subject: Graft Preparation With Hair Transplants [print this page] Graft Preparation With Hair Transplants Graft Preparation With Hair Transplants
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 insures 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. Arguing what is natural and what is not natural in appearance is a completely different subject, but will be summarized as follows. Hairs grow in natural follicular clusters called follicular units. Hairs do not grow in mini-grafts, full size grafts, or micro grafts in nature. Therefore, these unnatural entities will not be discussed in this talk.For the purpose of this talk we must consider three densities. The first is the hair density and is the number of hairs in a given surface area. The second is the follicular density and is the number of follicular units in a given surface area. The third is the calculated density and equals the dividend of the total number of hairs in a given surface area divided by the number of follicular units in the same surface area. The calculated density projects the number of hairs you should expect from each follicular unit and consequently impacts the size of the average graft.When donor tissue is excised it contracts. The reduction in surface area results in a higher hair density and higher follicular density. The higher densities increase the technical difficulty in graft dissection. They also artificially increase the density of any graft larger than a natural follicular unit. This phenomenon is the primary reason that any graft larger than a natural follicular unit detracts from a natural appearance.There are two primary methods of donor extraction. The first is the multiple strip harvest with a multi-blade scalpel. The second is an ellipse with a one or two bladed scalpel. The multiple blade scalpel has a very high trans-section rate and thus, deters from one of our objectives - maximal yield. Therefore, it will not be discussed further. The ellipse reduces the risk of trans-section so we must consider the single blade and the double blade scalpel. The two bladed scalpel results in a trans-section rate between 2 and 5 % of all hairs. The mean rate is approximately 2% on "careful" two bladed strips in on going studies. The trans-section rate with a single blade scalpel is generally< 2% of all hairs. Since the trans-section rate of the single blade and the "carefully guided" double blade scalpel are reasonably close in most patients, you may choose either as a means of graft dissection. The trans-section rate on the second blade of the two bladed scalpel set at 1 cm total width averages 1.75 times as many transected hairs as the first blade of this scalpel due to the curvature of the skull.
After the strip is excised it is a flimsy ellipse or rectangle of tissue. Because the densities are increased and the strip is unstable, methods of graft dissection to minimize these negative variables were devised. Without these advancements the ellipse would have even more risk of trans-section than the muti-bladed scalpel. The first advancement was single follicular unit wide slivering, which was introduced by Limmer. This advancement is perhaps more important than his recommendations on microscopic dissection. The second advancement was the cutting board by Dr. Blugerman. This improvement sealed the technique proposed by Limmer as potentially the most efficient means of harvesting natural follicular units from the donor region.The cutting board principal allows the surgeon to fix one end of the flimsy strip to a silicone plug. The other end is held in place by a fine forceps with teeth. I use a small Castroviejo Forceps. The forceps allows the surgeon to apply traction to the loose end, which improves manipulation of the strip and helps to decrease density through opposing forces. These aids help the careful surgeon to decrease trans-section, improve visibility, increase speed, and improve control.The slivers are cut much like slices of bread. The slivers must be no more that one follicular unit wide to take maximal advantage of this technique. Anything wider than one follicular unit decreases visibility, decreases control, reduces transparency, and increases the risk of trans-section. With the sliver the follicular units are lined up like soldiers in formation. It is easy to understand the anatomy and separate the individual units from one another. There are certain pearls to consider in the production of slivers. First, the production of slivers is more difficult with curly hair, white hair, and patients with high follicular densities. Curly haired individuals frequently have a preponderance follicular units consisting of three terminal hairs. With curly haired individuals a single hair of the follicular unit has a tendency to invade the space of neighboring follicular units. This "cross over" increases the probability of inadvertent trans-section with graft production. White hairs are difficult to see, even with standard power on the dissecting microscope. Therefore, I recommend you try increasing the power on your scope to improve visibility. On my MEJI EMT I increase the microscope stage to 2X. On individuals with high follicular density (greater than 80 per square cm), the follicular units are much closer together so additional care must be exercised in the production of slivers. The risk of trans-section is reduced if the majority of advancement in slivering is done in the dermal and adipose portion of the sliver. If the epidermal cuts are predominantly directional as opposed to advancing, the risk of trans-section is minimized. Transparency and visibility is improved if the slivers are cut as close as possible to one side of the follicular unit. This minimized the depth of tissue on at least one side of the follicular unit.
