Influence of plate size and screw distribution on the biomechanical behaviour of osteosynthesis by means of lateral plates in femoral fractures.

Distal femoral fractures are fractures associated with high rates of morbidity and mortality, affecting to three different groups of individuals: younger people suffering high-energy trauma, elderly people with fragile bones and people with periprosthetic fractures around previous total knee arthroplasty. They have been classically treated with conventional plates and intramedullary nails and more recently with locked plates that have increased their indications to more types of fractures. The main objective of the present work is the biomechanical study, by means of finite element simulation, of the stability achieved in the osteosynthesis of femoral fractures in zones 4 and 5 of Wiss, by using locked plates with different plate lengths and different screw configurations, and analysing the effect of screw proximity to the fracture site. A three dimensional (3D) finite element model of the femur from 55-year-old male donor was developed, and then a stability analysis was performed for the fixation provided by Osteosynthesis System LOQTEC® Lateral Distal Femur Plate in two different fracture zones corresponding to the zones 4 and 5 according to the Wiss fracture classification. The study was focused on the immediately post-operative stage, without any biological healing process. The obtained results show that more stable osteosyntheses were obtained by using shorter plates. In the cases of longer plates, it results more convenient disposing screws in a way that the upper ones are closer to fracture site. The obtained results can support surgeons to understand the biomechanics of fracture stability, and then to guide them towards the more appropriate osteosynthesis depending on the fracture type and location.