The terms “corner fracture” and “bucket handle fracture” describe fractures at the metaphyses of the long bones that are highly specific for non-accidental trauma, since nonambulatory children cannot inflict this type of injury on themselves (Box 18.2). The fractures result from tractional and torsional force applied to an extremity and are virtually diagnostic of child abuse, particularly in children under 1 year of age. Violent shaking of an infant causes tearing and injury at the level of the zone of provisional calcification of the physis; the detached bone creates a curvilinear density that constitutes the bucket handle fracture [11] (Fig. 18.1). If this fragment is viewed in tangent, it appears as a detached corner, whereas if it is viewed partially en face it appears as a bucket handle. CMLs involve the metaphyses of long bones and are most common at the proximal or distal tibias, distal femurs, and proximal humeri; they are frequently bilateral [18]. They usually involve the posteromedial aspect of the distal femurs, proximal tibias, and distal tibias. At the proximal humeri, they are usually lateral and are best seen with external rotation.

Rarely, a similar lesion may result from birth trauma [19] or from manipulation during orthopedic procedures. The timing of injury and the clinical history differentiate such fractures from abusive trauma. These fractures should also be differentiated from the normal subperiosteal bone collar and normal metaphyseal spur seen in rapidly growing long bones of young children, which are attached to the adjacent bone with no intervening lucency (Fig. 18.2) (see Chap. 2).

Rib fractures are the most common and highly specific injury found in abused children, with positive predictive values as high as 95 % in children less than 3 years of age [18]. Furthermore, in some patients, rib fractures are the only skeletal manifestation of child abuse. Although involvement can be anywhere along the rib, unilateral, bilateral, or multiple posteromedial rib fractures are most specific for child abuse (Fig. 18.3). This is in keeping with the mechanism of how these fractures are sustained when the chest is squeezed in the anteroposterior direction, levering the posteromedial ribs against the transverse processes. For similar fractures to occur in the setting of accidental trauma, massive forces must be generated, such as in deceleration dashboard injuries or high-velocity vehicular impact. Cardiopulmonary resuscitation does not cause posteromedial rib fractures [20].

Routine chest radiography may not clearly demonstrate rib fractures, particularly if they are acute, incomplete, and non-displaced or if they are posterior. For this reason, oblique views, follow-up imaging after 2 weeks, and bone scintigraphy have been suggested to improve detection of such fractures. CT of the chest has also been advocated in highly suspicious situations [14] (Fig. 18.4).

Skull fractures are common in both accidental and non-accidental injury and are therefore low-specificity lesions. Linear skull fractures occur most frequently, usually upon impact after low-velocity falls. However, complex fractures (such as concentric, star-shaped, or eggshell fractures) imply high-velocity/high-energy trauma and carry a higher positive predictive value for abuse [21, 22] (Fig. 18.5).

A skull fracture is often the only evidence of abuse. It is therefore important that even these low-specificity lesions are accurately identified and correlated with the clinical history and reported mechanism of injury. This can sometimes present difficulties, especially in subtle cases, where the complex development of the infantile skull may make it difficult to differentiate between a linear fracture and an accessory suture. CT with three-dimensional (3D) reconstruction is very helpful in evaluating a suspicious fracture. Characteristics which favor fracture include a sharp lucency with non-sclerotic edges, fracture line widening as it approaches a suture, and associated soft tissue swelling [23] (Fig. 18.6).

The presence of long bone diaphyseal fractures in a nonambulatory infant should raise concern for non-accidental injury. Such fractures usually result from application of a bending or rotational force, as the extremity is grabbed [22].

However, in older children, long bone fractures usually result from accidental trauma. These fractures are therefore generally of low specificity for abuse. Although spiral midshaft fractures have long been associated with abuse, more recent studies have concluded that the type (spiral, transverse, or oblique) as well as the location of the fracture (diaphyseal or metaphyseal) does not necessarily differentiate accidental from abusive injury. Given the appropriate mechanism of injury, these fracture types can occur in the setting of accidental trauma [24, 25].

Fractures from child abuse have been described in virtually every bone [4]. However, spine fractures in the absence of documented high-energy trauma are rare in childhood and should suggest abuse. Mechanisms include hyperextension, hyperflexion, and/or axial loading from violent shaking, deliberate dropping, or throwing. Injury usually involves multiple vertebral levels, often near the thoracolumbar junction (see Chap. 4). Spinous process fractures, as well as vertebral body compression fractures with associated endplate defects, may be seen [26].

Other unusual fracture sites in infants and toddlers include the scapula (Fig. 18.7), sternum, phalanges, metacarpals, metatarsals, and pelvis. Fractures in these locations should also raise the possibility of non-accidental trauma, unless there is a legitimate history of an unusual mechanism of injury. Clavicular fractures—especially involving the middle third—are common and thus in general low-specificity lesions. They may also result from birth trauma but should be attributed to birth only if callus is apparent by age 11 days [11].

The presence of multiple fractures without a convincing history of accidental trauma should also raise suspicion for child abuse. There is a significant association between multiple unexplained fractures and child abuse: up to 74 % of abused children have two or more fractures [27]. Bilateral, symmetrical fractures involving the upper or lower extremities in non-ambulatory children are also associated with child abuse (Fig. 18.8).