Analyse des images échographiques du tendon équin

Les articulations du cheval de sport de haut niveau sont très sollicitées, ce qui peut entraîner de multiples tendinopathies telles que la déchirure ou la rupture du Tendon Fléchisseur Superficiel du Doigt (SDFT). L’imagerie par échographie, peu coûteuse, non invasive et propice à l’exploration de la structure interne du SDFT est régulièrement utilisée pour évaluer l’intégrité du tendon. Cependant, le pronostic fonctionnel sur l’état des tendons à partir des examens cliniques est souvent difficile à poser. Cette difficulté résulte du manque d’information a priori des structures visibles sur les images échographiques cliniques qui peut entraîner une interprétation subjective ou erronée sur l’état du tendon. Une autre difficulté est le manque d’outils en imagerie pour supporter les vétérinaires dans leur prise de décision. Dans cette recherche, nous nous intéressons à développer une méthode d’analyse pour évaluer objectivement la structure interne des SDFTs à partir des examens cliniques. Deux axes de recherche sont privilégiés : − La simulation, dans des conditions réalistes, de la propagation des ondes ultrasonores à travers la structure tendineuse, dans le but de reproduire l’aspect général clinique des images échographiques. Les résultats de la simulation nous aideront à déduire l’information sur le contenu structural observé sur les images cliniques des tendons sains et lésés. Cette information servira ensuite à : − L’élaboration de méthodes de segmentation de la structure interne et de la quantification de la densité des faisceaux fibreux des tendons SDFTs à partir des examens cliniques. La simulation nous a permis de noter d’une manière objective que les structures hyperéchogènes observées sur les échographies des tendons normaux sont les résultats de la rétrodiffusion des ondes ultrasonores sur les interstices qui entourent les faisceaux fibreux. Les interstices qui génèrent les structures hyperéchogènes à une fréquence de 7,5 MHz sont ceux qui ont des épaisseurs supérieures à la longueur d’onde acoustique λ (~256 μm) selon l’axe de propagation des ondes ultrasonores. Les méthodes de segmentation utilisées se résument en deux approches principales : une première méthode est dédiée exclusivement à la segmentation des échographies du SDFT et combine une méthode de décompression logarithmique et des opérations morphologiques. Une deuxième approche, plus générale, est dédiée à la segmentation des échographies et des macrophotographies du SDFT. Elle se base essentiellement sur un nouvel algorithme d’amincissement morphologique. La quantification de la structure interne des tendons SDFT a permis de discerner objectivement les tendons normaux des lésés. L’analyse statistique sur la densité des faisceaux fibreux, évaluée à partir des examens cliniques sur des sites préférentiels des SDFTs normaux a montré une faible densité sur le site distal. Cette analyse a été corroborée par l’application de la même approche de segmentation et de quantification sur une base de données d’images macrophotographiques des SDFTs. Cela peut traduire une faiblesse en traction mécanique du site distal et expliquer la fréquence élevée des blessures sur ce site. Ces résultats pourront éventuellement être adaptés à l’étude des tendons et des ligaments chez l’humain

Mechanical Behaviour of Tendinopathic Tendon: An Engineering Perspective

Tendinopathy is a debilitating disease affecting millions of people worldwide. The aetiology of this disease is not well understood, and treatment remains difficult due to a lack of evidence-based management. This dissertation sought to quantify the mechanical behaviour of tendon in order to understand the difference between healthy and tendinopathic tendons. The findings in this dissertation offer insights that may contribute toward the development of better clinical management of tendinopathy

