The Hair Transplant Glossary -- Terms for Patients Considering Surgical Hair Restoration

The terminology that is used by the scientific community when discussing hair transplants and other hair restoration procedures can be a bit daunting to the average patient. The follicular unit -- a fundamental part of modern hair transplants -- was first defined by in 1984 in the following terminology: "consisting of two to four terminal follicles, and one, or rarely two, vellus follicles, the associated sebaceous lobules, and the insertions of the arrector pili muscles... a single follicular unit is circumscribed by the investing stroma, the perifolliculum." What does this mean to an average patient trying to make a decision about his or her hair loss?

Below is a list of terms that may be unfamiliar to an average patient who is collecting information about his or her baldness. It is important for patients considering hair restoration procedures, including hair transplants, to gather as much information as possible. If you have additional questions about hair loss, contact a hair restoration doctor.


Follicular Unit -

The follicular unit of the adult human scalp is a naturally occurring grouping of hair follicles. The follicular unit consists of 1-4 (and occasionally 5) terminal hair follicles along with 1 (or rarely 2) vellus follicle. In addition to the hair follicles, the follicular unit includes all of the supportive muscles and tissues that surround and define the unit (associated sebaceous lobules, the insertions of the arrector pili muscles, its neural and vascular plexuses, and the perifolliculum).


Follicular Unit Graft -

The follicular unit graft is a graft that is obtained by dissecting out the individual, naturally occurring follicular unit. This is also referred to as a follicular unit implant, a term which implies that (unlike most grafts) the ratio of hair/skin is greater in the follicular unit implant than in the original donor area, since some of the non-hair bearing tissue has been trimmed away in the dissection.


Micrograft -

A micrograft is a hair graft containing 1-2 hairs. It may consist of naturally occurring one and two-hair follicular units or be derived from larger units which are subdivided.


Minigraft -

A minigraft is a hair graft containing 3-6 hairs that are derived from either a single follicular unit, multiple follicular units, or multiple, partial follicular units.


Slit-graft -

A slit-graft is a 3-6 hair graft derived from either multiple follicular units, or multiple, partial follicular units where the dissection technique specifically attempts to produce a linear arrangement of follicles, or follicular units. This may be further classified into small slit-grafts of 3-4 hairs, and large slit-grafts of 5-6 hairs.


Follicular Unit Dissection -

Follicular unit dissection is a technique in which naturally occurring, individual follicular units are dissected from donor tissue that has been removed as a single strip (rather than with a multi-bladed knife of more than two blades) in order to keep the follicular units intact. Some non-hair bearing tissue is removed to decrease the overall bulk of the implant. Stereo-microscopic dissection is required.


Mini-Micrografts or Slit-grafts Cut to Size -

This is a dissection technique whereby the donor strip is subdivided to produce grafts of specific sizes as defined by the number of hairs they contain and/or the size of tissue that will fit into a specific recipient site. The removal of excess skin is not required. The dissection can be performed with or without magnification and the donor tissue may be removed as a single strip or with a multi-bladed knife.


Follicular Unit Transplantation -

Follicular unit transplantation is a method of hair restoration surgery where hair is transplanted exclusively in its naturally occurring, individual follicular units. Single strip harvesting and stereo-microscopic dissection are required. The grafts must be placed into small recipient incisions. This procedure is also referred to as follicular transplantation.


Mini-Micrografting -

This is a method of hair transplantation which uses grafts containing 1-6 hairs, in groups that do not necessarily correspond to the naturally occurring follicular units. The recipient sites may be either incisions, excisions (tissue removed), or both.


Front -

The frontal portion of the scalp comprises the frontal hairline, a zone of transitional density, and the area immediately behind it, which generally has the greatest density in the transplant. It is bounded posteriorly by a line drawn from one fronto-temporal corner to another. The frontal area often represents, on the average, approximately 50 cm2.


Midscalp (Top) -

The midscalp lies immediately posterior to the front and extends to the vertex (crown). It is bounded laterally by the temporal/parietal fringes. The hair on the top portion of the scalp points in a predominantly anterior or anterior/diagonally inferior direction.


Terminal Hair Follicle -

Terminal hairs are typically thicker, longer and darker in comparison to vellus hairs. The growth of terminal hairs is influenced by hormones.


Vellus Hair Follicle -

Vellus hairs are typically lighter in color and thinner than terminal hairs and are usually no more than 2mm in length.


Vertex Transition Point -

The description of this point has been recently defined as the point in the posterior aspect of the scalp where the horizontal starts to become vertical. It is the most posterior point of the top or midscalp and generally lies just behind the highest part of the skull. It is the approximate point where the hair changes direction from a predominantly anterior, or radially anterior direction, to a whorl. This point is important in that it represents a natural stopping point for the transplant when the reserves are limited and/or the planning conservative.


Vertex (Crown) -

The vertex is the region of the scalp posterior to the vertex transition point where the hair takes on a whorl pattern.


References -  

1. Stough DB, Bondar GL: The Knudsen nomenclature: Standardizing terminology of graft sizes. Dermatol Surg 1997;23:763-5.

2. Avram MR: Accurately communicating the extent of a hair transplant procedure: a proposal of a follicular-based classification scheme. Dermatol Surg 1997;23:817-818.

3. Headington JT: Transverse Microscopic Anatomy of the Human Scalp. Arch Dermatol 1984;120:449-456.

4. Rassman WR, Pomerantz MA: The art and science of minigrafting. International Journal of Aesthetic and Restorative Surgery 1993;1:28-29.

5. Bernstein RM, Rassman WR, Szaniawski W, Halperin A: Follicular transplantation. Int J of Aest Rest Surg 1995;3:119-132.

6. Limmer B: Elliptical donor stereoscopically assisted micrografting as an approach to further refinement in hair transplantation. J Dermatol Surg Oncol 1994;20:789-793.

7. Arnold J: Mini-blades and a Mini-blade Handle for Hair Transplantation. Am J Cosm Surg
1997;14(2):195-200.

8. Unger WP. Laser hair transplanting. Int J of Aest Rest Surg 1995;3:137-142.

9. Choi YC, Kim JC. Single hair transplanting using the Choi hair transplanter. J Dermatol Surg Oncol 1992;18:945-948.

10. Bernstein RM, Rassman WR: Follicular transplantation: Patient evaluation and surgical
planning. Dermatol Surg 1997;23:771-784.

11. Bernstein RM, Rassman WR: The aesthetics of follicular transplantation. Dermatol Surg 1997;23:785-799.

12. Unger W. Nomenclature of minis & micros. Hair Transplant Forum International Vol 3, No 1:11 1992.

13. Beehner M: Where is Thy Crown, Your Majesty? Hair Transplant Forum International Vol 8, No. 1:18-19 1998.