Headless Compression Screw Versus Kirschner Wire Fixation for Metacarpal Neck Fractures: A Biomechanical Study

Abstract

This study aimed to determine the biomechanical stability of headless compression screws in the fixation of metacarpal neck fractures and to compare them with another common, less invasive form of fixation, K-wires. The hypothesis was that headless compression screws would show higher stiffness and peak load to failure than K-wire fixation. Eight matched-paired hands (n= 31), using the ring and little finger metacarpals, had metacarpal fractures simulated at the physeal scar. Each group was stabilized with either a 3.5-mm headless compression screw or 2 0.045-in (1.1-mm) K-wires. Nineteen metacarpals were tested in 3-point bending and 12 in axial loading. Peak load to failure and stiffness were calculated from the load displacement curve. Bone mineral density was recorded for each specimen. Bone mineral density was similar in the 2 groups tested for 3-point bending and axial loading. Stiffness was not significantly different in 3-point bending for headless compression screws and K-wires (means, 141.3 vs 194.5 N/mm) but it was significant in axial loading (means, 178.0 vs 111.6 N/mm). Peak load to failure was significantly higher in headless compression screws in 3-point bending (means, 401.2 vs 205.3 N) and axial loading (means, 467.5 vs 198.3 N). Compared with K-wires, headless compression screws for metacarpal neck fractures are biomechanically superior in load to failure, 3-point bending, and axial loading. Headless compression screws demonstrate excellent biomechanical stability in metacarpal neck fractures. In conjunction with promising clinical studies, these data suggest that headless compression screws may be an option for treating metacarpal neckfractures.