NHT Medical Center is dedicated to the research and development of hair restoration and its techniques. During the course of several years of experience, we at NHT Medical Center have performed several of our own studies in our pursuit in the advancement of hair restoration. In this section, you will find several studies performed by NHT Medical Center.

Comparison Study between the Follicular Unit and Modified-Follicular Unit Ten years after surgery. Size of the hair grow from modified follicular unit is as big as the donor site hair. But the single follicular unit hair reduced 24%. Updated Nov. 2011.

Scalp Stretch Exercise

Scalp Stretch Exercise

To have the best scar and widest donor size possible, we strongly recommend you to do the Scalp Stretch Exercise twice a day, ten minutes each time.

Scalp Stretch Exercise


Direct View Donor Harvesting

Presented by Dr. Steven C. Chang in International Society of Hair Restoration Surgery 12th Annual Meeting: August 2004 at Vancouver, Canada.


Even if we check the donor cutting from time to time during donor harvesting, it is always too late. The damages are already done. By using the direct vision method (keep cutting area open all the time), we can correct the direction right away.


To improve the quality of donor harvesting, at the same time prevent nerve and vascular damage.

Materials and Methods

Material: Two skin hooks.

Method: One hook held by the surgeon, another one held by the surgical technician. Try to open the incision all the time. And check the lowest incision every time when you change the hook location.

Trick of correction:
“See head to head, see tail to tail”-will explain during presentation


1. Knowledge of follicular direction at different parts of the scalp
2. Observation of hair angle and flow
3. Tumescent
4. Wedge Blade
5. At the edge areas-Dr. Pathomvanich’s approach


The advantages of the direct vision method:
1. Take 3 minutes to learn
2. One to Two minutes to cut
3. Reduce the trans-section rate right away (no learning curve)
4. Useful for both Strips and Ellipse harvesting methods

A Quick, Easy Method to Estimate Number of Grafts and Donor Area

Presented by Dr. Steven C. Chang in the workshop of International Society of Hair Restoration Surgery 9th Annual Meeting: Oct. 2001 at Puerto Vallarta, Mexico. Also published in the “Hair Transplant Forum International, Volume 11, July/August 2001


Estimating the number of grafts is not an easy job. I would like to present the approach that we have been using for three years in our facility.

We first have to calculate the total area of coverage. Based on the total area of coverage, we can decide the size of donor area that should be harvested. From the size of donor area we can then find out the number of grafts depending on the size of grafts. The sequence is very important.

• Same coverage area with pre-set density = same number of grafts.

If we ask ten hair transplant surgeons to estimate the number of grafts needed on a particular patient, I am very positive that we will get ten different answers. With this system, every surgeon, consultant, and even the patient can reach the same number of grafts as long as same coverage area, pre-set density, and same size of graft.

• Patient will not have unrealistic expectations. Today, a natural looking transplant is not difficult to achieve with the micro and follicular technology. The density is the problem that we are facing. When we tell the patient that he needs either 500 grafts or 1,000 grafts, it doesn’t make any sense to him because he doesn’t know what 500 grafts or 1,000 grafts can do for him. He may expect a full head of hair after one session. With our method, we tell the patient that we will deliver 25%, 30%, or 35% of his original donor site density on the receipt area. He will have a better idea of the thickness of his new hair and will not expect a full head of hair after only one session of surgery. The patient may ask if he needs four surgeries (assuming to achieve 100% density) to achieve the normal appearance. At this time we can show him our former patients’ pictures that have 25% and 50% density transplanted. This will give patients a much better understanding of the outcome.

• No over or under harvesting. With this method, we decide the size of donor area first then determine the type and number of grafts. This way, the error of over harvesting and under harvesting is minimized.

• Same coverage area for consultation and surgery day. Because we have the photocopy of the transparent sheet and the digital photo of patient’s scalp on file, we do not need to go through the process of measuring on surgery day. We just need to make sure the coverage area is the same before we start the surgery. And we have an idea of what kind of hairline we had mutual agreement on at the consultation.

• Give surgeon the ability to estimate the maximum coverage area. We all agree that the maximum usage of permanent donor hair is about 50%, and if 50% donor site density is adequate, then: —If permanent area /coverage > 1, the patient MAY have enough hair to cover the whole bald area. —If permanent area/coverage < 1, the patient ABSOLUTELY WOULD NOT have enough donor hair to cover the whole area.

• No actual density measurement. To measure the actual hair density is almost impossible. The hair density is different over the whole scalp; for instance, occipital area has higher density than temple area. The method mentioned above uses a “relative comparison.” We do not tell our patients how many grafts are in 1cm² of donor strip; we only tell them that we deliver 25% of their own density. For example, to cover 100cm² of baldness, we harvest a 25cm² donor strip. After cutting it into smaller grafts, we implant them back to the scalp completely. This gives a 25% density. We do not have to count how many hairs to reach 25% density. Our goal is a natural looking appearance. To achieve it, relative density is more important than actual density.

