A 32-year-old man is brought to the emergency department 2 hours after a flame burn injury sustained while cooking. On examination, he has erythema and blistering over both forearms, anterior chest, and upper abdomen. The dorsal surfaces of both hands are also affected with similar findings. Using the Rule of Nines, what is the approximate percentage of body surface area (BSA) involved in this burn?

## Body Surface Area Estimation Using Rule of Nines **Key Point:** The Rule of Nines is the most commonly used method for rapid BSA estimation in adult burn victims in the emergency setting. ### Anatomical Distribution (Adult Rule of Nines) | Body Region | Percentage of BSA | |---|---| | Head and neck | 9% | | Each upper limb (arm + forearm + hand) | 9% | | Anterior trunk (chest + upper abdomen) | 18% | | Posterior trunk (back + lower abdomen + buttocks) | 18% | | Each lower limb (thigh + leg + foot) | 18% | | Genitalia | 1% | ### Calculation for This Patient **Affected areas:** - Both forearms: 2 × 4.5% = 9% (forearm is 4.5% per side) - Dorsal surfaces of both hands: 2 × 0.5% = 1% (hand is 0.5% per side) - Anterior chest and upper abdomen: 18% **Total BSA = 9% + 1% + 18% = 28% ≈ 27%** **High-Yield:** In the Rule of Nines for adults: - Each arm (shoulder to fingertips) = 9% - Each arm subdivides as: upper arm 4.5%, forearm 2.25%, hand 1.25% (approximately 4.5%, 2.25%, 2.25% for practical purposes) - Anterior trunk = 18% (chest 9% + upper abdomen 9%) **Clinical Pearl:** The Rule of Nines is less accurate for small, scattered burns (use the "palm method" — patient's palm ≈ 0.5% BSA) and for children (head = 18%, each leg = 13.5%). **Mnemonic: "9-18-36-18-9-1"** — Head (9), each arm (9), anterior trunk (18), posterior trunk (18), each leg (18), genitalia (1).