A: The goal in surgical hair restoration should be to achieve the best results using the least amount of donor hair (the patient’s permanent reserves) and not simply to transplant the most grafts in one session. In my opinion, although large sessions are very desirable, the recent obsession with extremely large numbers of grafts in one session is misplaced. The focus should be on results.

For example, I would prefer to have full growth with a properly placed 2,500 – 3,000 graft hair transplant session than partial growth in a 5,000 graft session. Of course, the 5,000 graft session will look fuller than 2,500 grafts but, in my experience, never twice as full, and never as full as two 2,500 graft sessions.

The ability to perform large sessions is possible because of the very small recipient sites needed in Follicular Unit Transplantation (FUT). It is one of the main reasons that we developed this procedure in back in 1995. See the first paper on this subject: Follicular Transplantation.

However, like all good things, the technique loses some of its advantage when taken to extreme.

In “very” large sessions, the long duration of surgery, the increased time the grafts are outside the body, the increased amount of scalp wounding, risk of poor growth, wider donor scars, placing grafts where they are not needed, sub-dividing follicular units, and the decreased ability to plan for future hair loss, can all contribute to suboptimal results. These problems don’t always occur, but the larger the session, the greater the risk. Therefore, it is important to decide if one’s goal is simply to transplant the maximum amount of hair that is possible in one session, or to get the best long-term results from your hair restoration.

Follicular Unit Preservation

One of the most fundamental issues is that doctors using very large sessions are not always performing “Follicular Unit Transplantation” and, therefore, in these situations the patients will not achieve the full benefit of the FUT procedure. Although doctors who perform these very large sessions take the liberty of calling their surgery “Follicular Unit Transplantation,” in actuality it is not, since naturally occurring follicular units are not always kept whole. The procedure is defined as follows: “Follicular Unit Transplantation is a method of hair restoration surgery where hair is transplanted exclusively in its naturally occurring, individual follicular units.” (see Hair Transplant Classification)

By preserving follicular units, FUT maximizes the cosmetic impact of the surgery by using the full complement of 1 to 4-hairs contained in naturally occurring follicular units. A whole follicular unit will obviously contain more hair than a partial one and will give the most fullness. Keeping follicular units whole also insures maximal growth since a divided follicular unit loses its protective sheath and risks being damaged in the dissection.

It can sound impressive to claim that you performing very large hair transplants, but if the large numbers of grafts are a result dividing up follicular units, then the patient is being short-changed. The reason is that, although the number of grafts is increased, the total number of hairs transplanted is not. A 3-hair follicular unit that is split up into a 1-hair and 2-hair micro-graft will double the graft count, but not change the total number of hairs actually transplanted. In fact, due to the increased dissection, more fragile grafts, and all the other potential problems associated with very long hair transplant sessions, the total number of hairs that actually grow may be a lot less. Please look at the section “Limits to Large Hair Transplant Sessions” on the Graft Numbers page of the Bernstein Medical – Center for Hair Restoration website for a more detailed explanation of how breaking up follicular units can affect graft counts.

Donor Scarring

Since there are around 90 follicular units per cm2 in the donor scalp, one needs a 1cm wide by 28cm long (11inch) incision to harvest 2,500 follicular units. A 5,000 follicular unit procedure, using this width, would need to be 22 inches long, but the maximum length one can harvest a strip in the average individual is 13 inches (the distance around the entire scalp from one temple to the other).

In order to harvest 5,000 grafts, one would need 5,000 / 90 FU/cm2 = 55.6cm2 of donor tissue. If one takes the full 13 inch strip (33cm), then it would need to be 1.85 cm wide (55.6cm2 / (33cm long) = 1.85cm wide) or 1.85/2.54= ¾ of an inch wide along its entire length. However, one must taper the ends of a strip this wide (you can’t suture closed a rectangle) and, in addition, you can’t take such a wide strip over the ears. When you do the math again, it turns out that for most of the incision, the width must be almost an inch wide, an incredibly large amount of tissue to be removed in one procedure.

