Biomechanical comparison between two headless screw configurations for fixation of coronal shear capitellum humeri fractures.

BACKGROUND: Surgical treatment of coronal shear capitellum humeri fractures remains challenging due to limited access to the articular fragment and no universally established operative techniques. Smaller approaches implementing one headless compression screw (HCS) are used to minimize cartilage damage and risk of fracture fragmentation. Aim of this study was to investigate biomechanically two HCS fixation techniques of coronal shear capitellum humeri fractures. METHODS: Sixteen human cadaveric humeri with simulated Dubberley IA (AO/OTA13-B3) coronal shear fractures were assigned to two groups for fixation with either one anteroposterior 3.0 mm HCS (Group 1) or two anteroposterior 2.0 mm HCSs (Group 2). All specimens were tested under quasi-static and progressively increasing loading until failure at 20° elbow flexion. Interfragmentary movements were monitored via motion tracking. FINDINGS: Initial stiffness did not differ significantly between groups (p = 0.327). Axial displacement and angular flexion displacement were significantly bigger in Group 1 versus Group 2 (p ≤ 0.016) whereas angular abduction displacement remained not significantly different between the groups (p = 0.545). Cycles to clinically relevant failure and corresponding failure load were significantly lower in Group 1 versus Group 2 (p = 0.036). INTERPRETATION: From a biomechanical perspective, fixation of coronal shear capitellum humeri fractures with two 2.0 mm HCSs provides greater stability compared with fixation using one 3.0 mm HCS. The observed biomechanical differences suggest that the two-screw construct may offer improved resistance to displacement under dynamic loading conditions. Future clinical studies are required to determine the relevance of these findings for patient outcomes.