Importance of Permanent Donor Zone in Hair Transplant
In simple words donor zone is the area from where the tissue is being borrowed for placement in another location. In hair transplant this is a ribbon shaped area centered over a bony prominence in the skull called occipital protuberance. This area described as "Universal Safe Zone" forms the basis of hair restoration surgeries. It extends from the area around ear going back towards temples over to the occipital protuberance and is best seen in Norwood VII patients.
|Norwood VII is the "Universal Safe Zone" for scalp hair.|
The height of donor area is around 5-6 cm in midline and it is approximately 30-35 cm long. If we were to utilise all of it there would be no hair left in the donor zone of a class VII patient. However, it is possible to utilise around 50% of this hair without a visible reduction in hair density on the back. This means a total usable area of around 90-100 square cms.
Assuming an average density of 100 FUs /cm square in caucasians and 80 FUs / cm square in east asians, this gives us a total of 10,000 FUs to 8000 FUs of movable follicular units having approximately 15 to 20, 000 permanent, DHT resistant scalp hair. Of course, if you have a higher density you will get more hair and vice versa.
Having 10,000 movable follicular units does not mean that all of them can be harvested at the same time. The number of units that can be taken out in one session depends upon your scalp laxity. Harvesting too narrow a strip will give smaller number of follicular units and harvesting too broad a strip may result in wide unsightly scar. So, it's a compromise between the two. A patient with high donor density and good scalp laxity will have significantly higher yield than one with low donor density and poor scalp laxity.
Remember, donor zone is the single most important factor in any hair restoration surgery. As a plastic surgeon I have learned to give utmost respect to donor zone but many a times under-qualified doctors do not give adequate attention donor zone. If you look at the stage VII of Norwood class you will realise that hairline recedes not only from the front and top but also creeps up from the neck and temples. That is why follicular harvest from areas above or below this zone may result in visible scarring.Over harvesting from the donor zone may result in wide unsightly scars and thinned out see through look in the donor area. This is so unnatural that the whole exercise of hair transplant becomes futile. Although I am a strong proponent of large sessions, for the aforementioned reasons, larger sessions are not always better for you.
|Example of a bad strip scar.|
This patient underwent follicular unit transplant by strip method
at a clinic in New Delhi. 500 FUs were grafted.
Every one is different and every hair restoration needs to be individualised. Do not rush to the doctor who is offering highest number of grafts for same area. You may end up losing precious donor hair in the bargain. Think, deliberate, consult and research before taking your decision for money can not bring these hair back.