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H. Maas

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6 records found

A musculoskeletal model of the hand and wrist

Model definition and evaluation

Journal article - M. Mirakhorlo, N. Van Beek, M Wesseling, H. Maas, H.E.J. Veeger, H.E.J. Veeger, H.E.J. Veeger, Ilse Jonkers

To improve our understanding on the neuromechanics of finger movements, a comprehensive musculoskeletal model is needed. The aim of this study was to build a musculoskeletal model of the hand and wrist, based on one consistent data set of the relevant anatomical parameters. We bu ...

Single finger movements in the aging hand

Changes in finger independence, muscle activation patterns and tendon displacement in older adults

Journal article - Nathalie Van Beek, Dick F. Stegeman, Dick F. Stegeman, Ilse Jonkers, Chris L. de Korte, Chris L. de Korte, H.E.J. Veeger, H.E.J. Veeger, H.E.J. Veeger, H. Maas

With aging, hand mobility and manual dexterity decline, even under healthy circumstances. To assess how aging affects finger movement control, we compared elderly and young subjects with respect to (1) finger movement independence, (2) neural control of extrinsic finger muscles and (3) finger tendon displacements during single finger flexion. In twelve healthy older (age 68–84) and nine young (age 22–29) subjects, finger kinematics were measured to assess finger movement enslaving and the range of independent finger movement. Muscle activation was assessed using a multi-channel electrode grid placed over the flexor digitorum superficialis (FDS) and the extensor digitorum (ED). FDS tendon displacements of the index, middle and ring fingers were measured using ultrasound. In older subjects compared to the younger subjects, we found: (1) increased enslaving of the middle finger during index finger flexion (young: 25.6 ± 12.4%, elderly: 47.0 ± 25.1%; p = 0.018), (2) a lower range of independent movement of the index finger (young middle = 74.0%, elderly middle : 45.9%; p < 0.001), (3) a more evenly distributed muscle activation pattern over the finger-specific FDS and ED muscle regions and (4) a lower slope at the beginning of the finger movement to tendon displacement relationship, presenting a distinct period with little to no tendon displacement. Our study indicates that primarily the movement independence of the index finger is affected by aging. This can partly be attributed to a muscle activation pattern that is more evenly distributed over the finger-specific FDS and ED muscle regions in the elderly. @en

Increased enslaving in elderly is associated with changes in neural control of the extrinsic finger muscles

Journal article - M. Mirakhorlo, H. Maas, H.E.J. Veeger, H.E.J. Veeger

Aging has consequences for hand motor control, among others affecting finger force enslaving during static pressing tasks. The aim of this study was to assess whether the extent of finger force enslaving changes with aging during a task that involves both static and dynamic phase ...

Mechanical Interaction Between the Tendons of the Extrinsic Finger Flexors

Journal article - H. Maas, G. Geusebroek, G. C. Baan, H.E.J. Veeger

Humans possess an incredible capacity for dexterity, but independent finger control is limited. One factor constraining finger independence is the connections between the tendons of the extrinsic finger muscles. The aim of this study was to assess to what extent the linkages betw ...

Mechanical Interaction Between the Tendons of the Extrinsic Finger Flexors

Journal article - H. Maas, G. Geusebroek, G. C. Baan, H.E.J. Veeger

Outcome of medial hamstring lengthening in children with spastic paresis: A biomechanical and morphological observational study

Journal article - Helga Haberfehlner, Richard T. Jaspers, Jules G. Becher, H. Maas, Annemieke I. Buizer, Erich Rutz, J. Harlaar, J. Harlaar, Johannes A. Van Der Sluijs, Melinda Witbreuk, Kim van Hutten, Jacqueline Romkes, Marie Freslier, Reinald Brunner

To improve gait in children with spastic paresis due to cerebral palsy or hereditary spastic paresis, the semitendinosus muscle is frequently lengthened amongst other medial hamstring muscles by orthopaedic surgery. Side effects on gait due to weakening of the hamstring muscles a ...

Contributed

1 records found

Model-based validation of a tracking algorithm to quantify strain in muscles from two-dimensional ultrasound images

Master thesis - J. de Graaf, A.C. Schouten, W. Mugge, C. Kasbergen, H. Maas, Rob Herbert, B. Bolsterlee

Fascicle shear is theoretically a mechanism by which skeletal muscles lengthen. Existing ultrasound based techniques allow measurement of muscle architecture parameters, but not the quantification of shear strain. In this study, an algorithm that tracks the shear strain from ultrasound images using a continuum representation of the muscle was developed. Errors in strain tracking may arise due to misalignment of the imaging plane, movement artifacts and non-uniform strain within the muscle. The goal of this study was to develop and validate the newly developed strain tracking algorithm. Various potential sources of error are investigated. A computer model was created consisting of a three-dimensional (3D) synthetic volume, representing the muscle. Virtual ultrasound images were then sampled from the 3D volume by intersecting the synthetic volume under a known angle of the imaging plane. The measurement error was defined as the difference between the known strain that was imposed virtually to the 3D muscle volume and the strain calculated with the tracking algorithm. The measurement error was determined for conditions of combined axial and shear strain, plane misalignment, plane rotation and non-uniform strain. Conditions were simulated between 30 and 100 times, each time with a different synthetic muscle volume. The developed strain tracking algorithm provided strain measurement of sub-pixel accuracy and precision when the imaging plane was aligned with the fascicles. Rotation of the ultrasound transducer relative to the muscle resulted in invalid measurements. Axial strain was overestimated when the muscle exhibited a non-uniform axial strain pattern. Largest errors (underestimation of strain by up to 65%) were caused by misalignment of the imaging plane with the fascicles. The large effect of misalignment emphasizes the need for careful transducer placement that requires anatomical information about the muscle structure. Strain tracking methods based on three-dimensional avoid the need for alignment, potentially allowing more accurate measurement of strain.