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Follicular unit grafting typically involves clusters of how many hair follicles?
Describe a trychophytic closure.
Incision made with knife beveled perpendicular to hair follicle. Wound closed such that the hair grows through the scar.
What is follicular unit extraction or the follicular isolation technique?
Hair is removed with <1mm punch and transplanted to sparse areas. This is in contrast to the "strip technique" where a strip of skin is removed and follicles isolated from it under microscope for transplant.
Pros and cons of follicular unit extraction/follicular isolation technique
- Pros: no linear scar (can have close cropped hair), good for mild hair loss in young men
- Cons: hyper/hypopigmented dots, moth eaten appearance of donor site, limited use in curly hair, higher number of transections/damaged follicles.
Indications for follicular unit extraction other than hair loss
- Scar camouflage (facelifts, browlifts)
- reorient hair follicles from prior hair transplant
Typically believed that __% of hair is lost when it becomes noticeable.
Describe the growth cycle of a hair follicle.
Growth Cycle: anagen is the growth phase; catagen is the involuting or regressing phase; and telogen, the resting or quiescent phase. Normally up to 90% of the hair follicles are in anagen phase while, 10–14% are in telogen and 1–2% in catagen. The cycle's length varies on different parts of the body. For eyebrows, the cycle is completed in around 4 months, while it takes the scalp 3–4 years to finish; this is the reason eyebrow hair have a much shorter length limit compared to hair on the head. Growth cycles are controlled by a chemical signal like EGF. DLX3 is a crucial regulator of hair follicle differentiation and cycling.
Describe a Norwood class III
- Class I: not bald, generally rests on the upper brow crease.
- Class II: hairline that sits a finger's breath (1.5cm) above the upper brow crease, with some temporal recession.
- Class III: deepening temporal recession or early hair loss in the crown (vertex).
- Class IV: further frontal hair loss and enlargement of vertex, still a solid band of hair separating front and vertex.
- Class V: bridge of hair separating the two areas begins to break down.
- Class VI: single large bald area on the front and top of the scalp.
- Class VII: only a wreath of hair remaining in the back and sides.
Describe a Norwood class A pattern.
The Norwood Class A patterns are characterized by a front to back progression of hair loss. Less common than the regular pattern (<10%), but appear very bald even when the hair loss is minimal.
Describe follicular unit transplantation (aka the “strip” procedure).
Considered the gold standard and is the least expensive and has the highest success rate. Large numbers of hairs are harvested with the aid of a 10 power binocular microscopes, from a strip of excised full thickness scalp. These naturally occurring follicular clusters, each containing 1–4 hairs, are then planted into needle holes in the balding area. FUGH is indicated over mini/micrografting technique in 90% of cases except in pts with gray, white, blond, or salt and pepper hair, who would do better with larger minigrafts containing 25 hairs.
Medical treatments for alopecia
- corticosteroid: cream, PO, injection
- minoxidil: topical vasodilator
- finasteride: 5 alpha reductase type 2 inhibitor. Suppresses circulating DHT and affects vertex balding more than frontal hair loss.