The proximal fragment of scaphoid after fracture is predisposed for Avascular Necrosis because:
## **Core Concept**
The scaphoid bone is one of the carpal bones in the wrist, and its blood supply enters distally. Due to this unique blood supply pattern, the proximal fragment of the scaphoid is more susceptible to avascular necrosis (AVN) after a fracture.
## **Why the Correct Answer is Right**
The blood supply to the scaphoid bone primarily enters through its distal end. When a fracture occurs, particularly in the proximal part of the scaphoid (scaphoid waist or proximal pole), the blood vessels supplying the proximal fragment can be disrupted. This disruption compromises the blood supply to the proximal fragment, leading to ischemia and potentially avascular necrosis. The **proximal pole** of the scaphoid is particularly at risk because it is farthest from the site where the blood vessels enter.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, incorrect options might mention unrelated factors such as muscle pull, type of fracture, or other bones.
- **Option B:** Similarly, without the specific content of Option B, we can infer that it might suggest another reason not directly related to the blood supply.
- **Option D:** This option might propose an alternative mechanism or location not relevant to the scaphoid's unique blood supply pattern.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that fractures of the scaphoid are the most common fractures of the carpal bones, and due to the risk of AVN, especially in proximal fractures, early diagnosis and treatment are crucial. A helpful mnemonic is that the blood supply to the scaphoid comes from **distal to proximal**, making the proximal pole more susceptible to AVN.
## **Correct Answer:** . Proximal pole fracture