What is Transection?
In hair restoration, the act of transection is an unintentional severing of the hairs during a transplant. This can occur at two points of the procedure: first, it can occur in the area of the scalp that is donating hair for transplant, otherwise known as the donor zone. Second, it can occur when transplanting hair to the area of the scalp in need, otherwise known as the recipient zone.
What Causes Transection?
In the recipient zone, transection usually occurs when little care is taken to make incisions far enough away from the surroundings hairs. In the donor zone, it can occur if too much pressure is applied to the scalp when using a punch device (manual or motorized), or if the blade is held at an incorrect angle.
Does Transection Guarantee that the Hair is Unusable?
No, not necessarily. A transected hair graft’s survivability depends on exactly where the follicular unit sustained damaged. Generally speaking, the lower portions of the hair follicle contains the most important structures for long-term growth. If a follicular unit is transected across the top, its chances of survivability are much higher. In the worst-case scenario, the damage is caused to the hair bulb itself, which prevents the follicle from growing new hair.
What is an Acceptable Transection Rate?
During the course of any hair transplant, thousands of follicular units are extracted and implanted. When handling grafts of this magnitude, a small percentage of hairs are going to inevitably become transected. A 2000 study monitored the results of fifty hair transplants using the follicular unit strip surgery (FUSS) technique. Researchers found that the FUSS technique incurred a 1.9% transection rate when removing follicular units from the donor zone, and a 1.2% transection rate when the follicular units were dissected into hair grafts. Therefore, of all the follicular units used, an average of 3.1% of them were lost due to transection.
Sharp Tips versus Blunt Tips
When using a manual or motorized punch, the surgeon may choose to switch to a blunted tip after making the initial incision. Using a blunt tip over a sharp tip will reduce the likelihood of transecting hairs. Switching from one tip to another, however, creates extra steps, which is why some physicians choose to use only sharp-tipped punches throughout the procedure. Neither decision is right or wrong – in fact, an experienced physician will be able to minimize the number of transected hairs despite using a sharp tip exclusively.
When using a combination of sharp and blunt tips, there is a two-step procedure and a three-step procedure. A study in 2010 found that the grafts extracted with the two-step procedure yielded an 8% increase in the number of harvested follicular units, whereas using a three-step procedure increased the amount of hair yielded by just under 20%.
Transection Rates and Race
Different races can experience different transection rates due to the average diameter of their hair. In fact, some races may experience a lower transection rate from using a slightly larger-than-normal punch. Therefore, genetics also plays a minor role in the likelihood of transecting hairs.