techniken der Hamstringsehnen-Verankerung kann das plastische und elastische Dehnungsverhalten durch die Verankerung mit Interferenzschrauben deutlich verbessert werden, wobei jedoch das mechanische Verhalten des Patellarsehnen-Transplantates nicht erreicht wurde. Die tierexperimentelle Analyse zeigt auf, dass die ossäre Integration durch die Kompression des Transplantates auf Gelenkniveau soweit verbessert werden kann, dass sog. Tunnelaufweitungen, als Zeichen einer gestörten Einheilung vermieden werden und, dass das Transplantat mit einer direkten Bandinsertion, entsprechend des nativen vorderen Kreuzbandes, auf Gelenkniveau einheilt. Schlussfolgerung: Die hier vorgelegten Untersuchungen haben erstmals umfassend die Rahmenbedingungen der Interferenzschrauben-Verankerung der Hamstringsehnen beschrieben; einer Technik die inzwischen weltweit verbreitete Anwendung findet. Durch eine anatomische Transplantatverankerung auf Gelenkniveau besteht nun die Möglichkeit, mit optimierten mechanischen und biologischen Rahmenbedingungen eine adäquate Alternativtechnik zur konventionellen Verwendung der Patellarsehnen anzubieten. / Introduction: The use of hamstring tendon grafts as a substitute for anterior cruciate ligament reconstruction presents a less invasive procedure compared to the conventional bone-patellar tendon- bone graft. Current techniques of hamstring tendon anterior cruciate ligament reconstruction utilise an extra-cortical fixation. An extra-cortical fixation, however, shows inferior structural parameters with respect to construct slippage or stiffness. These factors may contribute to less stable knees after reconstruction and a delayed osseous integration of the grafted tissue. An anatomic hamstring tendon graft fixation close to the joint line may overcome these problems and may present an alternative to the conventional bone-patellar tendon-bone graft by means of optimised mechanical and biological boundary conditions. We therefore studied anatomic interference fit fixation of hamstring tendon grafts in different mechanical and animal experimental setups. Methods: In six different biomechanical projects and two animal studies, we studied the capability of hamstring tendon interference fit fixation to be used as a secure and reproducible technique of anterior cruciate ligament reconstruction and compared these data to the bone-patellar tendon-bone graft and other conventional hamstring tendon graft fixation techniques. Results: We could demonstrate that the initial femoral fixation strength, as well as a hybrid fixation is sufficient. However, the tibial fixation presents the weak link and underlies different variables, such as bone density and screw geometry. Compared to conventional extra-cortical fixation techniques, the viscoelastic and viscoplastic deformation behaviour could be optimized, but did not reach comparable data to the bone-patellar tendon-bone graft. Animal experiments could clearly demonstrate that interference fit fixation promotes osseous tendon incorporation and minimises the likely hood of a tunnel enlargement. We further found that in contrast to conventional fixation techniques the use of interference screws resulted in the development of a direct ligament insertion anatomy, directly at the joint line, like it is found with the native anterior cruciate ligament. Conclusion: With the present studies we could first describe the mechanical and biological boundary conditions of hamstring tendon interference fit fixation, a technique which gains increased world wide attention as a standard procedure in cruciate ligament surgery. By using an anatomic joint line fixation of hamstring tendon grafts, there are optimised boundary conditions, which therefore presents an adequate alternative to the conventional bone-patellar tendon-bone graft in cruciate ligament reconstruction.

