The Epidemiology of Infant Shaft Fractures of Femur or Humerus by Incidence, Birth, Accidents, and Other Causes

Abstract Background: Knowledge of femur and humerus shaft fractures during infancy is scarce. The purpose of this population-based registry study was to analyze both birth-related femur and humerus shaft fractures and those diagnosed later in infancy, as regards incidence, perinatal characteristics, other diagnoses, and reported accidents.Methods: Children born in 1997–2014, diagnosed with a femur or humerus shaft fracture before age 1 year, were identified in the Swedish Health Registries. Rate of birth fractures were estimated by combining femur and humerus shaft fractures coded as birth-related with femur and humerus shaft fractures diagnosed during day 1-7 without registered trauma, abuse, or bone fragility disorders. Incidence was computed by comparing infants with femur or humerus shaft fractures to the total at-risk population. Results: The incidence for birth-related femur shaft fractures was 0.024‰ (n=45) and that for birth-related humerus shaft fractures was 0.101‰ (n=188). The incidence was 0.154‰ for later femur shaft fractures (n=287) and 0.073‰ for later humerus shaft fractures (n=142). Birth-related femur shaft fracture was associated with preterm, multiple birth, breech, cesarean, and small-for-gestational age, while humerus shaft fracture was associated with preterm, multiple birth, birth weight > 4,000 g, and shoulder dystocia. A bone fragility diagnosis was recorded in 5% of those with birth-related or later femur shaft fractures. Among infants with birth-related humerus shaft fractures, 1% had a bone fragility diagnosis; the figure for later fractures was 6%. Maltreatment diagnosis was associated with both fracture types, especially among those aged < 6 months, where approximately 20% and 14% of cases, respectively, were associated with abuse. Fall accidents were reported in 73% and 56% among those with later femur and humerus shaft fractures, respectively. Conclusion: This study provides data on epidemiology, birth, parental characteristics, and reported accidents in relation to femur and humerus shaft fractures during infancy. Few children had a bone fragility diagnosis. Fall accidents were the main contributor to femur or humerus shaft fracture during infancy; however, the proportion of fractures attributed to maltreatment was high in children under 6 months.