A 62-year-old man with a history of chronic hip pain undergoes imaging for suspected femoral head avascular necrosis. Regarding the arterial anatomy of the femoral head, all of the following are true EXCEPT:

Explanation

## Femoral Head Blood Supply: Clinical Anatomy ### Overview **Key Point:** The femoral head has a precarious blood supply derived primarily from the medial and lateral femoral circumflex arteries. Understanding this anatomy is critical for recognizing avascular necrosis (AVN) risk. ### Correct Statements (Options 0, 1, 3) | Artery | Origin | Role | Notes | |--------|--------|------|-------| | **Medial femoral circumflex artery (MFCA)** | Profunda femoris | **Dominant supply** (~80%) to femoral head | Passes posteriorly around femoral neck; most vulnerable in hip dislocation or femoral neck fracture | | **Lateral femoral circumflex artery (LFCA)** | Profunda femoris | Supplementary supply (~20%) | Passes anteriorly; less critical but contributes to anastomotic ring | | **Extracapsular arterial ring** | MFCA + LFCA branches | Forms at base of femoral neck; penetrates capsule | Supplies femoral head via ascending cervical branches | | ~~Obturator artery (artery to ligamentum teres)~~ | Obturator artery | **Minimal/negligible** in adults | Functionally obliterated in most adults; NOT a primary source | ### Why Option 2 (Obturator Artery) Is INCORRECT **High-Yield:** The obturator artery gives off the artery to the ligamentum teres, which is **NOT** the primary blood supply to the femoral head in adults. **Clinical Pearl:** This is a common misconception. While the ligamentum teres artery may be patent in children and can contribute minimally in young adults, it is functionally obliterated or severely reduced in most adults and plays NO significant role in femoral head perfusion. **Warning:** NEET PG frequently tests this distinction. Students often conflate "artery to ligamentum teres" with "main blood supply to femoral head" — they are NOT the same. ### Risk of AVN: Why Blood Supply Matters ```mermaid flowchart TD A[Femoral Neck Fracture or Hip Dislocation]:::urgent --> B{Which artery is disrupted?}:::decision B -->|Medial femoral circumflex| C[Loss of 80% of blood supply]:::urgent B -->|Lateral femoral circumflex| D[Loss of 20% of blood supply]:::outcome C --> E[High risk of AVN]:::urgent D --> F[Lower risk of AVN]:::outcome A --> G[Extracapsular ring disrupted]:::urgent G --> H[Ascending cervical branches cannot reach femoral head]:::urgent H --> I[Femoral head ischemia → AVN]:::urgent ``` **Mnemonic:** **MFCA-80** = Medial Femoral Circumflex Artery supplies ~80% of femoral head (the critical vessel). ### Clinical Correlate: Femoral Neck Fracture Fractures of the femoral neck (especially intracapsular) carry high risk of AVN because: 1. The MFCA is disrupted as it passes posteriorly around the neck 2. The extracapsular ring is compromised 3. The ligamentum teres artery cannot compensate (it is vestigial in adults) [cite:Clinically Oriented Anatomy 8e Ch 5; Harrison 21e Ch 297]