Design and finite element analysis of cross-screw fixation strategy for Sanders IIB calcaneal fractures

Abstract

Background Clinicians are increasingly opting for minimally invasive cross screw fixation (CSF) in the treatment of non-severely comminuted calcaneal fractures. However, there is a dearth of design and theoretical guidance regarding the fixation strategy for calcaneal fractures using minimally invasive CSF in clinical practice. The objective of this study is to design a fixation strategy for Sanders type II B calcaneal fractures based on commonly used screw placement methods in clinical practice. Furthermore, we aim to compare the biomechanical stability of different strategies through finite element analysis. The findings of this study will serve as a valuable reference for clinical surgical screw placement. Methods To create a Sanders type II B calcaneal fracture model, we utilized the most up-to-date research on calcaneal fracture heatmaps. By incorporating the anatomical characteristics of the calcaneus and commonly employed minimally invasive screw placement methods in clinical practice, we developed three-dimensional digital designs of CSF strategies on this model. Subsequently, biomechanical experiments were conducted on each strategy within a virtual environment using finite element techniques. The stress distribution, stress magnitude, and displacement of the fracture model were carefully observed and analyzed. Results When subjected to identical loading conditions, Strategy 4 demonstrated smaller maximum displacements of the calcaneus, screw, and fracture gap compared to the other strategies. Among all the strategies, Strategy 5 exhibited the highest maximum stress in the calcaneus, while Strategy 6 had the highest maximum stress in the screw. The three-dimensional digital designs of CSF strategies were developed on this model by integrating the anatomical characteristics of the calcaneus and commonly utilized minimally invasive screw placement methods in clinical practice. Conclusion Our designed Strategy 4 involved the insertion of dual longitudinal screws in a parallel manner from the superior aspect of the calcaneal tuberosity. Additionally, two transverse screws were utilized to fix the articular facet fragment, and one transverse screw was employed to secure the lateral wall of the calcaneus. This fixation method demonstrated superior fixation strength and reduced stress concentration compared to the other strategies. As a result, Strategy 4 serves as a valuable reference for surgeons performing actual clinical screw placement during surgical procedures.