According to the Rule of Nines, what percentage of body surface area (BSA) is covered by the anterior surface of one lower limb in an adult?

Explanation

## Rule of Nines in Adult Burn Assessment **Key Point:** The Rule of Nines is the most widely used rapid assessment tool for estimating total body surface area (TBSA) affected by burns in adults. It divides the body into segments, each representing a multiple of 9% or 18%. ### Adult Rule of Nines Distribution | Body Region | Percentage of TBSA | | --- | --- | | Head and neck | 9% | | Anterior chest | 9% | | Posterior chest | 9% | | Abdomen | 9% | | Anterior right upper limb | 4.5% | | Anterior left upper limb | 4.5% | | Posterior right upper limb | 4.5% | | Posterior left upper limb | 4.5% | | Anterior right lower limb | 9% | | Anterior left lower limb | 9% | | Posterior right lower limb | 9% | | Posterior left lower limb | 9% | | Genitalia | 1% | | **Total** | **100%** | **High-Yield:** Each lower limb (anterior + posterior) = 18% TBSA. Therefore, the anterior surface of one lower limb = 9%. **Clinical Pearl:** The Rule of Nines is most accurate in adults and children >10 years. In young children, the head accounts for a larger percentage (18%) and lower limbs for a smaller percentage (13.5% each). **Mnemonic:** **"9-18-9 Rule"** — Head (9%), each arm (9%), each leg (18%), trunk (36%), genitalia (1%).