A supracondylar fracture is a type of bone fracture that afflicts the humerus in the upper arm. Named for the location of this particular break, a supracondylar fracture occurs just above the epicondyles of the humerus. The epicondyles are the pair of rounded bony prominences found at the lower end of the humerus bone, just above the elbow joint. Often seen in children but comparatively uncommon in adults, the supracondylar fracture typically involves a posterior break of the bone, in which the bone breaks off in a backward direction.
Most commonly caused by a fall in which an attempt is made to catch oneself on one’s hand, this type of injury is most often seen in the still-developing bones of children ranging from five to 15 years old. A supracondylar fracture occurs when, on stretching out the hand to brace against the impact of falling, the elbow is hyperextended, or straightened beyond its normal range of motion. The humerus then absorbs the impact of the fall and in 80 percent of cases snaps posteriorly, an injury known as an extension fracture.
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Less common types of supracondylar fracture are the flexion type, in which the bone snaps forward, as well as the displacement fracture. A displacement fracture occurs when the separated portions of bone slide past each other slightly. This typically occurs where the distal or lower section of bone slides backward, but it also can be accompanied by a shift toward the body, or away from the body, or by a rotation. In most cases, the break demonstrates a combination of extension fracture and posterior displacement. As many as 21 percent of cases are also accompanied by other complications like damage to the nearby brachial artery or median nerve.
When a supracondylar fracture occurs, the humerus is broken but the elbow joint generally remains intact. This joint is found at the rounded base of the humerus where the bone fits into a semi-circular notch in the top of the ulna bone, shaped like a crescent wrench, called the semilunar or trochlear notch. As the arm straightens, the curved upper portion of the ulna above the notch known as the olecranon process curves into a niche in the humerus between the two epicondyles, a space known as the trochlea. Flexible ligaments holding the bones together at the elbow aid in absorption of the impact of the fall, while the rigid humerus takes the brunt of the impact. The result is that the bone breaks off just above the joint where it is narrower and weaker, an injury that presents with pain and an ability to move the elbow and that demands immediate medical attention.