This 4 y.o. boy fell on outstretched right arm, now with elbow pain.
Tenderness and swelling of right elbow.
Positive fat pad sign (anterior and posterior), anterior humoral line projecting anterior to middle third of capitellum.
1) Lateral condylar fracture
2) Medical epicondylar fracture
3) Medial condylar fracture
4) Olecranon fracture
Dx: Humerus, supracondylar Fracture
Dx Confirmed by: Radiographic and physical exam findings.
Conservative - For less severe cases - splinting in 90Â° flexion
Surgical - For more severe cases - percutaneous lateral pin fixation or ORIF with cross pinning.
Companion Case in Adult patient:
Supracondylar fractures account for 60% of all elbow fractures in children, followed by fracture of the lateral epicondyle (15%), and separation of the medial epicondylar ossification center (10%) (2,3) In children, supracondylar fractures are typically caused by hyperextension from a fall on an outstretched hand. The anterior portion of the humerus fractures and displaces the olecranon posteriorly into the olecranon fossa. If there is minimal or no displacement, these fractures can be occult on radiographs.
Initial evaluation of the elbow for evaluation of a suparacondylar fracture should consist of evaluation of the anterior humeral line. This is an imaginary line drawn on a lateral radiograph along the anterior surface of the humerus. This line should pass through the middle third of the capitellum. If a displaced supracondylar fracture is present, the anterior humeral line will pass through the anterior third of the capitellum due to posterior bending of the distal humeral fragment. If the fracture is occult, the use of fat pad displacement is another useful tool for further evaluation.
The anterior fat pad is a combination of both radial and coronoid fat pads that lie in their respectively named fossae with overlying brachialis muscle. The posterior fat pad lies in the olecranon fossa and is pressed posteriorly by the triceps tendon and the anconeus muscle. The fossa is deep and on lateral radiographic films, should not be visualized unless displaced posteriorly. According to Skaggs, et. al, (1), the value of visualizing the posterior fat pad on lateral radiograph was predictive of an occult fracture following trauma in 76% of children that had no radiographic evidence of fracture.
Fat pads of the elbow are intracapsular. however, they are extrasynovial and serve as useful markers when evaluating an elbow for underlying occult fracture. Under normal circumstances, on a true lateral radiograph of the elbow in 90 degrees flexion, fat is visualized as a narrow sliver of lucency anteriorly and should not be visualized posteriorly. Joint distention causes displacement of the anterior fat pad anterior and superior, and the posterior fat pad is displaced posterior and superior. The fat pads take on this characteristic appearance on lateral radiographs. Joint capsule expansion can occur due to a joint effusion, hemarthrosis, infection, inflammation, or neoplasm. (2) This provides value in the setting of trauma in children who often have subtle radiographic changes. In the case presented, the osseous structures appear normal. However, upon closer evaluation, the anterior fat pad is displaced giving a â€˜sail signâ€™ and the posterior fat pat is visualized.
In the case presented, no gross fracture lucency is seen, however, the child has an abnormal anterior humoral line. There is anterior displacement of the anterior fat pad giving the â€˜sail signâ€™. The other sign that is concerning, is the visualization of the posterior fat pad. Remember, normally the posterior fat pad is not visualized unless there is an effusion causing displacement. In this setting, the posterior fat pad indicates, in the setting of trauma, that a subtle supracondylar fracture is present. The patient was splinted for 6 weeks and had followup films which demonstrated resolution of the effusion, indicating healing supracondylar fracture.
1) Skaggs, et. al. The Posterior Fat Pad Sign in Association with Occult Fracture of the Elbow in Children. Journal of Bone and Joint Surgery 81:1429-33, 1999.
2) Goswami, Gaurav. The Fat Pad Sign. Radiology 222:419-420.
3) Rogers LF. The elbow and forearm. In: Rogers LF, eds. Radiology of skeletal trauma. 2nd ed. New York, NY: Churchill Livingstone, 1992; 751-754.
Lesion/Condition Name: Supracondylar fracture
Synonyms: Gartland Fracture
Demographics: Common in children < 10 years old. Median age if incidence is 6 years old. Males > Females.
Radiology: Positive fat pad sign. Transverse metaphyseal lucency. Mid-capitellum not crossed by anterior humeral line.
Prognosis and Treatment: Depending on the grade, splinting in 90 degree flexion versus percutaneous lateral pin fixation or ORIF with cross pinning in more serious cases.
Complications: Failure of reduction. Vascular injury. Median nerve injury. Volkmann contracture secondary to unrecognized untreated acute vascular injury.
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