Supracondylar humeral fracture
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Supracondylar humeral fractures, often simply referred to as supracondylar fractures, are a classic pediatric injury which requires vigilance as imaging findings can be subtle.
Simple supracondylar fractures are typically seen in younger children, and are uncommon in adults; 90% are seen in children younger than 10 years of age, with a peak age of 5-7 years 4,6. These fractures are more commonly seen in boys 4 and are the most common elbow fractures in children (55-80%) 8.
These injuries are almost always due to accidental trauma, such as falling from a moderate height (bed/monkey-bars) 4.
Rarely (<5%) supracondylar fractures are seen due to a fall onto the flexed elbow. They occur in older individuals and require different management and are discussed separately: see flexion supracondylar fracture 5.
There are two types of supracondylar fractures: extension (95-98%) and flexion (<5%) types.
Extension type supracondylar fractures typically occur as a result of a fall on a hyper-extended elbow. When this occurs, the olecranon acts as a fulcrum after engaging in the olecranon fossa. The humerus fractures anteriorly initially and then posteriorly. They result in an extra-articular fracture line, and (when displaced) posterior displacement of the distal component.
Classification of supracondylar fractures is relatively straightforward and based on three types 6,7:
type I: undisplaced
type II: displaced with intact posterior cortex
type IIa: no rotational deformity
type IIb: rotational deformity
type III: complete displacement
Lateral and AP radiographs are usually sufficient, and in many instances demonstrate an obvious fracture. Often, however, no fracture line can be identified. In such cases assessing for indirect signs is essential:
anterior fat pad sign (sail sign): the anterior fat pad is elevated by a joint effusion and appears as a lucent triangle on the lateral projection
anterior humeral line should intersect the middle third of the capitellum in most children 2 although, in children under 4, the anterior humeral line may pass through the anterior third without injury
After ensuring that the films are technically adequate, assessment should include:
description of the fracture
location and especially presence of articular involvement
angulation (use the anterior humeral line)
alignment of the radius and ulna with the distal humerus
description of additional features
Treatment and prognosis
Although in many cases the fracture is easily seen, in some instances all that may be seen is soft tissue swelling or an anterior fat pad sign. Even in the absence of an obvious fracture, the patient needs to be treated with a cast. Repeating radiographs after inflammation has subsided may be helpful in demonstrating the fracture; this is typically done 7-10 days later.
Management depends on the type and degree of angulation 5,7.
Type I (undisplaced) fractures are stable and can be treated with cast immobilization for approximately 3 weeks.
Type IIa usually requires reduction (especially when angulation is more than 20 degrees). Although traditionally these fractures were treated non-operatively with cast immobilization of the flexed arm to 120 degrees, this however dramatically increases the risk of ischemic contracture (Volkmann contracture), as such most authors recommend percutaneous pinning (CRIF) and cast immobilization with less than 90 degrees flexion 5,7. Type IIb always required reduction +/- fixation.
Type III fractures can sometimes be treated similarly to type II (closed reduction and percutaneous pinning, CRIF) although frequently the fracture is held open by interposed soft tissues requiring open reduction 7.
When K-wires are used they are generally used either from a lateral approach ( 2 or 3 wires) or as crossed pins (one wire medially, one wire laterally) 8.
There are three main complications 2,3:
most commonly injured at the time of injury is the anterior interosseous nerve (AIN; a branch of the median nerve), followed by the radial nerve and then the ulnar nerve. Ulnar nerve injury is more common in flexion type fractures.
Most AIN, radial and ulnar nerve injuries resolve spontaneously without any intervention 8.
Osteonecrosis is a rare complication and is described as two types 9:
type A: lateral ossification center osteonecrosis resulting in a defect in the apex of the trochlea resulting in a fishtail deformity
type B: entire trochlea +/- part of the metaphysis