This large incision obviously increases the risk of having a wide donor scar – probably the most undesirable complication of a hair transplant. Needless to say, very large graft counts are achieved by sub-dividing follicular units rather than exposing the patient to the risk of an excessively large donor incision.

Popping

There are other issues as well. Large sessions go hand-in-hand with very high graft densities, since you often need these densities to fit the grafts in a finite area. The closer grafts are placed together, the greater the degree of popping. Popping occurs when a graft that is placed in the skin causes an adjacent one to lift-up. When a graft pops (elevates above the surface of the skin) it tends to dry out and die. Some degree of popping is a normal part of most hair transplant procedures and can be easily controlled by a skilled surgical team, but when it is excessive it can pose a significant risk to graft survival.

The best way to decrease the risk of popping being a significant problem is to not push large sessions (and the associated very dense packing) to the limit. In a patient’s first hair restoration procedure, it is literally impossible to predict the likelihood of excessive popping and once a very large strip is harvested, or the recipient sites are created in a very large session, it may be too late to correct for this. In addition, popping can vary at different times during the procedure and in different parts of the scalp adding to the problem of anticipating its occurrence.

Even if the distribution of grafts is well planned from the outset, a very large first session may force the surgeon to place hair in less-than-optimal regions of the scalp when popping occurs. This is because the surgeon must distribute the grafts further apart and thus over a larger area to prevent popping.

Blood Flow

Particularly where there is long-standing hair loss, the blood flow to the scalp has decreased making the scalp unable to support a very large number of grafts. This is not the cause of the hair loss, but the result of a decreased need for blood when the follicles have disappeared. In addition, persons that have been bald for a long time often have more sun damage on their scalp, a second factor that significantly compromises the scalp’s blood supply and may compromise the follicles survival when too many grafts are placed in one session. As with popping, the extent of photo-damage, as seen when the scalp gets a dusky-purple color during the creating of recipient sites, often only becomes evident once the procedure is well under way.

In the healing process following the first hair transplant, much of the original blood supply returns and this makes the scalp able to support additional grafts (this is particularly true if one waits a minimum of 8-10 months between procedures). This is another reason why it is better to not to be too aggressive in a first session when there is long-standing baldness or significant photo damage and where the blood supply may be compromised.

Limited Donor Supply

Another issue that is overlooked in performing a very large first session is that the average person only has about 6,000 movable follicular units in the donor area. When 5,000 grafts are used for the 1st procedure there will be little left for subsequent sessions and limit the ability of the surgeon to increase density in areas such as the frontal forelock or transplant into new areas when there is additional hair loss.

Conclusion

There are many advantages of performing large hair transplants, including having a natural look after one procedure, minimizing the number of times the donor area is accessed, and accomplishing the patient’s goals as quickly as possible. However, one should be cautious not to achieve this at the expense of a wider donor scar, poor graft growth, or a compromised ability to plan for future hair loss.

Achieving very high graft numbers should never be accomplished by dividing up the naturally occurring follicular units into smaller groups, as this increases the risk to the grafts, extends the duration of surgery, increases the cost of the procedure (when charging by the graft) and results in an overall thinner look.

For further discussion see:

• The last section in Graft Numbers titled “Limits to Large Hair Transplant Sessions”
• Commentary: How large should hair transplant sessions be?

A: My goal is not to transplant as many grafts as possible, but to get the best results possible without exhausting a person’s donor supply. It is important to keep reserves for future hair loss. Unnecessarily large sessions also risk poor growth and have a greater incidence of donor scarring.

A: In a person with average donor density there are approximately 100 follicular units per square centimeter. A 15 cm long strip would have slightly less than 1500 grafts due to the tapering of the strip ends.

Therefore, in a hair transplant of 1500 follicular unit grafts, one should take out a 17 cm x 1cm strip (that includes the tapered ends). This is 15cm2.

A: The Telogen phase of the hair cycle is about 3 months long and about 12% of follicles are in this phase at any one time. It is speculated that the follicles may be empty for perhaps 1/2 that time (this number may vary significantly between people). Therefore, approximately 6% of the hair follicles may be in telogen at any one time.

