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Registered in 2008, TÜV Certificated service quality since 2012!
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Information Center 128 City Road, EC1V 2NX

Hair transplant DHI

The DHI Technique, Pen Method, or Choi Pen Direct Hair Implantation Method

Hair transplants have proven to be a good measure to use on one’s thin hair spots. Nowadays, the DHI technique (Direct Hair Implantation) is increasingly used to implant the removed hair. The small, specific areas can be transplanted with it.

The Procedure

In the DHI procedure, the hair follicles are removed froö the donor site using the FUE technique and immediately reattached to the affected region. This procedure aims to achieve an optimal result despite a shortened intervention time. A unique 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 directly implant hair follicles into the affected area after being removed from the donor region with the pen. This is another reason why the procedure is called the Choi, Pin, or Percutaneous Technique.

The Risks

Possible damage to the graft when pressing into the pins

At the Choi pen’s tip, 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.

Hair Transplant DHI

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. On a normal hairy scalp, there are about 80 to 110 hair roots in one square centimeter. 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 centimeter should be used. Otherwise, the surrounding tissue can hardly 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 the Choi-Pen is inserted directly into the scalp and no micro-receptor channel is prepared in the natural hair’s growth direction, 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 specific 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.