Hair Restoration, Hair Transplant, Hair Loss Treatment Clinic

Follicular Unit Growth at Four Different Hair Transplant Densities

There is a need to find the “threshold” density at which follicular unit (FU) graft recipient sites may be placed and yield excellent survival following a hair transplant. It is necessary to find the threshold density at follicular unit recipient sites where there will be good survival probabilities after a hair transplant. It also needs to be determined whether or not a smaller recipient site makes a difference in graft survival. This study looks at hair survival in two patients 18 months after they were each transplanted with four different densities.

The objective of the study was to determine the optimal density for “dense packing” FU grafts without causing loss of hair from vascular compromise or other factors that can affect graft growth during hair restoration surgery.

In the study, two male patients, both with Norwood Class VI patterns of hair loss, were examined. Two-hair FUs were planted respectively at densities of 20,30,40, and 50 follicular units per cm2 . 19 gauge needles were used for the boxes with 20 and 30 grafts per box, and 20g needles were used for the boxes with 40 and 50 grafts/cm2. The grafts were placed using a “stick-and-place” method.

The author concluded that both patients had excellent growth of the transplanted hair at densities of 30/cm2. However, one patient had decreased density at 40/cm2 and 50/cm2. Based upon this very limited study, the researcher suggested that there are probably individual factors unique to each patient which can affect graft survival of transplanted hairs at high densities.

The author proposes that the patient to patient variation at high densities may be due to variations in 1) scalp thickness, vasculature (atherosclerotic changes or differences in collateral circulation), presence of past transplant work or surgery with resultant “micro-scarring”, amount of epinephrine used in recipient area, or technique and care to grafts by cutters and placers.