Placing Grafts: An Overview of Basic Principles and Current Techniques

Ronald Shapiro, MD, Hair Transplantation 4th Edition, Revised and Expanded, Unger & Shapiro, 2004, Chapter 13A: 533-539

INTRODUCTION

The ability to place grafts successfully is a critical step in the hair transplant procedure, and its importance grows as surgeons increasingly use smaller grafts in larger numbers. Placing a large number of tiny grafts into small incisions is technically difficult and increases the likelihood that problems will occur during this step of transplantation. The complications lead to poor yield—most often caused by dehydration or physical trauma—or decreased naturalness—for example, pitting or poor orientation—and the need to overcome them has resulted in a variety of clinical innovations and modifications in the placing technique.

In this chapter, I examine some of the more common problems that occur during placing. I also discuss the basic principles and methods used to combat these dilemmas.

BASIC PLACING PROBLEMS

Dehydration — Prolonged exposure to air, especially the dry, dehumidified air of a surgical room, leads to graft dehydration, which is one of the major causes of decreased graft survival. The potential for dehydration is greatest when placing a larger number of small grafts. Two reasons for this are:

• Smaller grafts dehydrate more quickly than larger grafts. Smaller grafts have a greater surface area-to-volume ratio than larger grafts and, therefore, are more vulnerable to the dehydrating effects of air exposure.
• Smaller grafts take more time to place, thus increasing the potential for prolonged air exposure both during insertion and while waiting “on deck” to be placed. Grafts on deck wait either on the placer’s hand or on another area until he/she picks them up for insertion.

Physical trauma—“Direct physical trauma” during placement potentially reduces the graft survival rate. It commonly occurs due to one of the following:

• Squeezing the graft between the tips of a forceps with excessive force, or
• Crushing the graft between a placing instrument and the wall of an incision site.

The amount of direct physical trauma increases when the difficulty of placing leads to multiple, failed attempts at insertion. Inexperienced placers have higher numbers of failed attempts, and they also have a tendency to grab a graft with greater force.

The clinical significance of direct physical trauma is somewhat controversial and deserves morediscussion. An early study by Greco shows that major microscopic change occurs in the cell structure of the bulb when forceps severely crush it. However, more recent studies by Gandleman suggest that crush injuries do not show the same degree of microscopic change when forces typical of those in the clinical setting are applied to the graft.(1) In addition, Gandleman finds that the microscopic changes associated with dehydration are much more severe than those associated with direct physical trauma. Other studies, such as Kim’s, show a 70% survival rate of grafts when the surgeon or staff removes their bottom thirds.(2) If such severe physical trauma still results in a 70% survival rate, it would suggest that mere crush injury, during graft insertion, would have relatively limited effects on graft survival.

The clinical significance of these findings has practical implications when applied to the adage, “do not grab a graft by the bulb.” In general, it is prudent to limit direct physical trauma by grasping the graft either inferior or lateral to the bulb. However, in specific situations, tissue around the bulb is either sparse or friable. In these cases, attempting to avoid the bulb creates a tenuous grip on the graft and often results in multiple failed attempts at insertion, which indirectly increase the graft’s degree of trauma and its potential exposure to dehydration. In such cases, therefore, it is better to accept a small degree of trauma by gently grasping the bulb than a greater degree of damage by frequently attempting and failing to insert the graft.

Prolonged time out of the body — Studies indicate that graft survival does not decrease in grafts that remain out of the body for up to six hours. Limmer, supporting this claim, shows a graft survival rate of about 92 % for FUs kept out of the body for up to six hours; but he also finds a decrease in graft survival rate of about 1% per hour after six hours. At 24 hours, the survival rate is about 70%. Kim shows a survival rate of over 90% for FUs kept in saline for up to six hours. In his study, there is no difference between the survival rate of grafts kept at room temperature and grafts kept at 4° centigrade, as long as the grafts remains moist. Placing a large number of small grafts can take longer than six hours, especially when carried out by inexperienced hands. While most experienced physicians finish a procedure of 1500 grafts in less than six hours, larger sessions or sessions performed by less experienced surgeons not uncommonly take from 8-10 hours. Developing more efficient and quicker methods of placing, therefore, should be an ongoing effort. No matter what techniques the physician uses, however, experience and skill remain the two most important factors for expedient and successful placing. It is essential for practitioners, especially novices, to be aware of their limitations and not to take on a large procedure that is above their skill level, which can lead to grafts that remain out of the body too long.

