Dynamics of FUE Hair Transplantation

FUE Dynamics
Dr. Alan Feller

Dynamics

This section on dynamics is probably the most important in the book as it gives the physician the information necessary to visualize in the mind’s eye what is happening during each phase of an FUE attempt.

FUE is the most exacting kind of hair transplantation, one that allows little room for error. A thorough knowledge of the involved physiology and how it responds when undergoing FUE is necessary for achieving success, and so it is useful to examine each part of the procedure and how it affects every other part in turn.

By returning to the three core elements of FUE, Angulation, Depth Control, and Delivery, we can study what obstacles present themselves and then offer solutions to overcome them.

Angulation  

The three most important layers of tissue in hair transplantation are the epidermis, the dermis, and the adipose. These structures, together, were designed by nature to protect the skull in multiple ways including injury from blunt trauma. A necessary consequence of this benefit is that it unavoidably lends a flexible quality to the scalp that tends to work against our desire to remove grafts intact.

When the target FU is selected, and the punch is lined up with the exiting hair and mons folliculi, as previously described, the application of pressure on the punch will then cause a distortion of the scalp tissue . No matter how sharp the punch is, the area just under the tool will want to buckle and invaginate. This, in turn, will cause the FU itself to “kneel” or “compress” thus expanding its diameter and greatly increasing the chances that the punch will either transect it as it travels down, or shear the follicles as the punch is rotated.

The solution to this problem is, well, solution. Saline solution that is. By pumping the target area up with fluid prior to scoring, the skin can temporarily be made hard as rock. The presence and pressure of the fluid will also increase the distance between the FU s allowing for a more generous range of attack angles, while at the same time decreasing the chances of transecting a neighbor follicular unit.

This application of saline creates a new variable that must be taken into account, hydrostatic pressure. In a hydraulic system, a small amount of pressure on one end of the system can result in a large force and displacement in the other end of the system.

Show photo of hydraulic lift system dental chair physics

It becomes necessary to take this effect into account when performing FUE since the proper angle of the FU may be significantly altered. One way to do this is to squeeze down on the skin with a finger of the non-dominant hand opposite the direction of force when the punch is applied. The hydrostatic force will then be redirected toward the target making it that much more sturdy thereby preserving the desired angle while pushing neighboring follicles even further away. I typically wrap a gauze around the index finger of my non-dominant hand and press toward the graft prior to scoring.

Show photo of finger pressing down on skin

Depth Control

With the presence of the saline, the follicles hover much higher above the skull than they normally would. Since they won’t compact down on themselves as easily, the punch can be slid in deeper than it otherwise could. Furthermore, the saline temporarily decreases the relative tissue density of the area it has been injected into, allowing the punch to more easily and controlably pass through the skin layers.

Depth control does not merely refer to achieving a desired depth, but to the forces involved in getting there. The hand must be used as a clutch, and the practitioner must constantly monitor the tissue to know whether to increase pressure or decrease pressure.

If too little pressure is exerted, the proper depth will never be achieved. If however too much pressure is exerted, the punch may overshoot its desired depth resulting in one of several kinds of transections that will be presented later.

PICTURE OF TRANSECTION FROM GOING TOO DEEP

While the use of guards can be utilized to limit the depth of the punch, the best and most reliable method is for the practitioner to develop a sense of feedback that makes depth control almost automatic. Guards are a good idea in theory, but offer little practical value since the variations in depth are so wide, even in the virgin scalp. I usually mark my punch tool with a horizontal line made with a razor blade prior to the start of the procedure. This gives my eye a reference point which is sufficient for me to gauge deep the punch is actually going.

Delivery

Perforation

As mentioned before, even if the optimal depth is achieved every time, the graft may not release from its hole, even when significant traction is applied. In many patients, there is just too much collagen in the deep dermis to allow for easy delivery, or the pili-erector fibers are just too tough to snap free without more “incentive”. The force necessary to overcome the collagen or the muscle fibers usually results in a torn follicle, so the extra step of perforation must be performed.

As traction is applied to the partially released graft, the bottom part of the FU, where it connects to the dermis, “tents” like the top of a circus tent when the center pole is installed.

Show drawing of tenting

This physiological state, combined with the force of traction, makes the area ripe for tearing, when even a single perforation from a 22-gauge needle is applied. After the first perforation the practitioner can feel the shift in forces and an adjustment in traction direction becomes almost automatic. By perforating in a logical fashion such as starting at the 12 o’clock position, then 6, then 3, etc, the safe delivery of the follicle is almost always assured.

Traction

Grasping the partially scored graft is a delicate matter as the FU is in its most vulnerable state at this point. Success or failure hinge on the proper balance of tension and compression; but rather than focusing on the patient’s physiology, it would be better to look at the physician’s as the key to success.

If the graft delivers easily, then all is well, and the physician moves on. If however there is difficulty, the natural instinct is to pull harder on the graft. Perhaps the extra force will overcome the connective tissue holding the graft in and success will be just around the corner, but most likely this won’t happen.

To increase traction, the physician must increase his grip on the graft or it will slip out of the forceps. The danger here is that the greater compression the forceps must exert on the tissue may either crush the follicles, or cut them in half.

It then becomes tempting to grab the FU just below the epidermis since it seems as if it could act as an edge or flange to prevent slippage, while at the same time allowing the physician to decrease compression of the forceps. If this is attempted however, more often than not, the epidermis will simply tear off and the FU will retract deep into the hole.

While practicing FUE it is useful to treat as “law” the fact that the higher you grab with your forceps, the more likely the tissue will just tear away under traction. It is very tempting to grab the shallow parts of a graft since they are right there, presenting themselves to you, but resist, as you can be confident that the tissue will not cooperate.