In upper motor neuron diseases, like spinal cord injury, cerebral palsy and stroke, motor areas in the brain and/or spinal cord are damaged or fail to develop normally. Patients suffer from... Show moreIn upper motor neuron diseases, like spinal cord injury, cerebral palsy and stroke, motor areas in the brain and/or spinal cord are damaged or fail to develop normally. Patients suffer from increased joint stiffness, diminished range of motion and flexion deformity. The underlying neural reflexive and non-neural tissue (i.e. muscle slack length and stiffness) contributors of these motor disorders cannot be distinguished by current clinical tests. This distinction of contributors is however important for treatment selection and to understand the mechanism of functional recovery. To quantify the neural and non-neural contributors, an instrumented electromyography driven non-linear neuromuscular modeling approach was developed, validated and applied in patients with stroke and cerebral palsy. The clinical potential of the modeling approach was illustrated by the development over time of neural and non-neural contributors in the sub-acute phase post-stroke and by the effect of botulinum toxin A treatment on these contributors in chronic stroke patients. The results from longitudinal assessments are a step forward in answering “when” to treat a stroke patient. The results also give direction to the question “how” to treat stroke patients, i.e. which treatment option is most effective in each individual patient. Both are a prerequisite for personalized treatment. Show less
The aim of this thesis was to explore the neuromechanics of recovery of arm-hand function after stroke. A literature review revealed six articles that measured biomechanical and electromyographical... Show moreThe aim of this thesis was to explore the neuromechanics of recovery of arm-hand function after stroke. A literature review revealed six articles that measured biomechanical and electromyographical outcome measures simultaneously, while applying active and passive tasks and multiple movement velocities to separate neural and non-neural contributors to movement disorders after stroke. Therefore, a neuromechanic assessment protocol was developed. Parameters were responsive to clinical status and had good to excellent test-retest reliability. Selective muscle activation was assessed with high measurement reliability and was significantly lower in chronic stroke patients compared to healthy participants. Longitudinally, neuromechanical parameters were combined with data on arm-hand function at six months after stroke. Paresis and diminished modulation of reflexes were associated with poor functional outcome. Changes in tissue properties were represented by a shift in wrist rest angle towards flexion and decline in passive range of motion. Increase in active range of motion and steady rest angle contributed most to prediction of functional outcome. The precision diagnostics provided by a neuromechanical assessment protocol could support clinical decision making and should be used in prediction models and as biomarkers in recovery of arm-hand function after stroke, for example by improving the selection of time-window and patients. Show less
Clavicular fractures are among the most common fractures of the shoulder. Displacement or comminution of the fracture fragments may lead to shortening of the clavicle, but could also cause mal... Show moreClavicular fractures are among the most common fractures of the shoulder. Displacement or comminution of the fracture fragments may lead to shortening of the clavicle, but could also cause mal-union or non-union of the clavicle and might lead to poor functional outcome. These fracture characteristics are therefore important in clinical decision making. The diagnostic aspects of clavicular fractures are evaluated in the first part of this thesis, whereas the second part describes studies on treatment and clinical outcomes. The third part of these thesis focuses on the complex biomechanics of the shoulder after a displaced midshaft clavicular fracture. The findings on diagnostic aspects underline the importance of fracture characteristics for classification and of two-view radiography for treatment decisions for clavicular fractures. Clavicular shortening after a midshaft clavicular fracture is deemed the most important factor in deciding whether or not to operate, but no clinically relevant changes after clavicular shortening in the scapular kinematics and functional outcome were demonstrated. Clavicular shortening should therefore not be used as the only reason to justify operative treatment. Show less
The Subacromial Impingement Syndrome (SIS) is the most prevalent disorder of the shoulder in primary health care. Acromionplasty, as the main surgical treatment of SIS, is one of the most performed... Show moreThe Subacromial Impingement Syndrome (SIS) is the most prevalent disorder of the shoulder in primary health care. Acromionplasty, as the main surgical treatment of SIS, is one of the most performed orthopedic surgeries. However, its results are highly variable. Possibly, there are different etiologic subgroups of patients, that might need specific treatment approaches. Several etiologic mechanisms have been described for subacromial narrowing or __impingement__: i.e. 1) structural causes, including acromion shape, subacromial bony spurs, osteophytes; 2) narrowing of the subacromial space due to humerus cranialisation in patients with (micro)instability, or scapular dyskinesia; 3) intrinsic mechanisms such as primary degenerative tendinopathy of the rotator cuff. The aim of this thesis is to unravel the clinical entity __Subacromial Impingement Syndrome__ and to develop methods for identifying distinct etiological patient subgroups that need specific diagnostics and treatment strategies. To this end, we explore the terminological problems and opinions on the main characteristics of SIS amongst international health practitioners, study the prevalence of previously reported etiologic mechanisms in patients with SIS symptoms, develop clinical and biomechanical methods to evaluate and categorize patients with SIS symptoms in diagnostic subgroups, and compare treatment outcomes in trials and follow-up studies. Show less
Wall shear stress (WSS) exerted by flowing blood at the vessel wall, is defined as the velocity gradient at the vessel wall times the blood viscosity. Low WSS is related to atherosclerotic risk... Show moreWall shear stress (WSS) exerted by flowing blood at the vessel wall, is defined as the velocity gradient at the vessel wall times the blood viscosity. Low WSS is related to atherosclerotic risk profiles and WSS is low or oscillating at locations where plaque development is observed. In vivo cross-sectional images of blood flow suffer from limited resolution and lack of info on local viscosity. However, WSS can be assessed by modeling of velocity profiles and blood viscosity. Already with a first approximation of velocity profiles by an imprecise model, such as a paraboloid, and under the assumption of a constant (average) human blood viscosity, correlations between various cardiovascular risk factors and WSS were found. Also the effect of treatment with pravastatin on WSS has been demonstrated with this model. The more detailed the model, the more accurate WSS can be assessed. An accurate 4D WSS assessment can be obtained by application of a so-called Finite Element Method (FEM) calculation. Blood velocity was simulated for a certain vessel segment. A model of the vessel geometry composed of bricks (a so called mesh) was created in order to simulate the blood flow. Show less
