Musculo-Skeletal Trauma: What is Unique and What Not to Miss

Fracture site

Percentage

Distal forearm

Hand, Phalanges

Carpal-metacarpal

Clavicle

Ankle

Tibia, diaphysis

Tarsal-metatarsal

Foot, phalanges

Radius-ulna diaphysis

Supracondylar humerus

Proximal humerus

Facial skeleton

Skull

Femoral shaft

Radial neck

Vertebral fracture

Typical Pediatric Fractures (General)

The relatively large and more extensive Haversian canals, together with the increased elasticity of the pediatric skeleton often result in the so-called incomplete fractures:

Torus or buckle fractures are caused by axial load compression forces. This results in kinking, buckling or notching of the cortex. The metaphyseal region is most vulnarable because the cortex is relatively thin.
Greenstick fractures are caused by axial loading forces and bending when the bone is bent beyond the point that spontaneous recovery is possible. This results is an incomplete fracture at the tension side of the bone whereas the cortex at the compression side remains intact.
Lead-pipe deformity is a combination of a greenstick fracture and a buckle fracture. At the tension side the cortex is ruptured and on the compression side the cortex is buckled (Fig. 1).
Plastic bending/bowing fractures are also caused by axial loading forces and bending. They can be considered as a “forme fruste” of the greenstick fracture in which the bone is bent beyond its physiological limits but without visible rupture of the cortex. These fractures can be very subtle and sometimes comparison with the contralateral bone is helpful. Bowing fractures are common in the forearm.
CAST (Childhood Accidental Tibial Spiral fracture) or Toddler fracture is a nondisplaced spiral hairline fracture of the tibial shaft, often difficult to recognize on the radiograph [2]. It is caused by relatively mild rotational forces that occur when a todder stumbles and falls or tries to extricate its foot from between bars of a playpen or portable crib [3].

Fig. 1

A 10-year-old girl with a leadpipe deformity: rupture of the cortex at the ventral side (arrow) and a buckle fracture on the dorsal side (arrowhead)

Typical Pediatric Fractures (Growth-Plate Related)

The growth plate is unique for children. Therefore all fractures that have some relation to the growth plate also are unique for children. Amongst these fractures are Salter-Harris fractures and the epiphyseal transitional fractures (triplane fractures and Tillaux fractures). All growth plate-related fractures are at risk for focal epiphysiodesis (premature focal closure of the growth plate).

Salter-Harris Fractures [4–6] (Fig. 2)

Type I follows the growth plate, separating the metaphysis and epiphysis. The growth plate remains attached to the epiphysis and usually there is no damage to the growth plate. Type I is seen in particular in young children. Relative incidence is 8.5%.

Fig. 2

The Salter-Harris classification

Type II runs through the metaphysis and (in part) the growth plate along the metaphyseal transition zone. It is the most common type (relative incidence 73% ), generally in children >10 years of age. Type II heals fast.

Type III runs through the epiphysis and (in part) the growth plate. It is quite rare (6.5%) and often seen at the lower legs in children in whom the growth plate is partially fused.

Type IV runs across the epiphysis, growth plate and metaphysis. The relative incidence is 12%. The risk for focal epiphysiodesis is substantial and treatment is typically surgical rather than conservative.

Type V is a compression fracture due to axial loading, commonly seen in knee and ankle. It is rare (<1%) and usually occult on initial imaging. The risk for focal epipysiodesis is high.

Epiphyseal Transitional Fractures [7, 8]

These fractures typically occur in the distal tibia during the 18-month period of closure of the growth plate between the ages 12 and 15 years. Closure of the distal tibial growth plate starts centrally and medially before progressing laterally. This partial closure leaves the ankle vulnerable to these types of fracture, especially during external rotation.

The triplane fracture configuration consists of (1) a fracture line along the coronal plane through the posterior metaphysis, (2) a fracture line along the sagittal plane through the epiphysis and (3) a fracture line along the transverse plane through the growth plate. The fracture may consist of 2–4 fragments. The triplane fracture appears as a Salter-Harris type II on lateral radiographs and as a Salter-Harris type III on AP radiographs. CT has a definite impact on fracture classification, displacement and treatment [7, 9]. A gap of >2 mm is considered by some authors as the threshold between conservative and surgical treatment [10]

The Tillaux fracture occur in adolescents within 1 year of complete physeal closure. At that time only the anterolateral part of the growth plate is open and vulnerable to injury. This results in a Salter-Harris type III fracture of this anterolateral part of the epiphysis (the Tillaux fragment).

