Okay, let's tackle this question about avascular necrosis of the femoral head due to femoral neck fractures. The question is asking which artery's rupture leads to this complication. First, I need to recall the blood supply to the femoral head.

The femoral head's blood supply is crucial here. I remember that the main artery is the medial circumflex femoral artery. It gives off branches like the retinacular arteries that supply the femoral head. The lateral circumflex might contribute a bit, but the medial is the primary. The deep femoral artery branches into the circumflex arteries. The superior gluteal artery is more for the gluteal region, not the femoral head. The obturator artery might have some anastomoses but isn't the main source.

So, when there's a femoral neck fracture, especially in the subcapital region, it's the medial circumflex femoral artery that's at risk. Rupture or disruption of this artery would cut off the blood supply, leading to avascular necrosis. The other options like the lateral circumflex or superior gluteal aren't the main suppliers here. The deep femoral artery is the parent artery, but the specific branch is the medial circumflex. So the correct answer should be the medial circumflex femoral artery. Let me make sure I didn't mix up the arteries. The obturator artery's ascending branch might supply some parts, but the medial circumflex is the key. Yeah, that's right. So the answer is the medial circumflex femoral artery.

**Core Concept**
Avascular necrosis of the femoral head following femoral neck fractures results from disruption of the blood supply to the femoral head. The **medial circumflex femoral artery** (a branch of the deep femoral artery) is the primary supplier, with its **retinacular arteries** forming the blood supply network.

**Why the Correct Answer is Right**
The **medial circumflex femoral artery** provides 80-90% of the blood supply to the femoral head via its retinacular branches, which anastomose around the femoral neck. Fractures in the subcapital or transcervical regions directly damage these vessels, leading to ischemia. The lateral circumflex femoral artery contributes minimally, and collateral circulation is insufficient to prevent necrosis in most cases.

**Why Each Wrong Option is Incorrect**
**Option A:** *Superior gluteal artery* supplies gluteal muscles and skin; not the femoral head.
**Option B:** *Obturator artery* may contribute via ascending branch but is not the primary source.
**Option C:** *Lateral circumflex femoral artery* provides <10% of femoral head blood supply. **Clinical Pearl / High-Yield Fact** Remember **"Medial = Majority"** for femoral head perfusion. Subcapital fractures (most common femoral neck fractures) almost always disrupt the medial circumflex artery, making avascular necrosis a high-risk complication. **Correct Answer: C. Medial circumflex femoral artery**

✓ Correct Answer: D. Medial circumflex femoral