Hair Transplantation Surgery（1）
Manoj Khanna
Indian J Plast Surg. 2008 October; 41(Suppl): S56–S63.
PMCID: PMC2825128
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2825128/
Abstract
Techniques in hair transplantation have evolved recently which make results look more natural. Hair restoration is one of the most exciting and innovative surgical fields in aesthetic surgery today. A precise appreciation of anatomy has allowed the use of follicular unit grafts. With better methods of harvesting and implantation, hair transplantation results represent a blend of art and science.
Keywords: Hair transplantation, Follicular unit, graft, Kolkata slit
INTRODUCTION
Hair transplantation is one of the most rapidly evolving procedures in aesthetic surgery, accompanied by regular improvement in techniques. The recent advances in technology and the concept of using follicular unit grafts have made this procedure reach a new height. The ability to provide very natural-looking results has encouraged larger number of balding men and women to opt for this surgical solution.
PATHOPHYSIOLOGY
The clinical onset of baldness in both men and women is generally around the age of 30 to 40 years. A strong family history is one of the best indicators of Male pattern baldness or Androgenic alopecia, which is the most common cause of hair loss. An autosomal dominant genetic linkage is believed to cause this hair loss. Male pattern baldness may begin in the teen years, and becomes more common with increasing age. It is known that the male hormone, Testosterone, gets converted to another male hormone, 5-dihydroxytestosterone (5-DHT), in the hair follicles. Under the influence of 5-DHT, hair follicles in the front and the top of the scalp begin to become more fine over the years in genetically susceptible men. Hair growth also gets restricted and eventually the hair disappears completely.
Like most tissues, hair undergoes a continuous turnover throughout life. Hair follicles are replaced periodically, and at any given time, they are in one of three stages of their growth cycle. The actively growing stage (Anagen phase) is followed by a brief period of morphological change or the involution stage (Catagen phase). This is then followed by a resting stage (Telogen phase). In normal human beings, the total number of scalp hair is usually 100,000. Hair grows at the rate of 1～2 cm every month and the duration of the anagen phase is 2～4 years while that of the telogen phase is 100 days. Approximately 40～100 hairs are shed daily; this rate increases in late summer and early autumn, and decreases in late winter or early spring, due to the effects of temperature. Norwood has classified baldness into seven stages [Figure 1]. In women, the frontal hairline is usually spared and baldness in females has been classified separately by Ludwig.
Figure 1
Hair loss classification
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