**Question:** Graft used in infrainguinal by pass is -

A. External iliac artery
B. Femoral artery
C. Great saphenous vein
D. Innominate artery

**Core Concept:**
Infrainguinal bypass surgery is a common procedure in vascular surgery to bypass occluded segments of the infrainguinal arteries, which include the common femoral, profunda femoris, superficial femoral, popliteal, tibial common, tibial posterior, and tibial anterior arteries. The goal of the bypass is to restore blood flow to the lower limbs.

**Why the Correct Answer is Right:**
The correct answer is **C.** Great saphenous vein graft, also known as the femoropopliteal bypass. This is because the infrainguinal arteries have a relatively low-flow demand, and the great saphenous vein is an ideal graft material due to its suitability for low-flow bypass, ease of harvesting, and minimal patency loss over time.

**Why Each Wrong Option is Incorrect:**

A. **External iliac artery (D):** This option is incorrect because the external iliac artery is usually too large to be used as a graft in infrainguinal bypass, and harvesting it may cause significant morbidity due to its large diameter.

B. **Femoral artery (B):** The femoral artery is too large and not suitable for infrainguinal bypass. Additionally, harvesting it may cause significant morbidity due to its size and proximity to the femoral nerve.

D. **Innominate artery (D):** The innominate artery is located in the neck and is too far away from the infrainguinal region to be used in infrainguinal bypass. Furthermore, it is not directly accessible for harvesting.

**Clinical Pearl:**
The choice of graft material is crucial in infrainguinal bypass surgery to ensure patency and limb salvage. Adequate graft choice involves considering factors like size, suitability, morbidity associated with harvesting, and the patient's anatomy.