A 68-year-old man sustains a displaced intracapsular femoral neck fracture. Which is the most common serious complication that occurs as a consequence of the vascular anatomy of the femoral neck?

Explanation

## Vascular Anatomy and Complications of Femoral Neck Fractures ### Blood Supply to the Femoral Head The femoral head receives its blood supply from three main sources: 1. **Lateral epiphyseal vessels** (primary) — arise from the medial femoral circumflex artery, run along the posterosuperior aspect of the femoral neck 2. **Medial epiphyseal vessels** — arise from the medial femoral circumflex artery, run along the posteromedial aspect 3. **Ligamentum teres artery** — supplies the foveal region (minor contribution, often absent in adults) **Key Point:** Intracapsular femoral neck fractures disrupt the lateral and medial epiphyseal vessels, which run along the femoral neck outside the joint capsule. This vascular disruption is the primary anatomical reason for avascular necrosis (AVN). ### Incidence of Avascular Necrosis | Fracture Type | Displacement | AVN Incidence | |---|---|---| | Subcapital | Undisplaced | 10% | | Subcapital | Displaced | 30–40% | | Transcervical | Undisplaced | 5–10% | | Transcervical | Displaced | 15–30% | | Basicervical | Displaced | 5–10% | **High-Yield:** Displaced intracapsular fractures (both subcapital and transcervical) have the highest risk of AVN because: - Complete disruption of the lateral and medial epiphyseal vessels - Loss of collateral circulation from the ligamentum teres (often absent in elderly) - Intracapsular hematoma compresses remaining blood supply - Fracture displacement prevents revascularization **Clinical Pearl:** AVN typically becomes clinically evident 6–12 months post-fracture, presenting with: - Sudden onset of hip pain - Progressive loss of hip motion - Collapse of the femoral head on imaging (Ficat stage III–IV) - May require total hip arthroplasty **Mnemonic:** **VEIN** — **V**ascular disruption (lateral epiphyseal vessels), **E**vidence of AVN (6–12 months post-fracture), **I**ntracapsular location (highest risk), **N**ecrosis of femoral head. ### Why AVN is the Most Common Serious Complication AVN is the most common serious complication because: 1. It is a direct consequence of the vascular anatomy and fracture displacement 2. It occurs in 15–40% of displaced intracapsular fractures 3. It leads to long-term disability and often requires surgical intervention 4. It is largely preventable only by early anatomical reduction and secure fixation [cite:Rockwood and Green's Fractures in Adults Ch 50]