The epidemiology of infant shaft fractures of femur or humerus by incidence, birth, accidents, and other causes

BACKGROUND: The purpose of this population-based registry study was to analyze both birth-related femur and humerus shaft fractures and 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 or abuse. 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 per 1000 children (n = 45) and that for birth-related humerus shaft fractures was 0.101 per 1000 children (n = 188). The incidence was 0.154 per 1000 children for later femur shaft fractures (n = 287) and 0.073 per 1000 children for later humerus shaft fractures (n = 142). Birth-related femur shaft fracture was associated with shoulder dystocia, cesarean, multiple birth, breech, preterm, and small-for-gestational age, while humerus shaft fracture was associated with maternal obesity, dystocic labor, shoulder dystocia, vacuum-assisted delivery, male sex, multiple birth, breech, preterm, large-for-gestational age, birth weight > 4000 g, and injury of brachial plexus. 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 later fractures of both types, especially among those aged < 6 months, where approximately 20% (femur) and 14% (humerus) 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