Morphometric Analysis of the Human Scalp Hair Follicle: Practical Implications for the Hair Transplant Surgeon and Hair Regeneration Studies

The study analyzed hair follicles from 29 individuals to provide measurements useful for hair transplantation and regeneration research. It found that the average length of a scalp hair follicle is 4.16 mm, with the bulge stem cell region extending from 1 mm to 1.8 mm in depth. For hair transplant procedures, it is recommended to cut at a depth of less than 1 mm to preserve the bulge zone. The study also noted that the infundibulum can be removed without impacting hair regrowth, and that the permanent portion of the hair follicle (infundibulum plus isthmus) constitutes 40% of the total length. The findings suggest that the level of transection significantly affects the follicle's regenerative capacity, highlighting the need for precise measurement in hair follicle research.