Inveed “3” sign seen in –
**Core Concept**
The "3" sign, also known as the "3 sign of the thumb," is a radiological finding associated with a specific condition. This sign is observed in a particular type of fracture or dislocation, where the alignment of bones and surrounding soft tissues creates a distinctive three-point pattern.
**Why the Correct Answer is Right**
The "3" sign is typically seen in a Bennett's fracture-dislocation, which involves a fracture of the base of the first metacarpal bone and dislocation of the carpometacarpal joint. This occurs when a person falls onto an outstretched hand, causing the thumb to be forced into hyperextension and the metacarpal bone to fracture. The resulting displacement of the bone and surrounding soft tissues creates the characteristic "3" sign on radiographs. The mechanism of this injury involves the disruption of the carpometacarpal ligaments and the fracture of the metacarpal bone.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the "3" sign is not typically associated with a fracture of the scaphoid bone, which would result in a different radiological pattern.
**Option B:** This option is incorrect because the "3" sign is not seen in a Colles' fracture, which involves a fracture of the distal radius and ulna, resulting in a different radiological appearance.
**Option C:** This option is incorrect because the "3" sign is not associated with a fracture of the distal phalanx, which would result in a different type of injury pattern.
**Clinical Pearl / High-Yield Fact**
The "3" sign is a classic radiological finding in Bennett's fracture-dislocation, and its presence should prompt the radiologist to consider this diagnosis. It is essential to recognize this sign to avoid missing a potentially complex and challenging injury.
**Correct Answer: D. Bennett's fracture-dislocation**