Follicular Unit Extraction

Abstract

The follicular unit (FU) was first defined by Headington and the conceptual framework for using FUs in hair transplantation was laid out by Bernstein and Rassman. It became clear to most hair restoration practitioners that the single-strip harvesting and stereomicroscopic dissection techniques developed by Limmer in 1988 were the best way to both harvest and isolate FUs. Although single-strip harvesting is an extremely efficient means of obtaining tissue for subsequent dissection into FUs, it results in a linear scar. Careful technique with thin donor strips will produce very fine scars, but if the strips are taken too wide, the scar can widen to an unacceptable degree. Covering the donor area with longer hair was the only solution to widened scars, as surgical repairs of these wounds generally proved to be ineffective. As a result, a number of patients became hesitant to undergo a procedure that had a potentially difficult-to-treat widened linear scar. In the mid-1990s, Rassman set out to find a way around this problem by directly extracting FUs from the donor area using a small punch. Early attempts were frustrated by high transection rates in a significant number of patients until Richard Shiell brought the work of Masumi Inaba to his attention. Inaba's technique varied slightly, using a similar punch but only partially cutting down on the hair follicle and then removing the remainder with forceps. Inaba's insight led to Rassman and Bernstein describing follicular unit extraction or the FOX procedure (FOllicular unit eXtraction), outlining an entire hair transplant procedure without strip harvesting [Fig 17.2.] After performing the FOX procedure on patients of various nationalities it became obvious that extraction proved to be quite variable. Histologic analysis was used in an attempt to elucidate the cause of patient variability and the FOX Test was introduced, an important surgical recommendation tool to determine patient candidacy.