A 68-year-old man is brought to the hospital 36 hours after a fall from a height at his home. He has severe right hip pain and is unable to move the right lower limb. On examination, the right leg is held in flexion, adduction, and internal rotation. X-ray shows a displaced femoral neck fracture with the fracture line extending across the entire neck with significant angulation. The patient has no significant comorbidities and is otherwise healthy and independent. What is the most likely complication if this fracture is managed conservatively, and what is the best definitive treatment?

Explanation

## Clinical Context and Fracture Classification **Key Point:** This is a **displaced femoral neck fracture** (Garden Grade III–IV) in a relatively young, fit patient. The 36-hour delay and displacement significantly increase the risk of avascular necrosis (AVN). ## Pathophysiology of Avascular Necrosis in Femoral Neck Fractures ```mermaid flowchart TD A[Femoral Neck Fracture with Displacement]:::outcome --> B[Disruption of Medial & Lateral Circumflex Arteries]:::outcome B --> C[Loss of Blood Supply to Femoral Head]:::urgent C --> D{Time to Fixation}:::decision D -->|>48 hours| E[Ischemia of Femoral Head Bone]:::urgent D -->|<48 hours| F[Partial preservation of blood supply]:::action E --> G[Necrosis of Osteocytes & Marrow]:::outcome F --> H[Lower AVN risk]:::outcome G --> I[Collapse of Femoral Head]:::urgent I --> J[Post-traumatic Osteoarthritis]:::outcome ``` ## Why AVN Is the Most Likely Complication **High-Yield:** Displaced femoral neck fractures carry a **40–70% risk of AVN** depending on the degree of displacement and time to fixation. The blood supply to the femoral head is entirely dependent on the medial and lateral femoral circumflex arteries, which run along the femoral neck. Displacement disrupts these vessels, leading to ischemia of the femoral head. **Clinical Pearl:** The risk of AVN increases with: - Degree of fracture displacement - Delay in treatment (>48 hours significantly increases risk) - Age >60 years (relative ischemia) - Comminution ## Best Definitive Treatment: Total Hip Arthroplasty **Key Point:** In a young, fit patient with a displaced femoral neck fracture, the optimal management is **total hip arthroplasty (THA)** rather than internal fixation, because: 1. **High AVN Risk:** Even with internal fixation, displaced fractures have a 40–70% AVN rate, necessitating eventual THA anyway 2. **Single-Stage Solution:** THA eliminates the femoral head entirely, avoiding the need for revision surgery later 3. **Functional Outcome:** Young, fit patients tolerate THA well and achieve excellent long-term functional outcomes 4. **Timing:** THA should be performed urgently (within 48–72 hours of injury) to minimize complications **Mnemonic:** **DAVE** (Displaced, Age variable, Vascular compromise, Early THA): - **D**isplaced fracture → high AVN risk - **A**ge: In younger fit patients, THA is preferred over internal fixation - **V**ascular compromise due to displacement - **E**arly THA (within 48–72 hours) is the standard ## Comparison: Internal Fixation vs. THA in Displaced Femoral Neck Fractures | Feature | Internal Fixation (Cannulated Screws) | Total Hip Arthroplasty | |---------|---------------------------------------|----------------------| | **AVN Rate** | 40–70% (high) | 0% (femoral head removed) | | **Nonunion Rate** | 10–15% | N/A | | **Revision Surgery Rate** | 30–50% (due to AVN/nonunion) | 10–15% (aseptic loosening over 15+ years) | | **Best Suited For** | Undisplaced or minimally displaced; elderly/unfit | Displaced; young/fit patients | | **Functional Outcome** | Variable; depends on AVN development | Excellent in young patients | [cite:Rockwood & Green's Fractures in Adults Ch 48] ## Why Conservative Management Fails **Warning:** Conservative management of a displaced femoral neck fracture leads to: - Nonunion (20–30% rate) - Malunion with hip flexion deformity - AVN (40–70% rate) - Loss of hip function and mobility - Chronic pain and disability This is NOT an acceptable option in a fit, young patient.