An elderly woman was admitted with a fracture of the neck of right femur which failed to unite. On examination an avascular necrosis of the head of femur was noted. The condition would have resulted most probably from the damage to:
First, I need to recall the blood supply to the femoral head. The femoral head is a bone that's prone to AVN after fractures because its blood supply is delicate. The main arteries supplying the femoral head are the medial and lateral circumflex femoral arteries. These branches come from the profunda femoris artery. The medial circumflex femoral artery is the primary supplier, giving off the retinacular arteries that run up the femoral neck.
In a femoral neck fracture, especially a displaced one, the retinacular arteries can be disrupted. This would cut off the blood supply to the femoral head, leading to AVN. The medial circumflex femoral artery is more at risk here because it's the main supplier. The lateral circumflex might contribute some, but the medial is the key one.
Now, looking at the options (even though they're not listed here), the correct answer would be the medial circumflex femoral artery. The other options might be other arteries like the superficial femoral artery, which isn't involved in the femoral head's blood supply. The obturator artery might have some anastomotic connections, but they're not primary. The external iliac artery is upstream, so damage there would have more systemic effects, not just AVN.
The clinical pearl here is that the medial circumflex femoral artery is the critical vessel for the femoral head. Any disruption, like in a femoral neck fracture, can lead to AVN. Students should remember that the blood supply is retrograde, coming up from the medial side through the retinacular arteries. This is a classic exam point in orthopedics and trauma.
**Core Concept**
The femoral head's blood supply primarily originates from the **medial circumflex femoral artery (MCFA)**, a branch of the profunda femoris artery. Disruption of this vascular supply during femoral neck fractures leads to **avascular necrosis (AVN)** due to compromised retrograde perfusion via retinacular arteries.
**Why the Correct Answer is Right**
The **medial circumflex femoral artery** provides **retinacular arteries** that supply the femoral head via the ligamentum teres and through the femoral neck. In displaced femoral neck fractures, these vessels are disrupted, causing ischemia and AVN. The MCFA is the **primary vascular source**; its damage is the most direct cause of AVN in this clinical scenario.
**Why Each Wrong Option is Incorrect**
**Option A:** *Superficial femoral artery* – Supplies the thigh and leg; not involved in femoral head perfusion.
**Option B:** *Obturator artery* – Provides minor anastomotic connections but is not the primary supplier.
**Option D:** *External iliac artery* – A proximal vessel; injury here would cause broader ischemia, not isolated AVN.
**Clinical Pearl / High-Yield Fact**
Remember the **"retinacular arteries"** from the MCFA as the **critical blood supply** to the femoral head. Trauma or displacement in