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Growth Rate of Body Hair Obtained by FUE and the Benefits of Acell

Scalp donor area is the ideal source of hair for transplantation in Androgenic Alopecia.  Unfortunately, the scalp donor area is limited in all individuals.  For this reason, the availability of alternative sources of donor area is desirable.  One source is body hair.  Unfortunately, the yields and coverage potential of body hair are often unpredictable and often produce results that are not ideal.  Therefore, it is potentially beneficial for us to identify means to improve the survival rate and coverage value of body hair.  One potential way to improve coverage of body hair is through the application of Acell, an extracellular matrix.I compared the yield from beard hair transplanted to a donor area strip scar pretreated with Acell to the yield of chest hair transplanted to a donor area strip scar that was not pretreated with Acell.  The objectives of the study were to evaluate the yield of two different sources of hair and to see if Acell offered any potential increase in the survival rate of body hair.

Methods:I made all the recipient sites with a 1.3 mm solid core needle attached to a counting incision device available from Cole Instruments.  I obtained 50 beard hair grafts using a 0.9 mm punch Cole Instruments (CI) punch set at 2.3 mm depth on a (CI) minimal depth handle.  I extracted 25 beard hair grafts from the right side of the neck and 25 beard hair grafts from the left side of the neck.  I then obtained 6 chest hair grafts using the same 0.9 mm (CI) punch on a CI depth control handle set at 2.4 mm.I chose a patient with 4 different strip scars.  I treated a 0.5 cm X 7 cm donor area strip scar located in the mid-line of the donor area superior most of 4 other strip scars with 50 beard grafts.  This scar was located in Boxes 1 and 5 as I defined in Donor Area Density differences in Asians andCaucasians.  I treated the 3rd most superior strip scar that measured 0.4 cm X 3.5 cm that was located in box 6 with six chest hair grafts.I pre-treated the scar that received 50 beard hair grafts with 2 cc of a solution containing 1mg/cc of Acell.  I injected the Acell into the full layer of the scar.  I did not pre-treat the scar that received 6 chest hair grafts.

Results:After six months I evaluated the growth in each scar.  I counted the growing hairs by attaching the tip of a Gentian Violet marker to a Counting Incision Device.  Each time I counted a hair, I made a mark on the hair.  The CID recorded each mark accurately.The growth of the beard hair was 46 out of 50 grafts.  The growth of the chest hair was 0 of 6 grafts.

Discussion:In the past I have noted a variety of differences in the survival rates of body hair.  Most studies where minimal density is attempted suggest an optimal rate of growth is 60% for body hair of any type.  Scalp hair on the other hand often ideally has a yield of 90%.Survival rate studies often are impaired by the lack of means to accurately record the number of hairs that are produced.  The use of the CID, which I developed, equipped with a gentian marker on the tip allowed me to accurately record the number of hairs that grew.   In this manner I was able to insure that no hair was either counted twice or missed.  I was also able to insure that the recorded count was absolutely accurate.This study shows both a difference in the survival rate of beard hair as compared to chest hair, as well as a difference in the survival rates for grafts placed into a recipient area pre-treated with Acell compared to a recipient area that was not pre-treated with Acell.  I performed an informal investigation to evaluate the survival of chest hair grafts placed into a strip scar that was pre-treated with Acell a year ago.  I noted that the growth of chest hair in this patient was not as good as the growth of his beard hair from a procedure performed 2 years ago.  As a result I wanted to see if pre-treating the scalp with Acell had an improvement in the growth of chest hair.  I anecdotally found that the Acell improved the survival of chest hair in follow up 6 months later.  The natural follow up to this evaluation was to objectively evaluate the survival rate of body hair in donor scars in the absence and presence of Acell.Strip scars are often devoid of hair growing in them.  Even with trichophytic closure, hair is often absent in strip scars.  Without the trichophytic closure one can usually count on these scars to be predominately devoid of hair.  The advantage of such a barren area is that they are useful for measuring transplant yields.  While it is true these areas are not normal skin, strip scars readily accept grafts and produce good yields.  Bald areas due to androgenic alopecia on the other hand often have dormant hairs that may resume growth at any point following the start of a hair yield study.  Unknown variables such as exogen hairs in an otherwise bald zone that resume growth prior to follow up may confuse hair growth yield studies.  Such regrowth may produce spurious results that are higher than actual yields.  Similarly existing hairs in a predominantly bald zone that are counted at the beginning of a study might evolve into the exogen phase prior to the follow up evaluation and result in an inaccurate lower yield than expected.  Scars rarely have such exogen hair issues.  Thus they are truly bald skin and potentially ideal for analyzing hair growth yields.The use of a donor template allows us to more precisely define regions of the donor area and allow us to follow specific regions in the donor scar to evaluate hair growth yield.  Each zone or box is predictable based on 8 major regions and 6 minor regions.  The presence of scar in any box may be easily annotated prior to a procedure.  Furthermore, any action in a specific box may be recorded during a procedure so that a physician can follow the consequences of any action, as well as monitor the density of follicular units in any given region.  Procedures may include removal of grafts via FUE or the location of any scar.  It could also allow for the annotation of a skin lesio that is present prior to a procedure.Prior body hair survival rates suggest that a 60% yield is quite good.  Higher densities can negatively impact the yield.  Conversely, lower densities can result in better yields.  High body hair densities can occasionally produce high yields.  In this instance we did not seek a higher density, as we did not want to evaluate this variable.  Therefore all body hair densities were kept low in this study.

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The length of hair growth for the beard hair suggested that many of the beard hairs began growing at the time of implantation based on a mean growth rate of 0.4 mm/day, which is similar to scalp hair.  Most body hair grows at a rate of 0.2 mm/day, but increases to 0.35 mm/day upon transplantation to the scalp.  Beard hair grows at a much faster rate than most other types of body hair.The advantage of using beard hair for transplantation is that it produces a better cosmetic result even when different sources produce a similar or slightly higher yield.  The rational for such improved coverage is the increased diameter of the hair shaft, which results in improved hair volume.  Doubling the diameter of a hair shaft quadruples the volume of hair coverage since the volume of a cylinder of hair is equivalent to the formula: V = Õ r2 h.  Furthermore, body hair often seems to become finer upon transplantation to the scalp whereas beard hair seems to retain its larger diameter.  Finally, beard hair generally grows with a characteristic wave that adds to the coverage or volume in the scalp.  These features make beard hair more ideal to produce a cosmetic benefit to the coverage of the scalp than other sources of body hair.  Unfortunately, the added curl or wave can produce an unacceptable contrast in the grafted hair compared to the scalp hair in those with straight hair particularly when the scalp hair is straight and fine.

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