The basic unit of hair restoration surgery is the pilosebaceous unit. Dr. Jung Chul Kim called this pilosebaceous unit a "bundle graft" long before it acquired its present name, the follicular unit, by hair restoration surgeons. The objective of graft dissection is to remove intact follicular units from an excised strip or strips of donor tissue in a manner that ensures the highest probability of survival. One may go further to state that the objective should assist in the overall cosmesis and natural appearance of the hair transplant.
By John P. Cole, MD and Arthur Tykocinski, MD
The first part of this section is written by John P. Cole, MD. This section detail how we produce grafts at Cole's Clinic. The second part is written by Arthur Tykocinski, MD and discusses graft preparation in general.
The pilosebaceous unit termed a “bundle graft” by Dr. Jung Chul Kim but now called the follicular unit, is the most basic part of hair transplants and restoration surgeries. Follicular units are obtained through the means of graft dissections, which extract strips of the units from hair donors. The two main objectives of graft dissections are to ensure a high survival rate of the follicular units and producing the most natural-looking results. Since hair does not grow naturally in any size of grafts, there are three densities that need to be taken into consideration when performing graft dissections:
Hair Density- Hair density pertains to the number of individual hairs growing in a specified area of the scalp.
Follicular Density - To find the follicular density of an individual, the number of follicular units found in specific parts of the scalp needs to be counted.
Calculated Density - Perhaps the most important density to consider, the calculated density is determined by dividing the hair density with the follicular density of an individual. The calculated density is a close estimate of the number of hair strands that will grow from a singular follicular unit. It is also the calculated density, which determines the size of hair graft that a particular hair transplant patient will need.
There is a particular natural occurrence that complicates the procedure of graft dissections. When a graft is greater in size than the natural follicular unit, there is a tendency for the implanted graft to take on an unnatural appearance. This phenomenon occurs due to the contraction of donor tissue the moment it is extracted. When the tissue contracts, it gives the illusion of increased hair and follicular density, which in turn results in more technical difficulties for the actual graft dissection.
Two main methods are employed for the donor extraction process, namely multiple harvesting of strips through the use of a multi-blade scalpel and ellipse harvesting via a single or double-bladed scalpel. Since the multiple strip harvest does not produce the maximum yield due to the trans-section rate of the multiple blade scalpel, the ellipses are the most recommended method by doctors. The choice then falls to the use of a single or double blade scalpel. With studies continually being conducted on the trans-section results of the two blades, results have shown that single blade scalpels normally have a less than or equal to 2% trans-section rate. The average trans-section rates for double-bladed scalpels are at 2%. The difference with this scalpel is that the second blade, which is 1 centimeter apart from the first blade, has a mean of 1.75 times higher of a trans-section rate than the first blade. The higher rate in the second blade is caused by the natural curve of the skull. In a majority of the patients, the rates of trans-section between the two kinds of scalpels are relatively even, thus making either a very viable option.
As mentioned earlier, when strips of hair follicles are taken from the donors, the graft is essentially a very fragile piece of tissue with a tendency for the densities to go up. Two advancements, which without would make ellipses even riskier than multi-bladed trans-sections, were created to help decrease the chances of negative results:
Considered an improvement on Limmer’s technique, the cutting board technique was introduced by Dr. Blugerman and has been recognized as the method of efficient follicle harvesting with the most potential. For the cutting board method, the weak graft is affixed to a silicone plug on one end while forceps secures the other. With traction provided by the forceps, the surgeon gains more control and manipulation over the graft and also helps to lower trans-section. The speed, visibility, and control over the graft also get much better.
Grafts must be taken from the donor with precision and in a very particular way. As a rule of thumb, the slivers of the graft must, under no circumstance, be larger or wider than a single follicular unit. Surgeons risk low visibility, transparency, and control if the slivers if the grafts are any larger than a single follicular unit. The slivers actually help to keep the follicular units in lines, however, when producing these slivers there are a few other things to consider when working with different kinds of hair. Production becomes more difficult when working with the following hair types:
The first step, the removal of the donor strip, is arguably the most important part of graft dissections. It is during this step that an extreme amount of care must be used to ensure that the adipose on the donor strip is minimized. The smaller the amount of adipose on the strip, the faster it is to produce grafts. The steps needed in the cutting phase are also lowered. To keep the strip healthy and to ensure that desiccation does not take place, one of the side effects of long excision, the strip should be encased in moist gauze. Another way to combat against desiccation is to section the strips at set times. These sections should be immediately put in moist casings.
