Abstract
Introduction and aims
Biomechanical testing has been a cornerstone of the development of surgical implants for fracture stabilisation. To date most fracture surgery implant design and testing has been dominated by the use of standard bench top biomechanical testing. Although such methods have been used to successfully reproduce certain clinical observations, there are very clear limitations. More recently however, computerised engineering technology using finite element analysis (FEA) has been used to research orthopaedic biomechanical testing. This study aims to use FEA technology to further understand proximal femoral fractures, simulating falls, recreating fracture patterns and analyse fracture fixation devices for such fractures.
Study design and results
In a multi-disciplinary collaboration, novel clinically relevant models were developed at Swansea University 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 modeling the changing trabecular structure & bone mineral density in progressive osteoporosis. Falls from standing were modeled in a variety of directions, (with & without muscle action) using analysis programs 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 have been successfully recreated.
Discussion
The results highlight significant progress in FEA simulation and biomechanical testing of fractures. 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 the modes of failure of tried and tested 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.
