The donor area strip is removed and hemostasis secured

A sewing edge is obtained with a sweeping movement of a #10 blade through the subcutaneous tissue on both sides of the wound. This is rarely accompanied by significant bleeding. In first time harvesting, or even in secondary harvesting when the tissues are mobile and well vascularized, this step alone usually allows for a simple one or two layer closure as preferred. If, however, the wound remains refractory to closure, proceed to step 3.

Further undermine the wound edges, but not for more than another 1 cm or so than detailed in Step 2. Evert the superior wound edge and place a PDS 2/0 suture in the deep dermis as far away as possible from the wound margin, for example, 6-7 mm from the wound margin. Suture this as inferiorly as possible to the deep fascia (not to the deep dermis) in the bed of the most inferior part of the wound. Use moderate tension only (Fig. #19).

It is stressed that sutures are placed from deep dermis to deep fascia and not from dermis to dermis. Several sutures may be necessary depending on the length of the wound and degree of difficulty in closing. Alternate each suture placement, that is, from as superior as possible in the dermis of the superior flap to as inferior as possible in the deep fascia in the inferior-most reaches of the wound and the adjacent suture from as inferior as possible in the dermis of the inferior flap to as superior as possible in deep fascia in the superior part of the wound (Fig. # -20). Alternate from superior to inferior and from inferior to superior until the wound edges are approximated. All knots are should be buried. The skin is closed with 3/0 or 4/0 nylon placed either as running or interrupted sutures.

The above is not a simple technique and requires practice to perfect. Because of its complexity, it is an excellent five-finger exercise for improving surgical skills. Its main benefit, however, is to facilitate low-tension closures in fibrotic donor areas or when a wide strip is being taken and in situations in which the surgeon is experiencing difficulty closing the wound for whatever reasons. Its rationale is based on surgically minimizing wound tension and thereby obviating embarking on tension-inducing methodologies in order to effect closure.

Seery has also provided a biomechanical rationale for deep plane fixation closure,* and it is quoted here:

"Tension created at the wound on closure is responsible for multiple adverse sequelae (see below). The standard method of combating tension is to attempt to overcome it with a combination of extensive undermining and traction with tension clamps, big needles, heavy suture and muscular force. The methodology of donor site closure, detailed above, is a modification of deep plan fixation. This eschews extensive undermining and traction closure. The rationale for its use depends on two tenets of surgical practice:

• Channeling tension forces through non-undermined tissues notably limits their adverse effects as compared with tension transmitted in extensively undermined tissues * and
• tension vector forces channeled away from superficial "at-risk" tissue into deep plane tissues allows the adverse effects of tension to be dissipated in tissues other than the wound.*

The most important criterion in deciding the width of the strip that may be successfully harvested, without creating undue tension at closure, is the laxity of the tissues.* Donor area tissues may be either naturally tight or tight as a result of prior harvesting. A combination of each is the worst possible scenario. The belief that closure problems posed by tight scalps can be solved by extensive undermining and stretching is in serious need of review. The scalp is made up of collagen, elastic fibers, blood and lymphatic vessels, and nerve fibers with mucopolysaccharide ground substance and tissue fluid. All of these elements are adversely affected by extensive undermining and stretching. The ability of skin to recover from stretch resides in its elastic component. When skin stretches, the elastic fibers elongate in the direction of the stretching force, allowing the convolutions in collagen to straighten out. The resultant elongation is a function of progressive displacement of ground substance and tissue fluid, which accompanies collagen realignment.* This continues until there is a structure of parallel collagen fibers that resists further extension. This complies with a principle of Physics that states that stress (stretch) is directly proportional to strain (elongation) provided the elastic limit is not exceeded. The elastic limit of skin (or any substance) is that point at which the components commence to rupture and the stress/strain ratios no longer apply. It is accompanied by adverse tissue changes. The elastic limit for skin elastin is about 100% and that for collagen 10%. When skin elongates more than 100% of its resting length, the elastic fibers rupture.* The impaired elastic is now no longer able to return the collagen to its normal resting state even when stress is removed. This results in permanent, irremediable adverse consequences for the tissues called plasticization, better known to surgeons as stretch-atrophy. (thin, dry, brittle, poorly vascularized skin) commonly seen following donor area traction closures and after overly ambitious alopecia reductions.* Stretch-atrophied tissues are relatively unsatisfactory for subsequent harvesting or hair transplantation.* Skin stretching also attenuates blood vessels decreasing tissue perfusion which, if allowed to continue unchecked, will ultimately exceed the critical closing pressure and perfusion stops. Lesser degrees of stretch will reduce circulation. Elongation of nerves and reduced lymphatic drainage causes pain and edema, respectively.*

Non-undermined skin is better able to withstand the ill effects of tension stretching than undermined skin. Extensive undermining is also ineffectual. In a clinical research study by Seery, * two groupings of mid-line alopecia reductions were described, the only difference being that one had undermining of 15 cm bilaterally and the other only 5 cm of undermining bilaterally. The excision widths in each group were identical at 39 mm. There was no significant difference in stretch-back. The suggested the extra undermining of 10 cm bilaterally contributed nothing in terms of increased tissue excision. This conclusion is scientifically supported by Raposio * who, in an excellent paper on tensiometric measurements in serial scalp reduction, reported "the benefits of an extensive (15 cm) undermining were minimal as compared with those obtained with 5 cm undermining." As a practical matter, it is unlikely that undermining of much more than 2.5 cm from the donor wound edge is worthwhile."

Figure 13 The graph of straight, curly, and kinky hair.

Table 8. Percentage of naturally occurring surface hair groups per follicular cluster based on regional location in the individuals, who are a Norwood Class III-VI.⁶⁰