Seager, for example, when trying to obtain 2,500 to 3,000 or more FU, commonly removes a strip that is 8 mm wide superior to the auricle, but is usually 1.2 to 1.5 cm wide, and occasionally even wider, in the mid-occipital region, yet only approximately 7 mm wide in the post-auricular area.* In trying to produce such large numbers of FU in a single session, he generally will excise the maximum width of tissue that allows for closure with reasonable tension in each area. The effect of the preceding is that the shape of the donor strip is often "wave-like" rather than a long rectangle or ellipse, and is usually no more than 1.2 cm wide at its widest point.

This wave pattern is most frequently achieved by scoring the skin with double-bladed knives of various widths, at various points along the proposed strips – but joining the scored lines with a single blade as the strip is excised. In subsequent sessions, the initial widths may be decreased because of scarring from previous harvests that have decreased scalp laxity. Alternately, he may increase these widths to compensate for the presence of the hairless scar line within the donor strip and decreased hair density on either side of the scar, if scalp laxity allows for this. Towel clamps are used in most patients to assist in donor area closure during each session, and staples are preferred to sutures.

As implied by the foregoing, in most instances he includes previous donor scars in new harvests from the same general area and rarely leaves more than two scars in the donor area regardless of the number of sessions undertaken. Extra separate and smaller excisions may sometimes be later taken from the least lax but still usable portions of the parietal areas, during the course of any patient’s series of treatments.⁵² These are the areas in which the previous strips were narrowest because of low scalp laxity but the safe donor area was wider than in the temporal or occipital areas.

Most practitioners use shorter and/or narrower donor strips. Avram, Shiell, Stough, and Beehner, and Shapiro, for example, usually limit their strips to a width of 8-10 mm and Mangubat to 8-12 mm. Bernstein and Rassman generally range between 1.2 and 1.5 mm in strip width. Unger’s and Cole’s approaches are described in detail at the end of this chapter.

Should One Excise Old Scars Within New Donor Strips?

Should scars from previous donor strips be included in subsequent harvests, or should strips always include only unscarred tissue? Unger and Cole prefer the former. Bernstein and Cole discussed multiple potential problems that may result from a donor excision that includes previous scars.* They are summarized below along with additional comments by Cole:

When the donor area is excised, the defect is closed by stretching the edges of the wound and suturing them together. This skin stretch decreases the follicular density of the skin adjacent to the scar.

Scar formation distorts hair growth direction immediately adjacent to it. Cole and Bernstein have noticed that this directional distortion tends to be greater on the inferior side of the scar than the superior side, and creates a potential problem in future donor area excisions, which incorporate the pre-existing scar. The bulbar region of hairs, inferior to the scar, generally appear to be pulled more inferiorly than the infundibular segment of the same hair shaft, resulting in a somewhat curved hair. Because the hair exists in a parabolic fashion, it is impossible to excise the curved hair with a straight scalpel blade without transecting it. Hairs superior to the scar are generally distorted only marginally, if at all, most likely because the preponderance of stretch comes from the neck. In brief, hair transection is more likely when excising a scar, especially on the inferior side of the scar.

The scar is significantly harder than the non-traumatized adjacent skin, so greater force is required to dissect through the tougher scar tissue when grafts are being created from it. Greater force requires more manual dexterity during the dissection process, in order to minimize damage to the hair follicles. In other words, the margin for error is reduced.

Scar tissue is less translucent than non-scar tissue and thus, increases the technical difficulty of preparing un-transected hairs.

Skin stretch also reduces donor area compliance around the scar. This means that the maximum width of donor area excision will be reduced in subsequent procedures that incorporate the scar and the new scar will likely be somewhat wider.

Scar, of course, contains no hair. If a scar is 1 mm wide, future harvests that include it may result in a reduction of potentially 10 FU/cm² due to the presence of the scar alone. Because the scar width varies significantly along its path, FU estimation is also made more complex. Moreover, when scars form in the donor region, they may be larger deep to the hair papillae than they are on the surface of the skin. This can result from leaving a space below the hair papillae that heals by secondary intention.

In reply to the preceding arguments, it should be pointed out that:

a) Both decreased hair density and follicle angle distortion are significantly affected by the closing tension of the donor site. Minimal tension will produce minimal change in each. The routine excision of wider strips, such as the 12 to 15 mm wide ones that Bernstein prefers, will no doubt often result in greater wound closing tension, that will have a far greater effect on adjacent hair density and angle, for example, than that seen with the 8-10 mm wide strips that Avram, Shiell, Beehner and others typically use. Moreover, once wound tension starts to increase, it does so exponentially in Unger’s experience. A mere I mm increase in donor strip width, often is the difference between no tension on closing and substantial tension that is disproportionate to the small increase in strip width.

b) If previous donor scars are not excised as part of the donor strip(s) in subsequent sessions, each session will add an extra scar to the donor area. Six sessions will, for example, leave six scars instead of one or two scars, and can result in an unnatural zebra-like pattern of scarring in the patient’s donor area.

c) Multiple scars may well reduce scalp mobility and the width of future harvests more than one or two scars do.

d) Each scar interrupts, to some extent, the blood supply superior to it. This is true whether the scar is wide or fine. Taking a strip from an area superior to a previous scar, results in a reduced blood supply to the inferior flap of the new wound. It also results in the area between the old and new donor area having its blood supply cut-off inferiorly as well as superiorly, and increases the risk of telogen effluvium or necrosis in that section of the donor area. Each additional donor strip, superior to the preceding ones, increases the risk to good healing of the new wound and the donor area tissue between all old and new harvests and scars. If instead, subsequent donor strips are taken inferior to each prior one, the inferior flap of the new donor wound will always have an intact blood supply. But, the superior wound flap blood supply will be more profoundly affected than was the inferior wound flap in the first example. This is because, with a scar superior to the wound, the blood supply will come to the superior flap area primarily from an inferior location, and the new incision interdicts this source. Thus, the superior wound flap has its blood supply reduced superiorly (by the old scar) and completely cut-off from the more important inferior source of blood supply by the new incision.

Unger minimizes follicle damage, wound tension, and other potentially negative sequelae about which Cole and Bernstein have been concerned (1) by keeping old scars well away from the blades, and never using more than two-bladed scalpels when he sees significant hair angle differences, inferior and/or superior to an old scar, (2) by harvesting narrower strips in those few instances when he anticipates more than average donor wound tension. The instances are "few" because he only uncommonly tries to transplant more than 1500 to 1750 FU (or its equivalent in other types of grafting) per session and usually uses two contralateral donor strips instead of one. He therefore, generally harvests significantly narrower strips than most of those who, like Cole, Seager, and Bernstein, use a single donor area per session and (3) by beginning with narrower donor strips and taking slightly wider donor strips, if necessary, in subsequent sessions. This approach increases the likelihood that wound tension will be acceptable even after multiple sessions in the same area. It can also compensate for any decreased hair density adjacent to old scars as well as for the absence of hair in the scar which is usually very fine because of low closing tension. If one is anticipating only carrying out two or three sessions in an individual, Seager’s and Bernstein’s approach is not that problematic, but Unger prefers a more measured utilization of donor tissue in four to six, or even more sessions, for reasons explained in Chapter 6, and later in this one. Cole is able to obtain five or more large sessions with his technique averaging 1500 grafts each and over 2000 grafts in some individual sessions. Cole believes the average donor region contains at least 7000 movable follicular units.