Besides for the possibility of a halo formation, another reason to proceed with caution in the vertex is the angle of hair growth giving an appearance of less density here. An analogy should help with the explanation. When someone drives through a pine forest, the forest appears much denser than if he flies over it, looking straight down on the individual trees simply because of the angle he is viewing it from. Similarly, if the same number of follicular units were transplanted into the frontal scalp as into the vertex, and these two recipient areas were equally bald to begin with, the transplanted front would look much better than the transplanted vertex. It all depends on the perspective. When someone judges results in front, he does it by looking directly into a mirror. He is looking through the transplant. In order to judge the vertex, he must now take a second mirror directed to reflect straight down onto the vertex. Even though the follicular units grow the same in both locations, the growth in the vertex will look thinner because of the viewing angle.

Another factor to consider when contemplating a transplant is the final thickness of the transplant. Despite some advertising, a single transplant does not give full
thickness. Only someone with coarse, curly hair may look like they have close to full thickness after a single transplant. For someone with average hair, and, in fact, even for many with coarse, curly hair, higher densities will only be reached by re-implanting this same area at a later time. I prefer to wait a minimum of six months before re-transplanting this same area for several reasons. First, I like to be able to be sure we are implanting the second series of follicular units between the first set and not on top of them. Second, the sutured donor site will be well healed at this time and, hopefully, the surrounding scalp will be relaxed so that I can harvest a strip with good width on the second excision. If they are willing, I encourage my patients to wait a full twelve months before deciding about a second transplant. Many patients who give it this extra time realize that by letting the transplant get some length to it and by styling it in certain ways, they actually do not need another transplant. Although it is not full thickness, it looks good. They realize they just needed some, not all, of their hair replaced.

Depending on the nature of the hair and on how closely the follicular units are spaced during planting, the patient probably will require two to three transplants, at least, to take a balding area and give it the impression of full thickness. I say “impression” because it has been shown that we do not require our original density of hair to look like we have full thickness. If I took a scalp that had no previous hair loss and started plucking individual hairs, I would have to remove approximately 50% of the hairs before it would start to look like it was thinning.

Sometimes, looking at the density issue mathematically is helpful. In my experience, the majority of men have approximately 70 to 80 follicular units per square centimeter in the donor area. These are dissected down to individual follicular units and then re-implanted into the recipient area of the scalp. The average number of follicular units per square centimeter in the recipient area after transplantation is usually around 20, although at times we will make it much denser. The density in the transplanted area after regrowth then is approximately 25% full density (20 being 25% of 80). However, as noted above, if the patient can get
approximately 50% of the original number of hairs transplanted, then he may begin to look like he has full density. All of this is a gross generalization. Many factors influence how closely the follicular units can be packed during transplantation, and the packing density of 20 follicular units per square centimeter is not necessarily used throughout the entire transplanted area or in every scalp.

A look at the math is also helpful in dealing with the distribution of the transplanted hair. Many patients hear me refer to thousands of follicular units and mistakenly assume that more of the scalp can be covered then is realistic. Before the average person begins to lose hair, he has approximately 100,000 hairs on his scalp. Using an easy number to work with, if I move 2000 follicular units during a transplant, this means that I am actually moving about 5000 hairs on average. I get 5000 by multiplying the 2000 follicular units by the average number of hairs in a single follicular unit, which is approximately 2.5. Thus, if a very large transplant is performed with 2000 follicular units, in reality I am only moving 5% of that patient’s original volume of hair (5000 being 5% of 100,000). In most cases, the balding area in advanced stages of male pattern baldness will exceed 50% of the scalp. Thus it becomes obvious that moving 5% of a patient’s original volume of hair, even three separate times, will not yield enough to give full coverage. That is just another reason why I stress to the patient that I need to make sure that the front looks good first.

-Content Provided By Blaine Lehr, MD
Web: http://www.norwood-lehr.com
Email: lehr@norwood-lehr.com
IAHRS Recommended Hair Transplant Surgeon