The Pediatric Elbow: A Review of Fractures, Part 2
By Deborah Pate, DC, DACBR
Editor's note: Part 1 of this article appeared in the July 2011 issue and focused on evaluating X-rays for joint effusion, misalignment and abnormal ossification centers in the pediatric elbow.
Fractures by Type
Supracondylar fractures make up 60 percent of all fractures involving the elbow in children. There are two types of supracondylar fractures based on the mechanism of injury: 96 percent are extension-type fractures and 4 percent are flexion-type fractures.
The extension-type fracture is caused by a fall on the outstretched hand with the elbow hyperextended. The distal fragment of the humerus will angulate and displace posteriorly, depending on the severity of the trauma. There is a relatively high risk of nerve injury (approximately 10 percent of fractures) associated with this injury.
When there is nerve injury, the radial nerve is most commonly involved, followed by the median nerve and then the ulnar nerve. Radiological evaluation of these fractures can be difficult depending on the amount of displacement. The fat pad sign is very helpful. Also use the anterior humeral line, which normally intersects the middle third of the capitellum; in supracondylar fractures, the line often intersects the anterior third of the capitellum or beyond.
Lateral condyle fractures are the second most common fracture, accounting for about 15 percent of elbow fractures. Two mechanisms of injury have been proposed. First, the injury may result from a fall on the outstretched hand with the forearm supinated, which transmits a force through the forearm extensor musculature to its attachment on the lateral condyle. Second, these fractures may also occur with a force directed to the outstretched hand with the elbow flexed. The fracture can be easily identified radiographically if the capitellum is well-ossified and displaced. In more difficult cases, oblique radiographs may be helpful.
Medial epicondyle fractures are the third most common fracture, accounting for approximately 10 percent of elbow fractures. These are typically seen in an older age group, most commonly adolescent males. This injury results from a valgus force combined with contraction of the forearm flexor muscles.
If the valgus force is great enough, elbow dislocation can result, in addition to avulsion of the medial epicondyle.
Radiographic diagnosis is not difficult in displaced fractures. In non-displaced fractures, the apophysis of the medial epicondyle may appear wider than normal. Comparison with the contralateral side will often be helpful in these situations.
Proximal radius fractures are the most common fracture of the elbow in adults, but only account for about 8 percent of fractures in the pediatric population. These fractures also differ from those seen in adults because they usually involve the radial neck and physis, rather than the radial head, as in adults. These injuries can result from a fall on the outstretched hand with the elbow extended. In the skeletally immature, the force is transmitted through the head, which is mostly cartilage, and directed to the physis and metaphysis. These fractures may also occur in association with posterior dislocation of the elbow.
Displaced fractures are usually easily diagnosed via radiographs. However, non-displaced fractures can be difficult to visualize radiographically. Oblique views of the radius may be helpful. To perform oblique views, simply place the elbow in an AP position and then externally rotate the arm 45°; this profiles the anterior and anterolateral aspect of the radial head and neck, and the articular surface of the capitellum. If the arm is internally rotated 45°, this will profile the tip of the coronoid process and the margin of the trochlea.
One other common elbow injury that occurs rather frequently in children less than 5 years old is displacement of the annular ligament; commonly referred to as nursemaid's elbow. When the forearm is pulled or jerked up, as in lifting a child up onto a step or pulling them up from a seated position, the radial head moves distally and the annular ligament slips over the radial head, becoming trapped within the joint. This is because the annular ligament that binds the radial head to the ulna is loosely attached to the radial neck. This problem can be resolved by supination of the forearm, if you are clever enough to distract the child to perform the maneuver.
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