A direct bone tendon junction consists of four zones: tendon, uncalcified fibrocartilage, calcified fibrocartilage, and bone. The uncalcified and calcified fibrocartilage together forms the transition zone. This organization ensures a gradual transition in stiffness and material properties, and protects the junction from failure. Transition zone regeneration during bone tendon junction healing is important to restore this unique protective mechanism. / Bone tendon junction repair is involved in many orthopaedic reconstructive procedures. Healing is observed to be slow. The junction often heals by fibrous tissue formation. Previous attempts to enhance bone tendon junction healing have resulted in increased bone formation. However, fibrocartilage transition zone is not restored. / This thesis describes a series of studies on transition zone regeneration in bone tendon junction healing using two partial patellectomy animal models. The healing process inside a bone trough was first studied and characterized. Little transition zone regeneration was observed except near the articular cartilage cut surface. The possibility of using articular cartilage to stimulate transition zone regeneration was explored. Both articular cartilage autograft and allogeneic cultured chondrocyte pellet implantations resulted in significantly increased fibrocartilage transition zone regeneration. Cell tracking indicated that the regenerated tissue likely originated from host cells. To elucidate the mechanism of stimulation by allogeneic cultured chondrocyte pellet, the role of cellular and matrix component needed to be differentiated. Freezing and rapid freeze thaw cycles permanently devitalized the allogeneic cultured chondrocyte pellet, but retained its structural integrity and matrix contents. Preliminary results indicated that implantation of the devitalized allogeneic cultured chondrocyte pellet could still increase fibrocartilage transition zone regeneration. Cellular activity seemed not to be essential for the stimulatory effect. / With further research and development, it is envisioned that a cartilage-based stimulation method for fibrocartilage transition zone regeneration in bone tendon junction healing will be developed for clinical application. / Wong Wan Nar, Margaret. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3423. / Thesis (M.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 216-231). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Compliance to strict home exercise programs is understood to be a mainstay of post-surgical flexor tendon rehabilitation. Therapists recognise the potential of poor compliance (overuse or under-use of prescribed exercise) and spontaneous movements during rehabilitation. Some therapists may suggest that compliance to specific exercise regimens and control of spontaneous or general movements are fundamentally important in optimising the rehabilitation outcomes and minimising the potential of adverse events. Yet there is little objective data to document the actual levels of exercise or spontaneous finger movement performed outside the clinical setting. The purpose of this study was to document both diary and instrumented methods of reporting finger movement during a 48hr period. Following surgical repair of the flexor tendon, subjects attending a private hand therapy clinic provided consent and reported subjective diary (n=16) data of sets and repetitions of exercise for up to 6 weeks post-operatively. Nine subjects also had instrumented data logged on 3 occasions during the first 6 weeks of rehabilitation and were not fully aware of the purpose of the instrumentation. All subjects were instructed to perform 10 passive followed by 10 active exercises every waking hour, for the first 6 weeks and were assessed on range of motion, DASH, pain and strength. Results demonstrated that patients reported, via their diaries, that they are on average 80% compliant. Parallel data logger information suggests that this figure is more likely to reflect 50% compliance. A significant (p< .05) increase in spontaneous movements in the last 2 weeks of the 6 week assessment period was detected. No significant correlation between patient's level of compliance or spontaneous movement and their outcome were detected.

Made available in DSpace on 2016-06-02T20:19:23Z (GMT). No. of bitstreams: 1 5783.pdf: 3013658 bytes, checksum: 554232e857a534b5beaacd869958f849 (MD5) Previous issue date: 2014-02-27 / Universidade Federal de Minas Gerais / Background: Shoulder pain is one of the most common and disabling complaints, and shoulder impingement syndrome (SI) is one of the most common causes of this symptom. Recently, several records of pressure pain threshold become useful tools as topographical pressure pain sensitivity maps to assess the state of awareness on various musculoskeletal conditions. However, there are no studies that have proposed topographic maps to assess shoulder sensitivity. Objective: To develop topographical pressure pain sensitivity maps of the shoulder in subjects with SI as compared with healthy subjects, and to analyze the intra-rater