As per leading hair restoration physicians, transplanted hair isn't usually placed uniformly throughout the balding scalp during hair transplant surgery. For that matter, neither is hair loss. Thus, hair density isn't consistent typically throughout the scalp as someone is losing their hair.
Leading hair replacement surgeons typically dense pack more hair in the front and gradually taper off as they approach the crown. This is because people are viewed from the front much more frequently than from the back or top of the scalp. Obviously, a hair surgeon will be flexible on this approach depending on a patient's individual hair restoration goals.
Consider a Norwood 6 level patient that has approximately 300 cm2 of baldness to cover - which is essentially the entire top of the scalp and some below the crown.. In order to achieve 50 FU/cm2 (approximately 50% to 70% of original native hair density before any hair loss) uniformly over a 300 cm2 bald area, a patient would need approximately 15,000 follicular units. To cover 200 cm2 of bald area at 50 FU/cm2 uniformly which is a patient somewhere between a level 4 and 5 on the Norwood scale, he'd need approximately 10,000 FU grafts.
Most leading hair restoration physicians can densely pack 50 FU/cm2 and even higher in some cases without compromising vascularity or hair growth yield. The actual number will depend on the number of hairs per follicular unit, the patient's hair characteristics (thin, fine, coarse, etc.), available donor hair, risk of future hair loss, and the actual density a patient requires to achieve the illusion of density. Remember, just because a certain hair density can be achieved doesn't mean it's appropriate for each patient.
So can men restore a full head of hair with hair transplant surgery? It depends how you define "full". Hair transplant surgery is about creating an adequate illusion of fullness. The good news is, only 50% of original hair density is required to make hair appear as full as it was originally before any hair loss. However, sometimes less will be used in a single procedure to reserve more donor hair for future hair loss in the future. Thus, sometimes, less can be more.
Bill - Managing Publisher of the Hair Transplant Network, the Coalition Hair Loss Learning Center, and the Hair Loss Q & A Blog.
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