Telogen Phase

In an FUT Hair Transplant, What Percentage of Telogen Phase Follicles in Donor Strip are Wasted?

Q: When a donor strip is taken out during a hair transplant and separated under the microscope, you can read on the internet that there is a wastage of grafts (about 15%), because of those unseen telogen hairs. What do you think about that and how does it affect the hair restoration? — T.B. Baldwin, New York

A: The Telogen phase of the hair cycle is about 3 months long and about 12% of follicles are in this phase at any one time. It is speculated that the follicles may be empty for perhaps 1/2 that time (this number may vary significantly between people). Therefore, approximately 6% of the hair follicles may be in telogen at any one time.

On average about 15% of the follicular units are 1-hair units (but this also may very greatly between patients). If 6% of all follicles are “empty” telogen follicles, then there should be .15 x .06 = .009 or about 1% of the patient’s 1-hair follicular units in the empty telogen phase that can’t be identified and will be missed on dissection.

The 1% isn’t very large. However, also consider that the remaining 5% of the empty follicles are associated with larger follicular units (i.e. those with 2-4 hairs). If these follicular unit grafts are closely trimmed, as is the practice with very dense packing, a much more significant number of follicles are at risk of being lost. With chubby follicular unit grafts (i.e., where the microscopic dissection leaves a protective sheath of tissue around the follicles) the risk should be closer to the 1%.

The lesson for hair transplantation is that over-trimming of grafts, for the sake of very dense packing, may waste telogen hairs as well as place the grafts at an unnecessary risk of mechanical trauma, drying and warming.