A 28-year-old male presents with a pulsatile swelling in the femoral triangle following a stab wound to the groin. Regarding the structures at risk and their anatomical relationships, all of the following are true EXCEPT:

Explanation

## Clinical Anatomy of the Femoral Triangle: Injury and Vascular Access ### Femoral Artery Compression Point **Key Point:** The femoral artery can be compressed against the underlying pectineus muscle at the level of the inguinal ligament. This is the standard site for emergency hemorrhage control in groin trauma. **Clinical Pearl:** Compression should be applied just below the inguinal ligament, where the artery lies against the pectineus muscle, which provides a firm backing. ### Femoral Vein Anatomy and Injury Risk **High-Yield:** The femoral vein lies **posteromedial** to the femoral artery within the femoral sheath. During femoral artery puncture or catheterization, the vein is at significant risk of injury because: 1. It is immediately adjacent to the artery 2. It lies posterior and medial, making it vulnerable if the needle trajectory is too deep or medial 3. Venous injury can lead to thrombosis, hematoma formation, or arteriovenous fistula ### Saphenous Opening and Great Saphenous Vein **Key Point:** The great saphenous vein (GSV) joins the femoral vein at the saphenous opening (fossa ovalis), which is located **medial** to the femoral vessels. This is an important landmark in femoral triangle anatomy. **Anatomical Relationship:** - GSV approaches from the medial side - Joins the femoral vein just below the inguinal ligament - The saphenous opening is covered by cribriform fascia ### The Femoral Nerve — Position Within the Sheath **Warning:** This is the key trap in this question. **Correct anatomical position:** - The femoral nerve is **LATERAL** to the femoral artery, NOT medial - The femoral nerve lies **OUTSIDE** the femoral sheath (in the iliopsoas compartment) - The femoral vein is the **MOST MEDIAL** structure within the femoral sheath **Clinical significance:** - During femoral artery puncture, the femoral nerve is at LOWER risk because it lies lateral and outside the sheath - The femoral vein (medial) is at higher risk than the femoral nerve - Femoral nerve injury during arterial puncture is rare; it typically occurs from external compression or hematoma expansion ### Mnemonic: Lateral to Medial Arrangement **Mnemonic:** **LAM** (Lateral to Medial) - **L** = Lateral: Femoral **N**erve (outside sheath) - **A** = Artery (within sheath) - **M** = Medial: Femoral **V**ein (within sheath) ### Summary Table: Femoral Triangle Structures | Structure | Position | Within Sheath? | Risk in Arterial Puncture | | --- | --- | --- | --- | | Femoral nerve | Lateral to artery | No | Low (outside sheath) | | Femoral artery | Central | Yes | Target structure | | Femoral vein | Posteromedial to artery | Yes | **High** (adjacent, medial) | | GSV | Medial, joins at saphenous opening | No | Low (superficial) | [cite:Gray's Anatomy 42e Ch 45; Clinically Oriented Anatomy 8e Ch 6]