PubMed Health⌕ Search

Biomedical subjects

A Huson

Publications and source records attributed to A Huson.

At least 19 recordsLinked to original sources
PubMed1995

Daily physical activity of schoolchildren with spastic diplegia and of healthy control subjects.

OBJECTIVE: To assess the differences in daily physical activity between children with spastic diplegia and healthy schoolchildren, to determine whether special physical activity programs are needed in the population with cerebral palsy. DESIGN: Cross-sectional design. SETTING: Children's rehabilitation center Franciscusoord (day care center) and elementary schools. SUBJECTS: Children with spastic diplegia (5 boys; mean (+/- SD) age 8.0 +/- 1.4 years; 9 ambulant, 1 wheelchair use) and healthy children (5 boys; mean (+/- SD) age 8.4 +/- 1.0 years). MEASUREMENTS: Total daily energy expenditure (TEE) and sleeping metabolic rate (SMR) were measured by the doubly labeled water technique and a respiration chamber. The TEE/SMR ratio was used as an index for the level of daily physical activity. RESULTS: The TEE/SMR ratio under normal daily conditions in the children with cerebral palsy (mean +/- SD): 1.56 +/- 0.19) was significantly lower (p < 0.05) than in their healthy peers (mean +/- SD: 1.83 +/- 0.23) and was similar to the TEE/SMR ratio in a room-sized chamber. CONCLUSION: Children with spastic diplegia are considerably less active than their healthy peers. We recommend special physical activity programs for these children.

Body Height↗
PubMed1991

Nonlinear dynamic behavior of the human knee joint--Part I: Postmortem frequency domain analyses.

Characteristics results of postmortem experiments on five knee-joint specimens are reported. The experiments were performed to investigate the applicability of a local linearization technique that would make it possible to describe the dynamic behavior of the joint in terms of transfer functions. The results indicate that the stiffness of the bracing wires, attached to muscle tendons to create a static equilibrium position, can be accounted for when determining the stiffness of the joint. Besides the static equilibrium configuration, the magnitude of the dynamic load and the type of dynamic load applied to the joint can be shown to have their influence. As the influence of the dynamic load is significant, it has to be concluded that in essence the knee joint has to be regarded as a nonlinear system, making application of a Local Linearization Technique questionable. However, when the magnitude of the dynamic load is included as an additional measurement parameter, an indication can be obtained about the behavior of the joint and the degree of nonlinearity.

Biomechanical Phenomena↗
PubMed1991

Nonlinear dynamic behavior of the human knee joint--Part II: Time-domain analyses: effects of structural damage in postmortem experiments.

A description is given of the results obtained for step excitation for two human knee joint specimens using a time-domain analysis technique. As was expected from the results of a previous study, the magnitude of the dynamic load applied has a marked influence upon the stiffness and damping values for the two observed vibration modes. Deliberate damaging of selected joint elements also yields a well observable change in the dynamic behavior of the joint although these changes are difficult to interpret. Here the use of a nonlinear dynamic numerical model of the knee joint seems indispensable. An important observation is, however, that the experimental method discussed here enables to quantify the behavior of the joint and therefore may provide a valuable tool for validation of such a model.

Anterior Cruciate Ligament↗
PubMed1991

A model of force transmission in the tibio-femoral contact incorporating fluid and mixtures.

An axisymmetric finite element model is formulated which comprises a rigid spherical indentor, a meniscal ring and an articular cartilage layer, both considered as mixture materials which are interacting with an ideal fluid sub-system. From parameter studies it is concluded that the application of the mixture theory in comparison with solid modelling only leads to significant effects when the outer surfaces of the components are not sealed. The load distribution appears to change enormously during relaxation of the models. Initially the largest fraction of the load is borne by the fluid in the cavity, while at the end, when the system has reached its final configuration, the meniscal ring bears the major part of the load. Further, the length of the relaxation period appears to depend on the magnitude of the step change of the load. Finally, the curvature of the spherical indentor appears to have significant effects on the loading of the meniscal ring, only immediately after the step changes of load are applied, and these effects disappear as soon as the fluid starts to exude from the models.

Biomechanical Phenomena↗
PubMed1991

Active force-length relationship of human lower-leg muscles estimated from morphological data: a comparison of geometric muscle models.

Muscle fibre lengths, pennation angles, and sarcomere lengths were measured (the latter by a diffraction technique) for each of the muscles of three embalmed lower-leg specimens. From these data and filament lengths from Walker & Schrodt (1973), the optimum fibre lengths were determined. Relationships between length and active force (at full activation) of the lower-leg muscles were calculated by use of (i) a unipennate muscle model, (ii) a bipennate model, and (iii) bipennate models in which the cosine of the pennation angle is approximated as length independent. It is concluded that the first two models are equally useful and that the use of the last models is discouraged in case of strongly pennated muscles. Non-uniformity of fibre parameters within one muscle appears to have little effect on the force-length relationship.

Aged↗
PubMed1990

Estimation of instantaneous moment arms of lower-leg muscles.

