The DHI technique, pen method or Choi pen Direct hair implantation method
Hair transplants have proven to be a good measure to use one’s own hair at lightening areas. Nowadays, the DHI technique (Direct Hair Implantation) is increasingly used to implant the removed hair. A central argument, which is often put forward for the use of this method, are the small areas, certain areas, which can be transplanted with it.
In the DHI procedure, the hair follicles are removed at the donor site using the FUE technique and immediately reattached to the affected region. The aim of this procedure is to achieve an optimal result despite a shortened intervention time. A special instrument developed at Kyunpook National University in South Korea – the Choi Implanter Pen – is used for this purpose. As the name suggests, this pen is used to implant hair follicles directly into the affected area after they have been removed from the donor region with the pen. This is another reason why the procedure is called the Choi, Pin or Percutaneous Technique.
Damage to the graft when pressing into the pins
At the tip of the Choi pen, there is a hollow needle that surrounds the graft and inserts it into the problem zone. This tamping process increases the risk of damaging the hair follicle due to the shearing and rotational forces of the Choi Pen. If a damaged graft is inserted into the recipient tissue, the chances of healthy growth decrease – the graft will fail again.
But also healthy grafts are endangered. Many clinics and surgeons advertise to transplant as many follicles as possible. Allegedly, this increases the chance that a full hair picture will appear again quickly. But: On a normal hairy scalp there are about 80 to 110 hair roots in one square centimetre. With a hair transplant one would like to reach this number again. In a graft, however, there are at least two, if not three or four, of these hair roots. Accordingly, a maximum of 60-80 grafts per square centimetre should be used. Otherwise the surrounding tissue is hardly able to supply the excess of hair roots with the necessary nutrients.
Another critical aspect of the DHI method is the uncontrollable growth direction of the implanted hair. Since no micro-receptor channel is prepared in the growth direction of the natural hair, but the Choi-Pen is inserted directly into the scalp, no surgeon can predict the later growth direction of the implanted hair. The result is an inharmonic hair pattern. Therefore, the Choi-Pen should only be used for certain areas.
Many surgeons, including the doctors from our partner clinic, are critical of the DHI method and many false arguments that are put forward – even though they have perfect mastery of the procedure and can also perform it on request. However, they prefer manual implantation with the slot technique because it looks most natural.