Follicular Unit Transplantation – The End of the Evolution?

Robert M. Bernstein, MD

After four decades of evolution from the large plugs of the late 1950’s to the extensive mini/micrografting of the early 1990’s, possibly the central development in hair transplantation today is the recognition that the naturally occurring, individual follicular unit may represent the ideal way in which to transplant hair. The underlying tenet of follicular unit transplantation is that the follicular unit is sacred and should always be transplanted intact.1 While not all hair transplant surgeons agree on the importance of using follicular units exclusively for the entire transplant, or in every patient, the central role of this previously unrecognized anatomic structure in modern hair restoration surgery is without dispute.

Follicular units are distinct groupings of usually one to four, and occasionally five terminal hairs, surrounded by a circumferential band of collagen called the "perifolliculum."2 It also includes one, or rarely two, vellus follicles, the associated sebaceous glands, the insertions of the arrector pili muscles, and a neuro-vascular plexus. It has been demonstrated that hairs seperated from other hairs of a follicular unit do not grow as well as the same number of hairs transplanted keeping follicular units intact.3 The follicular unit is thus a physiologic, as well as an anatomic entity.

Follicular unit transplantation offers the surgeon the unique ability to transplant the maximum amount of hair with the minimum amount of non-hair bearing skin. In this way, recipient wounds may be kept small, healing is facilitated, and with proper technique, large numbers of grafts may be safely moved per session. The use of these discrete anatomic units also helps to ensure that the cosmetic result of the transplant will appear completely natural.

In contrast to follicular units, micrografts (1-2 hairs), and mini-grafts (3-6 hairs), are small grafts cut randomly from donor hair, not specifically as individual intact follicular units. They may consist of partial follicular units, single follicular units, multiple follicular units, or multiple, partial follicular units.4 In mini-micrografting, the partial units may be at risk for sub-optimal growth, and the multiple units will contain extra skin that will demand larger recipient sites. This, in turn, causes more wounding to the recipient bed and may limit the number of grafts that can safely be transplanted in a session.

It has often been said that with multiple sessions, minigrafts can look fairly natural in patients with ideal hair characteristics. However, even in these circumstances, on close inspection, minigrafts can look unnatural compared to follicular units. As the public becomes increasingly more discriminating, the future of hair transplantation is therefore likely to involve an increasing demand for procedures that are performed using follicular unit transplantation exclusively.

It is felt by most surgeons who perform follicular unit transplantation routinely, that single strip harvesting and complete stereo-microscopic dissection are required to properly dissect follicular units from the surrounding tissue4. The reasons for this are relatively straightforward. Harvesting with a multi-bladed knife will break up follicular units and transect follicles, whereas removing the donor tissue as a single strip will yield the highest proportion of intact follicular units. Once the single strip has been removed, the stereomicroscope, with its 10x magnification and intense illumination, will provide the best visualization for the dissectors to accurately subdivide the strip and to isolate the individual units. Lower power loop magnification does not provide sufficient resolution for precise follicular unit dissection and back-lighting will not penetrate the intact strip.5

Although, it is hard to argue the supremacy of the follicular unit in theory, in practice, follicular unit transplantation is tedious, demanding on the physician and staff, and requires a relatively high degree of expertise to be properly performed. It is, therefore, reasonable to assume that in situations where follicular unit transplantation is impractical or impossible, the patient might be better served by a more simple technique. In this vein, the standard practice of mini-micro grafting is seen by some as a more practical alternative to follicular unit transplantation.

The advantages of mini-micrografting are that it is faster and requires less staff. In addition, it is felt that the damage produced by the multi-bladed knife (used in mini-micrografting) is somewhat offset by the advantage of not having to carefully trim around follicular units, which in itself can be a source of follicular injury (if not done with care). On the other hand, in mini-micrografting, the slightly larger grafts and concomitantly larger wounds do not permit the total naturalness that is achieved with follicular unit transplantation. In addition, the split follicular units and greater number of hair fragments (produced by the use of the multi-bladed knife and less precise dissecting techniques) may result in less than optimal growth.

The important factors affecting graft survival are still controversial. Graft trauma can take multiple forms. Do longer transplantation procedures lead to greater graft desiccation, donor tissue anoxia (time-out-of-body) and lower yield or does violating the follicular unit microanatomy lead to a lower yield? These important questions lack the controlled studies required for meaningful answers, but the future direction of hair transplantation surgery may, in part, depend upon their outcome!

As we will discuss in subsequent sections, new technology may soon substantially change how both follicular unit transplantation and mini-micrografting are performed. However, regardless of how the technical parameters of each procedure evolve, the debate of follicular unit transplantation vs. mini-micrografting will undoubtedly hold the attention of the hair transplant community for years to come. In the meantime, the answer to which procedure is used may unfortunately lie less with the needs of the individual patient, than with the resources and capabilities of the operating surgeon and his staff.

