Donor Area Harvesting, what everyone needs to know

Donor Area Harvesting, what everyone needs to know: The limits of a safe donor area extraction of grafts over the lifetime of a patient depends mostly upon the donor density found in that person’s donor area. There is a relationship between the donor supply and the recipient area demand for grafts. The larger the need for hair (the balder you are), the more the donor area must be harvested; however, there are limits to how many grafts the donor area can supply, particularly in the very bald patient. We are all born with different donor densities. The Caucasian has generally the highest donor density (110,000 hairs on their heads), the Asian often has a 20% less hair than the Caucasian (between 88,000-90,000 hairs on their head), and the African has between 30-40% less total hair on their heads (between 66,000-77,000 hairs on their head). Regardless of the total hair count, the permanent zone reflects only approximately 20% of the total original hair population so the only place that hair can be extracted is from the 20% fringe, which conforms to the balding patient shown below. Hair always remains in this zone regardless of a person’s genetic balding pattern and it is this zone of hair that the hair transplant surgeon focuses upon as a donor source for hair

Figure 1

It should be evident by looking at figure 1, that the size of the bald area is much larger than the size of the permanent zone where hair still remains (five times larger) so the key to having a good hair transplant surgeon is to find a doctor who understands how to exploit this very privileged and limited donor area, and not produce balding in the donor zone where the hair was taken from. The two patients in Figure 2, had too many FUE grafts removed. They both have some degree of permanent balding or thinning in the donor area resulting from overharvesting of FUE grafts. The man on the left has not yet allowed his hair to grow out to see if he gets any ‘cover’ from longer hair. Doctors would like you to believe that FUE is a scarless surgery but as you look at the man on the left, it is clear that he is very scarred and will have to cover the scar somehow. The patient on the right, covers the thin donor area by keeping his hair longer. I can’t tell if the man on the left will be so lucky. Scalp MicroPigmentation (SMP) can usually provide camouflage to this balding area especially when the hair is kept longer, but SMP is not hair, it is a cosmetic tattoo that works to mimic the fullness that hair brings. The message here is that donor site depletion reflects poor planning on the doctor’s part and poor education on the patient’s part because each patient must hold his surgeon responsible for any balding in the donor area, especially if it came as a surprise after the FUE was done.

Figure 2

The donor area contains approximately 20% of the patient total hair count, so for a typical Caucasian who often has more hair than Asians and Africans, the donor area has approximately 23,000 hairs, or 10,450 follicular units or grafts (each follicular unit contains approximately 2.2 hairs). Likewise, the Asian has approximately 8360 grafts and the African has approximately only 6270 grafts in this permanent zone. In modern FUE transplant surgery, the surgeon tries to move only the follicular units with more hair (2-4 hairs each) because the use of the follicular units that have more hair is what makes the hair transplant look fuller. In the Asian, the number of 3 and 4 hair grafts are few, if any, so the surgeon tries to excise the two hair grafts to get the greatest amount of hair from these patients. The permanent donor hair population is an absolute number for each patient and that number will get lower each and every time you have an FUE performed. Sooner or later the donor supply will run out of grafts as more and more hair is moved to the balding area and the donor area will become thinner and thinner. Ask your doctor “(a) How many grafts can be taken from my donor area for the hair transplant procedure and (b) how many grafts will remain after the surgery is done for future needs?”  Never go forward with a hair transplant without understanding the answer to these two questions and to be sure that your surgeon understands this as well.

To answer these question, we always measure the donor density of our patients, a constant for every patient. For a typical Caucasian with an average weight hair that is wavy, dark brown and with a tan skin color, the surgeon can safely remove approximately 6,272 follicular grafts in total, leaving behind approximately 4,180 grafts to provide the needed cover for the donor area. When the skin is very pale, or the hair is very straight or fine in character, or if the hair is black, then the limit for harvesting grafts might be less than 6,272 grafts. On the other hand, if the hair is coarser, or the hair is blonde, salt and pepper or white in color, or the hair is very curly or kinky (typical African hair) the total number of potentially harvested grafts may be much higher as a percentage of the patient’s donor supply.

Those patients destined to develop advanced patterns of balding are caught in conundrum:  The larger the area of projected need, the more distributed the grafts must be when transplanted. The more distributed the hair is placed, the thinner will be the look of the end result. Overall harvesting numbers are altered downward in the various races (Asians and Africans) with calculations that are similar to those described in the Caucasian model illustrated above.

