Harvested vs estimated follicular units in hair transplantation

The follicular unit transplantation strip harvesting surgery is one of the gold standard methods of hair transplantation; the counting follicular unit ratio and hair density is a major step in donor site evaluation.

We conducted the study for analyzing the preoperative donor site evaluation and comparison of the actual harvested and estimated follicular units in hair transplantation.

In this retrospective study, we enrolled 65 male patients with androgenetic alopecia who underwent follicular unit transplantation. Before the donor strip harvesting procedure, we counted the follicular unit density and calculated the percentage of each follicular unit. And then, we compared them to actual harvesting grafts.

The number of actual harvested transplanted hairs (3162.22 ± 958.30) were less than estimated transplanted hairs (3319.25 ± 1007.86). Both the number and percentage of actual harvested 1-hair follicular unit were more than estimated 1-hair follicular unit. In contrast, the number and percentage of actual harvested 3-hair follicular unit was less than estimated 3-hair follicular unit. The follicular unit density was lower in older patients. Those received more than one session of hair transplantation tended to have lower follicular and hair density (P = 0.007 and 0.01, respectively). The scalp laxity was lower in older patients and those received multiple sessions of hair transplantation.

The actual harvested grafts yield more 1-hair follicular units and less 3-hair follicular units than estimation. Old age and multiple sessions of hair transplantation caused more limitation of harvesting donor scalp.