The "sail sign," observed in a lateral elbow radiograph, indicates what condition?

• A. Radial head fracture
• B. Joint effusion
• C. Collateral ligament injury
• D. Fracture dislocation

Answer: (B)

The "sail sign," which is characterized by the appearance of a curved radiolucent line at the anterior aspect of the elbow, indicates the presence of joint effusion. This sign is most commonly seen in lateral views of the elbow radiographs when there is fluid accumulation in the joint space, often due to trauma or inflammation.

In the context of elbow injuries, a joint effusion typically occurs alongside various conditions but is particularly diagnostic for identifying the presence of hidden injuries or fractures that may not be immediately obvious on the radiograph. The elevation of the fat pads, which results in the "sail sign," suggests that there is intra-articular fluid, raising suspicion of associated injuries, such as a fracture.

Other conditions, while of concern in cases of elbow trauma, may not specifically present with the "sail sign" or do not clearly indicate joint effusion. For example, a radial head fracture might be the underlying cause of the effusion but would not be directly represented by the appearance of the sail sign itself. Similarly, collateral ligament injuries and fracture-dislocations are significant concerns, but they do not exhibit the characteristic "sail sign," which is uniquely indicative of joint effusion.