Finite element analysis modelling of proximal femoral fractures, including post-fixation periprosthetic fractures.

Biomechanical testing has been a cornerstone for the development of surgical implants used in fracture stabilisation. In a multi-disciplinary collaboration complex at the University of Wales, Swansea, novel computerised clinically relevant models were developed using advanced computational engineering. In-house software (developed initially for commercial aerospace engineering), allowed accurate finite element analysis (FEA) models of the whole femur to be created, including the internal architecture of the bone, by means of linear interpolation of greyscale images from multiaxial CT scans. This allowed for modelling the changing trabecular structure and bone mineral density as seen in progressive osteoporosis. Falls from standing were modelled in a variety of directions (with and without muscle action) using analysis programmes which resulted in fractures consistent with those seen in clinical practice. By meshing implants into these models and repeating the mechanism of injury in simulation, periprosthetic fractures were also recreated. Further development with simulated physiological activities (e.g. walking and rising from sitting) along with attrition in the bone (in the boundary zones where stress concentration occurs) will allow further known modes of failure in implants to be reproduced. Robust simulation of macro and micro-scale events will allow the testing of novel new designs in simulations far more complex than conventional biomechanical testing will allow.