A 32-year-old man is admitted to the burn unit with 45% total body surface area (TBSA) thermal burns sustained in a house fire. During the initial assessment, you perform the Rule of Nines to estimate burn extent. Which of the following is the most common site of severe burns in adults presenting with flame injuries?

Explanation

## Most Common Sites of Flame Burns in Adults **Key Point:** In flame injury (the most common type of severe burn in adults), the **upper extremities and trunk** are the most frequently affected sites, accounting for the majority of TBSA involvement in hospitalized burn patients. ### Anatomical Distribution in Flame Burns | Site | Frequency | Clinical Significance | |------|-----------|----------------------| | **Upper extremities & trunk** | Most common (40–50% of cases) | Exposed during escape attempts; protective reflex less effective | | Lower extremities | Common (30–40%) | Exposed; patient often in upright position during fire | | Head and neck | Moderate (15–25%) | Often spared if patient escapes quickly; affected in unconscious/trapped victims | | Perineum/genitalia | Rare (<5%) | Protected by clothing and position | **Clinical Pearl:** The **Rule of Nines** allocates: - Each upper extremity (arm + forearm + hand): **9%** - Anterior trunk: **18%** - Posterior trunk: **18%** - Each lower extremity: **18%** - Head and neck: **9%** In flame injuries, patients instinctively raise their arms to protect the face and head, exposing the upper extremities and trunk to prolonged flame contact. ### Why Upper Extremities & Trunk Predominate 1. **Protective reflex:** Flexor muscles contract more strongly than extensors, causing the "pugilistic stance" — arms flex upward, leaving trunk exposed. 2. **Escape behavior:** Patients attempt to shield the face with raised arms, increasing upper extremity exposure. 3. **Clothing ignition:** Loose clothing on the trunk ignites easily and burns longer than fitted sleeves. 4. **Flame convection:** Hot gases rise and concentrate around the upper body. **High-Yield:** In **contact burns** (e.g., touching a hot object), the site reflects the contact surface (e.g., palm for a stove). In **immersion burns** (e.g., scalding), the distribution is uniform. In **flame burns**, the upper body predominates — this distinction is frequently tested. **Mnemonic:** **FLAME** — **F**lexor reflex raises arms → **L**ower extremities less exposed → **A**rms and trunk most affected → **M**idline trunk vulnerable → **E**scape posture determines distribution.