We have shown that fractures are rare in otherwise healthy children under the age of 12 months, with a 10-fold increase in those between 12 and 24 months. Moreover, that fractures to the femur and tibia predominate in the youngest as opposed to tibia and forearm fractures in the oldest age group, with an increase in forearm fractures with increasing age. While falls from a low height was the most commonly reported mechanism amongst those sustaining a fracture, crush-injuries predominated in children without a fracture. In 13.6% of the fractures, the mechanism was unknown.
The annual fracture incidence of 5.4 per 1000 found in the current study did not differ according to gender, as opposed to a male predominance seen in older children [2, 11, 12]. Except for a study by Clarke et al., reporting a similar fracture incidence of 5.3 per 1000 children under the age of two , the number of epidemiological studies addressing fracture rates, types and mechanisms in otherwise healthy infants aged 0–2 is sparse. This contrasts the substantial body of studies on children and adolescents up to 19 years of age [4, 5, 11, 13,14,15,16,17], of which a few report on figures for those under two, specifically [11, 15]. In his classical study from 1983, Landin found that fractures to the clavicle predominated in children under the age of two, with incidences of 1.8 and 2.2 per 1000 for boys and girls, respectively, followed by fractures to the skull and tibia . In a more recent study from 2007, Rennie et al. reported a fracture incidence of 3.6 per 1000 infants under the age of one. Again, fractures to the clavicle predominated . Similar findings have been reported by others, however, with no incidences given [18, 19].
We found that most of the long bone fractures were located distally, a finding also reported by others . Further, fissures were most often seen in the distal tibia in children aged 12–24 months, consistent with Toddler’s fractures in ambulatory children. Occasionally, these fractures are very subtle and may be missed radiographically. In cases with a mis-match between symptoms and findings, a follow-up radiograph after 2 weeks can help to establish the diagnosis.
As opposed to others [1, 11, 15], we did not see any fractures in infants under 7 months of age, however, infants sustaining head- or high energy injuries were not included in our series as these children are routinely admitted to hospital. Thus, it is reasonable to believe that the occurrence of these fractures types is relatively similar in our population.
Of note is that nearly all children included in our study were otherwise healthy, with a normal bone structure judged radiographically. Still, most of both fracture-suspected injuries and fracture injuries in our study were due to low energy trauma, in this particular setting caused by falls from chairs, tables or beds, or falls from the child’s own height, as opposed to traumas caused by car accidents or falls from heights. However, the distribution of fractures, with femur fractures predominating in infants younger than 1 year of age is intriguing. Our estimated incidence rate of 0.36 per 1000 was significantly higher than that reported in a recent study from England . This study, including 1852 closed, isolated femoral shaft fractures in children aged 0–15 years, reported a mean annual incidence rate of 0.06 (95% CIs 0.02–0.10) per 1000 population for children aged < 1 year, rising to 0.12 (0.08–0,16) for those aged 1–2 years. The age of peak incidence was 2 years for both boys and girls, decreasing with increasing age. Falls less than two metres was the most common injury mechanism across all age categories, but this was most pronounced in the 18 months to 3 years age category. Unfortunately, the TARN (Trauma Audit & Research Network / NHS) database does not include the exact height fallen, nor was there any information about the child’s mobility. The authors state that most falls in toddlers represent a low energy impact which can result in spiral femoral shaft fractures. Their study found non-accidental injury (NAI) to be a suspected cause of femoral fractures in 3.8% of children. In contrast, one of five femur fractures in our cohort was suspect of NAI. The child, a 7 months old girl with an oblique/spiral fracture to the distal femur, was allegedly dropped onto the floor by a parent. She was admitted to hospital, where a skeletal survey showed an additional old fracture to the left clavicle. The remainder four femur fractures were seen in three non-mobile children aged 7–9 months, and in one 14-months-old, caused by falls from low heights/child’s own height or dropped by a parent. According to existing literature, a child sustaining a femur fracture has approximately a 1 in 3 chance of having being abused, and femur fractures resulting from abuse are more commonly seen in children who are not yet walking [21, 22]. This knowledge is mirrored in our national guidelines, having a low threshold for performing a skeletal survey in infants presenting with a femur fracture with no plausible explanation being offered .
Around half of the fractures were seen in children aged 18–24 months, with forearm and tibia/fibula fractures accounting for around 60%; findings that are in line with those reported by Clarke . The mechanism of these fractures was primarily fall from furniture or own height. In nearly 15% of the fractures, no injury mechanism was offered, a figure that should be read with caution due to the retrospective nature of our study. Of note is, however, that an inconsistent fracture history was considered in almost 20% of the children as compared to 15% in Clarke’s study. Some of these children and their families were referred to the child protection service (CPS) for further assessments, according to national guidelines.
Similarly, an unexplained delay in presenting to an emergency department following an injury can be indicative of abuse or maltreatment [24, 25]. In our series, more than 50% of the 408 injured children were brought to the BLV within 6 h of the injury, rising to 76% within 24 h, as compared to 27% and around 50%, respectively, in the study by Clarke . Seventeen children attended BLV after more than 3 days, of whom 5 had fractures, and in 49 cases, the interval between injury and visit was unknown, of whom 18 had fractures. It is unclear how many of these children were referred to CPS, underscoring the importance of accurate and detailed medical notes in infants presenting with a fracture. In a study by Banaszkiewicz et al., the authors conclude that in 28%, abuse had been initially underestimated as a cause of injury . In order to systematically address possible NAI, new prospective studies with generalized forms and standardized follow up routines, could have the potential to identify, address and help young children and their families at an early stage after injury. However, the need for declarations of consent, is a limitation to this type of study.
We acknowledge several limitations to our study - firstly, there is its retrospective nature prone to missing or incomplete data. Secondly, we did not validate the classification of fractures prior to analysing the radiographs, however, this was not our intention with this study. Thirdly, we did not include new-borns sustaining birth injuries or infants sustaining high energy injuries, as these were admitted directly to the emergency unit at the University hospital. The strengths of this study include the detailed review of all clinical data, the detailed consensus review of all the radiographs, high-resolution images and the population-based approach.