Examination of the Exit Angle of Hair at the Skin Surface versus the Internal Angle of Hair as It Relates to the FUE/FIT Harvesting Method

Abstract

The FUE/FIT (follicular unit extraction/follicular isolation technique) procedure continues to gain acceptance as a method for harvesting donor grafts. The procedure is based on removing follicular units (FUs) or portions of FUs to use as grafts. A manual punch, mechanized punch, or robotic device is used to remove the FUs. No matter which method of harvesting is selected, there is concern regarding recovering intact FUs and avoiding transection of hair follicles. A common approach is to align the opening of the punch used with the path of the trimmed hair follicles of an FU and dissect along this path. While some hair follicles under the skin may follow the angle above the skin, others may not, which can lead to greater transection rates. Hair follicles within dissected slivers were examined from 13 patients. The internal and external hair growth angles of over 300 follicles were examined. Below, we examine the approach to harvesting and the means to decrease transection rates by understanding the path of hair follicles within the skin and as they emerge from the skin.