Apophyseal Injuries

An apophysis can be considered as a nonarticular epiphysis that serves as attachment for muscles or tendons (e.g. trochanter, coracoid process, tibial tuberosity, anterior iliac spines, epicondyles of humerus). Injury of apophyses can be acute or chronic. Acute injury results in an avulsion fracture through the subjacent growth plate. Chronic injury is caused by repetitive microtrauma that exceeds the rate of repair. Apophyseal injuries are age-dependent:

Acute pelvic avulsions: 14–25 years of age
Medial epicondyle avulsions: 9–14 years of age
Tibial tuberosity avulsions: 13–16 years of age
Osgood Schlatter disease: 10–15 years of age.

Pelvic avulsions can be classified as Type I (not displaced), Type II (<2 cm displacement), type III (>2 cm displacement) and type IV (symptomatic nonunion or exostosis) [11].

Conventional radiographs show displacement, ossific irregularity, fragmentation, heterotopic ossification and soft tissue swelling. CT demonstrates the displacement and heterotopic ossification to a better extent whereas MRI is superior in demonstrating bone marrow- and soft tissue edema.

Typical Pediatric Fractures (Anatomy Related) [12–14]

Elbow fractures are not uncommon in children and sometimes difficult to detect because of the complicated anatomy with many epiphyses and apophyses that have a specific ossification pattern:

Capitellum starts to ossify at 1–2 years of age
Radial head: 3–6 years
Internal (medial) epicondyle: 4–6 years
Trochlea: 8 years
Olecranon: 6–12 years
External (lateral) epicondyl: 10–11 years

CRITOE is a mnemonic to memorize the chronological order of visibility of these ossification centres. For instance, if the ossification center of the internal (medial) epicondyle is not visible in a child with a visible trochlear ossification center, this is suspect of a traumatic displacement of the apophysis of the medial epicondyle when the child sustained a trauma to the elbow.

The supracondylar humeral fracture is the most common pediatric elbow fracture caused by a fall onto an extended forearm. Mean age is 5–7 years. In subtle cases a positive posterior fat pad sign may be the only sign of a fracture and also the anterior humeral line is helpful in detecting occult fractures: this line should extend through the middle 1/3 of the capitellum (Fig. 3).

Fig. 3

Supracondylar humeral fracture in a 4-year-old girl who fell from a table. The anterior humeral line does not pass through the middle 1/3 of the capitellum because of dorsal displacement of the capitellum. Note the fracture line and both anterior and posterior fat pad signs

Lateral condylar fractures are typically Salter-Harris IV fractures and account for 10–20% of pediatric elbow fractures, best seen on an internal oblique radiograph. Peak age is 6 years (mean 5–10 years). Fractures with >2 mm displacement are most commonly treated surgically.

Medial epicondylar fractures are apophyseal avulsion fractures (see also paragraph on apophyseal injuries). It is the 3th most common elbow fracture (10%). Displacement >5 mm needs surgical treatment.

A Monteggia fracture dislocation is a fracture of the ulnar shaft and a luxation of the radial head. If an ulnar fracture is present, no matter what type, one should look at the head of the radius for dislocation. The radiocapitellar line, drawn along the center of the radial shaft, should always pass the capitellum on the AP ánd lateral view in normal situations.

A Galeazzi fracture dislocation is a fracture of the radial shaft in combination with a dislocation of the distal radioulnar junction. The radial fracture typically involves the middle or distal third of the radius.

Non-accidental Injury (Child Abuse) [15–17]

Radiology plays an important role in the diagnosis of non-accidental injury because it can visualize objective sequela of child abuse, e.g. fractures, subdural hematomas and brain lesions. A radiologist may be asked to report on a skeletal survey in a child that is suspect for abuse, but a radiologist also may be the first to raise suspicion for child abuse when he finds an abnormality in a child that had a radiograph for unrelated reasons, e.g. healing rib fractures on a chest radiograph in a child with fever. Missing the diagnosis of child abuse can turn out to be a fatal mistake. On the other hand, wrongfully accusing parents or caretakers of child abuse can also have dramatic consequences on the social life of these persons.

Therefore the radiological diagnosis of child abuse needs to have a high sensitivity (not to miss the diagnosis) ánd a high specificity (no false positives). That is why it is important to: