Biomechanical evaluation and new improvement on ankle external fixator
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Date
2015
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Universiti Teknologi Malaysia
Abstract
An ankle external fixator is a medical device that can be used for temporary fixation in order to limit movement during treatment. This device has been effectively proven in clinical studies to promote the healing process. The stability of the construct could also be attributed to clinical outcomes. However, this knowledge is limited in the literature. Therefore, the main purpose of this study was to biomechanically evaluate and optimise the external fixator with the aim of producing a better construct for the improvement of stress distribution. In this project, the biomechanical study using a finite element method involved several analyses of the effects of external fixator designs as well as its material properties. In order to do that, first and foremost, a three-dimensional ankle model was reconstructed using CT data images which consisted of tibia, fibula, talus, calcaneus, navicular, three cuneiform, cuboid and five metatarsal bones. The cartilages were developed with an estimated uniform thickness of 1 mm. A total of 34 ligaments and 3 plantar fascias were also modelled. Two pathological conditions of ankle problems were simulated with the external fixator by applying axial compression loads based on the swing and stance phase. The results of the finite element study showed that the Delta frame configuration had better stability in terms of relative micromovement, displacement and von Mises stress as compared to the Mitkovic and Unilateral external fixators. In addition, the use of 6 mm pin and 11 mm connecting bar were more favourable options to provide a stable construction. However, the use of extra pins at cuboid and medial cuneiform bone did not contribute to enhance stability. For better improvement of the external fixator, additional hollow cylinder fitted at the pin was considered to decrease stress.
Description
Thesis (PhD. (Biomedical Engineering))
Keywords
Biosciences and medical engineering