## Distinguishing Intracapsular from Extracapsular Femoral Neck Fractures ### Anatomical Basis **Key Point:** The single best clinical/radiological feature that **distinguishes** an intracapsular fracture from an extracapsular (intertrochanteric) fracture is the **involvement of the greater and lesser trochanters in the fracture line** — a finding that is, by definition, present in intertrochanteric (extracapsular) fractures and absent in intracapsular fractures. ### Comparison Table | Feature | Intracapsular (Subcapital/Transcervical) | Extracapsular (Intertrochanteric) | | --- | --- | --- | | **Trochanter involvement** | No — fracture line within capsule | Yes — fracture line crosses trochanters | | **Fracture line location** | Within joint capsule | Below/at intertrochanteric line | | **Blood supply disruption (MFCA)** | Yes — high AVN risk (20–50%) | No — MFCA preserved | | **Risk of avascular necrosis** | High | Low (<5%) | | **Limb position** | Slight external rotation, minimal shortening | Marked external rotation and shortening | | **Age of presentation** | 60–70 years (relatively younger) | 75–85 years (older) | ### Why Option A is Correct **High-Yield:** Trochanteric involvement is a **direct radiological discriminator** visible on plain X-ray. By definition, an intertrochanteric fracture runs between (or through) the greater and lesser trochanters, whereas an intracapsular fracture is entirely within the joint capsule, proximal to the trochanters. This is the most reliable single feature to distinguish the two types on imaging — the question's core ask. ### Why the Other Options Are Incorrect - **Option B (External rotation and shortening):** These signs occur in **both** intracapsular and extracapsular fractures and therefore do NOT distinguish between them. They are general signs of any proximal femur fracture. - **Option C (MFCA disruption):** While MFCA disruption is a critical consequence of intracapsular fractures and explains AVN risk, it is **not a clinical or radiological feature** that can be directly observed on X-ray or clinical examination. It is a pathophysiological consequence, not a distinguishing observable sign. The question specifically asks for a "clinical or radiological feature." - **Option D (Age >80 years):** Both fracture types occur in elderly patients with significant overlap; age alone cannot reliably distinguish the two types. **Clinical Pearl:** On NEET PG / INI-CET, when asked what *distinguishes* intracapsular from extracapsular fractures on X-ray, always look for trochanteric involvement — present in intertrochanteric fractures, absent in intracapsular fractures. MFCA disruption is the key *complication* distinguisher, not the radiological one. [cite: Rockwood & Green's Fractures in Adults 9e Ch 53; Campbell's Operative Orthopaedics 13e] 
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