Prolonged periods in sitting or standing may negatively influence worker health. Integration of sit-stand workstations has attempted to mitigate these deleterious effects, and has generated positive results in terms of postural discomfort, injury risk and worker fatigue. Identification of how identical tasks are affected by sitting and standing is necessary to take advantage of loading differences between these configurations. The purpose of this research was to determine if differences in workplace configurations between seated and standing postures created changes in posture or muscular activity levels during manual materials handling tasks. Twenty male and twenty female participants performed four manual materials handling tasks: a 40N static push, a 40N static pull, a weighted bottle transfer set at 15% of the participant’s maximal arm elevation force, and a light assembly task in sitting and standing. Upper extremity electromyography was collected at 8 sites, and changes in local joint moments and body discomfort were calculated. Interactions between task and sit/stand configuration resulted in increases of up to 500% in some joint moments, 94% in EMG activity and 880% in some local body discomfort regions when tasks were completed in sitting. A main effect of sitting appeared primarily in joint moments and muscle activity, and generally resulted in increased loading in sitting. Important exceptions existed, which included resultant wrist joint loading 8.2 times larger in standing, and foot/shank discomfort increasing by up to 609%. Task differentially affected all EMG outputs, as well as most local joint moments and body discomfort regions. Future recommendations regarding upper extremity exposures during manual materials handling tasks should consider placing workers in standing postures instead of seated ones to minimize musculoskeletal loading to the upper extremity. In addition, the effects of task and sit/stand configuration should be considered in order to leverage differences between these positions, with tasks in standing generally resulting in decreased musculoskeletal disorder risks.

Reverse shoulder arthroplasty (RSA) is performed to decrease pain and improve function and range of motion (ROM) primarily for patients with rotator cuff arthropathy, an arthritis of the shoulder secondary to rotator cuff insufficiency. However, RSA has suffered from high early to mid-term rates of complication, with instability being one of the most common. The shoulder biomechanics post-RSA depend on multiple factors such as implant geometry, positioning, and cuff integrity. This study built upon prior finite element (FE) analysis of RSA to investigate the effects of glenoid lateralization and retentive liner design on shoulder stability. A previously validated FE model was extended to model shoulder external rotation (ER) after implantation of the Zimmer Trabecular Metal RSA system. The FE model included the scapula bone with an implanted glenosphere implant, the humerus bone with implanted humeral sections of the RSA implant, and muscle tendons representing the subscapularis, infraspinatus, and deltoid. Six different models matched glenospheres in three cases of lateralization (2mm, 4mm, and 10mm) with two humeral poly liner designs (normal: 150° neck shaft angle or retentive: 155° neck shaft angle). Using Abaqus/Explicit FE software, the proximal ends of the soft tissues were pulled to their anatomical positions, and then fixed in space while the humerus was externally rotated 80° about the humeral long axis from a neutral position with the shoulder abducted 25°. The displacements, deltoid and subscapularis forces, impingement-free ROMs, and subluxation gap distances were recorded. Although greater glenosphere lateralization was associated with higher impingement-free ROM, larger deltoid and subscapularis forces developed. Deltoid tension contributes to shoulder stability and control, but elevated amounts of deltoid tension may contribute to scapular fractures and greater stress at impingement sites post-RSA. Further analysis such as inclusion of more anatomical features and additional motions may offer greater insight to orthopedic surgeons when planning for RSA insertion.

