Femur shaft fractures in children : an epidemiological and biomechanical study

Sammanfattning: Aims: The purpose of this thesis is to describe trends in the epidemiology and treatment of femur shaft fractures in children, to identify risk factors for femur shaft fractures and to compare the stability of various configurations of intramedullary nails to manage these fractures. Background: There are no prior national epidemiologic studies of femur shaft fractures in children. Research indicates that sociodemographic factors are associated with increased incidence of childhood injuries. A child who suffers a fracture or a softtissue injury at a young age faces an increased risk of subsequent injuries during childhood. Intramedullary elastic nails are typically used to treat length-unstable femur shaft fractures among school age children. Another possible treatment is a semi-rigid pediatric locking nail. Methods: In Study I-III, children with a diagnostic ICD-code for femur shaft fracture were selected from the Swedish national inpatient register and compared with age and sex matched controls. Demographic, socioeconomic and injury data were based on record linkage between six Swedish registers. The following cohorts were studied: Study I: Children (n = 4,984), 0-14 years of age, diagnosed in 1987 to 2005. Study II: Children (n = 1,874), 0-14 years of age, diagnosed in 1997 to 2005 compared with matched controls (n = 18,740). Study III:Children (n = 1,404), 1-3 years of age, diagnosed in 1990 to 2005 compared with matched children (n = 13,814). In Study IV twenty-four femur models with a length-unstable oblique midshaft fracture were used. Three groups with different combinations of titanium elastic nails (TEN) with end caps and one group with a pediatric locking nail (PLN) were biomechanically tested. Results: Study I-III:The incidence of femur shaft fractures declined by 42% between 1987 and 2005. Treatment modalities shifted toward an increased use of operative treatment. Hospital stay decreased by 81%, from 26 days in 1987 to 5 days in 2005. Children whose parents had a university education had a reduced risk of femur shaft fractures during childhood. Fracture risk increased for older boys with younger parents and for older girls from low-income households. Neither family composition, number of siblings, birth order nor receiving social welfare influenced fracture risk. Boys with a femur shaft fracture at one to three years of age appeared to be at greater risk for a lower leg fracture that required inpatient care during childhood, but there was no significantly increased risk for upper-limb fractures or soft-tissue injuries. Study IV: PLN provided the greatest stability in all planes compared to TEN models with end caps, even though the difference from the two 4.0 mm or four 3.0 mm TEN models was small. Conclusions: During the study period of 1987-2005, the incidence of femur shaft fractures decreased, there was a shift in treatment modalities and the length of hospital stay became shorter. Data indicate that sociodemographic variables influenced the rate of femur shaft fractures; in older children the influence differs between boys and girls. The risk for subsequent fractures in the lower leg that required inpatient care during childhood increased for boys but not for girls with a femur shaft fracture between the ages of one and three. PLN gives a biomechanically more stable construct than TEN in a model of a length-unstable oblique midshaft femur fracture.