Popping — Popping occurs when tissue adjacent to the incision transmits enough lateral or inferior forces created during the insertion of the graft to expel the adjacent graft; that is, the previously inserted graft “pops out” of an incision while the surgeon attempts to insert another graft adjacent to it. Any increase in lateral or inferior force increases the potential for popping. Causes for such increases include:

• Grafts which are too large for the incisions
• Shallow incision
• Certain stiffer recipient area tissue types that transmit forces of insertion more efficiently. African American tissue, scar tissue, etc.)
• Inexperience and/or rough placing techniques. Experienced assistants master the fine motor skills and mechanics of gentle insertion. The “art of gentle insertion” limits both popping and direct physical trauma, and I describe it in more detail later in this discussion.
• Extra bleeding in the recipient site can produce a force below the graft that causes the graft to elevate and lift out of its site.

Piggybacking — Piggybacking occurs when the surgeon places a second graft on top of a graft previously placed in the incision. It leads to ingrown hairs and/or epithelial inclusion cysts.(3) Piggybacking occurs more often when it is difficult to determine if a graft has already been placed in the incision. Factors that limit visibility, such as poor hemostasis, not using magnification, etc., increase the potential for piggybacking; furthermore, when grafts are hidden below the surface, the chance of piggybacking also increases. It is important, therefore, to check all questionable sites before placing a graft into the incision and to try and limit the depth of the recipient sites so the initial grafts cannot sink beneath the surrounding skin surface.

Grafts placed too deeply — As noted above, this often occurs during the initial insertion or when patting the grafts with gauze; it also occurs spontaneously after the placer situates the grafts and has moved on to other sites. Just as with piggybacking, when grafts sink below the epithelium, cysts can form and ingrown hairs can develop. In addition, a pitted look can occur. During placing, it is important to check sites repeatedly and to adjust grafts so that they are positioned flush with, or slightly above, the surface epithelium.

Empty sites or missed sites — Sites can be left empty because the placer overlooks them or because a graft slips out unnoticed during the procedure. Persistent bleeding in an area may be a sign that a site has been left empty or that a graft has slipped out. Continually checking for missed sites is, therefore, essential to the success of the procedure.

“Bent” Grafts — Occasionally, when a surgeon places a graft in an incision, the graft bends with the root, coming up toward the surface. Bent grafts occur more often if the site is shallow or if the placer grips the graft too high and pushes rather than pulls it into the site. The fate of these grafts is unknown; possibly, they will not survive. Some surgeons believe that inserting bent grafts leads to kinky hair growth.

Improper direction or orientation of grafts — Hair normally exits the scalp at a specific angle and direction peculiar to that area. The angle and direction of the incision is the predominant determining factor of hair orientation. However, grafts must be placed deliberately to assure that the hair is oriented properly and with minimal physical trauma to the follicles. The importance of this placement varies with the type of graft. Regardless of the angle and direction of the incision, round grafts need to be rotated to face the right direction. Slit and slot grafts must face anteriorly or posteriorly. With FUs, the benefit of graft orientation is more subtle. When the hair is straight, there is no major benefit achieved in rotating an FU in its incisional site. When hair has a curl, however, it is beneficial to rotate the FUs so that all of the hairs exit with their curls pointing in the same direction. Similarly, “chubby” FUs have an inherent direction, just as slit grafts do and it is thus important to ensure correct orientation.