Sectioning, though, is not without its set of risks. Trans-section is a major risk when sectioning methods are employed because there is a decreased level of visibility, control as well as hemorrhagic exudates. Particular things to look out for and be careful of during sectioning are causing damage to the papilla and matrix of the strip as well as the lateral margins. When removing the strip, it is a good idea to leave the hairs that may have been incompletely transected by simply giving them a light trim. The slivers of follicular units must be kept in saline as soon as the slivering is completed. The saline can be either room temperature or chilled. Transparent and firm cutting boards that allow silicone plugs provide the best platform for sliver and graft production.
When producing grafts, there are two principals pertaining to light that must be taken into consideration:
In the process of producing hair grafts, speed is of absolute importance. Moving the sliver quickly in-between steps is one method of decreasing total time. Special pads, such as moist pads, also help to speed up the procedures. For instance, surgeons should have a moist pad close to the cutting board. The moment the tissue is cut, it should be settled on the moist pad so that when all of the slivers are cut they can be immediately transferred to a petri dish in a cold environment. Because there are covalent bonds present in moist pads, the tissue sticks to it. Regular saline and Ringers Lactate are viable options for the petri dish.
Moist pads also help increase the speed at which dissections are performed. Several grafts can be cut in quick succession with moist pads and with every fifty grafts successfully dissected, they are moved into the petri dish with the chosen fluid. Whether saline or lactate is used, there should be enough in the petri dish so that the grafts remain moist but not enough so that the tissue floats.
Graft dissection for curly or kinky hair taken from African American donors is also done with the same procedures and with the same principals in mind. The only difference of the graft dissections in these cases is that the dissection needs to follow the way the hair curves so that the risk of transected hair is decreased.
Single donor strip (single blade harvesting) - Nowadays the "ellipse" is considered the best method of donor harvesting due to the quality of the donor strip. Doing single blade harvesting you can better control the blade angle during the scalp incision and make it parallel to the hair shaft, thus avoiding hair trans-section.
single blade harvesting - Nowadays the "ellipse" is considered the best method of donor harvesting due to the quality of the donor strip. Doing single blade harvesting you can better control the blade angle during the scalp incision and make it parallel to the hair shaft, thus avoiding hair trans-section.
Multiple strips (multiblade harvesting) - Used to be very popular, but due to the high incidence of hair trans-section during the donor harvesting, it uses tend to be discontinued. But on the other hand, it is easier to produce grafts for beginners or if using automation. Because you can choose the strip width in a variation of millimeters when you are producing "cut to size" grafts you can easily meet the strip width with the desired graft size.
Anatomy of the hair follicle - Since 1984, Headington described the hair follicular units. The concept is: the hairs naturally occur in groups containing 1, 2, 3 or 4 hair per group. Each hair of the group contains it own dermal papilla (that produces the hair itself) and other structures. There is a fine capsule involving this group and sometimes they share the same sebaceous gland. This structure was a denominated follicular unit (FU). Each follicular unit is 1 to 1.5mm apart. The hairs in the follicular unit are very close in the surface but usually spreads out into the fat tissue, as reported by John Cole. Sometimes you have two follicular units very close together what could be called follicular grouping.
Hair cycle - Consist of three phases: anagen, catagen, and telogen. The anagen phase lasts for 3 to 5 years and is responsible for hair growth. More than 90% of the hair is in the anagen phase and during the graft preparation is basically what you see. The catagen phase is too short and less important. It lasts just 2 weeks and basically is preparing for the telogen phase. During it the hair bulb gets from the deep to more superficial. The telogen phase is a not growing phase. The hair is more superficial and thus less evident during graft preparation. Lasts till 3 months and basically is a "retention phase" of an inactive hair before it falls out. Due to its superficial root, it is sometimes inadvertently left during graft preparation and can compromise the aesthetic, especially when you are planning just "one hair graft" in the frontal hairline.
