Q: I have been reading about hair transplantation and I have a question concerning FUT (strip-harvesting). I understand, in this method, a strip is excised from the back of the scalp, the wound then closed. I wonder, then, is not the overall surface of the scalp reduced in this procedure? After two or three procedures, especially, (or even after one large session) will not a patient’s hairline also be shifted? That is, the front hairline would move back by the amount of scalp excised, or, more likely, the “rear hairline” (which ends at the back of the neck) must certainly be “moved upward.” At least, this is how I imagine it would be. Is my logic flawed? I’ve been trying to understand this in researching the procedure, but the point still evades me. — M.M., Great Falls, V.A.

A: The hair bearing area is much more distensible (stretchable) than the bald area and just stretches out after the procedure. As a result, the density of the hair in the donor area will decrease with each hair transplant session, but the position of the upper and lower margins of the donor area don’t move much – if at all. As a result, the major limitation of how much donor hair can be removed is the decreasing hair density, rather than a decrease in the size of the donor area.

With very low donor hair density the strip will yield so little hair that further sessions eventually become impractical. To say it another way, since a hair transplant decreases the donor density, in each succeeding hair transplant session, you need an increasingly larger donor strip to remove the same number of grafts.

This effect also explains why, in most instances, FUE will not allow the doctor to obtain any significant amount of additional hair, since the donor area is already too thin, and FUE would thin it further.