BASIC FACTORS THAT INFLUENCE PLACING

Visualization – Small incisions and tiny grafts are difficult to see, especially in a bloody field or amidst existing hair. A poor view exacerbates many of the problems listed above (piggybacking, missed sites, increased placing time, difficult insertion, etc.). Proper visualization of grafts and incisions, therefore, is a basic tenet of successful placing. To improve visualization:

1. Wear magnification loupes. While magnification loupes improve visualization, some assistants resist wearing them, claiming that their vision is “fine” without them. In my experience, however, if a person places well without magnification, he/she places better with magnification.
2. Limit looking away from the recipient site and “losing your place.” This tenet is similar to the adage, “Keep your eye on the ball.” Surgeons and assistants have a natural tendency to lose their place during insertion if, when picking up a graft, they look away from the recipient site incisions. “Losing your place” increases the possibility of piggybacking and/or of missed sites. It also leads to wasted time when the placer has to check and recheck the site for grafts. To minimize this problem:
   1. Keep grafts waiting to be placed (“on deck”) in the same general field of vision as the recipient site. Placers accomplish this by keeping grafts on the tip of their fingers or on moist gauze situated adjacent to the recipient site incisions.
   2. Follow a pattern. Placing grafts in an organized pattern rather than skipping around decreases the chances of “losing your place.”
   3. Leave the donor hair 3-4 mm long. Longer donor hair not only acts as a marker for filled incisions, but it also makes it easier for the placer to grab and to adjust grafts if necessary.
   4. Consider using a two-person-per-graft, or “buddy” technique, for insertion. “Buddying” eliminates the need for the primary placer to look away from the incision site. I describe this technique in more detail later.

Hemostasis (Bleeding) Control Controlling hemostasis is one of the most important factors for successful placing. Excessive bleeding not only limits visibility, but it also contributes to popping and to grafts that slip out of their incisions. Basic ways in which to control bleeding include:

1. Pre-operative measures: The adage, “an ounce of prevention is worth a pound of cure,” applies here. Before surgery, determine and address any factors that increase the risk of bleeding. These factors include, but are not limited to, medications, such as NSAIDs and Coumadin, or pre-existing conditions, such as liver disease, hypertension, or coagulopathies. They are described in detail in Chapters 7A, B, and C.
2. Anesthesia and patient comfort: Pain in the recipient or donor area indirectly leads to increased bleeding if the patient’s blood pressure and heart rate increase. During longer procedures, a sudden increase in bleeding sometimes indicates that the anesthesia is wearing off. In these cases, it is helpful to use a long-acting agent, such as bupivacaine (Marcaine). Here again, “an ounce of prevention is worth a pound of cure”: If the procedure is a long one, consider repeating the field blocks or nerve blocks at regular intervals before any pain is experienced—for example, if lidocaine is being used for a field block, repeat the field block in both donor and recipient areas three hours after the prior one was produced. (See Unger’s commentary in Chapter 8E.) Controlling the patient’s level of anxiety with anxiolytics and maintaining a calm atmosphere play indirect roles to limit bleeding.
3. Mechanical measures: With skill and experience, mechanical methods can control much bleeding. Occasionally, there is poor hemostasis in an individual site that bleeds heavily (“a bleeder”). Surgeons and staff control these sites with point pressure or by plugging them with a slightly larger graft or dilator. A constant, low-grade oozing from multiple incisions that gradually accumulates to obscure the surgical field occurs more often, however, than individual “bleeders.” Frequently spraying the incisions with a saline solution helps to minimize any decreased visibility of these incisions due to constant, low-level oozing. Diluted hydrogen peroxide solutions may also be used. Some concern exists regarding whether or not hydrogen peroxide is slightly toxic to grafts. Recent studies by Kim suggest that diluted concentrations of hydrogen peroxide solutions are safe to use for cleaning.(4) Chapter 8C discusses other suggestions to control bleeding without epinephrine.
4. Tumescent and epinephrine solutions: Surgeons hold a variety of opinions regarding the use of tumescent and epinephrine solutions to control bleeding in the recipient area.
   1. Low concentration epinephrine solutions — Some physicians use tumescent solutions with a low concentration of epinephrine to control bleeding. The concentrations range from 1:100,000 to 1:300,000 epinephrine and produce both vasoconstriction of superficial vessels and some protection of deeper vessels by distending the dermis and subcutaneous tissues. A potential problem with this technique, however, is that delayed refractoriness to epinephrine and reflex vasodilatation can occur later in the procedure after the epinephrine wears off. Other potential problems of using tumescence in the recipient site are: an increased degree of popping due to tissue turgor and a higher incidence of postoperative edema.
   2. Highly concentrated epinephrine solutions — Surgeons may administer small amounts of a high dose epinephrine solution, which has earned the nickname “super juice.” (5) Concentrations range from 1:10,000 to 1:50,000 epinephrine. Physicians inject only small amounts of solution (1-5 cc) in localized sites in a staged fashion. Some physicians reserve this solution for “as needed” situations only; others use it by moving systematically from one small area to another. A number of opinions co-exist concerning the safety of a higher dose epinephrine solution, especially with cardiac patients on beta-blockers. Sound clinical judgment and adequate monitoring are essential to this technique. (See chapter 8A.)