On average about 15% of the follicular units are 1-hair units (but this also may very greatly between patients). If 6% of all follicles are “empty” telogen follicles, then there should be .15 x .06 = .009 or about 1% of the patient’s 1-hair follicular units in the empty telogen phase that can’t be identified and will be missed on dissection.

The 1% isn’t very large. However, also consider that the remaining 5% of the empty follicles are associated with larger follicular units (i.e. those with 2-4 hairs). If these follicular unit grafts are closely trimmed, as is the practice with very dense packing, a much more significant number of follicles are at risk of being lost. With chubby follicular unit grafts (i.e., where the microscopic dissection leaves a protective sheath of tissue around the follicles) the risk should be closer to the 1%.

The lesson for hair transplantation is that over-trimming of grafts, for the sake of very dense packing, may waste telogen hairs as well as place the grafts at an unnecessary risk of mechanical trauma, drying and warming.

Skin & Allergy News
February 1999

Microscopic Dissection Offers Superior Yield
Articles by Anna Nidecker
Senior Writer

Washington — The dissecting microscope takes some getting used to, but using it makes more efficient use of donor hair during follicular unit transplantation than magnifying loupes with transillumination, reported Dr. Robert Bernstein of Columbia University College of Physicians and Surgeons, New York.

“A limiting factor in all hair restoration surgery is the patient’s finite donor supply. [...] Meticulous stereomicroscopic dissection should help preserve the supply and ultimately provide the patient with the most transplantable hair,” he said at the annual meeting of the International Society of Hair Restoration Surgery.

Dr. Bernstein compared the follicular unit graft yields of dissections performed with stereoscopic microscopes and with loupes and backlighting. Initial sectioning of the intact strip was done with loupes, as the staff had not yet mastered the skill of slivering that is needed to section the intact strip under microscopic guidance.

“This method may be useful for a team in transition, a model for staffs in transition to using the microscope,” the hair transplant surgeon suggested.

In 41 patients, the donor strip was harvested with a double-bladed knife from the midportion of the permanent zone in the back of the scalp.

The strip was divided into two equal parts along the midline; these were further divided into 2- to 3-mm wide vertical sections using loupes and a straight razor. Sections from one of these donor strip halves were further dissected into follicular units using a 10x power microscope; sections from the other donor strip half were dissected using magnifying loupes.

Follicular units cut using the microscope contained an average of 2.41 hairs; those cut using loupe magnification yielded 2.28 hairs. Use of the microscope also yielded 10% more follicular units and 17% more hair overall, compared with use of loupes.

The grafts were dissected and sorted into follicular units containing one to four hairs, and all hair and hair fragments judged to be potentially viable were counted towards the yield (Dermatol. Surg. 24[8]:875-80, 1998).

Microscopic dissection took from two to four times as long as loupe magnified dissection when technicians first began using the microscopes. After 3 months, the procedure still took twice as long with the microscopes. But by the end of the study 1 year later, it took only 10% longer, a rate they currently maintain, Dr. Bernstein said.

Hand-eye coordination was a factor which automatically improved, and the inefficient movement of grafts in and out of the microscopic field was solved with better organization, he said. Technicians with a tendency to obsessively sculpt grafts under the microscope can be educated to limit this sculpting, which does not affect the quality of the transplant.

Use of the microscope also led to fewer reports of back and neck strain by assistants. They also reported easier dissection when there was donor scarring, and with blond or light-colored hair.

Besides the benefit at the stage of dissecting the sections—as shown in this study—microscopes can improve yield by 5%-10% at the “slivering” stage. Yield can be improved an additional 15%-20% by avoiding use of the multibladed knife at the donor harvesting stage.

Loupe advocates argue that microscopes unduly slow down the procedure and that staff resistance to this new technology may be an insurmountable problem in some practices. They also lament the higher economic cost of purchasing the microscopes, training the staff, and slowing down dissection time with no clear benefits.

Dr. Bernstein said that the benefits of microscopic dissection far outweigh these minor inconveniences and should be incorporated into hair transplant procedures.