Once acupuncture points have been selected, the next step is to locate them on the patient’s body surface. Chinese physicians make use of two systems of measurement for this purpose: a body system based on the distance between two selected anatomical landmarks, and a digital system based on the patient’s own finger measurements. The basic units used are in the tsun, which is approximately 2.54 cm in length, and the fen, which is 0.1 tsun, or approximately 0.254 cm in length.
The following are some of the most commonly used anatomical relationships and their measurements in tsun.
Middle point of the eyebrow to the hair margin – 3 tsun
Anterior hair margin to the posterior hair margin – 12 tsun
Posterior hair margin to the seventh cervical vertebra – 3 tsun
Anterior hair margin to the mandible – 10 tsun
Distance between the mastoid processes behind both ears – 9 tsun
Distance between the nipples in men or the midclavicular lines bilaterally in women – 8 tsun
Suprasternal notch (angle of Louis), Tien Tu, to the lower border of the body of the sternum – 3 tsun
Lower border of the body of the sternum to the umbilicus – 8 tsun
Umbilicus to the upper margin of the symphysis pubis – 5 tsun
Anterior axillary fold to the transverse fold of the elbow – 9 tsun
Transverse fold of the elbow to the transverse fold of the wrist – 12 tsun
Greater trochanter to the lateral condyle of the femur – 19 tsun
Lateral condyle of the femur to the lateral malleolus – 16 tsun
Medial condyle to the tip of the medial malleolus – 13 tsun
Superior margin of the symphysis pubis to the medial condyle of the femur – 18 tsun
Distance from a point between the glabella to the external occipital protuberance – 12 tsun
Distance between the inner borders of the scapulae when the arms are crossed over the chest – 6 tsun
The digital system makes use of the patient’s own finger measurements and is the one most commonly used by acupuncturists because it is specific for each patient. Again, the basic measurement is the tsun, considered, in this system, to be the distance between the two interphalangeal folds of the middle finger when flexed. The width of the thumb is also equal to 1 tsun. The sum of the width of the index and middle fingers equals 1.5 tsun, and the sum of the width of all four fingers, excluding the thumb, equals 3 tsun.
Useful Anatomical Landmarks
When the head is bent forward and the neck is flexed, the most prominent spinal protrusion is the seventh cervical vertebra.
The inferior angle of the scapulae is at the level of the seventh thoracic vertebra.
A line drawn horizontally to join the highest points of each iliac crest bisects the intervertebral space between the fourth and fifth lumbar vertebra.
When the patient is in an upright position, with both arms vertical and held close to the body, the tips of the middle fingers just touch the point Feng Shih on the lateral aspects of the thigh (bilaterally).
When the index fingers and thumbs of both hands are clasped together, the point Lieh Chueh is found in the bony depression near the tip of the index finger on its dorsal aspect.