Hydration Control As mentioned previously, dehydration is a major cause of poor yield. Grafts are vulnerable to dehydration during the placing process during specific times:

1. While on deck and waiting to be placed;
2. During insertion, if it is a protracted procedure;
3. Following insertion, if the graft unknowingly slips out of an incision site.

To keeps grafts hydrated:

1. Repeatedly spray or add cool saline to the grafts on deck waiting to be placed.
2. Keep the on deck grafts close together or touching. Spreading grafts out instead of grouping them together increases the probability that they will become dehydrated, because spread-out grafts have a greater amount of surface area exposed to the drying effects of air exposure.
3. Limit the number of grafts waiting on deck to a quantity that can be placed in a time frame that does not threaten them with the risk of dehydration. This time frame varies depending on the skill and speed of the assistants and on the ability to keep on deck grafts moist. Many surgeons believe that grafts should not be left unprotected or exposed to air for more than five minutes.
4. Appoint one assistant to serve as a “loader.” The loader’s responsibility is to take grafts from the petri dishes and to put them on the placer’s finger or on other on deck areas, replenishing these areas with grafts as necessary. He/she also monitors the grafts for dehydration and rehydrates the grafts as needed. The loader not only helps to control hydration, but he/she also reduces the need for the placer to stop placing, to reload with more grafts, and to re-identify the present placing area.
5. Frequently check the recipient site for grafts that have slipped or popped out after placement.

Graft Sizing – It is important for the size of the graft to fit the size of the incisional site, because problems occur when the grafts are either too large or too small for the site. When grafts are too large, more forceful insertion, multiple failed attempts, and an increase in popping can occur. When the grafts are too small, they can either sink too deep or slip out later in the procedure, and they occasion more bleeding and less visibility.

Graft size varies from case to case depending on the caliber of the hair, donor area hair density, and the skill of the cutters. Graft size also varies depending on the amount of tissue that the physician instructs assistants to leave around the follicles (i.e. the degree of “chubbiness” the physician desires). Incision size varies depending on the blade used or the angle and depth of the incision. It is prudent, therefore, to test graft size to see how grafts fit, early in the procedure, before making too many incisions. If needed, either the size of the grafts or the size of the incision may be adjusted. Sometimes a minimal adjustment in size produces a major effect on the ease of placing.

Graft Spacing Graft spacing also influences placing, specifically with respect to popping. As mentioned earlier, certain patients have more trouble with popping than others. Increasing the spacing between incisions will decrease popping. Therefore, if the surgeon suspects that popping will be a problem, a slight increase in spacing is helpful.

Incision Depth and “Limited Depth Incisions” Incision depth also affects placing. Problems occur if incisions are too deep or too shallow. Incisions that are too deep lead to increased bleeding and increased pitting; therefore, many surgeons have recommended “limited depth” incision and have created instruments to help in making such incisions. (See Chapter 22D.) If, however, incisions are too shallow, insertion becomes difficult because of increased popping. It is important to understand that limited-depth incisions do not, in fact, mean incisions of a truly minimal depth. Put differently, the depth of an incision should not be limited to exactly the same length as the graft; rather, it should be slightly longer than the graft to allow for some “give” during insertion. Shallow incisions also present more problems under certain conditions, such as thin skin from burns or scalp reductions.

Dilators Dilators were created to assist with the placement of smaller grafts. They dilate incisions, mark empty sites, and aid in the control of bleeding. However, dilators are bulky, time-consuming, and awkward to use. They may also contribute to compression by allowing the placer to insert grafts that ordinarily would be too large for an incision site. As experience with smaller grafts grows, many assistants find they place just as well, if not better, without dilators, and, therefore, dilators are not as popular as they once were. Some physicians still use them, however, to plug and to control bleeding in individual incision sites.