• Find out the maximal ability of your surgery team. In the long run, you will find out the maximal pre-set density that your team is capable to deliver among different races and with different sizes of grafts. This will also prevent over harvesting.
The number of grafts enables us to predict the surgery time and effort but does not predict the actual outcome. Different facilities use different sizes of grafts; therefore, the total number of hairs can be different and even more than 100%. Unfortunately, when patients shop around for the price, they always believe the same number of grafts will have the same value and, supposedly, same outcome. To predict the outcome among different clinics, I personally consider that the ratio of donor strip size to coverage area (the density) is a much better indicator.
— Steven C. Chang, M.D

Prevention of Forehead Edema and Periorbital Ecchymosis after Hair Transplantation

Published on Hair Transplant Forum International

May/June 2005 Volume 15, Number 3

When informing patients about side effects associated with hair transplantation, we always must mention post-operative forehead edema and periorbital ecchymosis (“black eyes”). We know that nearly all hair transplant patients are at risk for developing forehead edema, and because edema may migrate from the scalp to the forehead to the orbits, a small number of patients—5%–10%—may develop periorbital ecchymosis. Generally, the earlier forehead edema develops, the more severe it eventually becomes.

While prevention of post-operative edema—for example, by pre- and/or post-operative administration of local or systemic corticosteroids—is always our goal, complete or significant prevention is often not realized. The goal then becomes decreasing the severity of the edema and/or ecchymosis.

Commonly used approaches to prevention or amelioration of forehead swelling include having the patient (1) apply cool packs several times daily to the forehead, (2) apply hand pressure to the forehead to massage fluid away from the forehead to the temple areas, (3) avoid the flat reclining position when sleeping for several days after surgery, and (4) apply an elastic band low on the forehead, above the orbits, to prevent fluid from reaching the orbits (by Dr. Damkerng Pathomvanich).

In my practice, I have found that use of a specially designed plastic forehead plate, an elastic headband, and locally administered corticosteroid will resolve nearly all instances of forehead edema and prevent periorbital ecchymosis in nearly all patients in whom post-operative forehead edema develops. The method has been successfully applied in 120 patients.

This technique utilizes (1) an elastic headband to fit just above the orbits, to keep fluid from reaching the orbits, and a plastic plate 13cm long by 4cm wide that is applied under the elastic headband, to direct fluid flow from the forehead to the lateral sides of the head (Figures 1 and 2), and (2) Triamcinolone 40mg (10mg/ml) mixed with 15ml tumescent solution, injected into the frontal recipient site.

The patient is instructed to apply the elastic headband and plastic plate if and when forehead swelling develops, or to apply the elastic band and plastic plate on the third post-operative day, whichever comes first.

The elastic band provides consistent pressure to prevent fluid migration to the periorbital area. The plastic plate slipped into place under the elastic band opens a channel for drainage of accumulated fluid from the forehead area to the lateral sides of the head toward the temples.

Application of the plastic plate has been effective even when the patient has forgotten to apply it before swelling reaches the periorbital area; when applied immediately in these circumstances, swelling has been seen to decrease in a matter of hours as fluid drains laterally from the forehead.


Surgical Correction of ‘Plugginess’ in Hair Transplants

Published on Hair Transplant Forum International

January/February 2006 Volume 16, Number 1

The pluggy look was a signature characteristic of hair transplants before improvements in surgical technique and instruments opened the way to the natural look by use of mini-, micro-, and follicular unit grafts. The large plug graft has had limited use since naturalness became a principal and achievable goal of hair transplantation. However, a number of patients remain with pluggy transplants from earlier surgery and some may have received recent transplants that resulted in plugginess rather than a natural look.

Whether a patient’s pluggy look is the result of earlier or more recent hair transplantation, he may present to the hair transplant surgeon with a request to revise plugginess to natural. If the patient has had progressive hair loss since the earlier surgery that resulted in plugginess, revision will have to be accomplished as part of a global hair restoration.

The Esthetic Problem in Plugginess
Naturalness is difficult to achieve using large plug grafts, usually not due to the plugs so much as to the bare scalp between the plugs. Large plugs cannot be implanted close enough together to achieve the uniform hair density seen with flap surgery or with use of small grafts. Large plugs can also be more difficult than smaller grafts to implant uniformly.

The esthetic deficiency defined as the pluggy look is fundamentally a matter of relative hair density. The density of hair in a large plug graft is 100%. The density of hair in the scalp surrounding the large plug graft is 0%. The eye of the observer easily discriminates 100% from 0% hair density and identifies the pluggy look. Islands of 100% hair density in a field of 0% hair density is esthetically unpleasing; the appearance is that of a contrived effort to overcome baldness. Baldness may even be esthetically superior to a scalp that resembles a cornfield as viewed from above.

While the human eye easily notes the difference between 100% and 0% hair density, it does not easily discriminate between 100% and 50% hair density. If scalp areas surrounding islands of 100% density can be transplanted to achieve an average 50% hair density, the areas of 100% density disappear to the observer’s eye and hair density is perceived as “natural.”

