Do reduced screws have a significant impact on fixation in medial open wedge high tibial osteotomy? A comparative fatigue and stability analysis.

Abstract

Medial opening wedge high tibial osteotomy generally employs T-shaped plates with three or more proximal screws to ensure stabilization. This study aims to evaluate the biomechanical necessity of the standard three screw proximal configuration of the T-shaped plates and investigates whether fixations with a reduced number of proximal screws provide sufficient stability and fatigue life under diverse loading scenarios using finite element analysis. Three fixation models were analyzed, a standard T-shaped plate with three proximal screws in the first row and two modified models with two proximal screws in the first row with or without an empty hole. Models were subjected to physiological axial loading, centrically, anteriorly, or posteriorly applied in the sagittal plane, to measure total deformation, displacement of the tibial plateau, fixation stiffness, and von-Mises stress. Furthermore, a fatigue analysis was conducted to evaluate the endurance of fixations under these varying loading conditions. The reduction in proximal screws resulted in a marginal stiffness decrease of less than 2%, with values remaining above 7700 N/mm under centric loading. Total deformation and tibial plateau displacement showed negligible differences between two screw and three screw configurations. In addition, all peak stresses remained well below the material's yield strength, maintaining a robust static safety margin across all configurations. The fatigue results indicated that while all models achieved infinite life (26.185 million cycles) under centric and anterior loading, the posterior loading emerged as a critical scenario, in which the standard model reached 1.08 million cycles, whereas two screw models reached approximately 0.74-0.78 million cycles. The findings demonstrate that T-shaped high tibial osteotomy plates with two proximal screws in first row offer biomechanical stability comparable to traditional three screw designs. While the reduced fatigue life under posterior loading suggests a need for plate optimization, the two screw configuration remains a viable surgical alternative that preserves bone stock for younger patients, reduces the risk of tissue damage and infection, and lowered the operative time and effort. Future studies focusing on hardware optimizations is needed to further enhance the long-term endurance of this promising fixation protocol.