Comparative two- and three-dimensional finite element modelling techniquesfor tibial fractures

Often the choice of a two-dimensional modelling approach over a three-dimen sional approach is made on the basis of available resources, and not on tas k appropriateness. In the case of simulating the mechanical behaviour of ir regular anatomical structures in biomedical engineering, the authenticity o f two-dimensional model behaviour and the interpretation of model solutions is of particular concern since little comparable two-dimensional and three -dimensional data have been published. As part of a research programme, a c omparison was made between two-dimensional and three-dimensional finite ele ment models (FEMs) that examine the stress-strain environment of a clinical bone fracture and callus. In comparison with the three-dimensional model, the two-dimensional model substantially underestimated peak compressive pri ncipal stresses in the callus tissue and peak equivalent strains. This was a consequence of geometrical and structural asymmetry in a plane perpendicu lar to the two-dimensional model. However, the two-dimensional model predic ted similar patterns of stress and strain distribution to the corresponding mid-longitudinal plane of the three-dimensional model, and underestimates of peak stress and strain were much reduced. This confirmed that despite th e irregular geometry and structure of the subject, the two-dimensional mode l provided a valid mechanical simulation in the plane of the fracture that it represented.