**Core Concept**
In a femoral neck fracture, the position of the leg is often altered due to the disruption of the normal anatomical alignment. The direction and extent of the deformity depend on the type and severity of the fracture. The hip joint and surrounding musculature play a crucial role in determining the final position of the leg.

**Why the Correct Answer is Right**
In a femoral neck fracture, the leg typically assumes an external rotation deformity due to the unopposed action of the external rotators of the hip. This occurs because the internal rotators of the hip, which are normally balanced by the external rotators, are stretched or torn. As a result, the leg rotates outward, away from the midline of the body. The extent of the deformity usually ranges from 15 to 30 degrees, but it can be less than 45 degrees in some cases. The external rotation deformity is often accompanied by shortening of the affected limb.

**Why Each Wrong Option is Incorrect**
**Option A:** Internal rotation deformity of less than 45 degree - This is incorrect because internal rotation is typically seen in fractures of the femoral shaft, not the neck.

**Option C:** Internal rotation deformity of more than 45 degree - This is incorrect because internal rotation deformities are not characteristic of femoral neck fractures, and the extent of the deformity is usually less than 45 degrees.

**Option D:** External rotation deformity of more than 45 degree - This is incorrect because while external rotation is a common feature of femoral neck fractures, the extent of the deformity is usually less than 45 degrees.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the direction and extent of the deformity in a femoral neck fracture can be influenced by the patient's position and the presence of any associated injuries. A thorough clinical examination and radiographic evaluation are necessary to accurately assess the extent of the deformity and plan appropriate management.

**✓ Correct Answer: B. External rotation deformity of less than 45 degree.**