Biomechanical finite element analysis of typical tibiotalar arthrodesis

Abstract

Tibiotalar arthrodesis (TTA) is a common surgical method for post-traumatic arthrosis and primary osteoarthrosis of ankle. Internal screw fixation exhibits such advantages of higher fusion rate and fewer complications that it has become the mainstream surgical procedure in clinics. However, there are still disputes over the choice of screw type, number and nailing method. In this study, a 3D model of tibiotalar joint was established based on CT data. Two representative types of screws were modeled according to their real objects. Preprocessing was done in Hypermesh 2017, and the finite element simulations of different surgical schemes and postoperative ankle joint movements were performed via Abaqus 2016. The stress distribution in tibiotalar joints and screws, interarticular displacement, and screw deformation were extracted for comparative analyses. The results show that: (1) the three-screw fixation scheme with smaller displacements and higher contact pressure is superior to the two-screw one; (2) the relative displacements of the tibia and talus of full-thread screw under all loads were reduced by approximately 50% compared with those of lag screw, showing better stability; (3) the 60° scheme is more favorable for joint fusion and more stable under vertical load, while the 75° has the best bending resistance; (4) the stress and strain distributions in screws indicate that the screw break is most likely to happen near its contact region with the bone inlet, the maximum stress reaches 212.2 ​MPa. This study is of great significance for the selection and optimization of the surgical plan.

Keywords

• Surgical design and optimization
• Screw type and number
• Stability
• Stress and strain analyses
• Finite element method