Hair features

The characteristics of the hair in a patient can make a difference in the level of results obtained in terms of the type of approach from the part of the surgeon. When we talk about the characteristics of the hair, we refer to the color, to the size or diameter of the hair (fine or thick), to the fact that the hair either curly or straight, and the contrast between the color of the hair and the skin.

All these aspects play an important role for the surgeon, who is planning the hair transplant surgery. There is also another important aspect to determine: The density the doctor considers necessary to obtain a natural result, that integrates seamlessly with the native hair.

The fundamental factors that help to predict what the outcome will be are the caliber of the hair shaft, the number of hairs per follicular unit and the general characteristics of hair. The hair caliber is the is probably more important than the density of follicular units per cm2. A patient can have a density per cm2 above average, but a miniaturized hair shaft, and considering a thinned appearance that is given by light when it penetrates through the hair and scalp and is reflected, having fine, miniaturized hair constitutes a disadvantageous factor.

The better the characteristics of the hair the easier it is to create a density that allows a natural look and obtain maximum coverage, especially in cases Norwood 5 or higher. Planning long-term becomes easier when a thicker hair gauge allows to give a larger coverage while maintaining a good density. The ideal characteristics of the hair include a thick gauge of the stem, often a wavy or curly hair, an elastic scalp and low contrast between hair color and the skin tone of the scalp. This explains why hair transplantation works and can give a 5 or 6 Norwood the illusion of coverage and density (donor permitting it) without it being necessary to replace one by one all the lost hair.

Average number of hairs per follicular unit

What is important is to give a definition of graft given that some doctors speak of graft, others of follicular unit and others of hair. There can be a large number of responses and consequently a different number of hairs, and this number is crucial to obtain the best possible result.

A follicular unit normally consists of 1 to 4 hairs growing in small groups. Usually this is considered a “graft” when it is removed from the scalp.

When people talk about a hair transplant and ask “how many do you have transplanted” it normally refers to “grafts” and much more rarely to the hairs. The number of follicular hair units is important for determining whether a person is a good candidate for a hair transplant or not. If the average number of hairs per follicular unit is low then there may be difficulties in treating cases of diffuse baldness on the entire scalp, but also cases of little thinning when there may not be sufficient hair to be strategically placed to give sufficient density for a natural look.

The image below shows 3 different donor areas that have the same density per cm2 of hair, but a different number of hairs per cm2.

Miniaturization Calculation

Hair appearance is given both by the thickness of the individual and the density of hair on the scalp.

Hair grows about 0.6-1.25 cm per month and usually its thickness and density decreases the older we get.

The caliber of the hair varies from fine to thick and is different from person to person and between different ethnic groups.

Fine hair have a diameter of about 50μm (microns) and because of this characteristic is more susceptible to breakage. The medium-diameter hair have a caliber of 60-90μm and this is the norm. Thick hair is stronger, with a caliber of 100 m or greater.

Miniaturization is an effect of hair loss and in particular of androgenetic alopecia.

The hair shaft begins to atrophy and the caliber of the hair begins to decrease both in the receiving area and the donor area. If miniaturization occurs in the donor this can decrease its capacity and even make the donor area unsuitable for transplant.

Transplanting miniaturized hair can lead to a poor cosmetic result.

The trauma caused by extraction can make hair to not grow back and this has a negative impact on the surrounding hair in the donor area. And it is normal to have a number of miniaturized hairs in the donor area, especially in older people, but if miniaturization exceeds 15% of the donor density, then hair transplant is not recommended (poor donor area).

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