Abstract
Abstract
Objective
Bi-condylar tibia plateau fractures are one of challenging injuries due to multi-planar fracture lines. The risk of fixation failure is correlated with coronal splits observed in CT images, although established fracture classifications and previous studies disregarded this critical split. This study aimed to experimentally and numerically compare our innovative fracture model (Fracture C), developed based on clinically-observed morphology, with the traditional Horwitz model (Fracture H).
Methods
Fractures C and H were realized using six samples of 4th generation tibia Sawbones and fixed with Stryker AxSOS locking plates. Loading was introduced through unilateral knee replacements and distributed 60% medially. Loading was initiated with six static ramps to 250 N and continued with incremental fatigue tests until failure. Corresponding FE models of Fractures C and H were developed in ANSYS using CT scans of Sawbones and CAD data of implants. Loading and boundary conditions similar to experimental situations were applied. All materials were assumed to be homogenous, isotropic, and linear elastic. Von-Mises stresses of implant components were compared between fractures.
Results
Fracture C showed 46% lower static stiffness than Fracture H, and it was 38–59% laxer than Fracture H during cyclic loading. Fractures C and H failed at 368±63N and 593±159N, respectively. Von-Mises stress distributions of locking plates indicated that for Fracture C peak stresses, observed around the proximal-inferior and proximal-threadless holes, were 55% higher than Fracture H's, which occurred around the kick-stand hole. The Kick-stand screw of Fracture C demonstrated 65% higher stress than Fracture H's.
Conclusions
Experimental outcomes revealed that coronal splits significantly reduced structural stability. Von-Mises stress distributions demonstrated that potential fatigue failure points of implant components depend on the fracture geometry. Therefore, coronal fracture lines should be counted to precisely assess different fixation methods and find the optimum option for this problematic trauma.