Speckle Detection in Ultrasonic Images Using Unsupervised Clustering Techniques

Research for the improvement of the quality of clinical ultrasound images has been a topic of interest for researchers and physicians. One of the challenges is the presence of speckle artifacts. This dissertation reviews the speckle phenomena in such images, and develops algorithms to better identify this artifact in sonographic images. Speckle artifact is categorized into two groups: partially developed speckles and fully developed speckles (FDS). This concept has been used, along with the classification techniques, to segment the ultrasound images into patches and classify the patches in the image as FDS or non-FDS. The proposed algorithms and the results of the experiments have been validated using simulation, phantom and real data that were created for the purposes of this study or taken from other research groups. Current speckle detection methods do not optimize statistical features and they are not based on machine learning techniques. For the first time this work introduces a novel method for searching and extracting the best features for optimizing speckle detection rate using statistical machine learning and ensemble classification. Potential applications include strain imaging by tracking speckle displacement, elastography, speckle tracking and suppression applications, and needle-tracking applications.Ph.D., Biomedical Engineering -- Drexel University, 201

Exploring the Role of Extracellular Vesicles in Equine Musculoskeletal Pathologies and Associated Regenerative Therapies

Horses are used in a variety of disciplines, including dressage, show jumping, eventing and racing. Thus, the equine athlete is predisposed to the development of musculoskeletal injury. Both equine osteoarthritis and tendon injury are significant causes of pain, lameness and are equine welfare concerns. Osteoarthritis and tendon injuries are usually diagnosed at late stage and treatment includes biological therapies, such as mesenchymal stem cell and platelet-rich plasma therapy. These therapeutics often produce variable clinical outcomes and their mechanistic action is not well characterised. It is hypothesised that extracellular vesicles may be involved in mediating the effect of biological therapies, and could offer a viable cell-free alternative therapeutic. The aims of this thesis were as follows; (1) To investigate extracellular vesicle structure and protein cargo from a longitudinal in vivo model of equine osteoarthritis treated with mesenchymal stem cells, in order to determine disease-associated extracellular vesicle cargo, and their potential role in mediating mesenchymal stem cell therapy. (2) Explore the differences in composition of extracellular vesicles from healthy horses and those with clinically diagnosed osteoarthritis using both spectroscopic and spectrometric techniques. (3) Explore the composition of platelet-rich plasma and platelet-rich plasma derived extracellular vesicles using mass spectrometry proteomics. (4) Investigate the effect of platelet-rich plasma and platelet-rich plasma derived extracellular vesicles in an in vitro model of equine tendon injury, using mass spectrometry proteomics and gene expression analysis. Extracellular vesicles were characterised and a range of spectroscopic and spectrometric techniques used including mass spectrometry. This thesis has catalogued extracellular vesicle cargo from synovial fluid in both an in vivo models of equine osteoarthritis (carpal osteochondral fragment model) and naturally occurring disease. As some protein content can be attributed to disease progression they could serve as potential biomarkers used in the development of diagnostic tests to aid earlier diagnosis and intervention in osteoarthritis. Further to this, my work has identified altered cargo in association with extracellular vesicles following mesenchymal stem cell treatment, and cellular cargo following platelet-rich plasma derived extracellular vesicle treatment, emphasising their role as mediators of therapy and their capacity to serve as future therapeutics. Therefore, they might be considered as a viable therapeutic alternative that warrants further investigation in the case of mesenchymal stem cell therapy, in order to deliver a safer more reproducible therapeutic. With respect to platelet-rich plasma, extracellular vesicles should be considered when optimising the composition of platelet-rich plasma for more efficacious outcomes, or considered as an alternative to platelet rich plasma

A Biomechanical Characterisation of Eccentric and Concentric Loading of the Triceps Surae Complex.

