Hair diameter evaluation in different regions of the safe donor area in Asian populations

There is little information about how hair diameter differences within the safe donor area. Thicker or thinner hair may be needed depending on the recipient area, hairline design, and surgical purpose.

Thirty-eight non-alopecic subjects (19 males and 19 females) were evaluated. The safe donor area was defined as the area contained within 28 cm from the horizontal plane of the upper border of the hair rim to the vertical line of the bilateral external acoustic meatus. Seven zones were defined starting 2 cm on each side (bilateral 4 cm) from the mid-occiput to the temporal side. The diameters of 10 randomly selected anagen hairs were measured from each of the seven zones.

The results showed significant differences in hair diameter by zone between males and females (P < 0.0001). In general, hair diameter tended to decrease from zone 3 to 7.

Our results suggest that safe donor areas between zones 4 and 7 could be useful for specific hair transplantation surgeries requiring thinner hair, such as eyebrows, eyelashes, and female hairline correction surgery, whereas hair from zones 1-3 could be more useful for those requiring thicker hair, such as male and female pattern hair loss. Our data could be clinically valuable for planning hair transplant surgery and choosing the most optimal donor region.