reliability of the topographic maps of the shoulder in healthy and asymptomatic subjects. Methods: Initially, 29 predetermined points and 4 points in fixed anatomical locations have been identified on both shoulders of 25 patients with SI and 25 healthy and asymptomatic subjects. The map was determined from anatomical landmarks and anthropometric measurements of each individual. Of all 32 points assessed, 11 are located in bony structures, 11 in muscle bellies, 9 in tendons, 1 on the coracoacromial ligament and 1 over the acromioclavicular joint. The pressure pain threshold was evaluated at all points in the dominant and nondominant side of healthy subjects and in the symptomatic and asymptomatic sides in subjects with SI. The sides and points were randomized prior to the evaluation. The pressure pain threshold was assessed 3 times on each point (20 s of rest), and the mean of each measure was considered for analysis. Results: The methodology used allowed us to characterize a topographic map for assessing shoulder pain sensitivity in subjects with SI. There was no difference between the SI and healthy groups (p> 0,05). However, the symptomatic side of subjects with SI showed higher sensitization (p <0.05), in some locations (points 6 and 7, located on the spine of the scapula and point 10, located on the infraspinatus muscle). The tendons were the most sensitive structures, followed by the bones for both groups. There was excellent intra-rater reliability between the trials of pressure pain threshold for each point (non-dominant side of healthy subjects, ICC: 0.86-0.98; dominant side of healthy subjects, ICC: 0.89-0.96). The standard error of measurement and minimal detectable change presented range, respectively, 28.4-55.9kPa and 66.7-131.4kPa (non-dominant side), 29.4-60.8kPa and 69.6-142.2kPa (dominant side). Conclusion: The proposed topographical pressure pain sensitivity maps of the shoulder was useful for detecting the state of peripheral hyperalgesia in different anatomical structures (bones, muscles and tendons) in subjects with SI, and was reliable for assessing pressure pain sensitivity on the shoulder in healthy subjects. / Contextualização: A dor no ombro é uma das queixas mais comuns e incapacitantes, e a síndrome do impacto do ombro (SI) é uma das causas mais comuns desta sintomatologia. Recentemente, mapas topográficos com vários registros de limiar de dor à pressão tornaram-se ferramentas úteis para avaliar o estado de sensibilização em diversas condições musculoesqueléticas. No entanto, não há ainda estudos que tenham proposto mapas topográficos para avaliar a sensibilidade dolorosa no ombro. Objetivo: Propor e caracterizar um mapa topográfico de sensibilidade dolorosa à pressão no ombro em indivíduos com SI e comparar a indivíduos saudáveis, e analisar a confiabilidade intra-examinador do mapa topográfico de sensibilidade dolorosa à pressão no ombro em indivíduos saudáveis e assintomáticos. Métodos: Inicialmente, 29 pontos pré-determinados e 4 pontos em localizações anatômicas fixas, foram identificados em ambos os ombros de 25 portadores da SI e 25 indivíduos saudáveis e assintomáticos no ombro. O mapa foi determinado a partir de pontos anatômicos e medidas antropométricas de cada indivíduo. De 32 pontos avaliados, 11 se localizam em estruturas ósseas, 11 em ventres musculares, 9 sobre tendões ou junções miotendíneas, 1 sobre o ligamento coracoacromial e 1 sobre a articulação acrômioclavicular. O limiar de dor à pressão foi avaliado em todos os pontos, nos lados dominante e não dominante dos indivíduos saudáveis e, nos lados sintomático e assintomático dos indivíduos com SI do ombro. Os lados e os pontos a serem avaliados foram randomizados antes da coleta de dados. O limiar de dor à pressão foi examinado 3 vezes sobre cada ponto (intervalo 20 s), e a média entre cada medida foi considerada para a análise. Resultados: A metodologia utilizada permitiu caracterizar um mapa topográfico para a avaliação da sensibilidade dolorosa do ombro em indivíduos com SI. Não houve diferença entre os grupos SI e saudáveis (p>0.05). No entanto, o lado sintomático dos indivíduos com SI apresentou maior sensibilização (p<0.05) em algumas localizações (pontos 6 e 7, localizados sobre a espinha da escápula e ponto 10, localizado sobre o músculo infraespinal). Os tendões foram as estruturas mais sensíveis, seguido dos ossos, para ambos os grupos SI e indivíduos saudáveis. Houve excelente confiabilidade intra-examinador, entre as repetições de limiar de dor á pressão para cada ponto (lado não dominante dos indivíduos saudáveis, ICC: 0.86-0.98; lado dominante dos indivíduos saudáveis, ICC: 0.89-0.96). O erro padrão da medida e a mínima diferença detectável apresentaram amplitude, respectivamente, 28.4-55.9kPa e 66.7- 131.4kPa (lado não dominante); 29.4-60.8kPa e 69.6-142.2kPa(lado dominante). Conclusão: O mapa topográfico proposto foi útil para detectar o estado de hiperalgesia periférica em diferentes estruturas anatômicas (ossos, músculos e tendões) em indivíduos com SI, e mostrou-se confiável para avaliar a sensibilidade dolorosa à pressão no ombro em sujeitos saudáveis.