REFERENCES
Bernstein RM, Rassman WR, Szaniawski W, Halperin A: Follicular Transplantation. International Journal of Aesthetic and Restorative Surgery 1995; 3: 119-132.
Headington JT: Transverse microscopic anatomy of the human scalp. Arch Dermatol 1984;120: 449-456.
Seager D. Binocular stereoscopic dissecting microscopes: should we use them? Hair Transplant Forum Int 1996; 6(4): 2-5.
Bernstein RM, Rassman WR, Seager D, Shapiro R, et al. Standardizing the classification and description of follicular unit transplantation and mini-micrografting techniques. Dermatol Surg 1998; 24: 957-963.
Bernstein RM, Rassman WR. Dissecting microscope versus magnifying loupes with transillumination in the preparation of follicular unit grafts. A bilateral controlled study. Dermatol Surg 1998; 24: 875-880.
Larger Grafts – "Back to the Future?"
Walter P. Unger, MD, FRCP(C)

Is there a role for grafts larger than individual follicular units or small follicular families in hair transplantation? In at least one of the "authors" view the answer is yes, and the reason is that it is felt that more density can be obtained by using larger grafts. Limmer has reported using follicular grafting alone and achieving densities of 81 hairs per sq. cm1, 2. I can achieve over 200 hairs per sq. cm with standard grafts3. Since cosmetically excellent results are possible with 60-80 hairs per sq. cm, and one can never be 100% sure of the ultimate donor/recipient ratio, more density is not a reasonable goal for a majority of patients but this does not mean "all" of them.

The use of grafts that contain more than 2 or 3 follicular units (or families), is generally limited to 10 to 15% of the patient population who a) want greater density, b) can afford greater density in terms of long term donor/recipient area ratio (usually because of an appropriate combination of family history, patient age and a positive physical examination), c) ideally have some persisting hair in the recipient area so any potential for transitory plugginess is minimized, and d) ideally have advantageous hair characteristics such as fine texture and light color, to minimize any possibility of transitional plugginess. Given the above parameters, very little transitional plugginess, if any, is noted by patients or people who see them and therefore the "price" of transitional plugginess is eliminated from the "price" the patients have to pay for this greater density. A zone of micrografting and minigrafting is always used anterior to the larger grafts to create a more natural looking hairline zone and to help camouflage the larger grafts. In addition larger grafts are never used in the posterior half of a patient with Type V or greater male pattern baldness (MPB).

Individuals who choose to use larger grafts must also be aware that, theoretically at least, the area treated with larger grafts must eventually be filled solidly (when all original hair has been lost). If not, when the hair is parted through the transplanted area, when it is wet or wind blown, plugginess may be noted. However, the density is usually so great that this is generally unnecessary even for relatively demanding patients.

The other type of patient in whom standard grafts are advantageous, are individuals who have been treated with standard grafts in the past and have obvious spaces between them with a so-called "Barbie-doll" appearance. If there is good hair density in the standard grafts on either side of a hairless space, the most efficient way of eliminating that space is to fill it with an appropriate sized graft containing hair of similar density to the flanking standard grafts. Punching out a portion of some of the larger grafts can be most useful as an adjunctive technique for this problem, rather than an alternative one.

Although it has been claimed that good hair yield cannot be accomplished if standard grafts are used5, Nordstrom showed a 90% survival6 and Unger showed a 90-110% survival7 in studies carried out many years ago. In addition, although it has been said that solid filling with standard size grafts is impossible, this has not been the experience of everyone. The argument that you need great expertise and practice to accomplish similar results and therefore most people cannot create this, is a self-fulfilling prophecy. One should aim for this level of expertise rather than abandon any attempt of achieving it.

Even physicians, who are generally follicular unit transplant enthusiasts, are again trying the use of larger grafts, containing more than one follicular unit, to produce more density. With time they may develop the confidence to try still larger grafts in properly selected patients. It is the hope of at least one of these authors that this trend will continue, so that the value of larger grafts once more becomes more generally recognized.

REFERENCES
Limmer B: The Density Issue in Hair Transplantation. Dermatol Surg 1997; 23: 747-750.
Limmer B: The Density Issue, A debate that refuses to die. Hair Transplant Forum Intl. 1998; 8(3): 1, 4-6.
Unger W: Different Grafts for Different Purposes. Amer Jour Cos Surg 1997; 14(2):177-183.
Unger W: Graft types. Hair Transplant Forum Intl. 1998; 8(3): 14-16.
Seager D: Comments. Hair Transplant Forum Intl. 1998; 8(3): 16-17.
Nordstrom REA: Evaluating the Efficacy of the punch hair grafting technique. J Dermatol Surg Oncol 1989; 15: 404-408.
Unger W: Hair Counts: A Scientific approach to the evaluation of various factors in the survival of hair transplants. Hair Transplantation, 1st Edition, Unger W(Ed), Marcel Dekker Inc., 1979, Appendix E, P. 203-210.
Maximizing the Donor Supply
Bobby L. Limmer, MD

Since all hair restoration procedures involve the redistribution of preexistent hair, the donor supply remains an important limiting factor in hair restoration surgery. For this reason, it is absolutely essential to preserve the maximum number of viable hair follicles in every procedure. Any avoidable cause of follicular wastage should be unacceptable to both the physician and the patient. Combining the follicular sparing aspects of single-bladed donor harvest, microscopically magnified dissection of follicular unit grafts, and careful, gentle implantation methods, consistently produces a growth rate of 90-95% of the harvested hair1. Although only a relatively small percentage of hair transplant surgeons currently utilize optimal harvesting techniques, this number should increase as the importance of preserving the donor supply is more widely recognized.

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