A three-dimensional finite element model of maximal grip loading in the human wrist

The aim of this work was to create an anatomically accurate three-dimensional finite element model of the wrist, applying subject-specific loading and quantifying the internal load transfer through the joint during maximal grip. For three subjects, representing the anatomical variation at the wrist, loading on each digit was measured during a maximal grip strength test with simultaneous motion capture. The internal metacarpophalangeal joint load was calculated using a biomechanical model. High-resolution magnetic resonance scans were acquired to quantify bone geometry. Finite element analysis was performed, with ligaments and tendons added, to calculate the internal load distribution. It was found that for the maximal grip the thumb carried the highest load, an average of 72.2 ¡ 20.1 N in the neutral position. Results from the finite element model suggested that the highest regions of stress were located at the radial aspect of the carpus. Most of the load was transmitted through the radius, 87.5 per cent, as opposed to 12.5 per cent through the ulna with the wrist in a neutral position. A fully three-dimensional finite element analysis of the wrist using subject-specific anatomy and loading conditions was performed. The study emphasizes the importance of modelling a large ensemble of subjects in order to capture the spectrum of the load transfer through the wrist due to anatomical variation

Mechanical testing and modelling of the Universal 2 implant

Understanding the load mechanics of orthopaedic implants is important to be able to predict their behaviour in-vivo. Much research, both mechanical and clinical, has been carried out on hip and knee implants, but less has been written about the mechanics of wrist implants. In this paper, the load mechanics of the Universal 2 wrist implant have been measured using two types of measuring techniques, strain gauges and Fibre Bragg Grating measurements to measure strains. The results were compared to a finite element model of the implant. The results showed that the computational results were in good agreement with the experimental results. Better understanding of the load mechanics of wrist implants, using models and experimental results can catalyse the development of future generation implants