by Dr Pedro Madureira MD MTTS
Balding is a major concern for many, and hair transplantation is the most common cosmetic surgery procedure performed on men today.
Hair transplantation is a surgical technique that removes hair follicles from one part of the body, called the ‘donor site’, to a bald or balding part of the body known as the ‘recipient site’. The technique is primarily used to treat male pattern baldness. In this minimally invasive procedure, grafts containing hair follicles that are genetically resistant to balding are transplanted to the bald scalp.
Since hair naturally grows in groupings of 1 to 4 hairs, current techniques harvest and transplant hair “follicular units” in their natural groupings. Thus, modern hair transplantation can achieve a natural appearance by mimicking original hair orientation. This hair transplant procedure is called follicular unit transplantation (FUT). Donor hair can be harvested in two different ways: strip harvesting, and follicular unit extraction (FUE).
FUE hair-transplant surgery is a relatively new field in hair-restoration surgery. This procedure offers a different approach to harvesting and has gained popularity in the last few years among hair-transplant patients and surgeons. Despite this popularity, there has not been much scientific research to compare different techniques that are used for this procedure.
The follicular unit – basic concepts
The follicular unit (FU) of the adult human scalp usually consists of two to four terminal follicles and one or rarely two vellus follicles, the associated sebaceous lobules, and the insertions of the arrector pili muscles of the terminal follicles. At superficial dermal levels, follicular canals may or may not join each other, although it is common to find two or three hair shafts within a single canal at the level of the infundibulum. The vellus follicle of the follicular units may remain separate or may be joined to the confluent infundibula of the terminal follicles.
Figure 1 -Follicular unit
A follicular group or follicular bundle is defined as a cluster of hair in the scalp that exit the skin near to each other and are separated by a gap from other clusters of hair. The follicular group may consist of more than one FU in a tightly packed distribution on the surface of the skin. In complex donor areas consisting of multiple large bundles or closely aligned bundles, the number of separate bundles obscures individual interpretation and leads to variable individual assessment.
Connective-Tissue Sheath (CTS) is the structure surrounds the intact follicle, consists of elastic filaments, and provides vital structural support for the intact harvested follicular unit. The CTS is also a major source of Type I collagen in the human scalp and skin. Harvested follicular units ideally should have the CTS intact to increase graft survivability.
Outer Root Sheath (ORS) encloses the inner root sheath and hair shaft. It is continuous with the basal layer of the interfollicular epidermis. In wound healing, the interfollicular epidermis can be regenerated from the ORS. Skeletonized harvested follicles increase the likelihood of ORS injury or fracture.
Inner Root Sheath (IRS) is an important structure of the inferior portion of the hair follicle that protects and surrounds the growing hair follicle. The IRS is made up of three separate layers (from outside in): Henle’s layer, Huxley’s layer, and a single layer of cells called the cuticle.
Dermal Papilla (DP) is in the centre and the most inferior portion of the follicle. DP cells are specialized mesenchyme cells. These cells play a vital role in the formation, growth, and hair cycling.
As with any surgical procedure but particularly in the aesthetic medical field, it is critical to evaluate a patient’s goals and expectations and plan accordingly. Establishing realistic expectations is of paramount importance. In order to provide a successful cosmetic result that will look appropriate and acceptable over the entire lifespan of the patient, one must consider the degree of hair loss (present and predicted for the future), donor-area capacity, and the expected number of hair follicles that ultimately will need to be implanted.
There are several medical concerns and conditions that could limit a patient’s candidacy for hair transplant, and these apply both to FUE and linear strip extraction procedures (FUT). It should always be pondered whether an underlying inflammatory condition or scarring alopecia is responsible for the patient’s hair loss. A thorough medical history should be undertaken with each patient, and this workup should include limited physical examination, appropriate laboratory evaluation, and scalp biopsy if indicated.
Before concluding that a patient is a good candidate for FUE hair transplant based on evaluation of the donor area, it is of utmost importance to establish how many follicles will be required to meet the patient’s aesthetic goals.
Figure 2 – Patient for FUE hair transplant (2022) who had a prior FUT hair transplant (2005)
Hair loss is a progressive condition, and despite medication to stabilize it, proper planning that considers lifetime recipient-area requirements should be considered and should be based on the likelihood of ongoing loss. Overtransplanting the anterior and/or vertex scalp in a younger patient and depleting the donor area may result in a paradoxical and unfortunate mismatch, in which the donor area appears overly sparse. This should be anticipated and avoided.
