The strip technique remains the most popular method of harvesting grafts. The challenge in every patient is to maximize the number of grafts while minimizing the scar. Fortunately, there are many ways to ensure that the donor site will be inconspicuous. This article reviews the details of planning for follicle graft harvesting, including formulae for assessing scalp laxity and calculating strip dimensions. The procedure is discussed in detail, from preparation of the donor site and estimation of graft total through closure of the incision. The author presents his preferences for the technique with rationale and surgical tips.
Key points
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Remove only enough donor width that will close without tension.
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Remove donor strip in portions to accurately judge graft yield and laxity in different areas and to avoid a large open wound.
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The lateral donor areas have less laxity, afford less camouflage, and yield fewer grafts.
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The deep stitch is critical in a good closure.
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Use a single incision when doing multiple sessions.
Introduction
The donor strip technique has been the predominant method of harvesting grafts for decades. Like every aspect of hair transplantation, it has undergone numerous refinements. These changes became necessary as patients began wearing their hair shorter and requesting larger graft sessions. Patients having more than one procedure expect to have just one incisional scar, not a series of stripes. It is no longer acceptable to have an excellent result at the recipient site and a telltale wide scar at the donor site. The following discussion highlights how we can accomplish the goal of harvesting adequate grafts via the strip technique with a resultant inconspicuous scar.
Introduction
The donor strip technique has been the predominant method of harvesting grafts for decades. Like every aspect of hair transplantation, it has undergone numerous refinements. These changes became necessary as patients began wearing their hair shorter and requesting larger graft sessions. Patients having more than one procedure expect to have just one incisional scar, not a series of stripes. It is no longer acceptable to have an excellent result at the recipient site and a telltale wide scar at the donor site. The following discussion highlights how we can accomplish the goal of harvesting adequate grafts via the strip technique with a resultant inconspicuous scar.
Preoperative planning
Safe Donor Area
Grafts should be harvested only from areas with terminal hairs that will grow forever. This safe donor area ( Fig. 1 ) is different for every patient, but a few guidelines are helpful. The superior boundary should be at least 2 cm below where crown thinning is predicted to occur. In class V-VII patients, this is easy to determine, but in patients who are still losing more hair it may be slightly challenging. The inferior boundary should be about 2 cm above the nape of the neck. Patients will often thin naturally in the lower occipital area so one does not want to harvest donor hair in this area. Laterally, one can harvest from the supra-auricular area, but it is important to keep in mind that the density here is less, the skin is tighter, and there is less superior hair for covering the incision.
Scalp Laxity
As we strive to harvest more grafts for accommodating large sessions, scalp laxity has become a very important issue. The parameters that influence the dimensions of strip size in the donor area are length and width. Length is more finite, as one can only go from one supra-auricular area to the other. The maximum length usually ranges from 24 to 30 cm depending on the size of the patient’s head. Width is much more variable and depends on local soft tissue laxity. Less width can usually be excised laterally and more in the occipital area. Depending on the baseline donor laxity, a safe strip width will generally vary from 10 to 25 mm. The upper limit of a safe strip width depends on being able to close the incision without tension, and this is primarily determined by scalp laxity.
Over the years, there have been many methods to predict donor site laxity. Laxity estimation can be accomplished most simply by squeezing the scalp between your fingers. This technique is, of course, very subjective and relies on experience, but for an experienced surgeon it often proves quite reliable. Alternatively, an experienced surgeon can determine the donor laxity parameter by measuring superior and inferior soft tissue excursion at the center of the planned strip excision site ( Fig. 2 ).
Scalp elasticity formula
Mayer and Pauls 3 developed a formula for determining scalp elasticity. With their method, a 50-mm line is first marked on the occipital donor area, and then the borders are squeezed together along the horizontal axis. Their formula is:
Scalp elasticity = (50 mm – x) (100%)/50 mm where x is the length of the compressed skin segment.
They found that scalp elasticity in 400 patients ranged between 10% and 45%, with the average being 24%. They concluded that 10% elasticity represents a tight scalp and 45% elasticity represents a very elastic scalp. From a practical consideration, these data suggest that a tight scalp (10% elasticity) may yield a 5-mm strip, an average scalp (24% elasticity) may yield a 12-mm strip, and a very loose scalp (45% elasticity) may yield a 22.5-mm strip.
Preoperative scalp massage is recommended to increase laxity. The results are variable, but it is quite simple and the potential benefits justify encouraging patients to use this exercise. They are instructed to vigorously massage the donor area in a vertical fashion for 3 to 5 minutes frequently during the day and to continue this regimen for 2 to 4 weeks before surgery.
Calculating Strip Dimensions
Predicting how many follicular unit grafts (FUs) can be harvested from the donor area is essential in every case. Most hair restoration surgeons calculate strip dimensions and donor graft harvest capabilities based on local follicular unit density and regional donor elasticity. First, the surgeon approximates regional follicular unit density with a device such as a densitometer ( Fig. 3 ). This magnification device allows the surgeon to quickly count the number of follicular units in one square centimeter, so as to allow for an overall appraisal of the donor site density. Next, the donor site elasticity is evaluated to determine the maximum safe width for the strip that will be removed ( Fig. 4 ). The donor density and the strip width calculations are then used to determine the necessary strip length for the required graft session size ( Fig. 5 ). These parameters will also allow the surgeon to calculate the maximum graft yield possible for any given individual.
