Optimisation of Locking Plate Fixation Methods for Periprosthetic Fractures

Periprosthetic fracture (PPF) of the Femur is a common complication of hip arthroplasty. With increasing rates of total hip replacements, the occurrence of periprosthetic fractures is expected to rise. These fractures are often challenging to treat effectively due the technical challenges presented with the combination of fractured bone and an unstable prosthesis. Failure of locking plate fixation of fractures around the tip of a stable prosthesis (Vancouver type B1) have been reported clinically, suggesting that further investigation into their treatment is needed. This study developed a computational periprosthetic fracture fixation model, using experimentally tested specimens to validate the model. Clear relationships could be identified between the experimental and computational results for the Intact Femur, total hip replacement (THR) and PPF cases. The model could predict the magnitude of the strain in the plate and hence the likelihood of plate fracture, as well as assessing the relative stiffness of different fixation scenarios. The model was suitable for the identification and prediction of changes in strain and stiffness between a set of comparative cases and was used to comment on their relative biomechanical performances. The angle of a periprosthetic fracture was shown to have a significant effect on stabilised construct mechanics and specifically, the direction of the fracture has a very large effect on fracture stabilisation. Fractures in the ML direction were less stable than fractures in the LM direction. The 45° Medial to Lateral fracture case was the least stabile and the instrumentation configuration used in this study is clearly not optimal for this fracture case. It is recommended that the orientation of the fracture should be taken into account by surgeons when deciding on B1 PPF management.