Good quality donor strip - To produce good quality grafts, you need a good quality donor strip too. It is very important to leave in the donor strip sufficient amount of fat tissue beneath the follicles to protect the dermal papilla. Even that some papers evidence that the hair shaft can regenerate from the bulge (a structure of the hair follicle close to piloerection muscle), it is important to assure the maximum viability to the hair regrow. After removing the donor strip, is important to examine the sidewalls of the donor strip seeking hair trans-section. It is important to avoid hair trans-section because it decreases the number of viable grafts.
Standard grafts: N. Orentreich published the first paper about hair restoration in 1959. He used a 5mm punch to remove the hair from the donor area and also to create the recipient site. He is a legend, and until today some surgeons use big grafts eventually some in the central area. But they are too big to use exclusively because it could create the "Barbie doll look."
2º - Mini grafts: After a while, surgeons started to decrease the graft size, either dividing the standard grafts in a quarter or using a smaller punch. The 2mm punch became very popular. When they start to remove the "ellipse" in the donor area, surgeons experimented to use thin rectangular grafts placed this time in small slit incisions. Then started the controversy: slit X punch.
3º - Micro grafts: With the advance of the micro grafts, finally an adequate cosmetic result could be achieved. The basic concept was to place one or two hair grafts (at that time they didn't know it was a follicular unit) in the frontal hairline as a refinement (micrografts) and immediately followed by mini grafts. This technique is used today and is called "Mini-micro grafting". Nevertheless, it still depends on the hair color and texture in contrast with the skin. For example, fine blond or gray hair, excellent results, in contrast to thick dark hair on fair skin giving a poor cosmetic result. This limitation happened because the follicular units used as a refinement could have 1, 2, or 3 hairs and are randomly used. As we naturally have just one hair per follicular unit in the hairline, when a coarse dark hair is used, a follicular unit containing 3 or 4 hairs would be too evident and look artificial.
4º - Follicular units: With the advance of the backlight and the stereomicroscope (3-D vision), visualize, dissect and classify the follicular units could be possible. Then, to control the desirable density, hairline pattern, and hair direction is not just a matter of technique but also a question of art.
Forceps: Fine tip is recommended. It could be serrated, with diamond dust or smooth. Also straight, angled, or curved. But it is a question of preference. You have to experiment with many to pick up your best.
Magnification: It is extremely important. You can choose a variety of loupes from 1.5x to 3.3x, but good quality glass lenses are recommended. If you are planning to do micrografts or follicular units, we strongly recommend you to use a 3-D microscope like the Meiji or Mantis. The last one is more friendly for beginners and more expensive, but they are equally good. We use a 10x magnification Meiji microscope with a strong light source and a backlight.
Cutting surface: Tongue blade soaked in a saline solution used to be very popular, but with the advent of the backlight, more and more surgeons had changed to it. The main advantage of the backlight is to visualize the follicular structures by transparence. If using it, the cutting surface should be transparent too, otherwise, it will block the light. A sterile scratched plastic surface is a good idea. We use the Grecco non-slick dissecting surface.
Standard (4-5mm punch): They used to be removed from the donor area with the same punch used for the recipient area. These big round grafts are ready to use. You just have to remove the excess fat tissue from the bottom of the graft and place them. They contain from 8 to 12 FU per graft.
Mini-grafts (1.5-3mm punch): They used to be created dividing the "standard" grafts in quarters or removing directly from the donor area. Nowadays, they are created by dividing the donor strip into small pieces. So, they are no longer round but "square" grafts placed in round holes. They contain from 2 to 5 FU per graft. The size of the graft should be "just perfect". Not bigger neither smaller than the recipient hole.
