The Rule of Nines calculator estimates the Total Body Surface Area (TBSA) affected by burns, using boolean inputs representing different body parts. Each body part has a predefined percentage score based on the Rule of Nines used in burn assessment.

Each input, such as "Head and neck" or "Left arm," is checked for whether the part is affected (true/false). The scoring system assigns specific TBSA percentages to each part: Head and neck = 9%, Genitalia = 1%, Left Arm = 9%, Right Arm = 9%, Anterior Trunk = 18%, Posterior Trunk = 18%, Left Leg = 18%, and Right Leg = 18%. The calculator aggregates the scores of affected areas to compute the total TBSA.

The interpretation of TBSA percentage is directly related to the score. If the score is 0, TBSA is 0%. The score increments then reflect corresponding TBSA values, such as 1 for 1%, 9 for 9%, etc. Notable scores include 18 for TBSA 18%, 55 for TBSA 55%, and 100 for TBSA 100%. This processed output provides both the numerical score and its interpretation as a percentage of body surface area affected.

Below is a summary of the key input-output relationships:

Input Parts | Score Contribution 
------------|------------------- 
Head and Neck | 9% 
Genitalia | 1% 
Left Arm | 9% 
Right Arm | 9% 
Anterior Trunk | 18% 
Posterior Trunk | 18% 
Left Leg | 18% 
Right Leg | 18% 

Total Score | Interpretation 
------------|---------------
0 | TBSA 0% 
1 | TBSA 1% 
9 | TBSA 9% 
10 | TBSA 10% 
18 | TBSA 18% 
36 | TBSA 36% 
54 | TBSA 54% 
72 | TBSA 72% 
99 | TBSA 99% 
100 | TBSA 100% 

The Rule of Nines is a clinical tool designed for estimating the total body surface area (TBSA) affected by burns. It is particularly useful in the initial assessment and management of burn patients, aiding in fluid resuscitation and burn severity classification.

The primary components of the Rule of Nines include the head, neck, and genitalia, upper limbs, truncal area, and lower limbs. Each of these body parts is assigned a percentage that approximates its contribution to the total body surface area. The head and neck, as well as each arm, are each assigned 9%. The genitalia are assigned 1%. The anterior and posterior trunk, as well as each leg, are each assigned 18%. 

The total score is determined by adding the percentages of all affected areas. For example, a burn affecting the entire anterior trunk and one arm would result in a TBSA of 27% (18% for the anterior trunk and 9% for the arm). 

The Rule of Nines allows for a quick and practical estimation of burn extent, which is crucial for determining the need for hospital admission, planning for fluid resuscitation, and predicting patient outcomes.

Rule of nines for estimating TBSA