What is the importance of hair characteristics in hair transplant surgery?
These characteristics are significant in that they determine to a great degree how much coverage of the scalp there is, in order to block light. When light is not blocked and penetrates through to the scalp, the appearance is of thinning or balding.
The other big factor here is the density, which is another topic unto itself. The density is the number of hairs or follicular units per unit area (square centimeters or square inches or whatever unit you prefer; the centimeter is the standard for physicians). Although this density usually gets most of the attention when discussing hair loss, hair characteristics are equally, if not more, important.
First let’s look at color. At first, one might think that the darker the hair, the better the coverage. This is generally not correct. Lighter hair usually goes with lighter skin, and the tow together tend to mask thinning very well. Darker hair can cover well, but in the case of poor hair transplant work (pluggy looking, or larger graft on frontal hairline) they may stand out much worse than lighter hair. We will discuss color in more detail when we discuss contrast.
Curl is another very important factor in coverage. Generally speaking, curly hair provides coverage in proportion to the degree of curl (i.e., wavy hair gives better coverage than straight hair, curly hair better than wavy, very curly better than slightly curly, etc.). This has to do with light blockage as well. The curlier the hair is, the more it creates a meshwork of sorts (kind of like a thatched roof) which “stands up” a little bit off the scalp and keeps the light from penetrating to the scalp.
Contrast has to do with the difference between hair color and skin color. The closer to each other the hair and scalp are, the better the coverage. In a way, this “fools” the eye of the observer into not noticing the decrease in density. If a person with blonde hair and light skin loses 50% or his or her density, they may appear much less affected than a person with equally light skin and jet black hair. In this case the dark hairs of the second example are highlighted against the light skin and it shows the sparseness of the hair. The person with the blonde hair reveals very little difference between the hair and scalp, in other words, the observer cannot detect where the hair leaves off and the scalp begins.
Last, let’s consider caliber. Thicker strands of hair provide more “hair mass”, which is a term doctors use to describe the total effect of length times caliber. The more hair mass in a given area, the better the coverage. This makes intuitive sense. Imagine covering a hut with logs. If you place 20 logs as a roof, which will give better coverage, skinny logs or big round ones with large diameters? Of course, the bigger ones, so the thicker hairs do the same over the scalp. And remember, what appears as thinning or balding is simply the appearance of light shining through to the scalp.