Calculating Total Surface Area for a Wrist Burn
Use the Lund-Browder chart to calculate the total body surface area (TBSA) of this wrist burn, counting only the portion of the hand/wrist segment that is actually burned, which in this case would be a fraction of the hand region (approximately 0.5-1% TBSA depending on patient age). 1, 2
Primary Assessment Method
The Lund-Browder chart is the standardized and most accurate method for calculating burn TBSA in both adults and children, as it accounts for age-related variations in body proportions 1, 2, 3.
The hand (including wrist) represents approximately 2.5% TBSA in adults on the Lund-Browder chart, but this varies by age in children 1.
For a burn that stops just before the base of the thumb on the wrist, you would estimate what fraction of the entire hand segment is involved—likely less than half of the hand region, resulting in approximately 0.5-1% TBSA 2.
Practical Application for This Specific Burn
Record only the area with actual epidermal detachment or detachable epidermis (Nikolsky-positive areas), not just erythema, as erythema alone has no prognostic value 2.
Use the Lund-Browder body map to shade in the specific anatomical area burned (wrist region stopping before thumb base) and calculate the percentage based on the proportion of the hand segment involved 1, 4.
The entire palmar surface of the hand (palm and fingers) represents approximately 1% TBSA, while the palm alone represents only 0.5% TBSA—this can serve as a reference point for estimating the wrist area 2.
Alternative Quick Estimation Method
If the Lund-Browder chart is impractical in the field, you can use the patient's own palm plus fingers (1% TBSA) as a reference to estimate how many "palm units" would cover the burned wrist area 2, 3.
For a wrist burn stopping before the thumb base, this would likely be less than one full palm unit, suggesting <1% TBSA 2.
Critical Measurement Considerations
Perform repeated assessments during the first hours of care, as initial TBSA estimates are frequently inaccurate and burns can evolve 2, 3.
TBSA is overestimated in 70-94% of cases, which leads to excessive fluid administration—be conservative in your estimation 1, 3.
Smartphone applications (such as E-Burn, FireSync EMS, or 3D Burn) can facilitate more accurate TBSA calculation and reduce overestimation bias compared to manual methods 1, 5, 6.
Common Pitfalls to Avoid
Do not use the Rule of Nines for this calculation, as it significantly overestimates TBSA and is not suitable for children; it also lacks the precision needed for small burns 1, 2.
Do not include areas of erythema alone in your TBSA calculation—only count actual epidermal detachment 2.
Avoid mental estimation without using a standardized chart, as studies show deviations of up to 62% among clinicians using conventional estimation methods 7.