Finger measurement means to take the length and width of the patient's finger(s) as a standard for locating acupoints because the fingers and the other parts of the body are in proportion. The following three methods are commonly used in clinical treatment.
1. Middle Finger Measurement
When the patient's middle finger is flexed, the distance between the two medial ends of the creases of the interphalangeal ) joints is taken as one cun, this method is used to measure the vertical distance to locate acupoints on the limbs and to measure the horizontal distance to locate the acupoints on the back. (See Fig. 2)
2. Thumb Measurement
The width of the interphalangeal joint of the patient's thumb is taken as one cun. This method is used for measuring the vertical distance to locate the acupoints on the limbs. (See Fig. 3)
3. Four-finger Measurement
The width of the four fingers (index, middle, ring and little fingers) close together at the level of the dorsal skin crease of the proximal interphalangeal joint of the middle finger is taken as three cun. This method is used to locate the acupoints on the lower limbs, lower abdomen and the back. (See Fig. 4)
Each finger measurement method has its own range of application and one cannot replace the others. Finger measurement should be done on the basis of bone-length measurement. If finger measurement and bone-length measurement cannot agree with each other, the latter should be taken as the standard.