A 72-year-old woman with osteoporosis sustains a distal radius fracture. On X-ray, the distal fragment is displaced volarly with volar angulation, and the ulnar styloid is intact. Which of the following is the most common complication at the time of initial injury in this fracture pattern?

## Smith Fracture Complications: Median Nerve Compression **Key Point:** The described fracture — distal radius with **volar displacement and volar angulation** — is a **Smith's fracture** (reverse Colles). At the time of initial injury, **median nerve compression in the carpal tunnel** is the most common acute complication, due to swelling, hematoma, and direct compression from the volarly displaced fragment. ### Why Median Nerve Compression Occurs Acutely 1. **Anatomy:** The median nerve passes through the carpal tunnel, which is bounded dorsally by the carpal bones and volarly by the flexor retinaculum. A volarly displaced distal radius fragment directly encroaches on this space. 2. **Mechanism:** Acute swelling and hematoma following the fracture increase carpal tunnel pressure, compressing the median nerve. 3. **Timing:** Symptoms (paraesthesia in the radial 3½ digits, thenar weakness) can appear **immediately or within hours** of injury — making this the most common **acute** complication. 4. **Incidence:** Acute median nerve symptoms occur in approximately 5–17% of distal radius fractures and are especially prominent with volar displacement patterns. **High-Yield:** Acute carpal tunnel syndrome after a distal radius fracture is a surgical emergency — urgent carpal tunnel release may be required if symptoms do not resolve with fracture reduction. ### Comparison of Complications in Distal Radius Fractures | Complication | Timing | Frequency | Clinical Finding | |---|---|---|---| | **Median nerve compression** | Acute (at injury) | Most common nerve complication (~5–17%) | Paraesthesia radial 3½ digits, thenar weakness | | **PIN compression** | Acute | Uncommon (<1%) | Loss of finger/wrist extension | | **AIN injury** | Acute | Rare (<0.5%) | Loss of thumb IP + index DIP flexion | | **EPL tendon rupture** | Late (6–12 weeks) | 1–5% of Colles fractures | Loss of thumb IP extension | **Clinical Pearl:** EPL rupture is the most common **late** complication of Colles fracture (dorsal displacement), not of Smith's fracture (volar displacement), and it does **not** occur at the time of initial injury. The stem specifically asks for the complication "at the time of initial injury," making median nerve compression the correct answer. *(Reference: Rockwood & Green's Fractures in Adults, 9th ed.; Campbell's Operative Orthopaedics)*