In May, I had the pleasure of addressing the American Society of Dermatologic Surgery about my study involving the survival of minigrafts harvested by the multibladed knife. The study was supported by a grant from the ISHRS. In the process of modifying the talk from the one presented last year in Washington to the ISHRS, additional developments have appeared that I would like to share with you. I would like to do so in the spirit of continuing the lively discourse currently involving follicular unit vs micro-/minigrafting techniques.
To briefly summarize my study, it looked at intact and intentionally transected 3 and 4 hair minigrafts and determined survival. Additionally, it assessed transection rates of minigrafts from over 50 cases when using the multibladed knife and when the 2mm strips were cut into grafts with 4× loops. Transection rates were 8% for the multibladed harvest and 4% for the conversion of strips to minigrafts. The overall survival rate was 98.4% at eight months with 104% of intact graft hairs present, and an overall 60% growth for transections. These findings are in line with transection rates reported by Limmer1 and survival rates of transected follicles reported by Kim2.
My conclusions were:
Excellent growth rates of transplanted hair are obtained with multibladed harvesting (MBH) and that it is unclear that elliptical excision and microscopic dissection (EEMD) is superior to MBH based on the results of this study.
With regard to cost/benefit considerations, in view of number 1 above and the increased difficulty of maintaining quality control, as well as the increased effort of producing grafts with EEMD (twice as many person hours and a longer technician learning curve), it would appear that MBH is superior to EEMD.
And, therefore, the hair transplant surgeon serves both quality control and efficiency by focusing efforts on his/her MBH technique rather than on training and supervising technicians to perform dissection with the microscope.
In a little over two years after the Nashville ISHRS meeting, where the follicular unit concept surfaced with seven talks titled around “megasessions,” “dense packing,” and “dissecting microscope,” the following reflects the sea change of opinion.
The term follicular unit is proposed to imply mandatory use of elliptical excision and microscopic dissection. Even more startling, these statements recently appeared in HTFI by two of our most revered fathers of hair transplantation surgery:
“It seems hard to understand how we managed to produce reasonable results without microscopes. I suspect that we destroyed many, many hair follicles.… I think here is the greatest tragedy of hair transplant surgery, namely, the quiet death of many donor follicles in the transplant process.”
—O'Tar Norwood, HTFI, 1999
“The unwaxed truth is that there are no logical, scientific arguments to be made against the obvious superiority of follicular unit transplantations, only egotistical, economic, and managerial ones.”
—Marritt, HTFI, 1999
I respectfully disagree that either statement is sound. Let's entertain the following line of thought:
“The Cornerstone”… or “To Live Happily with Another Illusion, Just Change the Cornerstone.”
“For almost 40 years the very foundation, indeed the cornerstone, of all hair replacement surgery has been the preservation of intact and uninjured hair follicles. No technological tour de force accomplishes this goal with greater predictable consistency than the stereoscopic dissecting microscope.”
—Marritt, HTFI, 1999
What if the cornerstone has unknowingly been the stem cell all of these years and not the architectural unit, i.e., the follicle? This makes the importance of “intact and uninjured hair follicles” less clear as the importance of preserving physiological integrity of the stem cells would supercede.
Work presented by Jahoda3 et al. at the Hair Research Society meeting in November 1998, where I represented the ISHRS with partial funding by Merck, suggests that such may be the case. The interaction of cytokines between the stem cells and the epidermis in the absence of follicular architecture appears to be sufficient to grow hair. When Jahoda wadded up some of these stem cells from the dermal sheath and stuck them into a hole in his wife's forearm they grew hair (though moderately deformed). Additional support regarding follicular growth being independent of intact architecture is Mel Mayer's study4 presented in Washington last year where follicles grew despite deliberate disruption of follicular architecture. Total resulting hair volume was admittedly not ascertained. To me it's conceivable then, that the proper timing of the use of Tony Mangubat's Manguwacker, which minimizes in vitro time, will better serve the vitality of the stem cell and, therefore, most optimal hair growth vs the laborious, time-intensive EEMD, which have cells exposed to prolonged periods of harsh, in vitro elements. All that can be scientifically said at this point is that we just don't know which method is superior.
Transplant studies using hair counts are fatally flawed. The final nail in the coffin to my hoping to reach dogmatism over this issue of the superior surgical technique came when I recalled John Cole's5 talk in Washington last year. The few studies done on survival of grafts use hair counts rather than hair volume or hair shaft diameter. As Dr. Cole points out, a fluctuation of an imperceptible 0.01 mm can result in as much as a 36% difference in hair volume. Thus, as will be clarified below, the hair survival rate differences used to compare EEMD and MBH in all current studies pale in comparison of magnitude to the actual parameter of interest, hair shaft diameter. In other words, all studies trying to quantify relative outcomes with different surgical techniques in hair transplantation are at best garbage and at worst misleading.