Muscle moment arms at the human knee and ankle were estimated from muscle length changes measured as a function of joint flexion angle in cadaver specimens. Nearly all lower-leg muscles were studied: extensor digitorum longus, extensor hallucis longus, flexor digitorum longus, flexor hallucis longus, gastrocnemius lateralis, gastrocnemius medialis, peroneus brevis, peroneus longus, peroneus tertius, plantaris, soleus, tibialis anterior, and tibialis posterior. Noise in measured muscle length was filtered by means of quintic splines. Moment arms of the mm. gastrocnemii appear to be much more dependent on joint flexion angles than was generally assumed by other investigators. Some consequences for earlier analyses are mentioned.

Achilles Tendon↗
PubMed1990

A numerical model of the load transmission in the tibio-femoral contact area.

An axisymmetric finite element model is applied to the analysis of the force transmission between the tibia-meniscus-femur. The model assumes linear elastic material properties, static loading and sliding contact between the components. The study explores the effects of (a) tibial surface geometry (plane, convex, concave), (b) inclusion of soft layers on the bony components and (c) anisotropic properties of the meniscus. When soft layers are absent, tibial surface geometry is found to affect the total axial stiffness of the model, the radial displacement of the meniscal ring as well as the meniscal share in load transmission. Inclusion of soft layers yields qualitatively the same results for the different geometries, under the understanding that axial stiffness decreases while meniscal radial displacements increase. However, the effect of tibial geometry on the meniscal share in load transmission almost disappears as soon as soft layers are applied, while at the same time a significant increase of this share is observed. Increased circumferential stiffness of the meniscal ring raises this share even more.

Biomechanical Phenomena↗
PubMed1989

A model study of muscle forces and joint-force direction in normal and dysplastic neonatal hips.

Orthopaedic treatment of congenital hip dysplasia does not always give the desired result. With the present model, prediction of the effects of various treatments on the force direction in the hip joint could help to improve and select treatment (the force direction is presumed to control the collum growth direction). The model contains three-dimensional mathematical descriptions of all muscles passing the hip joint, for various degrees of femoral dysplasia, and for various hip postures. Muscles run straight or curve round some skeletal parts. Muscle forces (all isometric) are calculated from muscle mass, density, pennation angle, mean fibre length, muscle elongation, and assumed activation levels. The latter serve as parameters for optimization. Resting lengths are taken from an assumed fetal posture, and from the observed neonatal posture. Differences between force directions before and after birth, as calculated with the model, agree with collum direction changes described by von Lanz and Mayet (1953).

Biomechanical Phenomena↗
PubMed1989

An experimental setup for the measurement of forces on a human cadaveric foot during inversion.

An experimental setup was developed for statically measuring seven vertical and three horizontal reaction forces on the foot. In the setup, the leg can be simultaneously loaded (1) by a vertical force, (2) by an externally applied axial moment, and (3) by simulated muscle forces. The foot is free to invert under influence of the external loads. Statical analysis and test experiments were used for evaluation. The setup can be used in combination with Roentgen photogrammetry to measure bone positions simultaneously with forces.

Cadaver↗
PubMed1989

A model of the human knee, derived from kinematic principles and its relevance for endoprosthesis design.

A mainly deductive kinematic model of the human knee is described. The modelling procedure is based upon the application of a four-bar mechanism. Emphasis has been laid upon elucidating the functional anatomical relationship between several morphological characteristics concerning the shape of the articular surfaces and the constellation of the cruciate ligaments. Starting from a simple planar model, which simulates motions in a sagittal plane only, a spatial model was developed, which allowed an additional longitudinal rotation of the tibia also. The conclusions drawn from this modelling procedure have been used to evaluate from an functional anatomical point of view the current designs of presently available endoprostheses for the knee.

Humans↗
PubMed1988

An experimental approach to evaluate the dynamic behavior of the human knee.

An experimental approach for an in vitro investigation of some aspects of dynamic force transmission through the human knee joint is presented. Essentially, the behavior of the joint was analyzed by measuring the responses to low level random excitation of the tibia while the femur was clamped. A global equilibrium position of the joint was attained by exerting static forces on the tibia via three tendinous muscle attachments. The responses to the applied dynamic loads were measured using a multi-channel dynamic measuring system and quantified by means of transfer function analysis techniques. Some preliminary experimental results are presented to illustrate the effects of variation of the direction and the magnitude of the applied dynamic and static loads.

Adult↗
PubMed1988

The collateral ligaments of the knee joint in the cat and man. Morphological and functional study of the internal arrangement of fibers.

The present investigation of fiber arrangement in the collateral ligaments of the knee was carried out in cats and man in various positions of flexion and extension, without compression load. In all knee joint positions, the fibers of the collateral ligaments are twisted except for the fibers in the meniscal part of the medial collateral ligament which have a parallel arrangement. Furthermore, most of the fibers in the collateral ligaments are taut in all positions of the knee joint in both cat and man. By means of planar models representing different fiber arrangements, the kinematic behavior of the collateral ligaments was analyzed. It appears that a crossed (twisted) arrangement of the fibers is most effective in rotatory movements, whereas a parallel orientation is most effective in translation. Our data further indicate that, in measuring the changes in lengths of ligaments during joint motion, one cannot neglect the internal arrangement of fibers and the geometry of the articular surfaces and menisci.

