Using finite element method in preoperative planning for wrist surgery

The wrist has a wide variation of 'normal' anatomy, which may explain the discrepancy seen in success rates of some clinical procedures between patients with similar symptoms. Previously published finite element models of the wrist joint have been based on a single geometry and/or single loading condition which does not give a full representation of the spectrum of normal wrists. In this study, three finite element models of the wrist were created and used subject specific boundary conditions thus building a set of models which can be identified as a part of a larger population. Systematic variations in anatomy and bone position were studied and the effect they have on the general load transfer through the normal wrist joint. That information can prove to be important for future surgical planning on the wrist joint

Loading on the Scapho-Trapezium-Trapezoid joint during gripping

The scapho-trapezium-trapezoid (STT) joint is believed to be highly vulnerable to wear and has been identified clinically as a high risk joint in arthritic patients. A theoretical model [1] of the load transfer through the wrist during gripping, suggests high activity in the STT ligaments in order to stabilize the carpus. During gripping complicated loading patterns are seen in the carpal bones and various intercarpal joints comprising the wrist joint. The aim was to investigate contact stresses at the STT joint in comparison to those occuring at the radiocarpal joint. Finite element model was created of the whole wrist joint with physiological loading conditions applied

Effects of partial wrist arthrodesis on loading at the radiocarpal joints

The radiocarpal joint plays an important role in the stabilization of the wrist joint. Degenerative diseases such as rheumatoid arthritis can destabilize the joint and compromise the kinematics of the carpal bones. Partial wrist arthrodesis in the rheumatoid wrist has been popular since its introduction in 1983 [1]. The procedure prevents ulnar drift of the carpus and prevents progression to a subluxed state as well as providing pain relief for the patient. The biomechanical consequences of arthrodesis at the radiocarpal joint have not been extensively explored. This study looks at the biomechanical changes on the load transfer through the radiocarpal joint after partial wrist fusion

On the creation of a subject specific finite element model of the wrist joint

Anatomy varies greatly between individuals and therefore it can be inaccurate to derive any clinical conclusions based on a single computer model. It is important to create models which are directly linked to a specific subject who then can be identified as a part of a larger population 1. By these means it is possible to draw conclusions about the discrepancy between two or more subjects or two or more subject groups. Advances have been made to create a subject specific finite element model of the hip, by using automated procedures 2. The hip poses a relatively simple geometry for such robust procedures to be implemented. However when faced with a more geometrically such as the wrist joint or the ankle joint, the procedure becomes more laborious since automatic procedures become impossible to apply. The geometry is the single most important factor for modeling such types of multi-bone systems and there needs to exist a good balance between creation time and level of accuracy and mesh refinement. In previously reported finite element studies of the wrist joint, ad hoc boundary conditions have been applied to the system. In creating a subject specific model it is important to apply boundary conditions that have been measured from the particular subject. Coupling subject specific boundary conditions with accurate application of material properties of the bones and soft tissues allows the creation of models to predict realistic in-vivo stresses on the carpal bones. In this study three subject specific finite element models were created of the wrist joint, ranging from the distal end of the radius and ulna to the proximal third of the metacarpals, a total of 14 bones were included in the model

Finite element model creation and stability considerations of complex biological articulation : the human wrist joint

The finite element method has been used with considerable success to simulate the behaviour of various joints such as the hip, knee and shoulder. It has had less impact on more complicated joints such as the wrist and the ankle. Previously published finite element studies on these multi bone joints have needed to introduce un-physiological boundary conditions in order to establish numerical convergence of the model simulation. That is necessary since the stabilising soft tissue mechanism of these joints is usually too elaborate in order to be fully included both anatomically and with regards to material properties. This paper looks at the methodology of creating a finite element model of such a joint focussing on the wrist and the effects additional constraining has on the solution of the model. The study shows that by investigating the effects each of the constraints, a better understanding on the nature of the stabilizing mechanisms of these joints can be achieved

Trophic interactions of meso- and macrozooplankton and fish in the Iceland Sea as evaluated by fatty acid and stable isotope analysis

A trophic study was carried out in August of 2007 and 2008 on the pelagic ecosystem in the Subarctic Iceland Sea. Carbon and nitrogen stable isotopes and fatty acid biomarkers were used to study trophic linkages and the trophic ecology of the most important pelagic species in this ecosystem, with emphasis on capelin (Mallotus villosus). According to 15N enrichment results, there are 3–4 trophic levels in this ecosystem excluding organisms of the microbial loop and birds and mammals. The primarily herbivorous copepod Calanus hyperboreus occupies the lowest trophic level of the animal species studied, and adult capelin and blue whiting (Micromesistius poutassou) occupy the highest level. Calanus spp. proved to be an important dietary component of most of the species studied, the euphausiid species Thysanoessa inermis and T. longicaudata being exceptions. The chaetognath Eukrohnia hamata is a pure carnivore, feeding heavily on Calanus spp., whereas most of the other zooplankton species studied practice an omnivorous–carnivorous feeding mode. The amphipod species Themisto libellula is important in the diet of adult capelin. Adult capelin and blue whiting share the same feeding habits and could therefore be competing for food

In vivo contact stresses at the radiocarpal joint using a finite element method of the complete wrist joint

A small number of cadaveric studies have been carried out looking at the force transmission through the radiocarpal joint. In this study subject specific finite element models were created of the whole wrist joint using measured biomechanical data to capture the forces acting on the wrist with the hand generating a maximum gripping force

Teaching English in Earth and Space Science: Content-Based Curriculum Development for Secondary Multilingual Learners

The number of English language learners in public schools continues to increase in Minnesota. Multilingual high school students having a WIDA English language proficiency level below three tend to experience a greater number of academic challenges and experience lower graduation rates. In order to combat these challenges, many high schools provide sheltered content classes co-taught by licensed content and EL teachers. While these courses help students succeed in mastering content standards, English language development is often relegated to incidental acquisition as a bi-product of the learning process. This capstone uses the connections model of content based instruction to answer the question: How can the curriculum for a sheltered Earth and Space Science course support the English language development of secondary multilingual learners? This project demonstrates that Earth and Space Science curriculum at the high school level can be used to meet multilingual learners’ needs for both content mastery and English language development