Surface Area/Volume Problem. EEMD is very vulnerable to suboptimal hair shaft diameter outcomes (e.g., stunted growth) with its unfavorable surface area/volume considerations. In view of this physiological principle, the importance of hair shaft diameter, and because of imperceptible 0.01mm changes of diameter making huge hair volume differences, I am very uncomfortable with follicular units being used for hair volume/density. We all remember from our training the increased vulnerability of the small child to environmental factors. They become hypothermic to exposure, hyperthermic to bundling, and dehydrated so much more easily than the adult because of their unfavorable surface area to volume ratio. The graft shows the linear relationship of surface area to increasing radius and the exponential increase of the volume to increasing radius. If I were a stem cell, I would much prefer the coziness and buffering factors afforded by being in a larger radius piece of tissue, that is, the larger graft. Wouldn't you?
When rereading Seager's6 article, he mentions the average transplant center has 50% mortality of follicular unit grafts (before the sine qua non of microscopic dissection). Do we really think transplanted hair follicle growth is a digital, yes/no, death/full terminal diameter phenomenon? Surely we all know from experience the transplanted follicular growth is analog—a full spectrum of hair shaft diameter from no growth, through a spectrum of increasing diameters to full terminal diameter. I have only to look at the transplant on my head to know that to be true. We should be very cautious about abandoning such a basic principle of physiology and surgery as surface area to volume ratios. And thinking of a plant's stunted growth from poor treatment during transplanting, well it's even a principle of gardening.
What's all the fuss about? But let's assume that hair survival counts are worth something. Limmer has stated that transections with EEMD can be 5% or less.1 He has also stated that transections with MBH is 8% to 15%. Kim's study suggests about 60% survival of transected follicles. My study supports these assumptions with 12% transection and 60% survival. The math then is 12% MBH transection minus 5% for EEMD equals 7% difference. Of this 7% transection difference, 60% will grow follicles leaving a 2.8% difference in growth rates between the two surgical techniques. This 3% for hair survival vs the 36% range for hair diameter reemphasizes the lack of worth (to put it politely) of the current studies that use hair survival as outcome. And that includes my study.
Two final points. Along the line of thought about hair density relative to the degree of recipient area wound, a point I tried to make at the Derm Surg meeting in Miami follows. The germ of this idea began with Jim Arnold's thought: “The smaller a graft becomes the larger the percentage of recipient wound is relegated to the requirements of the implanting tool.” I think that is why I can routinely put four hairs into a 2mm modified Beaver blade, perhaps with equal or better impact on the recipient vasculature, compared to two 1mm slits made by a #18 hollow core needle. I say “equal or better impact” because the shape to the beveled needle has to go deeper than I think I have to go to make the Beaver minislit. Two follicular unit sites with a hollow core #18 equals 2mm, which equals the length of the modified Beaver minigraft site. The twice as much volume required by the introducing tool to plant two follicular unit sites approximately offsets the area of the “useless” tissue of one 2mm minigraft. The “useless” tissue has buffering effects as we discussed.
Lastly, is a “tour de force” necessary to make the hair graft? Do we really need a dissecting microscope (6-10×) vs 4-5× loops? If follicular units are 1.0 to 1.2mm apart, then one is talking at least 0.5mm between follicular units, wouldn't you agree? A flea could drive his roadster through that kind of spacing. So trying for the finest balance of minimizing time in vitro and minimizing the number of and the learning curve for technicians out of respect for the architectural integrity of the hair follicle. Perhaps one is back to micro-/minigrafting where he/she groups tight follicular units to make minis and takes more separated follicular units to make micros.
Conclusions. Lacking sufficiently powerful science, the issue of superior surgical technique is at risk of being settled by popular sentiment and the most vocal among us, an intellectual fascism if you will. Repeating myself, we should be cautious about abandoning basic principles of physiology, surgery, and gardening to embrace a surgical technique deviant to these principles. Shame be on us if we allow the object of our passion, that is, the growth of the transplanted hair follicle, to be stunted by a premature rush to “obvious superiorities.” Lacking adequate underlying science, which I submit is the case with elliptical excision/microscopic dissection vs strip harvesting, no such conclusions regarding superiority are yet warranted.
- Copyright © 1999 by the International Society of Hair Restoration Surgery