Non-accidental injuries

Non-accidental injuries (NAI) represent both ethical and legal challenges to treating physicians. As radiologists we are often the first to suspect NAI when confronted with particular patterns, and a knowledge of these is essential if the opportunity to save a child from future neglect is not to be missed. At the same time it is essential that suspicion is not raised inappropriately as the consequences for an innocent but accused parent or guardian are significant. 

Epidemiology

In 2001 and estimated, 903,000 children were victims of maltreatment including:

• neglect : 57%
• physical abuse : 19%
  • cutaneous injury : most common
  • fractures are noted in 11 - 55% 
• sexual abuse : 10%
• psychologic maltreatment : 7%
• medical neglect : 2%

Clinical features

A number of features have been recognised as suspicious. These include:

• injury in non ambulatory /totally dependent child
• Injury and histoy given are incompatible
• delay in seeking medical attention
• multiple fractures with no family history of oesteogenesis imperfecta
• retinal haemorrhage
• torn frenulum
• history of household fall resulting in fracture 
  • despite falls being common, fractures are uncommon

Radiographic features

Skeletal injuries

Skeletal survey is performed in cases of suspected abuse to assess and document the extent of previous skeletal injuries. The so-called babygram is not an acceptable substitute. 

Bone scans are also able to detect radiographically occult fractures and should be considered when clinical suspicion is high. 

A typical skeletal survey comprises plain films of the following:

• AP / lateral  skull (a Townes skull  also if suspicious of occipital fracture)
• lateral cervial and thoraco-lumbar spine.
• chest x ray
• left / right  oblique ribs
• abdominal x ray
• left / right AP humeri
• left / right AP forearm
• left / right  AP hand
• left / right AP femora
• left / right AP tibia /fibula
• left / right  dorsoplantar feet

Specific fractures

A number of fractures have been recognised as highly specific to non-accidental injury (rather then accidental injury). They include:

• metaphyseal fracture (so called bucket handle fracture or corner fracture)
  • present in up to  39 - 50%  abuse infants < 18 months
  • said to be virtually pathognomonic of NAI
• rib fractures 
  • especially posterior ribs
  • may have no overlying bruising
  • although anterior rib fractures can occasionally be caused by vigorous CPR, posterior ribs do not occur
  • costochondral junction injuries / fractures
• skull fracture : suspicious features include:
  • non parietal skull fracture (a parietal fracture is more suggetive of  accidental injury)
  • involves multiple bones
  • diastatic sutures
  • cross sutures
  • depressed fracture
• scapula
• sternum

Dating injuries

The ability to date injuries is critical for medicolegal purposes, and thus must be done carefully (please refer to specialist text for specific guidelines). 

Traumatic periosteal injury can be seen up to 7 days post injury (and therefore can be used for dating). This can be seen on diaphyseal and rib injuries. Diaphyseal injuries start healing at 1 week. Healing should be complete by 12 weeks. Rib fractures are easily missed so current practice is to repeat chest films in 2 weeks to observe for any healing rib fractures.

Metaphyseal (and costochondral junction) injuries do not heal with perosteal reaction and if visible are less than 4 weeks old. Skull fractures also do not heal with periosteal reaction and if seen are less than 2 weeks old. 

Pit falls and false positives

One of the major, albeit uncommon, pit falls in diagnosing NAI are skeletal dysplasias (e.g oesteogenesis imperfecta I and IV), which may lack the florid features of full blown disease and can be easily confused with NAI.

Features to differiate osteogenesis imperfecta from NAI include :

• presence of osteopenia
• bowing/ remodeling of bones
• presence of wormian bones

Growth plates can also cause a degree of confusion, most notably at the hip , base of fifth metatarsal , elbow and acromion.

Intracranial injuries

A subdural haemorrhage in a child should be viewed with suspicion. On occasion the subdurals will demonstrate varying ages.