Saturday, May 12, 2007
Fat Pad Sign
Occasionally, a pediatric patient, or even the rare adult patient will have pain from a fall or traumatic injury, and there is no visible evidence of a fracture to the technologist or the radiologist. There is a tell tale sign that there is in fact a fracture without ever seeing the fracture itself... the fat pad sign.
It is usually seen on children, but can sometimes be seen on adults. The patient has decreased ROM or extreme pain when being positioned for their radiographs. The films show joint effusion marked by increased optical density surrounding the bone or joint. The provided film displays this increased radiographic density on the anterior and posterior borders of the humerus in the lateral projection.
Most radiologists (from my personal experience only) are comfortable calling a fracture when a fat pad sign exists. If I could paraphrase the reason for this as stated by a radiologist I used to work with: The other possible causes of this type of effusion can only occur with a ligament or tendon tear around a joint. If it is not directly involving the joint, it is reasonable to conclude that a fracture is what caused the effusion. It is not an injury that will require surgery, and whether the injury is actually a ligament/tendon tear or a fracture, the treatment will be the same; splint or soft cast and no surgery. A potentially incorrect diagnosis of "normal" would minimize the amount of time for immobilization and could potentially risk further injury if not allowed to heal fully.