A: The average donor strip is 1cm wide, although this will vary depending on the patient’s scalp laxity, density, and the number of grafts desired for the hair restoration.

The length also depends on the number of grafts needed. We average 90-100 follicular unit grafts per cm2 of donor tissue (that is the density of follicular units in an average person).

A 2,000 graft procedure, for example, would require a donor strip 22 cm long and 1cm wide. A 2,500 graft session would be 1.2 cm wide and 23 cm long.

A: Normally, the donor area contains hairs of very uniform diameter (called terminal hairs). In androgenetic hair loss, the action of DHT causes some of these terminal hairs to decrease in diameter and in length until they eventually disappear (a process referred to as “miniaturization”). These changes are seen initially as thinning and eventually lead to complete baldness in the involved areas.

These changes affect the areas that normally bald in genetic hair loss, namely the front and top of the scalp and the crown. However, miniaturization can also affect the donor or permanent regions of the scalp (where the hair is taken from during a hair transplant). If the donor area shows thinning, particularly when a person is young, then a hair transplant will not be successful because the transplanted hair would continue to thin in the new area and eventually disappear. It is important to realize that just because hair is transplanted to another area, that doesn’t make it permanent – it must have been permanent in the area of the scalp it initially came from.

Unfortunately, in its early stages, miniaturization cannot be seen with the naked eye. To detect early miniaturization a doctor must use a densitometer, or an equivalent instrument, that magnifies the surface of the scalp at least 20-30 times. This enables the doctor to see early changes in the diameter of the hairs that are characteristic of miniaturization. If hairs of varying diameter are noted (besides the very fine vellous hairs that normally occur in the scalp), it means that the hair is being affected by DHT and the donor area is not truly permanent.

In this situation, a person should not be scheduled for hair transplantation. If the densitometry reading is not clear, i.e. the changes are subtle and the doctor is not sure, then the decision to have surgery should be postponed. By waiting a few years, it will be easier to tell if the donor area is stable. Having surgery when the donor area is miniaturizing can be a major problem for a patient, since not only will the transplanted hair eventually disappear, but the scar(s) in the donor may eventually become visible. This problem will occur with both follicular unit transplantation (FUT) and follicular unit extraction (FUE).

A: The length of the donor strip incision is determined by the number of follicular unit grafts required for the hair restoration.

There are slightly less than 100 follicular units/cm2, so if a 1cm wide strip is used, a hair restoration procedure requiring 1800 grafts would need a strip that measured slightly more than 18cm in length.

A 2800 graft procedure would measure slightly more that 24cm if the strip were 1.2cm wide.

The width of the strip is determined by scalp looseness or laxity.

For more information, please see the Donor Area page on the Bernstein Medical – Center for Hair Restoration website.

A: You are correct. The best place to put the donor incision is in the mid-part of the permanent zone located in the back of the scalp. As more hair is needed the incision is extended towards the sides.

The vertical position can be found by feeling for the bump in the mid-part of the back of the scalp, also called the occipital protuberance. The strip should lie over this point.

If hair is removed too low on the back of the scalp, there is a greater chance that the wound will heal with a stretched scar from the movement of the underlying muscles. If the incision is too high, the hair will be subject to the same genetic balding and may not be permanent.

A: Strip harvesting is used in the majority of hair transplant procedures because it allows the surgeon the ability to perform hair transplant sessions using large numbers of grafts while minimizing injury to the patient’s hair follicles.

This is possible because once a strip is removed from the back of the scalp, the tissue can be placed under a stereomicroscope where dissection is accomplished using direct visualization of the follicular units. This allows the grafts to be dissected with minimal trauma.

This degree of accuracy is not possible with other hair restoration techniques, such as FUE, where the separation of follicular unit grafts from the surrounding tissue is accomplished “in vivo” (directly from the scalp).