Comparison of The Two Different Patella Fracture Fixation Technique: Finite Element Analysis

Abstract

Introduction: Fractures of patella account for 1% of bone fractures and this type of injuries can lead to severe knee funciton restrictions due to its role in extansor mechanism. The most common type of fracture pattern is transverse or comminute. According to the guidelines, the most often used surgical techniques are modified tension band wiring and circumferential cercle wiring. However there is no clear information about the configuration of cerclage wiring in the tension band technique. For this purpose, a transverse fracture line was created in the patella finite element model and biomechanical comparison was made in both figure of eight and zero configurations
 Material and Method: A transverse fracture line was created in patella and the k-wires were directed proximally at 90 degrees in coronal plane, perpendicular to the fracture line. A cerclage wire was wound on each finite element model in figure of zero (reference 1 model) and figure of eight (reference 2 model) configurations. These models were compared with each other in finite element model, with the knee at a 45 degree flexion angle and applying 200 Nm, 400 Nm and 800 Nm of force.
 Results: When the opening amounts of reference 1 and 2 models were evaluated under 200 Nm, 400 Nm, and 800 Nm loads, it was found that there were 14%, 8%, 13% less openings in the reference 1 model, respectively. When the amount of pressure in the fracture line was evaluated under the same loads, the average pressure was 10%, 15% and 12% higher in the reference 1 model compared to the reference 2 model, respectively.
 Conclusion: When the determined parameters were evaluated, although the amount of opening at the fracture line was better in the reference 1 model, there was no significant difference between the parameters in both models. Both fixation types allow early motion in clinical applications and help the prevention of displacement of the fracture.