## Rule of Nines in Adults **Key Point:** The Rule of Nines is the most widely used method for rapid estimation of body surface area (BSA) affected by burns in adults. ### Adult Distribution (Rule of Nines) | Body Region | Percentage | | --- | --- | | Head and neck | 9% | | Each arm (anterior + posterior) | 9% | | Chest | 9% | | Abdomen | 9% | | Each leg (anterior + posterior) | 18% | | Genitalia and perineum | 1% | | **Total** | **100%** | **High-Yield:** Each arm = 9% (both anterior and posterior surfaces combined). This is a fundamental fact tested frequently in burn assessment questions. **Mnemonic:** **9-18-1 Rule** - 9% = head, each arm, chest, abdomen - 18% = each leg - 1% = genitalia/perineum **Clinical Pearl:** The Rule of Nines allows rapid bedside estimation without need for body surface area charts, making it ideal for triage and initial fluid resuscitation calculations in burn units. [cite:Reddy and Menon Forensic Medicine 33e Ch 12]
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