This dissertation aimed to develop a joint protection program for people with shoulder arthritis. The program was developed throughout a two-phase process. The first stage in developing the Shoulder Joint Protection Program for patients with different stages of arthritis focused on comprehending existing research and understanding the factors that influence shoulder joint protection. We considered the priorities and preferences of both patients and therapists, integrating different types of evidence like systematic reviews, narrative and scoping reviews, and analysis of shoulder movement. This evidence guided the creation of a preliminary joint protection program. The second stage assessed the content validity of this program, using cognitive interviews with patients and therapists. The findings from each phase were then presented in separate chapters, providing a complete view of the Shoulder Joint Protection Program (SJPP) for individuals with shoulder arthritis. The evidence presented in Chapters 2 and 3 suggests that no single optimal program has been defined for patients undergoing total shoulder joint replacement surgery, including both anatomical and reversed types. Further high-quality RCTs are needed to provide more conclusive results. To assess outcomes, various patient-reported outcomes have been developed and validated. However, our study, as presented in Chapter 4, reveals inconsistencies and a lack of clarity in the conceptual frameworks of the identified PROMs. Our scoping review in Chapter 5 offers comprehensive research on shoulder biomechanics during various activities, and spotlights potential injury prevention strategies. These identified strategies can guide the creation of training programs, coaching practices, and rehabilitation strategies aimed at minimizing the risk of shoulder injuries and bolstering overall shoulder health. Results from Chapter 6 suggest that participants have the capacity to modify their movement patterns to implement joint protection strategies, potentially beneficial in post-surgery rehabilitation and enhancing shoulder function. The application of motion analysis software tools, such as MediaPipe, has yielded reliable results, indicating their potential for future kinematic studies. The developed SJPP comprises two sections: general joint protection principles and specific protective strategies for daily activities. Both digital resources and a printed version were developed to increase the accessibility of the program. The study (Chapter 7) presents a substantial contribution to the resources for patients with shoulder arthritis. It was designed to enhance their quality of life and enable them to navigate everyday activities with greater ease and less discomfort. Further enhancements, such as the inclusion of content on sports and recreational activities, could make the program even more comprehensive and beneficial. Overall, the study underscores the importance of evidence-based, user-friendly resources for patients with shoulder arthritis and provides potential directions for future research and enhancements, such as including content on sports and recreational activities. The SJPP's ultimate goal is to enhance patients' quality of life, allowing them to perform everyday activities with less discomfort. / Thesis / Doctor of Rehabilitation (RhD) / This Ph.D. research project set out to create a program to help people with shoulder arthritis protect their joints. The development process was broken down into two main stages. In the first step, we looked at what we already know from research and figured out the main things that affect how well someone can protect their shoulder joint. We thought about what patients and therapists want and need. We looked at many different kinds of studies and even how people move their shoulders. All this helped us make a first version of our plan. In the second step, we checked how good our plan was. We did this by talking with patients and therapists. We wrote about everything we found out in different chapters. This gave us a full picture of our Shoulder Joint Protection Program (SJPP) for people with shoulder arthritis. Our final SJPP has two main parts: general rules to protect the joint and special tips for everyday activities. We made it available online and on paper so it's easy to get. Our study is a big help for patients with shoulder arthritis. It's meant to make their lives better and help them do everyday things with less pain. In the future, we might add more tips about sports and fun activities, which could make it even more helpful. In conclusion, our research shows how important it is to have easy-to-use, research-based tools for patients with shoulder arthritis. We've also given some ideas for future research. The main goal of the SJPP is to make patients' lives better, helping them do everyday things with less pain.

La paralysie obstétricale du plexus brachial (POPB) est une paralysie du membre supérieur qui survient à la naissance et peut entraîner une déformation de l'articulation et un fonctionnement anormal de l'épaule. Bien que le traitement de la POPB tente de restaurer la fonction de l'épaule, la pathomécanique sous-jacente n'est pas encore clairement comprise. Les modèles computationnels sont efficaces pour fournir de telles informations, mais il n'existe aucun modèle d'articulation de l'épaule pédiatrique pour comprendre la POPB. Ainsi, ce travail de recherche a pour but de construire un framework combinant les avancées dans les domaines de la modélisation statistique de forme (MSF) et de la modélisation musculo-squelettique multi-corps (MCM). Due à l’insuffisance des données dans la cohorte pédiatrique, ce cadre a été mis en place pour l'articulation de l'épaule adulte. Pour cela, la précision de la MSF a été illustrée en prédisant 1) la forme de l'omoplate pré-morbide, et 2) les régions d'insertion musculaire sur l'omoplate et l'humérus. Cette méthode a ensuite été intégrée aux modèles MCM pour l'épaule adulte pour souligner l’importance des modèles spécifique-patient pour l’usage clinique. Pour le second objectif de cette thèse, j'ai développé un modèle MCM pédiatrique du complexe articulaire de l'épaule en utilisant le logiciel OpenSim. Grâce aux approches de cinématique et dynamique inverse, le modèle a permis de déterminer les différences de dynamique articulaires entre le côté sain et le côté pathologique. Les travaux futurs seront axés sur l’extension du travail réalisé pour la population pédiatrique afin de comprendre la pathomécanique de POPB. / Obstetrician Brachial Plexus Palsy (OBPP) is a common birth injury in children leading to shoulder joint deformity and abnormal function. While the management of OBPP disorder focuses on restoring the shoulder joint function, the underlying pathomechanics is not clearly understood yet. Computational models are effective to provide such insights, however, there is no pediatric shoulder joint model to understand the OBPP disorder. Thus, the global aim of this research work was to build a computational framework combining the advances in statistical shape modeling (SSM) and multi-body musculoskeletal modeling (MSKM) domains. Due to a lack of sufficient data in the pediatric cohort, I first developed the framework for adult shoulder joint. For this, I illustrated the accuracy of SSM in predicting 1) missing part of the scapula, and 2) muscle insertion regions on scapula and humerus bones. This method was then integrated with adult shoulder MSKMs to show the differences between generic and subject specific constructs. For the second aim of this thesis, I developed a pediatric MSKM of the shoulder joint complex using OpenSim software. Pediatric MSKM represented scapulothoracic, sternoclavicular, acromioclavicular, and glenohumeral joints with 13 degrees of freedom, and actuated by 52 musculotendon actuators representing 14 shoulder muscles. Using inverse kinematics and inverse dynamics approaches, the model was used to determine the differences in joint kinematics, and joint dynamics between healthy and unhealthy side of a single OBPP subject. Future work is focused on completing the framework on pediatric population and understanding the pathomechanics of OBPP.