The field of hair restoration is a dynamic specialty whereby advanced technologies enable surgeons to achieve more aesthetically pleasing results. Hair loss seems to have troubled humanity since the dawn of history evidenced in a prescription for restoring hair that was included in the 1500 B C. Ebers papyrus of ancient Egypt.
The success of modern hair transplantation depends on a phenomenon first described by Orentreich in 1957 as donor dominance. With this phenomena, hair taken from the permanent hair-bearing rim of patients with androgenetic alopecia (donor area) and transferred to non-hair-bearing areas of the scalp (recipient area), continues to grow in its new site for as long as it would have in the area from which it was taken.
The history of this field is summarized below
1804 - Baromio transplants hairy areas in animals
1822 – J. Dieffenbach performs auto-transplantation of hair into skin
1939 - Okuda uses 2- 4 mm punch grafts for restoration of alopecia
1943 - Tamura implants single hair grafts by injection for restoration of the skin overlying the mons pubis in the female
1959 - Orentreich utilizes hair-bearing auto-grafts for the correction of male pattern baldness
1980’s - Limmer uses microscopes for the creation of small 1 to 5 hair grafts inserted into needle slits.
1992 - Uebel performs the excision of a linear donor strip
1994 – Limmer single-strip harvests using stereomicroscopic dissection of individual follicular units, known today as FUT or the strip procedure.
1994 - Unger creates limitations of the donor-harvesting site by delineating the safe donor area
1995 - Woods harvests single follicular units using smaller circular punches (1 mm) with an acceptable aesthetic appearance and low transection rate
1997- Bernstein and Rassman describe their follicular unit transplantation technique, contributing the term “follicular unit” to the nomenclature
2002 - Rassman and Bernstein describe FUE as a surgical technique in medical literature
Hair varies among the different ethnic groups and among singular individuals. It has two separate structures: the follicle in the skin and the hair shaft, which is visible on the body surface. There are various hair types.
The majority of hair shafts emerge from the scalp as single-4 hair groupings . The groupings are the visible superficial portion of the follicular unit (FU). The FU generally consists of one to four terminal hair follicles and one vellus follicles.
Hair direction differs acording to the part of the scalp. Both the direction and the angle of the incision must therefore be individualized with regard to the part of the scalp.
The hair follicle is a dynamic organ . The cyclic activity requires the regeneration and new assembly of nonpermanent portion of the hair follicle during each cycle.
On average, the amount of new scalp hair formation matches the amount that is shed, thereby maintaining a consistent covering.
There are 3 main phases of the hair follicle cycle: an active growth (anagen); regression (catagen) and quiescent (telogen). How long each phase takes partly depends on the type of follicle and its geographic location. Recently, the two other stages of the hair cycle have been described: release (exogen) and lag time (kenogen).
Diseases that cause hair loss are categorized according to whether the hair loss is diffuse or localized, and to whether the follicle remains intact or is destroyed and replaced by scar. The potential trigger factors attributed to inflammation, genetics, the environment, and hormones.
Hair loss disorders have three essential mechanisms that involve hair follicle density, hair follicle size and hair growth cycle duration
Androgens have paradoxically different effects on human hair follicles depending on their body site. Testosterone is the major circulating androgen in men. Testosterone reduced to dihydrotestosterone (DHT) by 5α-reductase enzyme . DHT binds to the androgen receptor. In the balding scalp, 5α-reductase is increased, resulting in the increased production of DHT.
Androgenetic alopecia (AGA Male-pattern hair loss (MPHL))
AGA, is the most common cause of hair loss. It affects up to 70% of men in mid adult life. MPHL occurs in the presence of androgens in genetically susceptible individuals. Recently increased prostaglandin D2 level in the hair follicles is suggested as one of the major causes for AGA.
The key feature in MPHL is follicular miniaturization. The duration of active growth phase reduces from 2-6 years to a few months, whereas the quiescent stage relatively lengthen. New generations of hairs becoming shorter, finer, and lighter in color and they conceal the scalp less. The transition may be gradual or can come in waves, and the course and extent of MPHL are unpredictable.
The male pattern generally begins with bitemporal recession, followed by vertex baldness and mid-frontal hair loss; allowing the terminal hair follicles to be retained in the occipital scalp region. The most commonly used system to grade MPHL is the Hamilton–Norwood Scale.