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Non-accidental skeletal trauma

It is essential for all physicians involved in the care of children to be informed regarding the clinical and radiologic manifestations of child abuse. Radiologists should play an important role in the detection of abuse. This requires knowledge of patterns of injury associated with abuse as well as knowledge of appropriate differential diagnoses to be considered in light of the clinical history. Child abuse is also referred to as trauma X, battered child syndrome, inflicted trauma, and non-accidental trauma/injury. Annually, it is estimated that up to 2000 children die and as many as 2.8 million children are victims of physical abuse in the United States 1. Although this risk of abuse is associated with low socioeconomic status, the diagnosis should be considered in all infants and young children with unexplained fractures or multiple skeletal injuries, especially those highly specific for abuse Skeletal injury is a frequent manifestation of abuse and evaluation of suspected fracture is the most common reason for imaging an abused child. Certain types and patterns of injury have different specificities for the diagnosis of child abuse, and certain injuries result from specific physical mechanisms. Violent shaking of an infant results in anteroposterior compression of the thorax leading to characteristic injuries including posterior rib fractures. Twisting and traditional forces applied directly to the extremities produce strains that result in the classic metaphyseal lesion (CML). The following list groups types of injuries according to their relative specificity for inflicted trauma 1 3. This list has its greatest value in infants (children less than 1 year old). The highly specific injuries are not seen with a simple fall and should be investigated further. Highly Specific Fractures Metaphyseal lesions Posterior rib Scapula Spinous process Sternum Moderately Specific Fractures Multiple Fractures of different ages Epiphyseal separations Vertebral body Digit Complex skull Low Specificity but Common Clavicle Long bone diaphysis Linear skull Subperiosteal new bone formation High quality/detail radiographs are critical in the assessment of skeletal injuries suspected from abuse. A "babygram" (frontal image of entire child) will not suffice, as subtle metaphyseal lesions and other injuries can be missed. In fact a "babygram" has higher radiation and yields lower resolution than dedicated radiographs. A standard protocol for a skeletal survey in abuse includes the following projections with high detail technique 1: Chest: AP supine and lateral Humerus: AP Forearm: AP Hands: PA Pelvis: AP Femurs: AP Tibia/Fibula: AP Feet: AP Skull: AP and lateral Cervical Spine: lateral Lumbar Spine: lateral In addition, all lesions identified on the survey should be imaged in two projections. Oblique views of the ribs will increase fracture yield. In concerning cases or diagnostic dilemmas, a two-week follow-up skeletal survey and/or initial skeletal scintigraphy should be performed. Musculoskeletal MRI may also be useful in the detection of occult injury as well as soft tissue and solid organ injury. Birth to 12 months: Skeletal survey Follow up survey in 2 weeks 1 to 2 years: Skeletal survey or Scintigraphy (bone scan) 2 to 5 years: Skeletal survey or Scintigraphy (when abuse strongly suspected) Over 5 years: Focused radiographs Classic Metaphyseal Lesion These lesions are rarely caused by accidental trauma in a normally mineralized infant. The patterns of injury can be explained by the indirect forces inflicted on the infant as a result of violent shaking or grabbing of an extremity, and pulling or twisting. These injuries are associated with intracranial injury and shaken baby syndrome1 3. Facts: Also known as a metaphyseal corner fracture or bucket handle fracture Shearing forces result in transmetaphyseal disruption in infants Can occur anywhere in the skeleton Most commonly involves the distal femur, tibia, and proximal humerus Highly specific and the most important injury to recognize Rib Fractures 1 5: Unusual accidental fractures in infants Require severe mechanism such as an motor vehicle accident or a fall from significant height Rib fractures are unlikely to occur from cardiopulmonary resuscitation Fractures near the costovertebral articulations are common Compression forces from shaking or impact result in levering the rib over its transverse process Two-week follow-up radiographs are often helpful in identifying initially occult fractures Scapula Fractures 5: Less common These fractures require significant force, and do not result from simple falls Moderate specificity lesions are seen with both accidental and non-accidental trauma. Therefore, the radiologic findings must be closely correlated with the clinical history and the presence or absence of other skeletal pathology. Epiphyseal Separations 1 3: Fractures through the growth plate are less common than the CML Can be difficult to detect radiographically and may lead to deformity and/or growth disturbance Often mistaken for dislocation when the epiphysis is not ossified Ultrasound and/or MRI can be useful in difficult cases Vertebral Fractures 6: Uncommon manifestations of abuse Strong