肘关节损伤X线平片阅读技巧.docx

How to read the elbow XrayJuliet Caldwell MD, NewYork-Presbyterian Hospital/Weill Cornell Medical CenterFractures lines can be difficult to visualize after acute elbow injury, particularly in children. Below are eight sequential steps to aid in the radiographic recognition of occult signs of injury.Step1: hourglass signSearch for an adequate hourglass sign, or figure of eight at the distal humerus. If absent the study is not a true lateral and interpretation of steps 2 through 4 is less reliable. Heres an example of a true lateral; note the symmetric figure of eight/hourglass sign at the distal humerus; also notice the posterior fat pad? (see below.)Here is an imperfect lateral radiograph accompanied by a normal AP radiograph; notice how the figure of eight/hourglass is asymmetric:Step2: anterior fat pad evaluationA visible anterior fat pad can be normal; it is a small radiolucent shadow adherent to the anterior aspect of the distal humerus:An abnormal anterior fat pad is described as a sail sign because it is unusually prominent and bows outward to form a triangular shape. After trauma, blood can accumulate in the intraarticular space and push the fat pad anteriorly; a positive sail sign in the setting of trauma is a reliable indication of an intraarticular fracture – even if no fracture line can be identified. An atraumatic sail sign implies intraarticular fluid of an inflammatory nature. Step3:posterior fat evaluationRadiographic visualization of a posterior fat pad is never normal and always signifies fluid in the intraarticular space. Again, in the setting of trauma, this strongly implies fracture of an articular surface.Here is a radiograph with both a sail and posterior fat pad sign:Step4: anterior humeral lineThis line should intersect the middle third of the capitellum on the lateral view. Fractures usually result in displacement of the capitellum posteriorly (versus anteriorly). If the film is not a true lateral, interpretation of the anterior humeral line