PhDThis thesis presents a biomechanical characterisation of eccentric (EL) and concentric loading (CL) of the triceps surae. EL is commonly adopted as an effective treatment for Achilles tendinopathy, with notably better treatment success compared with CL. However, there is a lack of consensus about the most appropriate protocols for completing triceps surae exercises. Exercise parameters such as speed and load are important and may affect the stimuli sensed by the muscle-tendon unit and thus influence repair. This thesis aims to biomechanically characterise and compare EL and CL as a basis for trying to understand treatment effects. A measuring system comprising motion tracking, 2D ultrasound, force plates and EMG was adopted and a semi-automatic tracking algorithm developed to track the muscle-tendon junction throughout the loading cycle (Chapter 3). Having validated the accuracy of measurements (Chapter 4), the effect of variables such as speed of exercise (chapter 5) and addition of load (Chapter 6) were assessed on Achilles tendon force, stiffness, stress, strain and force perturbations as well as muscle activation and contraction frequency (Chapter 7), in healthy subjects. It was found that EL and CL do not differ in terms of tendon force, stiffness or strain. However, EL is characterised by lower muscle activation and by 10 Hz perturbations present within the tendon. These perturbations were found to be significantly dependent on movement speed and load applied during EL movements only. However, no effect of speed was found on tendon force, stiffness and strain during either exercise movement. Finally, temporo-spatial analysis of the calf revealed region specific variations in muscle activation during both EL and CL, with 10 Hz perturbations coming predominantly from medial soleus and medial gastrocnemius muscle activity. These studies provide new information about the biomechanics of EL or CL, which should enhance understanding, and development, of conservative Achilles tendinopathy management

Osteoarthritis: pathogenesis and therapeutic interventions for a whole joint disease

__Abstract__ Osteoarthritis (OA) is an invalidating disease characterized by progressive cartilage degradation. OA is the most prevalent arthritic disease and leading cause of disability that effects approximately 34% of the population in the United states over age 65. Also in the Netherlands, approximately 30% of persons aged 65 and older are affected in either the hip or knee joint by this severely disabling disease. Due to the obvious cartilage pathology, research has much focused on articular cartilage and chondrocyte pathobiology. Over the years more knowledge has been gained on complex biochemical and biomechanical influences of chondrocyte behavior. During the past decade, however, pathologic cellular and structural changes in subchondral and trabecular bone, ligaments, synovium, supporting musculature, fibrocartilagenous structures such as the meniscus, and intra-articular fat tissue support the idea that osteoarthritis is not just a cartilage problem. In the current dogma, OA is explained as ‘a whole joint disease’ that involves a degenerative continuum between multiple joint tissues and cell types

A combined in vivo and in vitro approach to assess supraspinatus activation and tissue responses to arm elevation demands

