Threaded K-wire vs cortical screw fixation in O'Driscoll type 2 and 3 coronoid fractures: a comparative biomechanical study

Background: Coronoid fractures significantly impact elbow stability, yet limited biomechanical data exists comparing fixation methods for different fracture types. This study aimed to compare the biomechanical performance of threaded K-wire versus cortical screw fixation in O'Driscoll type 2 and 3 coronoid fractures. Methods: Twenty-eight synthetic ulnar bones were divided into four groups (n = 7 each): Type 2 with K-wire fixation, Type 2 with screw fixation, Type 3 with K-wire fixation, and Type 3 with screw fixation. Fractures were created, reduced, and fixed under fluoroscopic guidance. Specimens underwent biomechanical testing using a custom-made apparatus to evaluate load to failure (N), displacement (mm), and stiffness (N/mm). Two-way ANOVA and post-hoc Tukey's tests were used for statistical analysis. Results: Type 2 fractures with screw fixation demonstrated the highest load to failure (1392.59 ± 76.77 N), followed by Type 2 with K-wire fixation (1155.00 ± 200.81 N), Type 3 with K-wire fixation (1093.65 ± 248.68 N), and Type 3 with screw fixation (1058.54 ± 320.46 N), though differences were not statistically significant (p = 0.086). For stiffness, Type 2 fracture fixation fractures exhibited significantly higher values (∼256 N/mm) compared to Type 3 fractures (∼160 N/mm) regardless of fixation method (p = 0.002, Cohen's d = 1.55). The fixation method itself (K-wire vs. screw) did not significantly affect any biomechanical parameter (p > 0.05). Conclusion: O'Driscoll Type 2 fracture fixation provide superior biomechanical stability compared to Type 3 fractures, primarily through enhanced stiffness. While Type 2 screw fixation demonstrated the highest load to failure values, K-wire fixation in Type 2 fractures offered comparable stiffness. These findings suggest that fracture type has a more profound impact on mechanical performance than the choice between K-wire and screw fixation, giving surgeons flexibility in fixation choice for Type 2 fractures while maintaining adequate stability for early rehabilitation.