Graft dissection begins with removal of the donor strip. The importance of this statement cannot be over emphasized. Removal of the strip should act to reduce the amount of adipose on the excised strip. Minimizing adipose helps to speed the rate of graft production from your assistants by decreasing steps in the cutting phase. This step takes longer to remove the strip, but decreases graft production time on every graft. Because the strip excision is prolonged, you should consider wrapping the strip in moist gauze to prevent desiccation of the strip. Alternatively, you may section the strip at regular intervals and immediately place the sections in a moist environment. Sectioning caries inherent risks of trans-section because control, hemorrhagic exudates, and visibility are not as great as on the slivering board, under the microscope and following cleansing. One must be careful to avoid damage to the matrix and papilla with strip excision and careful to avoid damage to the lateral margins of the strip with strip excision. You might consider leaving partially transected hairs in the donor region by trimming them off the lateral margins at the time of strip removal. The probability that these transected hairs will be discarded as waste if removed is significant. While there is no study to confirm that transected hairs have a higher probability of survival if they are united in close proximity with their other half, it makes sense that they would have a greater probability of survival than when they are separated from their other half of the hair follicle, much the same as approximating a fractured tibia.
Following slivering, the thin slivers should be placed in chilled or room temperature saline. Provided the procedure is completed within 5 hours from donor strip removal, there is no improvement in hair survival. The slivers are placed on a cutting board. I created a version of the Blugerman cutting board, which is firm, transparent, and allows for the silicone plug. This surface is ideal for the production of both slivers and grafts.There are two light principals to consider in the production of grafts. The first is reflected color. The second is transparency. Top lighting takes advantage of the principal of reflected color corresponding to the specific wavelength of the corresponding hair color. Unfortunately, the hair must have a color other than white, and the transparency of the tissue must allow for the reflection of the specific wave length. White hair reflects all colors and therefore is not possible to see them with reflective top lighting. One must depend on the visibility of the structure itself, which is only possible when enough surrounding dermis and adipose are removed to reveal the shaft. The principal of reflective light does not reveal the presence of deep pigmented hairs within the same follicular unit if the surrounding stroma is thick enough to reflect most of the light. Only the hairs close to the surface of the stroma may be seen with reflective top lighting. Careful dissection around the follicular unit will often reveal the presence of additional hairs within the same follicular unit. The principal of transparency is best seen with back lighting alone. In this case the more dense the structure, the less light will be penetrate to the other side. The thin nature of the sliver easily allows light to penetrate to the opposite side with back lighting. Pigmented hairs allow less light to penetrate and result in a shadow on the opposing side of the tissue. This principal allows the dissector to see hairs more clearly in the three dimensional structure of the sliver even when the amount of pigment is decreased. The clear cutting board I developed allows for the placement of a fiberoptic back light or a light or alternative source of back lighting. The One can create a degree of back lighting by placing aluminum foil on the bottom of the cutting board. The top light is refracted on penetration of the cutting board and is reflected back through the tissue by the aluminum foil. This method provides some back lighting, but impairs the "shadow" affect because of the top light. Any of these technique, however, allow for improved visibility, greater speed, and a reduced probability of damage.Speed is paramount to the graft production phase. One means of increasing speed is through the rapid movement of tissue from one point to another. The use of a special pad, " " allows for rapid movement. The moist pad is placed adjacent to the cutting surface. Immediately upon cutting a sliver, it is placed on the moist pad. When several slivers are cut they are moved collectively to a chilled, moist environment in a petri dish. The covalent bonds on the moist pad allow the slivers to adhere to the surface of the pad. Two fluids are acceptable for the petri dish. One is normal saline and the other is Ringers Lactate. When you are ready to dissect the slivers, several are moved collectively to the well on the cutting board, which is filled with normal saline or Ringers Lactate. One sliver at a time is dissected into individual grafts. Again a moist pad is placed immediately next to the cutting surface. Short movements of the cut graft to the moist pad improve dissection speed. Once about 50 grafts are cut, they are moved to the chilled petri dish containing normal saline or Ringers Lactate. Enough fluid should be in each petri dish to keep the grafts moist without allowing them to float or remain submerged for prolonged periods of time. Again covalent bonds allow for the rapid movement of tissue from the cutting surface to the petri dish. This same rapid movement occurs from the petri dish to the non-dominant hand of the graft placer.The same principals are used with the kinky hair of the Negro patient. The strip is cut into slivers. The slivers are dissected into grafts. The kinky nature of the hair requires that the graft dissection follow the curvature of the hair to minimize trans-section of the hair follicles.