Mini-grafts: regular blades (#11 or #15) - Very similar to the punch mini grafts, except that instead of "square" they are "rectangular". The width of the graft is enough not to be so tight in the slit. The length of the graft is according to the length of the recipient slit. Usually, the desired length is chosen when you remove the donor strip with the multiblade knife. You can choose from 2 to 4 mm.
Small mini-grafts: mini-blades (Beaver, Beaver-like blades, Mindi): You can choose smaller spacers in the multi-blade knife-like 1 or 1.5 mm to produce smaller mini grafts when using "beaver-like" blades. Then you take one of the strips, clean it removing the excessive fat tissue (but leaving enough to protect the follicular papilla) and using a blade (persona plus prep blade or surgical "Gillette-like" blade, scalpel #10, #15 or #11) to separate them in fine slices, following the hair direction and cutting in between the follicular units. You can cut then as you use a knife to cut beef or cut them vertically in one single movement as a "guillotine-cutter". Again, the size of the graft should fit the size of the slit in the recipient area.
Micro grafts: micro-blades (Sharpoint, Spearpoint, Mindi, No-Kor needles) or needles (18G, 19G or solid needles) - You can create micro grafts by cutting in-between the follicular units, under microscope or loupes. Using a backlight the task will be much easier. There are two differences between micrografts and follicular unit grafts: first, the micrografts are used randomly in the frontal hairline as a refinement of hair transplant, which means you can either use a follicular unit containing 1, 2 or 3 hairs. Secondly, the micrografts don't need to be excessively cleaned, because the micro blades are usually thicker and slightly bigger. You can also produce micro grafts using automation, like the Mangubat cutter. In such a device you place the fine 1mm width strip under a series of blades. Arrange the hairs parallel to the blades and make a fast pressure, cutting it almost at once. It is expected to have a higher incidence of trans-section, but it doesn't mean the hair will not grow. This question is still controversial.
"Slivering" the donor strip under a 3-D microscope - In my opinion, it is virtually impossible to cut "slivers" without a 3-D microscope. But what is to cut "slivers"? When you take the donor strip it will be something from 15,00cm x 1,00 cm to 27,00 x 1,30 cm. So, it is too thick and solid to be seen by transparency under the backlight. Thus, you need first to cut fine slivers of this strip, making possible to see the follicular units by transparency under the backlight. However, if you try to cut the follicular units without doing first the slivering, as a result, you will dramatically increase the follicular trans-section and consequently spoil many FU. By doing the slivering first, many surgeons, including me, experimented a 30% increase in the total number of follicular units produced with the same size donor strip. And how to do it? You need a good teaching videotape, like the excellent videos from Dr. Seager and Dr. Parsley. The main concept is to dissect fine "one follicular unit" width slice at a time. To do this you will need a 10x magnification stereo (3-D) microscope and a strong light source. Using a surgical "Gillette-like" blade in a plastic holder you have to cut the slices dissecting in between the follicular units. Holding the blade in one hand and using the fingers of the same hand to stabilize the strip, grab the tip of the strip with the other hand using a forceps. Close to the forceps start an in-and-out movement turning around the follicular structures. As you continue to cut, grab out the slice to increase the view. Cut the slivers by the side of the donor strip with the strip laying down by the side in the cutting surface. Start cutting the epidermis and use the forceps to grab the epidermis also. Doing that way you will not traumatize the graft. Once the slice is cut, place it in an appropriate container and start another sliver. Look carefully if you are cutting the slivers parallel to the hair shafts and avoiding hair trans-section.