Rotator cuff degeneration affects a large portion of the human population, yet knowledge surrounding which loading scenarios allow transition from healthy to diseased states remains largely unresolved. Mechanistic progression of rotator cuff pathology often originates in the supraspinatus before cascading to other tissues, leading to substantial degeneration. Posture, loading and repetitive motions are known risk factors that exacerbate shoulder injury progression. This suggests a causal relationship between specific upper extremity task scenarios and degenerative rotator cuff loading. This thesis intentionally explored regional activations of the supraspinatus and accompanying tendon loading across a range of postures. The global objective was to evaluate how postural and task intensity differences alter tissue-level mechanical parameters in both in vivo muscular activation and in vitro tangent stiffness, hysteresis and optical stretch ratios. These findings combine in vivo muscular activation and physiologically relevant in vitro mechanical testing results through novel methods to better understand supraspinatus loading. Three experimental studies provided the means to achieve this global objective. In Vivo Examination of Supraspinatus Activation: The purposes of this study were 1) to document the interplay of anterior and posterior supraspinatus activations and 2) to describe the influences of posture and hand loads on anterior and posterior supraspinatus activations. Forty participants completed arm elevations in seven planes of elevation with three hand loads that were normalized to the individual’s maximal elevation force. Indwelling electromyography was collected from the anterior and posterior regions of supraspinatus. Hand load and elevation angle interacted to affect the anterior region activation in most planes of elevation by up to 41% of maximal activation, but these changes were less influential for the posterior portion. Activation patterns between the two regions suggest different functional roles of the supraspinatus portions; consistent levels of activation in the posterior supraspinatus may indicate this region is primarily a glenohumeral stabilizer, while the larger anterior region acts to achieve glenohumeral motion. This work represents the most comprehensive concurrent evaluation of these supraspinatus regions over a large set of planes of elevation, hand loads and humeral elevations, providing more holistic descriptions of supraspinatus activation in a critical arm movement. Comparing Surface Electromyography of Supraspinatus to Anterior and Posterior Indwelling Recordings: The purpose of this study was to compare anterior and posterior supraspinatus indwelling electromyography responses to a surface supraspinatus signal across a range of arm postures in order to develop relationships between these two recording methods. Forty participants completed arm elevations with altering hand loads and planes of elevation at a fixed cadence. Indwelling electromyography of the anterior and posterior supraspinatus as well as a surface recording of supraspinatus were collected. Bivariate regressions of anterior and posterior indwelling electrodes relative to the bipolar surface electrodes were used to determine relationships between these signals throughout the range of these humeral elevations. Differences between these predictions were modulated by plane of elevation, elevation angle, load intensity and sex of the participant, but no interactions existed. Surface signals underestimated indwelling activation recordings at low elevation angles, then overestimated as humeral elevation angle increased. Surface recordings underestimated indwelling signals by up to 15% in unloaded conditions, while overestimating the posterior region by up to 17% at the highest hand load intensity. In addition, surface signals overestimated posterior supraspinatus indwelling activity by 21%. This work greatly expands current knowledge surrounding relationships between these indwelling and surface signals, both in the inclusion of the indwelling posterior supraspinatus recordings and the expansion of arm postures examined. These findings indicate that relationships between the surface and indwelling signals are altered by plane of elevation, load and elevation angle, and the surface signal more closely predicts anterior region activity. Examining Changes of In Vitro Supraspinatus Mechanical Properties in a Rat Model: The purposes of this study were 1) to complete in vitro mechanical tissue testing in scenarios emulative of empirical muscular activation and postural conditions in an animal model, and 2) to determine the relative influences of arm posture and external loading levels on tissue responses. Forty-eight shoulders harvested from Sprague-Dawley rats were affixed into custom 3D printed mounting pots and placed into one of eight testing groups combining glenohumeral posture and load magnitude. Orientations represented four different postures observed in vivo, and applied tensile load within the animal model was scaled from human activation of the two supraspinatus regions collected from in vivo research for 1500 cycles. A three-way interaction between elevation angle, load magnitude and cycle number occurred for tangent stiffness within specific cycles, with increasing angles, loads and cycles increasing stiffness by up to 49% in some scenarios; differences in maximum and minimum displacement indicated elevated tissue responses in higher elevation angles. Interactions between elevation angle, load intensity and cycle number altered stretch ratio characteristics, with increased elevation angles, loads and cycles increasing stretch ratios, as well as differentiating articular and bursal side responses. Complex interactions between angle, load and cycle number suggest higher abduction angles, increased load magnitude and subsequent cycles generated increased tendon response characteristics. Novel thesis contributions: Multiple novel findings and contributions originated from this work. This dissertation has combined in vivo and in vitro methodologies to advance understanding of rotator cuff mechanics. This dissertation supports the notion that supraspinatus loading varies throughout the range of motion, and postural and external load variations alter tissue-level supraspinatus responses. Activations of the anterior and posterior regions of the supraspinatus were collected from the largest collection of postures to date and described activation differences between these regions. These EMG activations were used to assist in determining applied force load levels for mechanical testing, representing the first known attempt to generate force-controlled tensile loading using physiologically derived exposure levels for the supraspinatus. This work is also the first to maintain a functional glenohumeral unit to complete mechanical testing using postures representative of those observed in vivo to examine supraspinatus responses. General conclusions: Posture and load magnitude have distinct and noteworthy effects on supraspinatus, both in muscular activation and tendon responses. This research combined in vivo muscular activation with in vitro mechanical tissue testing to generate novel findings for rotator cuff loading; further work should continue to pair in vivo responses with mechanical tendon loading to generate physiologically relevant research scenarios throughout the range of humeral postures. This work has established that the supraspinatus is sensitive to scenario conditions, but continued expansion of our understanding of exposure aspects would help diagnose or anticipate overexposure