Animals↗
PubMed1987

Mechanical properties of passive rat muscle during sinusoidal stretching.

The dynamic passive response of the left gastrocnemius medialis muscle of thirty male Wistar rats was studied as a function of muscle dimensions and absolute and relative amount of connective tissue. Values of the absolute active and passive length-force curves (active force, passive force, active working range) correlated well (coefficients of correlation in a range of 0.62-0.92) with morphological variables (such as muscle optimum length, mean muscle fibre optimum length, physiological cross section, muscle weight and amount of intramuscular connective tissue). To eliminate dimensional effects the active and passive length-force curves were normalized taking maximal active twitch force and muscle optimum length as reference values (100%). The width of the normalized active length-force curve (relative active working range) was correlated negatively with muscle weight, muscle optimum length and physiological cross section. Relative amount of connective tissue and passive tension at optimum length (both independent of muscle dimensions) were positively correlated, indicating that passive muscles are stiffer when relative amount of intramuscular connective tissue is higher. Sinusoidal movements with several amplitudes and frequencies of movement were imposed on the passive gastrocnemius medialis muscle over a range of muscle lengths. In accordance with the approximately exponential increase of static passive muscle force with length, muscle length has a large influence on the shape and magnitude of the hysteresis diagrams resulting from sinusoidal movements: the value of all variables selected increases approximately exponentially with muscle length with the exception of the value of loss tangent, a factor indicating the amount of energy dissipated during each cycle relative to the amount of energy stored and released elastically. Velocity of movement has only minor influence on variables of the hysteresis diagrams as is shown by changing the frequency of movement. As loss tangent and relative amount of connective tissue did not vary with muscle dimensions in the muscles studied, it is likely that material properties of the components causing passive resistance were similar in these muscles.

Animals↗
PubMed1987

Passive resistance of the human knee: the effect of remobilization.

Changes of circumferential dimensions and passive resistance of the human knee caused by immobilization, were studied during remobilization. Patients immobilized with a long leg cast after tibial fractures or ligamentous injuries were studied immediately after removal of the cast and after mean periods of 18, 36 and 81 days of remobilization. Immobilization resulted in a decrease of circumferential dimensions. The difference in mid-thigh circumference between the immobilized and the unaffected leg was still present after 81 days of remobilization both for the patients with tibial fractures and for the remobilization both for the patients with tibial fractures and for the patients with ligamentous lesions. An increase of midpatellar circumference was present exclusively in the patients with ligamentous lesions at all four testing dates, indicating that this is an effect of the ligamentous lesion and not of immobilization per se. Variables of the hysteresis diagrams, resulting from sinusoidal movement of the knee at a range of knee angles, were used to quantify passive resistance of the knee in the flexion-extension plane (the muscles crossing the knee are inactive). Variables related to the elastic storage and release of energy, and variables related to energy dissipation were discerned. During remobilization the increased resistance to flexion (shown by the variables related to the elastic storage of energy), as found immediately after removal of the cast, disappears and the resistance becomes identical to the resistance of the unaffected leg. This may indicate a rapid readaptation of the length of ventral structures (shortened due to immobilization in a shortened position) to almost normal values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Joints and movements of the foot: terminology and concepts.

In this paper a critical comment is given on the generally accepted terminology for the structural and functional description of the tarsal joints and their motions. Attention is given to the terms established in the officially canonized Nomina Anatomica (NA) of the IANC as well as to the widely used terms in clinical literature. This terminology has been reviewed in the light of underlying kinematic concepts developed by investigators of tarsal joint motions as found in the original papers and in a number of widely used handbooks. Conflicting points of these concepts are briefly discussed while referring to the results of recent biomechanical research.

Humans↗
PubMed1987

Lumbar back muscle activity during walking with a leg inequality.

The influence of an artificial leg length discrepancy (= ALLD) on stride times, pelvic rotations and activity of the intrinsic lumbar back muscles (= ILBM) was investigated for 20 subjects. An ALLD was created by shoes with a raised sole. Walking with an ALLD produced an increase of the swing phase time and a decrease of the stance phase time for both feet. The influence of an ALLD on pelvic rotations in the sagittal and frontal plane and on ILBM-activity was small. Changes in pelvic rotations in the sagittal plane were too small to observe. The mean pelvic rotation angle in the frontal plane was changed 1.52 degrees when walking with an ALLD of 40 mm (6.9 degrees while standing with an ALLD of 40 mm with extended knees). Only small changes were found in activity time due to an ALLD (not in EMG-amplitude). The activity time of the ILBM around heel strike of the raised limb was increased and unilaterally shifted from toe off in the direction of heel strike with the raised limb.

Electromyography↗