Hair Density and Correction of Plugginess
Surgical revision of the pluggy look to natural can be accomplished by removing plug grafts, cutting plugs into smaller grafts, and using the smaller grafts to fill space between the plug graft sites to increase overall hair density to 50% and eliminating areas of 0% density. Alternatively, without plug removal, only fill-in grafting between plug grafts can be accomplished with single follicular unit grafts.
Use of small grafts to fill in between large grafts has proven to be the simplest and most effective technique for revising plugginess and achieving the natural appearance desired by the patient. Large-graft removal is carried out only when fill-in grafting is not indicated:

1. When the plugs are located very low on the hairline, and fill-in grafting would contribute to placement of the hairline too low on the forehead, or
2. when the patient does not have enough donor hair to achieve 50% density between large grafts—for example, when the patient has 20 to 30 large plugs at the center of the vertex, no hair in surrounding areas, and limited donor hair.
Surgical Technique for Large-Graft Removal
Surgical removal of large plug grafts presents a significant risk for transecting follicles in the process of graft removal. As noted earlier, large plug graft removal is avoided if possible.

If large-graft removal is indicated, a manual punch is generally superior to a power punch because it gives the surgeon more control during the removal procedure. The punch incision is not sutured after graft removal. Rather, the punch incision is closed 1) with scar tissue removed from the donor area from the previous punch graft surgery, or 2) with bald tissue punched from the recipient site. Replacement of tissue at the site of plug graft removal ensures faster healing and no scarring.
Surgical Technique for Fill-in Transplantation
The single follicular unit is preferred for fill-in grafting to revise plugginess to natural. Use of larger fill-in grafts is made difficult by scar tissue around the large plug graft that increases risk for pop-up of larger fill-in grafts. Smaller grafts also can be implanted close together to achieve the goal of average 50% density between the 100% density plugs.

A strip is harvested from hair-bearing donor skin that includes old punch graft scars. The old donor punch scar area can be reduced in the process of harvesting the donor strip. Thus, plugginess correction provides an opportunity to revise the old punch scar area at donor site.

A highly scarred donor area may present some minor problems in association with removal of the donor strip:

1. The presence of scar tissue increases risk for transection of hair follicles, and
2. the presence of scar tissue may make it difficult to predict how much donor tissue should be harvested.

Fill-in transplantation to revise plugginess is usually planned for two sessions over a period of three to four months. The second session is required to complete fill-in transplantation 1) after the growth of grafts implanted at the first session has been confirmed, and 2) to deliver the goal of 50% hair density.

Single follicular unit grafts are inserted into slits created with an 18g needle. Higher density of fill-in transplantation is required as indicated by pre-transplant planning. For example:

• Density of 60% or more may be needed to achieve naturalness in a patient with sharp contrast between black hair and a light scalp skin tone.

• The hairline always requires special attention in pre-transplant planning. The hairline is often the most important site for fill-in grafting to revise plugginess. When fill-in grafting at the hairline is indicated, it is prudent to carry the fill-in grafts to at least a 1 inch width from the hairline; fill-in grafting that is too shallow is inadequate and allows plugginess to still be visible.

Case Presentations:
Photos 1-4 illustrate successful treatment of plugginess in a 28-year-old man whose hair transplantation was done outside the United States.

Photo 1: A frontal view demonstrates the degree of plugginess resulting from this 28-year-old man’s hair transplantation.


Photo 2: Close-up of the punch grafts.


Photo 3: A frontal view of the patient after two surgical sessions. Conversion of plugginess to natural was accomplished using fill-in grafting with single follicular units. Plugs were not removed.


Photo 4: A head-tilt view after two surgical sessions. 50% density of hair between plugs was accomplished.


Invention of Needle Guard

Needle Guard  (US Patent: 5,779,682)  is a device that prevents accidental needle sticks. It is a protective plate that has multiple slits at its center. The slits allow the needle cap to position through the needle guard. When a misaligned needle tip misses the cap and heads towards the user’s hand, the Needle Guard shields the user’s fingers and protects from possible sticking injury.

Dr. Steven Chang invented it to ensure the safety of our patients and our staff.


patent1 patent2


Needle Guard can be used on any size syringe.
Insert needle cap through the slits on the center of Needle Guard.
Place the Needle Guard up against the lip of the needle cap opening.
The Needle Guard will shield users’ hands and fingers, and protect users from sticking injury.
needleguard5 needleguard6

Identical Twin Study

The following is a study between two identical twin brothers, each using a different method to combat their thinning hair.

The Story of Tim and Pat


Being identical twins, the first thing people notice about them is their physical similarities. Even their friends had trouble telling them apart.


Also, their physiological similarities are remarkable.


From their childhood to their adult years, Tim and Pat shared several experiences with each other. They even shared the same male pattern baldness. But to cure their baldness, they both took different approaches. While Pat decided to take Propecia to help his problem, Tim decided to have a hair transplant session with Dr. Chang. After one year, there was a drastic difference between Tim and Pat. Now, their friends won’t have too much trouble telling them apart.

Can you tell which one had the hair transplant?
As you can tell from this twin’s comparison study, hair transplatation works much better than Propecia. You can see the dramatic changes with your own eyes.