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

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

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

Ulnar variance and load transfer in the forearm during maximal grip: a finite element study

The aim of the study was to simulate the effects, ulnar variance has on the load distribution to the radius and ulna during maximal gripping and compare to previously published measurements, which used load cells placed on the forearm bones to measure the load ratio

The importance of the radiotriquetral ligament for proximal row stability in the wrist : a finite element study

Conference paper on the radiotriquetral ligament for proximal row stability in the wrist

Environmental Health Risk Governance in Practice: Lessons Learned from a Flemish Case Study Approach

PURPOSE: Risk governance is being successfully inserted into scientific and political agendas as a way to understand and address complex problems, such as health problems that have both social and ecological dimensions. However, to date, the debate on risk governance has remained rather conceptual. This chapter addresses these lacunae through describing research that was conducted on the Flemish environmental health governance arrangement and draws on this empirical case study to suggest ways that risk governance can be put into practice. METHODOLOGY: The case study analysis was conducted through a mixed methods study that combined document analysis and data gathered through 22 in-depth interviews with environmental and health scientists as well as policymakers. FINDINGS: This research shows that the Flemish environmental health risk governance arrangement has succeeded in increasing the exchange of information between: (1) governments at a variety of levels; (2) scientists, policymakers and the general public and (3) environmental and public health civil servants. The analysis also provides insights into some shortcomings and makes recommendations for ameliorating this arrangement: (1) the integration of environmental health objectives into all relevant policy domains, (2) the need for additional research into environmental health indicators and (3) the facilitation of the co-production of knowledge and multi-actor governance. ORIGINALITY/VALUE OF PAPER: Empirical contributions and analysis about risk governance and policy formation processes are not often conducted. The added value of this Flemish case study is that it presents an example of good practice from which lessons for future risk governance arrangements can be drawn

The effect of anatomical variations on the load transfer characteristics of the wrist during gripping

Paper detailing the effect of anatomical variations on the load transfer characteristics of the wrist during gripping

A CT-based method to compute femur remodelling after total hip arthroplasty

Bone remodelling after total hip arthroplasty has been largely observed and investigated. Most studies rely on projective images and only few obtain 3D information with limited spatial resolution. This study proposes a method to provide quantitative, 3D high-resolution data about femur bone density variations, by means of CT volume processing. This would offer a tool for further research and clinical studies. Five patients subjected to primary, cementless total hip arthroplasty were considered. Calibrated CT volumes were acquired before, just after surgery and 1 yr later. Bone remodelling hinders accurate alignment of femur volumes acquired after a year; instead, prosthesis stem remains unchanged. Thus, after metal artefact reduction, prosthesis was segmented, and stem-based accurate alignment was obtained. A test to exclude prosthesis migration was performed by considering specific femur anatomical landmarks. Bone density error due to artefact reduction and realignment was estimated. Quantitative differences in bone mineral density were computed for each voxel, providing a resolution of about 1 mm. Preliminary results showed that the femur underwent consistent remodelling after a year. Widespread bone density losses appeared in those areas where strain-adaptive remodelling is normally expected, particularly about the calcar. Conversely, distal areas with clear stem-bone contact showed considerable density gains