What is Laxity?
The skin’s laxity refers to its overall elasticity. The looser the skin is, the more it can be pinched and pulled away from the body. Consequently, the tighter the skin is, the less it can be gripped and tugged. Skin around the knees, for example, is very lax when compared to skin on the chin.
Does Scalp Laxity Matter for Hair Restoration?
Yes, very much so. With hair restoration, the laxity refers to how much the scalp skin can be stretched. This is particularly important when performing follicular unit strip surgery (FUSS).
- A FUSS is when the hair restoration surgeon removes a strip of flesh from the donor zone – the donor zone is usually on the back of the scalp (occipital scalp). The purpose of removing the donor strip is so that the hair follicles can be harvested and grafted onto any areas of the scalp that are displaying hair loss (known as the recipient scalp). A donor zone with a high laxity allows for a wider strip to be taken, which yields more follicular units.
- Next, under advanced microscopes, the hair restoration surgeon dissects the follicular units from the donor zone and reassembles them into usable grafts.
- These grafts are then transplanted into customized holes made in the recipient scalp (known as recipient sites).
When hair restoration surgeons assess a patient for FUSS, they measure the donor’s density and laxity. Measuring these properties allows them to better estimate how much skin can be safely used for transplant. The ultimate goal is to take as much skin as possible from the donor zone without traumatizing the scalp.
How is Scalp Laxity Measured?
While there is no way to measure this attribute without a certain degree of guesswork, there are a number of different ways to obtain a fairly accurate estimation. Generally, the laxity of the scalp is determined by the distance of vertical movement both in the posterior scalp and the lateral scalp. Some methods determine the scalp’s flexibility by using vague categories that range from “very lax” to “very tight”. Others, such as the Mayer-Paul method, make two marks that are approximately 50 millimeters apart from each other, and approximately 5 millimeters away from the midline. The hair restoration surgeon presses their thumb into the scalp and takes a second measurement. The numerical difference between the two measurements is converted into a percentage. This percentage then serves as a general guideline when determining the width of the donor strip. A 2014 study notes that measuring the donor zone’s laxity “allowed for the use of wider strips, and resulted in smaller donor wounds and scars from hair transplantation”. However, it apparently did not help in estimating the total number of hair grafts needed for the procedure.
What Affects Scalp Laxity?
In general, scalp laxity is determined by genetics. Those with tighter-than-normal scalp skin are not very good candidates for an FUSS procedure because the taut skin tends to cause excessive scarring. The scalp’s skin becomes tighter after a FUSS hair transplant, and continues to become tighter after each subsequent procedure thereafter. As such, “virgin scalps”, or scalps that have not undergone any hair transplants, almost always have the best laxity of all. Aggressive and rapid weight loss can also improve donor laxity. However, this is temporary as the skin tends to contract to a degree after such weight loss is experienced. Finally, scalp laxity exercises can be performed to increase one's donor laxity. This is the vertical stretching of the occipital and lateral donor zones to induce traction of the donor tissue. This "stretches" the donor tissue and reduces tension thus allowing wider strips to be removed.