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

Abstract

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.