For example, if one estimates that a maximum donor width of 1 cm can be removed and that the average density throughout the strip measures 60 FUs/cm 2 , harvesting a 25-cm-long strip should yield approximately 1500 grafts. However, sufficient laxity for the safe removal of 2 cm from the donor would now require only a 12.5-cm-long strip to obtain 1500 grafts. Alternatively, assuming sufficient laxity, a 2-cm width could double the graft yield to 3000 FUs for the same 25-cm-long strip.
It is common to witness variable FU densities within different zones of the donor area. The temple region often demonstrates a significantly lower density than the central occipital scalp. It is prudent to evaluate donor density in a minimum of 2 different zones. Adjustments can be made for varying regional densities to ensure avoiding miscalculation of the graft harvest.
Hair Color
The presence or absence of color of the hair follicles is important. Patients with white hair often have follicles that are literally translucent. This makes it hard to see the follicles when excising the strip and equally difficult to see the follicles when preparing the grafts under the microscope. There is no ideal remedy for this. We have found it helpful to dye the donor area with a hair coloring solution to facilitate visualization of the hair shafts, but variable uptake of the dye onto the hair can limit its usefulness.
Preexisting Donor Scars
The goal is to have only one incision regardless of the number of sessions, so precise planning is necessary when a scar exists from a previous procedure. A scar will affect the donor site in numerous ways. A scar affects how wide the subsequent donor strip can be. Usually the removal of a preexisting scar along with a new donor strip will result in a much wider incision than one would expect. For example, if the previous scar measures 3 mm in width and the donor width to be removed measures 1 cm, one might expect the resultant wound to be 1.3 cm wide. However, this is usually not the case, and the wound width has the potential to widen much beyond the predicted 1.3 cm, with the possibility of even doubling to 2.6 cm. This scenario challenges the surgeon to close a much larger incision, possibly under significant tissue tension and leading to a widened scar. To avoid this problem, one may have to plan on removing a smaller donor strip, thus harvesting fewer grafts.
The donor wound will not spring open if harvesting grafts in an area where punch grafting was previously done. The scarring after punch grafting seems to secure the overlying tissue and the incision width does not routinely increase when the donor strip is removed.
In designing a new donor strip excision, the surgeon should ideally position the old scar at the inferior or superior border and not in the middle of the donor tissue. This makes separation of the scar from the follicles easier for the technicians preparing the grafts. Of note, the follicles adjacent to an old scar often have altered direction, so this should be considered and great care implemented when making the superior or inferior incision along the old scar.
As hair transplantation procedures have become larger and a second, third, or fourth session more common, the appearance of the donor site requires even more attention. It is imperative to leave as inconspicuous a scar as possible at all times, and this can occur only with a conservative approach to the tissue excised.
Preparing the donor site
With the patient either sitting up or prone the donor site hair is trimmed to a length of 2 to 3 mm. Having even this minimal length aids the appropriate direction of the grafts during their insertion phase into the recipient site. There is little need to trim beyond what will be excised, and in fact, long hair above the harvest site will help camouflage the incision. Next, the superior and inferior edges of the donor site are outlined with a surgical marker ( Fig. 6 ).
Positioning the Patient
I prefer donor harvesting using the prone position. There is much less chance of a vasovagal reaction compared with the sitting position. This also is a very comfortable position for the surgeon and assistant to work. The patient’s head rests in a Pron-Pillow ( Fig. 7 ). This pillow is both comfortable and allows air circulation along its periphery so the patient can breathe more easily. Metal hair clips or tape can be used to keep the superior hair out of the field. Harvesting a meticulous strip generally requires about 45 to 60 minutes. Patients have little problem remaining in the prone position for this relatively short time. The head remains stable in the pillow and the patient can move his or her head without any discomfort as the donor strip is harvested from one side to the other. The donor area can be cleansed with a number of antiseptic agents, but one must remember this is a “clean” procedure, not a sterile one. One last laxity check at this point is wise before injecting the local anesthetic, so that any modifications of the planned width can be implemented if necessary.
Donor Site Anesthesia
The superior and inferior edges are injected with local anesthesia. I prefer 1% xylocaine with 1/100,000 epinephrine. A neck vibrator wrapped in a plastic bag is placed over the injection sites to diminish discomfort. An ice cube can also be used to help reduce injection-related pain.
The lateral supra-auricular areas are often more sensitive than the occipital region, and the inferior border injections tend to generate more pain than those placed superiorly. Anesthetic infiltration into an old scar will also be painful. Thorough anesthetic infiltration along the superior and inferior edges is mandatory because this is where the cuts will be made. Infiltration from these border injections usually suffices to provide anesthesia along the base of the donor strip.
Harvesting the strip
The key to the donor strip technique is to visualize the follicles and stay parallel to the existing hair shafts to help ensure a negligible transection. I prefer a moderate amount of magnification and use a ×4 OptiVISOR with an attached headlight. This allows me to wear my own prescription glasses and also provides excellent eye protection.
Procedure
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I use a #10 blade to cut through the epidermis, scoring the superior and inferior strip borders. Usually this cut will extend into the upper papillary dermis ( Fig. 8 ).
