Today I will discuss donor density and how it affects the hair transplant procedure. Donor density is the amount of follicles per cm squared in the donor region. A secondary factor relating to density is the hair count, which is the number of hairs in the donor region. This is determined by finding the average follicular density per cm squared and then the average number of hairs per follicle and multiplying the two numbers. The average scalp has between 60-100 follicular units per cm squared and the average hair count is between 2.3-2.7 hairs per follicle. If the majority of the follicles are 2 hair follicles as opposed to 3 hair follicles then the overall hair count will be less. This is why not only the number of follicles is important, but the average number of hairs per follicle as well. The higher the hair count and follicle count, the greater the donor density. The greater the donor density the more hair that can be moved from the donor region to the areas of thinning. The donor region is an unchangeable area whether we do FUE or FUT to harvest the donor hair in the hair transplant procedure. This is why a high donor density and high donor hair count will lead to the ability to move more donor follicles to the areas of thinning.
I hope this helps to clarify donor density and how it impacts a hair transplant procedure.
All the best,
Marc Dauer, MD