๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Donor area calculations
Donor area calculations
In strip FUT, the number of grafts obtainable per square centimeter can be calculated using a densitometer or other similar magnifying device, though no method is absolutely precise. A simple assumption can be made that every 6-cm long and 1-cm wide strip will yield approximately 500 grafts based on an average density of 80 follicular units/cm2. This figure can be adjusted with significantly higher or lower donor densities that will vary between individuals and different zones of the donor scalp.
In the case of a preexisting strip donor scar, it is preferable to excise the scar within the new donor strip and replace one scar with another. This will affect the graft yield, and numbers need to be adjusted accordingly depending on the width of the previous scar.
With the patient either sitting up or prone, the donor site hair to be removed is trimmed to a length of 3 to 4 mm. This length will help guide the correct direction of the grafts during their insertion into the recipient sites. Leaving the hair longer outside the strip will help hide the donor site immediately postoperatively (Fig. 62-2).
One challenge with FUE is the need to shave the donor area ahead of harvesting. This allows the surgeon to extract evenly over the entire donor area to avoid pockets or thin areas. The safe donor zone in the estimation of the surgeon needs to be marked out on the scalp prior to shaving the hair in order to realistically assess the likely โpermanentโ hairs. The aim is to target 15% to 20% of the follicular units to harvest per procedure. In the patient with an average of 80 units per square centimeter, this translates into approximately 15 harvested units. In patients with potential for significant androgenetic alopecia in the vertex, this is the equivalent of an available safe area of about 180 cm2, generating a total of up to 2,700 grafts that may be harvested in a single procedure.
Figure 62-2. Typical postoperative appearance of strip FUT harvesting method.