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Dr. Bertram Medical Hair Transplant
眉 髮 醫 學 移 植 中 心 ( 香 港 ) |
( 852 ) 3421-1138
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What Happens to the Hair Follicles After Transplant ?
Paying money does not guarantee you a good result. A hair follicle is a living tissue whose survival is not depend on your cash. A lot of things take place after the follicle is planted into the new site. Your doctor's understanding of the natural histochemical process determines the final outcomes. This page is prepared for those who want to know more.
After the hair graft is removed from the donor area, its original blood supply is detached. Oxygen is depleted and waste products begin to accumulate. The ability of the graft to receive nutrients from the recipient site and undergo revascularization (formation of new blood vessels) therefore determines survival.
After the graft is inserted into one of the slits, the wound healing process immediately takes place. There is a cascade of cellular activities – edema ( swelling ), erythema ( redness ), hair shedding, new hair formation, and the revascularization of the hair graft.
Clinical Features
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Swelling
Most patients would have slight to moderate edema in the transplanted area immediately after surgery. The swelling usually disappears after one week.
Redness
Erythema is present after the surgery but decreases gradually over time. In most case the redness is not noticeable after 2-4 weeks.
The Scab ( Skin Debris )
It falls off after 1-2 weeks, facilitated by the use of olive oil.
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Histological Changes
- On day 1, only edema is found
- By day 3, important influx of neutrophils and occasional eosinophils
- By day 7, neutrophils and macrophages are both present
- By day 14, the predominant cell types seen are macrophages, fibroblasts, lymphocytes, and occasional histiocytes
- From days 21 to 28, inflammatory cells decrease and then disappear.
- Collagen III and IV present from day 1 to 6 months.
Wound Healing
Once a hole is made in the recipient area, wound repair starts immediately. Three phases are found: inflammatory, proliferative, and remodeling.
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Inflammatory Phase
Characterized by clot formation, deposition of fibrin, and an influx of inflammatory cells in the wound.
Proliferative Phase
Fibroblasts and epithelial cells migrate to repopulate the wound. Wound contracture and epithelization occurred during this interval. Multiple cytokine growth factors ( PDGF, TAGF, TBGF, EGF, and VEGF ) increased in the wound during the inflammatory and proliferative phases. |
Growth Factors
Growth factors are the engines or modulating factors that drive wounds to heal. Growth factor activity includes the following :
- Day 1 - the transforming alpha growth factor( TGFA ) appears
- Day 3 - the rest of the growth factors appears
- Day 7 to 21 - shows slight to moderate activity of all the growth factors
- By day 28, epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF) are the only ones present.
These growth factors play key roles in initiating and sustaining the phases of tissue repair. They ultimately diffuse or disperse from the wound site to be degraded by inhibitory proteases. Specialized fibroblasts and growth factors from the dermal papilla also play a key role in the control and induction of the normal follicular growth cycle.
Revascularization
After the graft is placed in the recipient site, a “ survival ” process occurs. Three phases of revascularization :
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Stage I Plasmatic Imbibition
1–3 days post-op, during which the graft absorbs plasma from the recipient site.
Stage I Primary Inosculation
3–7 days post-op, during which early revascularization occurs and connections form between the hair graft and recipient site.
Stage III Secondary Inosculation
Day 7, during which there are further changes in the blood vessels ( including lymphatics ) with coiled vessels extending deeply into the dermal papilla and with budding around the follicular implant.
These changes take place simultaneously with the increase in inflammatory cells and growth factors.
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Graft Survival
After the graft is harvested from the donor area, it is placed in a storage solution for preservation until implanted in the recipient area. It may take 4–8 hours to complete the insertion. The elapsed time is critical for hair growth and survival because increased time results in decreased survival.
Once the hair graft is detached from the donor area, oxygen is depleted and waste products such as carbon dioxide, sugar, and urea begin to accumulate. A newly planted hair graft will be acidotic. The first 48–96 hours after implantation is critical. If the circulation cannot be re-established (the primary inosculation) to correct the metabolic imbalances, the hair graft won’t survive and could die.
Reperfusion after ischemia can also produce apoptosis and/or necrosis of the hair graft and the release of free radicals. This is called "ischaemic re-perfusion injury". The revascularization phase for a hair graft is gradual. Therefore it is critical to decrease the ischemia time and accelerate the revascularization phase.
Maintaining a healthy blood supply to the scalp and minimizing hypoxia and ischemia of the hair graft during hair transplant surgery and up to a minimum of 4 to 5 days post-op should increase the survival rate.
Shedding of the Transplanted Hair
After the transplanted hair graft is taken and survives, the process may continue with one of the following scenarios :
- A small percentage of hair continues to grow from day 1 with no shedding
- Most hair will fall out after 1–6 weeks ( anagen effluvium )
- Some hair will take a longer 7–12 weeks to fall out ( telogen effluvium )
After the hair falls out a new hair will begin to grow 2–4 weeks later. By the 6th month most of the recipient area shows new hair growth. As hairs within a single follicular unit can have different hair cycles: some hair grew and some fell out. It is unpredictable but seems to be helped by the use of Minoxidil as adjuvant therapy.
Reference
David Perez-Meza, MD, Matt Leavitt, DO, Mel Mayer, MD Maitland, Florida."The Growth Factors, Part I: Clinical and Histological Evaluation of the Wound Healing and Revascularization of the Hair Graft After Hair Transplant Surgery."
Hair Forum, September/October 2007 Volume 17, Number 5 page 173
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