The Relationship Between Boxer’s Fracture and Aggression, Hyperactivity, and 2D:4D Finger Ratio in Children and Adolescents: A Prospective Case-Control Study

BACKGROUND: Boxer's fracture (fifth metacarpal neck fracture associated with the fist mechanism) is a common outcome of aggression-related intentional injuries, particularly in children and adolescents. This study aimed to compare the second-to-fourth digit ratio (2D:4D), aggression level, and attention deficit hyperactivity disorder (ADHD) symptoms in children and adolescents with a boxer's fracture against a healthy control group, and to evaluate possible relationships among these variables. METHOD: In this prospective case-control study, 100 children and adolescents (mean age: 13 y; range: 6 to 17) with a fist-mechanism fifth metacarpal neck fracture (group 1) and 100 patients presenting with nonaggression-related trauma (group 2) were enrolled at 2 hospitals over a 1-year period. All variables were assessed at presentation; as the design involved a single assessment point, no follow-up period was applicable. The 2D:4D finger ratio was measured in all participants using conventional hand radiographs. Aggression was evaluated using the Buss-Perry Aggression Scale and the Violence Propensity Scale, while ADHD symptoms were evaluated using the Level 2 ADHD Assessment Scale based on DSM-5-TR. Intergroup comparisons, correlation analyses, and multivariate logistic regression analyses were performed. RESULTS: The case and control groups were similar in terms of age, sex, and socioeconomic status (all P>0.05). The 2D:4D finger ratio was significantly lower in patients with a boxer's fracture compared with the control group (0.888 vs. 0.939, P<0.001). Physical aggression, anger, hostility, and total aggression scores were significantly higher in the case group (all P<0.001).A weak but significant negative correlation was found between the 2D:4D ratio and physical aggression (r=-0.23, P=0.001) and total aggression score (r=-0.23, P=0.001). In multivariate logistic regression analysis, a low 2D:4D ratio and a high total aggression score were independently associated with a boxer's fracture. ADHD subtypes (predominantly inattentive, predominantly hyperactive, and combined type) were strongly associated with a boxer's fracture in penalized logistic regression analysis. CONCLUSION: This study demonstrates that children and adolescents with a boxer's fracture exhibit a risk profile characterized by a lower 2D:4D finger ratio, increased aggression, and pronounced ADHD symptoms. The findings suggest that a boxer's fracture in childhood and adolescence may not only be an orthopaedic injury but also a clinical reflection of associated behavioral and neurodevelopmental risks. Therefore, multidisciplinary assessment and appropriate psychosocial screening approaches in children presenting with a boxer's fracture may contribute to clinical practice. LEVEL OF EVIDENCE: Level III: prospective case-control study.