association with abuse in infants Multiple Fractures 7: Multiple fractures in different anatomic regions should raise suspicion for inflicted trauma, particularly if they are of different ages Accidental trauma such as falls down stairs tend to involve one region/one extremity Low Specificity Lesions These injuries are commonly seen with both accidental trauma and abuse. Clavicle Fractures 5: Usually due to birth injury in neonates Callus formation no later than 11 days of age with birth injuries Consider inflicted trauma when an infant older than 2 weeks of age has a clavicle fracture without the expected callus Fractures from abuse may involve the medial and lateral ends of the clavicle, and often are associated with other fractures of the shoulder; e.g. humerus, ribs, scapula Skull Fractures 8: Simple linear fractures can result from low level falls, particularly if the impact is with a firm surface Long Bone Shaft Fractures 1: More common in the older infant and child Femoral and humeral shaft fractures in infants less than 1 year old are usually related to abuse, but they do occasionally occur with household accidents So-called toddler's fractures are common accidental spiral/oblique tibia fractures in newly ambulating children, but are suspicious injuries in non-ambulating infants. Subperiosteal new bone formation is a low specificity finding in the workup for child abuse. Facts about Subperiosteal New Bone Formation 3: Subperiosteal hemorrhage elevates the periosteum resulting in apparent thickening of the subperiosteum on radiographs usually seen after 7 to 14 days Skeletal scintigraphy can detect early subperiosteal hemorrhage The finding is nonspecific and can be seen in infection, trauma, and metabolic disorders "Physiologic" subperiosteal new bone formation can also be seen in young infants Osteogenesis Imperfecta Children with underlying metabolic disorders, neuromuscular disorders, or other syndromes that result in bone fragility are at an increased risk for fracture. However, the patterns of injury in these children usually do not match the patterns seen with the highly specific lesions of abuse. Fractures of long bone shafts and the other less specific injury patterns, can present a diagnostic problem. One must always keep in mind that abuse can still occur in children with an underlying disorder. Osteogenesis imperfecta (OI) typically has clinical features, e.g. blue sclera, abnormal skin texture, dentinogenesis imperfecta, that aid in its diagnosis. Typically, radiographs show generalized skeletal deformity, osteopenia and wormian bones. If the bone density is normal, the patient does not have OI. On occasion, problematic cases may require skin biopsy for collagen studies and/or genetic analysis to exclude OI Rickets and Scurvy Rickets and scurvy are also usually associated with osteopenia. Lesions associated with rickets consist of cupping and fraying of costochondral junctions and long bone metaphyses. The zone of provisional calcification becomes indistinct. Deposition of uncalcified osteoid at the metaphyses results in apparent separation between the epiphysis and the shaft of long bones on radiographs. Analysis of the long bones may reveal Looser's zones, transverse insufficiency fractures. These features aid in the differentiation between rickets and abuse. Healing rickets can present a diagnostic dilemma, as mineralization of the zone of provisional calcification can resemble a fracture 10. In scurvy, there is normal mineralization of the zone of provisional calcification, but abnormally radiolucent cortex and spongiosa. This results in the characteristic appearance of increased density of the zone of provisional calcification and periphery of the epiphyses with adjacent osteopenia and thin cortices. Subperiosteal hemorrhage is common and can be dramatic Caffey's disease affects infants younger than 6 months with painful subperiosteal new bone formation (SPNBF) and cortical thickening which can affect all bones. The mandible (75% of cases), clavicle and the ulna are involved most frequently. In Caffey's disease, periosteal reaction is usually more vigorous than seen with trauma. SPNBF and normal mineralization can be features of both abuse and Caffey's disease. However, metaphyseal abnormalities and fractures are not typical features of Caffey's 10. Differential Diagnosis: Normal Variants & Accidental Trauma Normal developmental variants may be confused with inflicted injuries. Normal contour irregularities of the metaphyses may raises concerns of a CML; a follow up study will show no change, whereas a fracture will demonstrate healing. Subperiosteal new bone formation is a common normal finding in the tibia and femur in infants 1-3 months of age. If it is <2mm in thickness and bilateral, it is probably normal 11. Differentiating accidental from inflicted trauma can be difficult. Aside from the previously mentioned high specificity lesions, injuries due to accidental trauma are often radiographically indistinguishable from lesions of abuse. The most important factor in the differential diagnosis is the clinical history, and detailed descriptions of the accident should be elicited from the caregiver. The patterns of injury from accidental trauma should coincide with the reported mechanism of injury