On elbow radiography (projection or CT), the fat pad mark, also known as the sailing , indicates a fracture of one or more bones at the elbow, possibly an occult fracture not directly visible. Its name comes from the fact that it has a spinnaker form (sail). This is caused by the displacement of fat pad around the elbow joint. Both the anterior and posterior fat pad signs exist, and both can be found on the same X-ray.
In children, a sign of a posterior fat pad indicates a humerus condyle fracture. In adults it shows a radial head fracture. The fat pad sign only occurs after an intra-articular fracture.
In addition to fracture, any process that produces elbow joint effusion may also show signs of abnormal fat pad. Increased intracapsular fluid is also seen in some conditions other than fracture and this results in an abnormal fat pad sign. (Toxic synovitis, septic arthritis, Rheumatoid Teen Rheumatoid, distal humeric physical osteomyelitis, and secondary joint septic). In this case, clinical history and examination in addition to laboratory outcomes (WBC, ESR, CRP) will guide the provider in determining whether to treat the condition as a supernatural fracture or continue examination for other pathologies.
The fat pad sign is particularly valuable in assessing the presence of an intra-articular fracture of the elbow. An anterior fat pad is often normal. However, the posterior fat layer seen on lateral elbow x-rays is always abnormal. Patients will not be able to flex their elbows and require orthopedic input.
Video Fat pad sign
Pathophysiology
The posterior fat pad is usually suppressed in the olecranon fossa by the triceps tendon, and therefore is not visible on lateral elbow radiographs. When there is a distal humerus fracture, or other pathology involving the elbow joint, the inflammation developing around the synovial membrane forces the fat pad out of its normal physiological resting place. This is seen as a "sign of the posterior fat pad" and is often the only visible marker of the fracture, especially in pediatric populations.
Maps Fat pad sign
References
Source of the article : Wikipedia
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