Answers

Short answers

1 Initial evaluation of any trauma in an infant should focus on the mechanism of injury, the plausibility in light of the infant’s motor development, how the caregiver noted a problem, the infant’s medical history, and the reports of witnesses to the event. Even when the history is compatible with the injury, as in this case, a fracture in a pre-mobile infant warrants an evaluation to rule out abuse or underlying pathology.

2 The major differential diagnosis for a fracture in an infant includes accidental injury, child abuse, birth trauma, metabolic bone disease such as rickets, and osteopenia as a result of premature birth or severe dietary deficiency. Rarely, fractures can be caused by congenital biochemical collagen disorders such as osteogenesis imperfecta.

3 A skeletal survey is needed to identify occult fractures and bone malformations. The threshold for neuroimaging should be low when abuse is suspected. Laboratory tests to evaluate possible metabolic bone disease include testing serum concentrations of calcium, phosphorus, alkaline phosphatase, calcidiol (25-hydroxyvitamin D) and parathyroid hormone.

Long answers
1 History
Under-recognition of childhood non-accidental injury is an important problem, despite the high documented incidence of childhood fractures attributed to abuse. In a meta-analysis of 13 studies of femur fractures—which included children of all ages and excluded motor vehicle accidents and known violent trauma—the probability that a femur fracture was the result of confirmed abuse was 0.28.¹ Femur fractures in infants who are not yet walking are much more likely to be the result of abuse: in one study, 10 of 24 pre-walkers with femur fractures were found to have been abused.²

A detailed history must be obtained in infants with a fracture of the femur, including the mechanism of injury (for example, if the child fell, from what height, the objects surrounding the fall area), precipitating events (for example, crying), timing, and parental response. "Red flags" for abuse include an unwitnessed trauma; an absence of history of trauma; and a history that is implausible, vague, changes with different tellings, or is incompatible with the degree of injury or the child’s developmental status.^{3 4}

It is essential to assess the infant’s medical history, including birth history, gestational age, nutrition, history of bruises, other illnesses, and visits to the emergency department or admission to hospital. Chronic medical conditions or behavioural problems might place the child at increased risk of abuse.⁵ A detailed social history, although difficult to obtain in stressful situations, is crucial. The history should include names of caregivers, parental mental illness or substance misuse, family discord, social supports, discipline practices, and dealings with child protective services.

Family dynamics and parent-child interaction should be observed; in particular, look for arguing, roughness, aloofness, inappropriate parental responses, or unrealistic expectations of the child.

2 Differential diagnosis
The differential diagnosis of infant fractures comprises abuse, accidental trauma, and a spectrum of inherited and acquired illnesses.⁶ Accidental fractures and those caused by abuse cannot be distinguished by morphology; transverse fractures are the most common type in both accident and abuse, and spiral and oblique fractures occur commonly in both conditions.⁷ Fractures of the extremities related to birth trauma are usually recognised soon after birth, and radiographs generally show definite signs of healing by 2 weeks of age. Preterm infants may develop osteopenia related to medical and nutritional complications of prematurity; risk factors are gestational age less than 28 weeks, birth weight under 1500 g, bronchopulmonary dysplasia, cholestatic jaundice, prolonged treatment with furosemide or glucocorticoids, or long term parenteral nutrition.^{8 9}

Several nutritional and metabolic disorders can cause pathological fractures. Rickets is characterised by bone changes caused by defects in mineralisation in the growing skeleton. Rickets can be the result of nutritional deficiency, inborn errors of metabolism, or renal or liver disease. Vitamin D deficiency, particularly in premature infants and breastfed infants in geographical areas that have low sunlight, has received recent attention. Rickets is diagnosed by physical examination and radiography: infants with rickets may have bowing of the legs; widening of the wrists and enlargement of the costochondral junction (rachitic rosary) and show poor mineralisation and metaphyseal cupping and fraying on radiography. Fractures and bone abnormalities can be the presenting signs of rare nutritional and metabolic disorders such as copper deficiency, Menkes syndrome, and scurvy. These disorders should be distinguished on clinical and radiographic grounds.^{10 11}

Osteogenesis imperfecta, a genetic mutation in collagen formation, causes bone fragility. Patients can present in infancy or later in life with single or multiple fractures. Associated features are blue sclera (owing to abnormal collagen), multiple wormian bones in the skull, poorly mineralised gracile long bones, and dentinogenesis imperfecta. Patients often have a family history of frequent fractures, short stature, dental problems, and early deafness.

3 Medical tests
Physical examination of an infant with a fracture should evaluate growth parameters and development. The examination should assess the presence or absence of specific signs of pain and skeletal deformity, the colour of the sclera, and hair quality, as well as signs of trauma including bruises, and scalp and oral injuries. Bruises at the fracture site are infrequent in both accidental fractures and fractures caused by abuse.^{12 13}

A skeletal survey, which entails taking high detail radiographs of each skeletal region (19-21 separate films), is needed to evaluate skeletal dysplasia as well as to identify occult fractures.¹⁴ The radiologist interpreting a skeletal survey must be familiar with normal variants in the infant skeleton as well as the subtle classic metaphyseal lesions that are highly concerning for abuse.¹⁴ The skeletal survey is positive in 24-47% of children under 36 months of age with suspected non-accidental injury.^{15 16} Some fractures may not be seen on initial radiographs and are visible only when healing callus forms at 10-14 days after injury. When fractures are identified, a follow-up skeletal survey 2 weeks after the initial survey is needed to rule out additional healing fractures.¹⁷ A nuclear bone scan may also be performed in selected cases.

Whether further evaluation should be conducted depends on the clinician’s level of concern for underlying pathology or inflicted injury. Non-contrast head computed tomography or magnetic resonance imaging should be considered in all infants less than 12 months of age in whom inflicted injury is suspected. In two retrospective studies, 10-29% of infants with non-accidental injuries and a normal neurological examination had findings of intracranial trauma on head computed tomography.^{18 19}

Ophthalmological examination is less sensitive than imaging at identifying occult intracranial injury and should not be used to identify infants who should receive head computed tomography or magnetic resonance imaging.¹⁹ In the presence of intracranial injury, identification of retinal haemorrhages might help distinguish accidental head trauma from head trauma caused by abuse.

Laboratory studies may be indicated when there are historical or radiographic indications of nutritional deficiency or metabolic disease. In rickets, alkaline phosphatase is higher than age specific norms. Other biochemical values—including concentrations of calcium, phosphorus, parathyroid hormone, and vitamin D—vary depending on the type of rickets. Additional laboratory studies, including complete blood count and clotting studies, should be obtained as indicated. When osteogenesis imperfecta is suspected, genetic evaluation and specific assays for this disorder can be performed.

When abuse is in the differential diagnosis, consultation or evaluation by a multidisciplinary child protection team is beneficial to enable integration of medical and social services and communication with law enforcement and child welfare.

Outcome
The skeletal survey in our patient revealed seven healing fractures of the posterior ribs. Head computed tomography and ophthalmological exam were normal. The father then confessed to police that he had twisted the baby’s legs vigorously when the baby was crying "to help relieve gas." He pleaded guilty to assault of a child.

Cite this as: BMJ 2009;338:b1583