Patients choosing FUE often believe that it is “scarless” surgery. This misconception should be addressed, while FUE does not result in a linear scar as seen in typical FUT excision, multiple pinpoint scars, sometimes referred to as hypopigmentation, appear as tiny pale, atrophic macules.
It is of the utmost importance to minimize scarring in FUE, and this can best be accomplished in two ways: by using the smallest-diameter punch suitable for each patient (generally 0.8-1.0 mm punch) and by avoiding overharvesting of grafts. The physician can limit the risk of inadvertently creating a fine linear scar when FUE donor harvesting by avoiding the harvesting of follicles that are too close together or avoiding removing follicles that are adjacent to each other. The appearance of a depleted, overly thin, and stippled donor area defeats the purpose of aesthetically acceptable hair-transplant surgery.
1 – Evaluating the donor area
Before surgery we must consider the availability and potential limitations of the donor hair that can be transplanted. In androgenetic alopecia (AGA), the safe donor area (SDA) refers to the area of the temporal, parietal, and occipital scalp that is considered to support “permanent” hair, suitable for transplantation.
The SDA differs for each individual and can be estimated to be centred around the occipital protuberance in the midline, arching upward and laterally in a crescentic manner to approximately 2 cm above the superior helix of the ear.
To estimate the projected future hair loss in a patient, microscopic examination to evaluate for extent of follicular miniaturization is helpful. Once the anticipated SDA is identified, it can be helpful to draw in the entire SDA while preparing the patient for hair transplantation.
There are several approaches to preparing the scalp for FUE, including shaving the entire donor area down to 1-1.5 mm or shaving small sections or “microstrips” with longer hair allowed to cover the shaved area.
Figure 3 – Surgical planning
2- Calculate the number of follicles available
To calculate the number of follicles available for hair transplantation, the surgeon must consider the resultant appearance of the donor area. There is no established protocol recommending a specific number of follicles that can maximally be obtained. However, a safe, cosmetically acceptable extraction ratio should not exceed one of every four follicles (25% extraction). An initial extraction harvest ratio of 1:6 (16.7%) or 1:8 (12.5%) intact follicles may be optimal.
Delineating the SDA with a skin marker should be followed by measuring the length and width, and then calculating the total area in square centimetres. Measuring the follicular density with a handheld densitometer should be performed at several areas in the donor zone, and the average density should then be calculated. Once the area and density of the SDA are measured, the total number of FUs present can be easily determined by multiplying the SDA (cm2) times the density.
To determine how many follicles can be obtained, divide the total number of FUs present by 6 for 16.7% extraction ratio; divide the total number of FUs present by 5 for a 20% extraction ratio; maximal harvestable follicles of 1 per 4 follicles can be determined by dividing total FUs by 4 (or 25% yield).
Later, the surgeon must project the number of follicles to be removed from each section or a quadrant of the donor area.
Injections in the scalp may be painful. To reduce pain with injections we should employ certain concepts and techniques:
1. The use of small needles for initial blocks, ideally 30G or smaller.
2. The needle passing through the skin slowly hurts more, thus inserting needles through the scalp rapidly reduces this sensation. We should avoid rapid injection rates during the initial ring block, as rapid distention of tissue is painful.
3. Intradermal injections to create tense turgor are painful and only should be administered when the area is completely anesthetized.
4. A needle passing through the skin causes more pain than it does passing within
the subcutaneous plane.
5. Minimize the number of scalp needle pokes by using longer needles and advancing the needle to its full length while injecting in the subcutaneous plane.
6. Vibration stimuli applied to the scalp in the form of a vibrator device or vigorously shaking the scalp during the injection reduces pain perception.
7. Buffering of lidocaine with sodium bicarbonate reduces the burning sensation caused by the low or acidic pH of lidocaine.
8. Use the lowest concentration of lidocaine (1% or less) possible for ring blocks.
9. Benzodiazepines as a premedication reduce anxiety and perception of pain.
Both ring blocks and tumescent anaesthetics are best injected as the needle is advanced. The spreading fluid creates a “wave” in front of the needle tip, which separates the skin and galea slightly and makes it easier to keep the needle in the proper plane. Because of its dilution, tumescent anaesthetic inadvertently injected into a vessel has little potential to cause side effects.
Figure 4 – Vibration stimuli applied to the scalp in the form of a vibrator during the injection reduces pain perception.
Sometimes is unavoidable to top-up local anaesthesia and to repeat donor and recipient ring blocks if the patient begins to feel pain. Bleeding is often the cause for anaesthesia begin to fade.
