Signs of fracture healing on radiography
Estimating the age of a bone injury involves the sequential analysis of six radiological parameters:
- Presence of soft-tissue swelling (soft-tissue swelling).
- Appearance of a periosteal reaction (periosteal reaction).
- Formation of a soft callus (soft callus).
- Formation of a hard callus (hard callus).
- Appearance of a bony bridge or fragment union (bridging).
- Bone remodeling process (remodelling).
Based on a combination of these signs, the trauma is classified as acute (< 1 week), recent (8–35 days), or old (≥ 36 days).
Differential diagnosis: accidental vs. non-accidental trauma
When identifying fractures in children, non-accidental trauma (child abuse) must be ruled out.
Accidental injuries (accidental injury) are the most common cause of fractures. The physician correlates the type of injury with the caregivers' account of the trauma mechanism and assesses whether the radiological age of the fracture matches the stated time of the incident. Statistics on typical injuries for the given age are also taken into account.
Birth trauma (birth trauma) (birth trauma) is also classified as accidental. The clavicle, femur, or humerus are most commonly affected. If no bone callus is present 11 days or more after birth, birth trauma can be completely ruled out.
In addition to trauma, the differential diagnosis includes generalized bone diseases (generalised bone disease), such as rickets, Menkes syndrome, various types of dysplasia, and osteogenesis imperfecta (which presents with angular fractures and fragmentation).
Suspected child abuse: red flags
Certain findings require vigilance:
- Inconsistency in history: the presence of fresh fractures in infants (e.g., of the humeral diaphysis and distal humerus) when caregivers cannot provide a plausible mechanism.
- Unrecognized injuries: radiolucent, irregular lines with surrounding sclerosis. If follow-up imaging after several weeks shows healing on one side but not the other, this indicates a fracture from an earlier, occult injury.
- Avulsion fractures (avulsion fracture), such as of the proximal humerus.
It is important not to confuse signs of trauma with normal variants. For example, normal widening of the posterolateral segments of the ribs in infants should not be mistaken for a periosteal reaction. Meanwhile, physiological subperiosteal new bone formation (a smooth band up to 2 mm along the diaphysis in infants) is normal and does not indicate pathology.
Briefly: answers to topical questions
Within what timeframe after trauma does a periosteal reaction appear on a radiograph?
Subperiosteal new bone formation (periosteal reaction) begins to appear on radiographs early — from 4 to 10 days after trauma. The peak visualization of this sign occurs between days 10 and 14. In later stages, changes are observed from day 14 to 21.
On which day after a fracture does a soft callus begin to be visualized in children?
The formation of a soft callus (soft callus) begins to be visualized on radiographs on days 10–14 after the fracture. During this period, the fracture line loses clarity. The peak of radiological changes associated with soft callus formation occurs on days 14–21. The process of its formation lasts for 5 weeks.
What types of fractures are considered highly specific for child abuse syndrome?
Several highly specific types of fractures are distinguished for abusive head/child abuse syndrome in infants. These include:
- Classic metaphyseal lesion (Classic metaphyseal lesion) — a series of microfractures across the entire width or part of the metaphysis.
- Rib fractures — especially of the posterior segments.
- Scapular fractures — a highly specific sign.
- Spinosum process fractures / Spinous process fractures — indicate a high probability of abuse.
- Sternal fractures — also classified as highly specific injuries.
What radiological features of fractures are characteristic of osteogenesis imperfecta?
Osteogenesis imperfecta (osteogenesis imperfecta) is characterized by extensive multiple fractures accompanied by fragmentation and specific bone deformities. Radiological features include:
- Corner fractures (corner fractures) — may be accompanied by fragmentation.
- Rib deformity — a "beaded" appearance (beaded appearance) in type II of the disease, as well as signs of healing fractures in type III.
- Femoral deformity — an "accordion" appearance (accordion appearance).
- Bowing deformity (bowing deformity) — occurs in long tubular bones as a result of multiple fractures.
Class and exam questions
How is the age of fractures classified in children?
Fractures are divided into acute (up to 1 week), recent (8 to 35 days), and old (36 days and older).
What are the main healing signs evaluated on imaging?
The physician evaluates soft-tissue swelling, periosteal reaction, the presence of soft and hard callus, bridging (bony bridge), and remodeling.
How to rule out a clavicle fracture during delivery?
If there are no signs of bone callus on the radiograph 11 days or more after birth, birth trauma is ruled out.
What else to study on this topic
- Mechanisms and signs of abusive head trauma (AHT)
- Pathophysiology of infant brain injuries (DAI, subdural hematomas)
- Neuroimaging algorithms in AHT (CT, MRI, Ultrasound)
- Radiological characteristics of skull fractures in children
- Differentiation of hemorrhages: SAH, epidural, and subdural hematomas
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