Mind the gap between the fracture line and the length of the working area: a 2-D finite element analysis using an extramedullary fixation model☆

Objective To determine the ideal working area for a simple transverse fracture line treated with a bridge plate. Methods A 2-D finite element analysis of a hypothetical femur was performed for the quantitative evaluation of a large-fragment titanium alloy locking plate based on the precept of relative stability in a case of a simple transverse diaphyseal fracture. Two simulations (one case of strain and another case of stress distribution) were analyzed in three unique situations according to the von Mises stress theory. Load distributions were observed when the bone was subjected to a single vertical load of 1000 N. Results The longer the length of the implant flexion, which coincided with the working area of the plate, the greater the flexion of the implant. The highest concentrations of stress on the plate occurred in the region around the screws closest to the bone gap. The closer the screws to the fracture site, the greater the demands on the plate. Conclusion When using a large-fragment titanium alloy locking plate to stabilize a simple transverse fracture based on the precept of relative stability (bridge plate), there must be considerable distance between the proximal and distal screws closest to the fracture line. The farther away this fixation is, the lower the stress on the plate and the greater the dissipation of force in the form of deflection.