Dissecting the follicular units - For this task, a backlight is strongly recommended. You can use either loupes or microscope, but a good quality stereoscopic microscope is of great value. You will need the "slivers" from the donor strip to create "follicular unit grafts". The higher quality the slivers are, the easier will be to separate the follicular units (FU), and more grafts you will be able to produce per sliver. A good quality sliver means an "intact" one FU wide sliver. A thin sliver like this will be easier to see over the backlight surface and consequently easier to identify the follicular structures, avoiding damage, trauma, and trans-section. Usually, a 1.3 cm x 1 FU sliver contains from 8 to 14 FU, average 10-11. First, arrange the sliver keeping the hairs as more parallel is possible. Then, cut in between the FU. After the FU is separated, you have to "clean" them, removing the excess tissue. The graft will be inserted in a very small aperture in the recipient site and if you leave it to big you can get graft compression and consequently decreasing blood supply and graft surviving. You should also avoid leaving the graft too skinny because doing this you can decrease the graft surviving capability. For this reason, you should leave the graft "chubby", it means, removing the maximum epidermis as possible in the top and leaving a sufficient amount of fat tissue around the papilla, at the bottom. The graft will look like a "drop". While cutting the FU you have to classify them in groups of 1, 2, 3, or 4 hairs per follicular units. It will be important later when you are placing them.
For a long time, we did not realize that hair follicles grew as units rather than single strands. From a distance, hair follicles may appear to grow as singular strands, but actually, most individuals have follicular units with multiple hair follicles. Understanding the anatomy of the individual groups is essential to the safe dissection of the grafts with minimal damage or trauma to the hairs, as well as, the assurance of the production of natural three hair follicular groups. Natural follicular groups consisting of three or more hairs assist with the grafting and coverage of the top of the scalp and internal frontal areas.
Now, we will discuss the three different types of natural three hair follicular groups. Type one consists of three hairs lined up in a row. Type two contains two hairs exiting the same follicular canal, with one hair exiting laterally to this in a separate follicular canal, and type three consists of three hairs exiting from the same follicular canal. Dr. Cole named the third type a T-pee formation because it resembles an Indian's T-pee. These three types were discovered and named by John P. Cole, MD in 1998.
Follicular units not only contain these three hair follicular groups, but they also consist of nerves, blood vessels, and the erector pilorum muscle, all of which are surrounded by collagen. Removing the unit intact is essential to performing a successful hair transplant. Using follicular units allows for a more natural-looking hair transplant. While the grafts must be placed in the proper path and dispersed accurately, this technique alone helps avoid the pluggy look.
A key benefit of using follicular units is that they keep the recipient sites as minute as possible and allow hair restoration surgeons to maximize the number of grafts transplanted per session. When using follicular units in hair restoration, the larger units are commonly used to cover the top of the head to add fullness, whereas, the smaller follicular units are used to create a natural hairline and temples.
Basic concepts of graft care - Basically two things can spoil the grafts: Trauma and dehydration. To avoid trauma, always grab the graft gently by the epidermis or superficial dermis, and avoid touching the dermal papilla or the bulge. You can also hold the graft by the fat tissue, but safely under the papilla. Many times you can find some connective tissue in the fat. Holding there will make it stronger than just fat and won't unbind. Dehydration is even worse because with trauma the graft can grow dystrophic but with graft dehydration, it will not grow. To avoid dehydration it is important to keep the grafts under saline solution or ringer lactate. Nowadays is very popular and useful to keep the grafts around 4 Cº, placing the Petri dishes over ice packs or special containers. But frequently the ice surface is irregular, making the Petri dishes, not plane causing dehydration of part of the grafts. So we assured to put a sufficient amount of solutions. Another mistake is to keep the grafts under a fan or wind current that will dehydrate them. And finally, don't put too many grafts on your hand when placing them. Try to keep them a maximum of 3-4 minutes out of the saline solution. Try to keep them moist and remember, the smaller the grafts are, the more sensitive to dehydration they are too.
Graft keeping and organizing - You can keep them in Petri dishes or metal containers, with saline solution or ringer lactate. It is recommended to keep them refrigerated, around 4 Cº. This is easily obtained by just keeping the graft container over an ice pack or an apparatus that you can fill with water and put it in the freezer. After the water turns to ice, place the petri dish over it. You can find also some expensive electric devices that keep them also refrigerated. To organize the grafts, we usually separate them in groups of follicular units containing 1, 2, 3, or 4 hairs. This is very important because you avoid placing a 2 or 3 hair graft in the frontal hairline. Other surgeons that use mini grafts can divide them into groups of regular mini grafts and small mini grafts, leaving the micro grafts for the frontal hairline.