Tendons are able to undergo repeated cyclic loading in vivo without permanent deformation or mechanical failure. However, diseased, traumatised and decellularised tendons gradually lose the ability to resist load and fail because of creep deformation. The molecular basis of the mechanical properties of tendon and how cells establish and maintain these properties is poorly understood. New knowledge in this area is required to develop novel medical strategies to improve tendon repair and regeneration. Recent advances in tissue bioengineering have led to the formation of fibrin-based tendon-like tissue (‘tendon constructs’) that display the mechanical properties and ultrastructure of embryonic tendon. This thesis presents the characterisation of the tendon constructs derived from primary fibroblasts to understand the relationship between the cells and matrix during tissue development, and to establish the standard of in vitro engineered tendons. These findings facilitated protocol development to engineer human tendon-like tissue derived from stem cells. Novel findings of constructs formed from differentiated human pluripotent stem cells in feeder and feeder-free systems are presented. Fibrin gels were seeded with human dermal fibroblasts (HDF), chick tendon fibroblasts (CTF), MAN5 (Manchester, embryonic stem) cells, human embryonic stem cells (HuES7) and induced pluripotent stem cells (iPS). The gels were cultured until isometric tendon-like constructs were formed (T0) or continued for four or ten days post-formation. The mechanical properties, histology and gene expression of the constructs were analysed and compared between the constructs seeded with the aforementioned cell types. Varying the initial cell number (tested in CTF-seeded fibrin and collagen based constructs) significantly affected the final cell count and the mechanical properties of the constructs differentially at T0 and T10. A non-linear relationship exists between the initial and final cell number, and, between the initial cell number and mechanical properties. However, the results showed that cell number impacted cell-matrix stabilisation as strength per se was strongly dependent on initial cell number. Collagen-based constructs showed a significantly lower stiffness compared with fibrin-based constructs at T0 and T10. The stem cells and primary cells reproducibly underwent morphogenesis to form a 3D tissue similar to embryonic tendon in vivo expressing ECM markers such as collagens type I and III. The tissue also exhibited the ultrastructural characteristics and biomechanical profile of immature tendons. RNA seq and qPCR results demonstrated the upregulation of tendon-specific genes. Tendon-like tissue generated from human stem cells and HDFs in vitro has the potential to replace functional tissue lost through disease and to advance the understanding of the molecular basis of human tenogenesis.

A failure associated with steel corrosion was identified in early 2011 in a bridge external post-tensioned tendon, approximately eight years after construction. Large voids in the grout and pockets of non-homogeneous material were identified. The non-homogeneous grout was characterized by high moisture content, and in most cases, the chloride content was lower than conservative threshold values. The non-homogeneous grout also had high pH and high content of sulfates (approximately in the range of 10,000-ppm). As a result, there was an interest in the study of possible corrosion development in repaired systems in which the affected tendons have been re-grouted with dissimilar grouts. The presence of two distinct grouting materials, manifested by the existing/simulated base grout and a newly introduced repair grout, provided the dissimilar grout condition studied. Corrosion activity was monitored in un-stressed mock up assemblies, in sections retrieved from the failed tendon, and in samples immersed in simulated pore solution. Corrosion activity was monitored through macrocell current, linear polarization resistance, open circuit potential, potentiodynamic scans, and electrochemical impedance spectroscopy. Samples in simulated pore solutions were studied at various pH levels and constituent concentrations. All samples were repaired or built with commercially available grouts. After analysis, no evidence of corrosion development was found when both existing and repair grout were free of material deficiencies. Corrosion activity was noted in the presence of nonhomogeneous grout and an increase in rate was observed due to macrocell coupling with sections containing normal grout. Results suggest that early exposure to sulfate to hydroxyl ion ratio as low 0.35 may prevent steel passivation and result in early high corrosion rates. Otherwise, sulfate to hydroxyl ratios as high as three may not be sufficient to initiate corrosion after formation of passive layer.

This Master’s thesis concerns a design of the highway bridge over Nitra River in Nitra, Slovakia. Three variants were designed from which one was selected and analyzed in detail. It is a three box cell girder made of post-tensioned concrete and constructed as a free cantilever bridge. The bridge is assessed according to Eurocodes. The limit states for persistent and transient design situations were taken into account at carrying out the design. There are drawings attached to this thesis as illustrative drawings of the bridge and its construction stages, drawings of the prestress tendons and reinforcement.

<p>If designed and constructed properly, post-tensioned construction can provide improved durability and offers the ability to construct longer span bridges and curved girders. Furthermore, this method of construction has become economically competitive with traditional, pretensioned concrete and steel plate girder bridges. A critical issue, however, has been corrosion of the steel strand. While grouting has been the primary corrosion protection method for the strand, experience has shown that grouting presents its own problems and limitations that compromised the durability and service-life of bridges. As a result, unbonded post-tensioning has gained interest as it eliminates issues with grouting and allows for inspection as well as future strand replacement. The behavior and strength of structures constructed with unbonded post-tensioning, however, is not well understood, especially shear strength. Therefore, the objective of this research investigation is to evaluate the structural performance of prestressed girders containing unbonded tendons with a primary focus on shear strength. The scope of this phase of the research was to develop the means and methods to construct and test girder specimens with multiple design criteria and allow evaluation of multiple test variables. The research developed the materials and procedures to enable the large scale testing program to be developed. Finally, the procedures developed were verified through the construction of the initial set of test specimens and testing of the first shear specimen.</p>