Mimicking natural hair patterns key to effective transplants

Louisville, Ky. - For the hair transplant surgeon, the important facets of hair anatomy and physiology are different from those on which other specialists tend to focus.

"The hair transplant surgeon needs to know the facets of hair anatomy and physiology that impact surgical technique and increase hair density and survival," says William M. Parsley, M.D., director of the Parsley Hair Center here. "Hair can be classified in several ways - by cycle, miniaturization, hormonal response, location on the body, and so forth," he tells Dermatology Times.

Dr. Parsley reviews the basic scalp-hair cycles:

HOW HAIR GROWS

Dr. Parsley says that terminal anagen hairs of the scalp typically grow approximately one centimeter per month, or about an inch every three months. He further cites a landmark 1984 article by J.T. Headington wherein the author observed that hair follicles are arranged in groupings of two to four terminal hairs and one or two vellus called follicular units (FUs).

"This study, combined with Dr. Bobby Limmer's study of stereomicroscopes to dissect these units intact for transplantation, transformed hair restoration," Dr. Parsley says. "Current high-end techniques deal with the use of follicular units to create the most anatomically natural result. A full understanding of the follicular unit is imperative for the hair-restoration doctor."

Dr. Parsley says that after the individual FUs are dissected from the donor strip, they must be properly angled and oriented to achieve a natural look. He notes that hairs in a follicular unit tend to be oriented linearly (in rows) and that the hair growth direction is nearly always perpendicular to these rows.

The FU looks very similar to a fork. In order for the hair direction of the grafts to be correct, the grafts should be planted with these rows perpendicular to the desired hair direction of the grafts.

"Also, because the curl tends to occur in a plane vertical to the hair growth, the intended direction of the hair in the grafts must be aligned perpendicular to these rows," Dr. Parsley says. "It has been shown by Drs. Hasson and Wong that orienting the direction of the grafts perpendicular to the alignment provides more effective coverage and the appearance of greater density from both the overhead and frontal views."

MIMICKING NATURAL HAIR PATTERNS

Dr. Parsley notes that along the frontal hairline, there are two natural hair patterns of irregularity that often are mimicked by transplant doctors in order to achieve a natural look.

"Macro patterns of irregularity are called peaks or mounds. They are visible from a few feet away and are often used to avoid the 'rounded bowl' look seen in some transplants," he says. "There are also micro patterns all along the hairline, consisting mainly of clusters and hairless gaps. These important irregularities are copied in nearly all transplants in order to avoid an abrupt appearance of the transplanted frontal hairline."

Macro patterns consist of large protrusions of the hairline, a familiar example being the frontal pattern known as a widow's peak. There are three natural peaks along the medial portion of the frontal hairline, and any given individual can have none or as many as three present. Dr. Parsley says the hair direction in these macro patterns is usually quite different than that of the surrounding hair, particularly in the widow's peak where the direction is often perpendicular to the surrounding hair.