Computed tomography-based analysis of the characteristics of fifth metacarpal neck fractures and its clinical applications

Purpose: Understanding the configuration and characteristics of the comminuted fifth metacarpal neck fractures is essential for successful operative treatment, especially for antegrade intramedullary Kirchner wire (K-wire) fixation. This study aimed to investigate the characteristics and shape of comminuted fragments in fifth metacarpal neck fractures and suggest the appropriate K-wire position. Methods: Forty-one cases of fifth metacarpal neck fractures operated from January 2010 to April 2022 were enrolled in this study. The length and width of the comminuted fragments were measured, as well as the distance from the articular surface of the fifth metacarpal head to the comminuted fragment (Da-c) and the distance from the articular surface to the proximal end of the metacarpal head (Da-h). The location of the comminuted fragments was categorized in terms of four quadrants: dorsal-ulnar (DU), dorsal-radial (DR), palmar-radial, and palmar-ulnar.Results: Among 41 patients with fifth metacarpal neck fractures, comminuted fracture fragments were observed in 35 cases (85.4%). The mean length and width of the comminuted fragments were 7.5±2.3 mm and 3.2±0.8 mm, respectively. The comminuted fragments were on the dorsal aspect of the fracture in all cases; 27 (77.1%) in the DU quadrant and 8 (22.9%) in the DR quadrant. The mean Da-c and Da-h were 5.3±1.6 mm and 10.9±1.5 mm, respectively.Conclusion: To ensure stable K-wire fixation, it is essential to identify the location and characteristics of the comminuted fracture fragments before surgery and subsequently choose an appropriate K-wire position.