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An Investigation on Normal Force Distribution and Posture of a Hand Pressing on a Flat Surface
Abstract
Hand strength data are needed to understand and predict hand postures and finger loads while placing the hand on an object or surface. This study aims to analyze the effect of hand posture and surface orientation on hand force while pressing a flat surface. Twelve participants, 6 females and 6 males ages 19-25, performed three exertions (100%, 30% and 10% MVC- Maximum Voluntary Contraction) perpendicular to a plate in 4 angles (-45°, 0°, 45° and 90° with respect to the horizontal plane) at elbow height. Exertions involved pushing in two postures: (1) whole hand and (2) constrained to only using the fingertips. Inter-digit joint angles were recorded to map hand and finger motions and estimate joint moments for each condition. Participants exerted twice the force when pushing with whole hand vs. fingertips. 72-75% of the total force was exerted over the base of the palm, while only 11-13% with the thumb for exertions at 90°, 45° or 0° plate angles. Males maximum force for pushing at 0°, 45° and 90° plates averaged 49% higher than females for the whole hand and 62% for the fingertips (p < 0.01). There was no significant sex difference (p > 0.05) for the -45° plate. Thumb joint loads were generally higher than the other individual fingers (p < 0.05) in all % MVC and accounted for 12% of total force during whole hand exertions. On average, joint moments were 30% higher during fingertip conditions vs. whole hand. Thumb and finger joint moment magnitudes when pushing the plate at 100% MVC indicated that Metacarpophalangeal (MCP) joint moments were higher (p < 0.05) than Distal Interphalangeal joints (DIP) and Proximal Interphalangeal joints (PIP) under whole hand and fingertips conditions.
... Tetrahedral Linear elastic E = 110 GPa; ν = 0.33 to the contact forces of the palm of the hand when pressing a flat surface at maximum voluntary contraction (Figueroa-Jacinto et al., 2018). Loads were evenly distributed on the lunate and triquetral bones with the magnitudes shown in Table 4. ...
Background: Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis. Methods: To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly. Findings: Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach. Interpretation: Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.
... Thus, the wrist was moved to a hyperextended position following (Moojen et al., 2002) with an extension of 30 • relative to the radius. This set of loads corresponded to the contact forces of the palm of the hand when pressing a flat surface at maximum voluntary contraction (Figueroa-Jacinto et al., 2018). Loads were evenly distributed on the lunate and triquetral bones with the magnitudes shown in Table 4. ...
L’arthrose de la main est une pathologie multifactorielle qui provoque une dégénérescence progressive des articulations touchées. Cette pathologie handicapante engendre des douleurs et une impotence fonctionnelle empêchant le bon usage des mains dans la vie quotidienne. D’un point de vue biomécanique, les connaissances actuelles ne permettent malheureusement pas de proposer des hypothèses sur l’apparition et le développement de l’arthrose de la main ni de fournir de réelles améliorations des traitements chirurgicaux. L’objectif de ce travail de thèse a donc été de développer numériquement un jumeau biomécanique de la main permettant à la fois d’estimer le facteur mécanique de l’arthrose et d’évaluer les performances mécaniques des traitements chirurgicaux. Ce jumeau numérique a été développé à partir de données d’imagerie médicale et de mesures expérimentales périphériques de préhension et grâce à une modélisation hybride combinant l’approche musculosquelettique à la méthode par éléments finis. Dans cette démarche, la géométrie des structures anatomiques a été représentée tout en leur attribuant des propriétés matériaux et en considérant l’action mécanique des muscles et des tendons qui les mobilisent. Cette méthodologie a ensuite été utilisée pour estimer les chargements mécaniques aux articulations du pouce et de l’index. Les estimations des intensités des pressions de contact articulaires ont permis d’éclairer l’influence du facteur mécanique dans l’apparition et le développement de l’arthrose de certaines articulations spécifiques de la main, alors que ces observations cliniques ne trouvaient jusqu’alors pas d’explications. À l’aide de ce jumeau numérique, des chirurgies virtuelles ont également été simulées pour comparer différents traitements chirurgicaux. Les contraintes mécaniques dans deux implants pour l’arthrodèse partielle du poignet ont été comparées lors de tâches de préhension et de manipulation. Les résultats de ces simulations permettent aux chirurgiens un choix éclairé s’appuyant sur une quantification des bénéfices et risques des deux techniques. De plus, une étude sur l’influence de l’angle d’arthrodèse de l’articulation distale de l’index sur la biomécanique de la main a permis d’apporter des éléments de décision supplémentaires sur le choix optimal de l’angle d’arthrodèse. En conclusion, ce travail montre que le développement d’un jumeau numérique de la main est en mesure de fournir des données quantifiées qui permettent une meilleure compréhension des facteurs de risques de l’arthrose et des conséquences des traitements chirurgicaux. À plus long terme, ce type de modélisation vise à aider les chirurgiens au diagnostic et à la prise de décision clinique sur la base de données quantifiées et individualisées pour une meilleure prise en charge de chaque patient.
... Thus, the wrist was moved to a hyperextended position following (Moojen et al., 2002) with an extension of 30 • relative to the radius. This set of loads corresponded to the contact forces of the palm of the hand when pressing a flat surface at maximum voluntary contraction (Figueroa-Jacinto et al., 2018). Loads were evenly distributed on the lunate and triquetral bones with the magnitudes shown in Table 4. ...
Background
Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis.
Methods
To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly.
Findings
Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach.
Interpretation
Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.
The hand represents one of the most remarkable expressions of humanization of the anterior limb. The anterior limb, at first ambulatory, underwent continuous evolution acquiring innumerable new functions. In the course of human evolution the hand has undergone continual structural and functional adaptations, characterized, among others, by enrichment of peripheral innervation and further development of the thumb. This development was accompanied by important changes in the brain and the relocation of the eyes, together allowing the muscle control and stereoscopic vision, necessary for a controlled grip. The anatomy of the hand is complex, intricate, and fascinating. Its integrity is absolutely essential for our everyday functional living. It is intimately correlated with the brain, both in the evolution of the species and in the development of the individual. Actually, we can state that we “think” and “feel” with our hands, hence, their contribution is essential to the mental processes of thought and feeling. The aim of this review is to evaluate the most typical hand quality, the prehensility and hence, the possibility of manoeuvring tools. Our attention is mainly focused on the hand anatomy and prehensility during pushing and pulling motions. In particular, our attention is directed toward the relationship existing between the hand prehensility and the volume of the object to be gripped. As an example, we use a grip of the paddle and, pushing and pulling motions during kayak paddling. Indeed, we are firmly convinced that the prehensility plays a crucial role not only in performing the stylistically correct paddling, but especially in realizing a more effective and powerful paddle stroke. This review highlights a great link existing between biomechanical and anatomical notions and sporting performance.