FUE in the pure form is the extraction of a single FU at a time, each FU containing natural 1 hair or multiple hair groupings, normally up to 4 hairs. The punch tool can vary in size greatly and have a significant effect on the donor area as well as the result in the recipient. Donor management for FUE is very different from FUT, although the surface area may be larger does not indicate that more FU can be removed. The safety zone for FUE can be measured and sectioned in to three areas; simply both sides and the back, and then the total surface area calculated. The density is then measured in each area and the approximate average number of hairs per FU and any miniaturisation. From this a calculation can then be determined what is available to harvest depending on the person s hair loss stage and hair characteristics.
Taking into consideration to not over harvest, Dr. Bisanga believes this figure is approximately 25-30% per cm2 and any more will lead to potential complications in the donor as the person becomes older and for future procedures. This educated protocol is not just to minimise visible scarring although that is a factor but also to preserve the donor and make it easier for any further extractions be it with FUE or FUT. The 30% rule is also not the harvestable amount in one procedure, but over multiple procedures. Dr. Bisanga has researched and feels that over 3000 FUE extracted in one procedure can potentially impair the healing in the donor because so many extraction wounds all trying to heal at the same time, and possibly even the yield in the recipient could be impaired.
The punch size used will affect the number of FU that can be safely removed; incorrect punch size can increase transection of the removed FU, damage surrounding FU and cause larger and more visible scarring and peripheral trauma to the skin. With a small punch there is a risk of transecting the FU being removed if the group is too large to be encompassed by the diameter punch, therefore cutting the FU causing the loss of a hair from that FU and reduce the total hair numbers placed. A larger punch may mean taking two genetic groups at the same time or splitting and transecting one of them, for example two 2 hair FU or maybe a 3 hair and a 1 hair in the same punch OR maybe taking an intact 3 hair FU and dissecting another and a likely conclusion is killing a hair and traumatising the surrounding hairs. More hair maybe removed possibly but then greater hair less areas are created and less harvestable area in the future. Dr. Bisanga has long used 0.75-0.8mm punch as his preferred sizes and finds that only in extreme cases he uses larger, maybe 0.85 for very large spread groups or high calibre hair characteristics.
Back to the actual harvesting protocol and how many can be removed, if we take an example:
Average density of 80 throughout the entire donor safety zone (much higher than average) and the surface area is measured to 30 x 7cm (a generous calculation) gives you the optimum FU numbers in that area; 16,800 approx FU (assuming there is no miniaturisation). Then an educated extraction pattern has to be used so as not to over harvest in a particular area; as most of the finer and small groupings are on the sides and generally the density is naturally lower less FU per cm2 will probably be removed, opposed to the areas of the back where the groupings and density is generally higher.
Using this better than average example of a man s donor if we were able to extract 30% in the best possible conditions, all FU aligned well, characteristics allowing etc that gives us 5000 intact natural genetic follicular units removed. This is considering very favourable conditions of donor and harvesting and by any means does not represent the average person, no miniaturisation or transection included in this calculation. 5000 FU, at 30%, any more will impair the donor and a man who started with an above average donor has potentially no more to harvest, with FUE. If this same man had undergone FUT there is a very good chance he could reach 5000 in one procedure, certainly close to it, and certainly a second procedure would have taken him close to 7000 grafts, then he still would have the choice of FUE to harvest outside the linear strip area.
The point being, with higher Norwood cases and for those solely looking to ever use FUE it may not be possible because without seriously over harvesting the donor the numbers just cannot be reached. If a person is emphatic that they do not want a linear scar then they need to think long and hard before starting with FUE because if the hair loss progresses the inevitable maybe to have FUT. Follicular Unit Extraction when the limitations are adhered to can be an excellent form of hair transplant. The limitations are the use of the correct punch size, not to extract a combination of FU in one punch; not to over harvest the donor to extract more FU and leave the donor thinned and importantly to assess the long term potential for future loss and plan accordingly.