With strip surgery, the excision of the grafts is only performed in the center of the permanent donor area; however, with FUE, the extractions are spread throughout the donor area.  For this reason, strip surgeries can often harvest more grafts than FUE. Determination of a safe extraction area in FUE must avoid extracting from areas that are likely to be affected by the genetic balding process. This usually means excluding the hair in the nape of the neck (which is not permanent hair) and the upper lateral fringe regions of the donor area.  In the illustration in Figure 3 below, the donor area was harvested outside the safe permanent zone (above and below it) so we can expect that this patient will eventually lose those hairs that were not taken from the non-permanent donor zone. Unfortunately, these patients may end up with significant scars from the FUE excision similar to those shown in Figure 2 above. The surgeon was very irresponsible when he/she pushed the harvested FUE numbers higher in this patient as the extractions were extended well outside the safe zone.

Figure 3

The most important number in calculating the donor supply is the donor density which may vary widely from person to person, even in people of the same racial background. This number will tell the surgeon how many total grafts the donor area can support over the lifetime of the patient (as discussed above). As genetic hair loss in men is not stable and patients with genetic balding may expect further hair loss for years, your present balding pattern most probably will advance as you age. For extraction estimates, the ‘average’ number of available grafts is higher when the donor density is higher, but it is also lower when the donor density is lower. The calculated harvested numbers are influenced by many other factors such as the thickness of the hair shafts in the donor area; fine, medium or coarse (coarse hair is the best of hair thicknesses), the character of the hair; straight, wavy, curly or kinky (curly or kinky hair is the best of hair characteristics), the color-contrast between hair and skin (lower contrast allows more donor grafts, so blondes or white haired men are terrific candidates for larger graft harvesting sessions) and the angle the hair exists from the donor area (the worst is when the exit angle of the donor hair creates a more acute angle where it exits the skin in the donor area). This is knowledge that your surgeon must know and discuss with you when estimating a specific number of grafts for a surgical session and in assessing your overall remaining donor supply over your lifetime. The 3 dimensional properties impacting the appearance of hair volume (e.g. straight vs wavy or curly hair, the exit angle of the hair and planned hair length that the patient wishes to use after the FUE is completed) can influence the surgeon’s decision on the number of grafts to harvest.  It is the doctor’s job to determine the safe maximum extraction density per square centimeter for each and every patient, always leaving enough residual hair in the donor area to (a) cover the extractions that were taken and (b) to be available for a future time, as needed.

If during an initial assessment of a patient’s donor hair style, bright light accentuates a see-through scalp visibility, one might anticipate that the patient has fine hair. People with coarse hair, on the other hand, never have a see-through look unless they lose their hair. Longer hair covers better and short hair because it provides more hair bulk to create the illusion of fullness. Very short hair in the donor area (i.e. stubble) eliminates any contribution from hair length, wave or curl, and strongly reduces the contribution of even the better coarser hair thickness in producing coverage. Short hair also seems to accentuate the ‘empty spaces’ left by the FUE from where each graft was taken.

An Example of safe total maximal extractions over lifetime of the patient

Hairs on HeadDonor Density Hairs/mm2Strip GraftsFUE Grafts
110,0002.26,2283450
80,0001.65,0162660
70,0001,439501888
60,0001.230001400

FUE’s remove the anatomic follicular units (grafts). The above chart defines the graft limit based upon the original donor density. The lower your donor density, the smaller will be a safe FUE or strip extraction surgery.

Strip surgery, is a good alternative or possibly a good second surgery, because the graft removals are done in the center of the donor area and easily concealed by the surrounding hairs. The appearance of a linear scar is a risk when too many strip procedures are done, but for just 1 or 2 strip surgeries, the overall linear scarring risk may be limited to one that measures just a couple of mm in width in most people, certainly far less scarring than shown in the patient on the left in Figure 2.

Conclusion: Donor harvesting is as much an art as it is a science. It demands that the doctor understand the nuances of relationships between donor density, hair thickness, the color/contrast between hair and skin, hair character and the exit angle of the donor hair. It is important for you, as a patient, to understand this as well, because if you don’t and your surgeon does not, then you run the risk of developing balding in the donor area. The chart may help you judge the numbers offered to you by your surgeon.