Rib fractures in children with non-accidental trauma

Features of rib fractures and their healing

Rib injuries in non-accidental trauma have a number of important clinical and radiological features. Fractures localized in the area between the costal cartilage and the anterior bony end of the rib heal in a specific way: gradual consolidation occurs, during which no bone callus is formed. This healing mechanism is identical to that observed in classical metaphyseal lesions. The main mechanism for the occurrence of such fractures is blunt chest trauma, which is often associated with concomitant abdominal organ injuries.

A key aspect of differential diagnosis is the exclusion of iatrogenic causes, in particular cardiopulmonary resuscitation (CPR). Unlike adult patients, pediatric rib fractures associated with CPR are extremely rare. If resuscitation measures do result in bone integrity disruption, the anterior or lateral arches are most frequently affected. Modern reports confirm that professional two-handed resuscitation can provoke fractures of the posterior, lateral, and anterior segments. In addition, isolated cases of fractures following intensive physiotherapy in infants suffering from bronchiolitis have been described in the literature. It is important to note that first rib fractures are extremely rare under any circumstances. For the most accurate visualization of healing fractures, it is recommended to use computed tomography (CT), as initial radiographs may be of suboptimal quality and obscure subtle changes.

Classical metaphyseal lesions (CML)

Classical metaphyseal lesions (classical metaphyseal lesions, CML) are considered one of the most reliable predictors of physical abuse. They are most commonly diagnosed in abused infants, with non-ambulatory children under the age of 12 months representing the highest risk group.

From a pathomorphological standpoint, CMLs represent a series of microfractures. They pass through the immature portion of the primary spongiosa (primary spongiosa) and can involve the metaphysis either partially or across its entire width. The main mechanism for the formation of such injuries is the action of powerful shearing forces (shearing forces), which occur during rough handling of an infant or vigorous shaking. The insidious nature of these injuries lies in the fact that they are clinically undetectable and completely asymptomatic.

Common sites for CML include:

• Distal femur;
• Tibia;
• Proximal humerus;
• Joints (elbow and wrist).

The injuries can be either unilateral or bilateral, requiring symmetrical skeletal evaluation during radiological examination.

Radiological patterns and differential diagnosis

The radiological presentation of classical metaphyseal lesions is highly specific. Depending on the projection and volume of the injury, three main patterns can be distinguished:

1. Bucket-handle fracture (bucket-handle fracture): visualized as a thin bone plate separated from the metaphysis with noticeable peripheral thickening.
2. Corner fracture (corner fracture): imaged as an exclusively thick margin of the fragment.
3. A thin bone disc with a thickened margin.

The healing process of small CMLs takes 4 to 8 weeks and occurs through gradual consolidation without the formation of a bone callus. If shearing forces injure or strip the adjacent periosteum, a subperiosteal hemorrhage forms. On radiographs during the healing process, this will manifest as a pronounced periosteal reaction. In isolated cases, such injuries can lead to local bone growth disturbance.

When interpreting images, it is critically important to perform differential diagnosis with normal physiological growth variants, such as the presence of a metaphyseal "step-off" (metaphyseal collar) or mild contour irregularities. Special caution should be exercised when examining children older than 15 months: in bow legs (bow legs), abnormal loads due to early walking can cause metaphyseal fragmentation, which visually mimics a bucket-handle fracture.

Fractures of long tubular bones

In addition to metaphyseal injuries and rib trauma, approximately one-third of children subjected to physical abuse present with fractures of long tubular bones. The tibia, humerus, and femur are most commonly involved in this process.

It is important to understand that in diagnostic imaging, there is no absolutely specific type of diaphyseal fracture that unambiguously points exclusively to non-accidental trauma. However, the nature of the fracture line, fragment displacement, and overall biomechanics of the injury can provide valuable information about the potential mechanism of the applied traumatic force, which, combined with other signs (e.g., CML), confirms the fact of abuse.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Biomechanics of shearing forces and shaken baby syndrome
• Radiological signs of normal bone growth variants
• Formation of periosteal reaction in subperiosteal hemorrhages
• The role of CT in detecting occult chest trauma in children

Other Topics in "Pediatric Diagnostic Radiology"

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