Burn Percentage for Feet and Legs According to the Rule of Nines
According to the Rule of Nines, each leg (including the foot) accounts for 18% of the total body surface area (TBSA), with both legs together representing 36% of TBSA.
Burn Surface Area Assessment Methods
Rule of Nines
- The Wallace Rule of Nines is a commonly used method for quick estimation of burn surface area in the field, though it significantly overestimates TBSA and is not suitable for children 1
- According to this method:
More Accurate Methods
- The Lund-Browder chart is considered the most accurate method for TBSA quantification and is the reference standard recommended by burn specialists 1, 3
- The Lund-Browder chart accounts for age-related differences in body proportions, making it suitable for both adults and children 1
- For quick estimation in the field, the patient's palm and fingers (approximately 1% TBSA) can be used as a reference point 1, 4
Accuracy Concerns with Different Methods
Limitations of the Rule of Nines
- The Rule of Nines significantly overestimates TBSA in 70-94% of cases 1, 5
- This overestimation can lead to excessive fluid administration during resuscitation 1, 6
- The Rule of Nines is particularly inaccurate for children due to their different body proportions 1, 4
Technology-Aided Assessment
- Modern smartphone applications like EasyTBSA have shown greater accuracy for burn size estimation compared to traditional methods 6
- In one study, EasyTBSA had the greatest accuracy (-0.01%, SD 3.59%) compared to the Rule of Palms (3.92%, SD 10.71%), Lund-Browder Chart (4.42%, SD 5.52%), and Rule of Nines (5.05%, SD 6.87%) 6
- Computer-aided tools have demonstrated improved consistency in TBSA calculations compared to traditional paper-based methods 7
Clinical Implications
Importance of Accurate Assessment
- Accurate TBSA assessment is crucial for determining burn severity and guiding appropriate management 3, 2
- Burns covering >10% TBSA in adults or >5% in children should be referred to a burn center 3
- For adults with burns >15% TBSA and children with burns >10% TBSA, fluid resuscitation should be initiated with 20 mL/kg of balanced crystalloid solution in the first hour 5, 3
Common Pitfalls to Avoid
- Overestimation of TBSA can lead to unnecessary transfers to burn centers and fluid overload during resuscitation 6
- Underestimation can result in inadequate treatment and increased morbidity and mortality 1
- Early specialist consultation is recommended to confirm TBSA assessment and guide management 5, 8
Special Considerations
- Burns to the feet are considered critical areas requiring specialized care regardless of TBSA percentage 3, 8
- Circumferential burns of the extremities may require escharotomy if they compromise circulation 1, 5
- The assessment should be repeated during initial management as the burn appearance may evolve 1