Lidocaine is the most common medical local anaesthetic agent. It is commonly supplied as a 1% or 2% solution with or without epinephrine. We could use it in two basic solutions:
- Ring-block solution: pH-buffered 0.8% lidocaine with 1:100,000 epinephrine prepared by adding 1 cc of 8.4% sodium bicarbonate, 0.1 cc of 1:1,000 epinephrine, and 5 cc of normal saline to 4 cc of 2% lidocaine.
- Tumescent solution: 0.1% lidocaine with 1:200,000 epinephrine prepared by adding 1.25 cc of 1:1,000 epinephrine and 12.5 cc of 2% lidocaine to 250 cc normal saline.
Follicular unit extraction (FUE) is a relatively new method for harvesting individual follicular units (FUs) from the donor region of the scalp. This technique is based on isolating and harvesting individual FUs from the donor area to use as grafts.
The method may be performed by a manual punch, a motorized punch device, or more recently by a robotic system. Follicular unit extraction has been gaining in popularity because it is considered a minimally invasive technique.
The follicles are considered as distinct organs with numerous organ functions not limited to follicular regeneration and wound and cellular repair. When extracted from the natural environment of the scalp, we deprive them of arterial blood supply, oxygen, glucose, and diverse nutrients. Donor harvesting may also damage follicles by transection if performed carelessly or with nominal skill sets and knowledge. Plucking hairs, dehydration of grafts, and trauma to the bulge region or any portion of the follicle may further impact hair regrowth after transplantation.
Graft can be damaged during the various stages of the procedure. It could occur at the:
A – insertion of the punch into the dermis
B – follicle extraction after scoring of the graft
C – time out-of-body while in liquid holding solutions and bioenhanced environments
D – during graft placement.
The perfect harvesting technique does not exist. It is often necessary for hair surgeons during donor harvesting to adapt to the difficulties or challenges that occur and not to hesitate to adapt their donor-harvesting methodology or technique.
Figure 5 – Extraction
The hair shafts within an FU are not always parallel to each other because of follicular splaying. If a smaller-sized punch is used and the physician operator does not limit the punch-penetration depth, follicular splaying potentially increases transection rates diminishing the quality of the extracted grafts.
A small punch causes less injury and a reduced wound size to the donor region of the scalp but can negatively affect the quality of the extraction decreasing ratio. Quite the opposite, a larger-sized circular punch may cause greater wound size, but the transection rate is lower, and a more successful harvest is appreciated.
Another factor that plays a role in the success of FUE donor harvesting is the use of punches with a thin wall because it reduces friction while scoring and dissecting tissue. A cutting edge allows for easier harvesting with sharp punches.
FUE pioneers have developed a consensus that punch sizes of 0.8 to 1 mm leave no noticeable difference in the donor-site appearance and produce both low transection rates and excellent harvesting rates.
Figure 6 – Follicular unit extraction technique with punch
Perhaps the most important emerging concept regarding FUE donor harvesting is the cosmetic end result left behind in the donor region as a result of selective follicular-unit targeting. This new emerging paradigm states that being strategic in follicle selection and in partial harvesting of a group of follicles rather than removing all the follicles in a group represents an important evolution of the FUE technique.
Hair surgeons realize that graft survival is dependent upon careful handling during graft preparation, storage, and reimplantation. The viability of grafts is one of the most challenging problems in the hair transplantation. This is especially important in case of mega sessions, when more than 3,000 grafts are transplanted during one surgical intervention.
As the FUs are harvested from the donor area, they are inspected under the microscope. They are stored in the slots in groups of 10 FUs. Grafts are classified as 1-, 2-, and 3-hair grafts. Transected hairs are trimmed away, and excess skin is removed in singles. In specific slots, FUs will be put with the same number of hairs. All these procedures take time. Studies affirm that spending time on the container during dissecting should not be more than 10 minutes, placing time during the transplantation no more than 4 minutes (optimally 2-3 min), and the optimal time in the fridge at +4-5°С around 3-4 hours (viability after 24h is about 71%).
To prolong graft survival and reduce ischemia reperfusion injury, bioenhanced storage solutions can be used. HypoThermosol FRS, for example, is an innovative, engineered, optimized hypothermic storage product which mitigates temperature-induced molecular cell-stress responses that occur during chilling and rewarming of tissue.
Grafts are different in FUE and FUT. In FUT, the grafts have tissue surrounding the entire length of the follicles. In FUE, the portion of the grafts near the bulbs often is stripped of tissue, which leaves them more vulnerable to both desiccation and trauma during removal, processing, and, most of all, insertion.