MECHANICAL IMPLANTER DEVICES

A number of mechanical implanter devices have been developed over the years in an effort to improve placing. The goal of a mechanical device is to increase the speed and efficiency of placing while simultaneously maintaining a consistently low level of graft trauma. Most devices, however, do not clearly exceed the efficacy or ability of an experienced assistant using a forceps. Currently, two devices have some merit: the Choi Implanter and the Hair Implanter Pen.

• The Choi Implanter: The Choi Implanter is composed of a needle that is left open along one side. The placer loads a single FU into the needle and then inserts the needle into the scalp, carrying the FU along with it. After insertion, the instrument allows the placer to withdraw the needle and, at the same, to leave the hair behind in the scalp. Doctors in Korea use this device extensively, and it works well for the very coarse hair of the native Korean population. It is unknown, however, if the Choi Implanter works as well for less coarse hair. Drawbacks of this device are its expense, its inability to be reused, the need for at least one extra person to place the graft in the implanter, and its minimal availability outside of Korea.
• Two new developments, however, may increase the use of this device in other countries: 1) the creation of a replaceable needle that significantly reduces the cost and increases the availability of this device, and 2) the modification/simplification of this device so that it only inserts the graft instead of both making the incision and inserting the graft, thus allowing practices that do not currently use a stick and place approach to employ the Choi Implanter adeptly.
• The Hair Implanter Pen (HIP): The HIP is a pen-like instrument that contains a tiny, hollow needle attached to a suction device. The placer turns the suction on simply by touching a hole on the side of the device with his/her fingertip. The instrument’s premise is that it automatically picks up a graft with suction instead of squeezing it between the tips of a forceps. After inserting the graft, the placer releases the fingertip from the hole, aborting the suction, and withdraws the pen, leaving the graft behind. The device is simple to use and studies show that beginners prefer it, finding it easier to employ than a forceps. However, the HIP offers no speed advantage when compared to experienced placers. In addition, it is not clear that using this device actually decreases trauma. Other problems with the HIP are that its suction is very noisy and that, presently, the instrument has some mechanical problems.

SINGLE PERSON PLACIN TECHNIQUE IN PRE MADE INCISIONS

The Mechanics Of “Gentle” Graft Insertion

Gentle graft insertion limits popping, trauma, and bleeding. The ability to insert grafts gently is a talent that comes with experience and the development of skill. Some of the specific steps and mechanical factors that lead to a gentler insertion are:

1. Proper body and hand positioning: The body should be positioned so that it is ergonomically easy to insert the forceps into the incision at the proper angle. Many assistants assume contorted positions, struggling to insert grafts. Simply turning the patient’s head or repositioning the assistant’s hand to a more ergonomically friendly position often dramatically increases the ease of placing.
2. Finding the angle: All incisions are made at a specific angle. When a forceps enters an incision at the proper angle, its tip slides straight down the path of the incision without touching the lateral walls or causing/requiring undue force. It is helpful to get a feel for the angle by performing test insertions with an empty forceps before placing begins.
3. Grasping the graft: Grasp the graft as proximally as possible, trying not to touch the bulb. However, if there is minimal tissue around the bulb, gently grasp the graft at the bulb rather than further up on the shaft. When grasped above the bulb, the graft is more difficult to insert and tends either to bend or to be compressed between the tip of the forceps and the skin. This is because the graft is not firm enough to be pushed down from above; instead it needs to be pulled into an incision from the proximal (bulb) end. To visualize this, imagine trying to push a piece of string instead of pulling it from its end.
4. Preparing for insertion: Once the graft has been gripped with the forceps, align its tip with the angle of the incision.
5. Initial insertion: Focus attention not on the graft but on the tip of the forceps. Concentrate on sliding the tip into and along the path of the incision. The graft will follow. Do not push the graft into the incision; it will be pulled into the incision behind the tip of the forceps.
6. Early release of the graft limits popping: When the graft is one-half to three-quarters of the way into the incision, release the graft and withdraw the forceps. Popping typically occurs here because of the combined mass of the forceps and the graft, which both occupy the site. Once the placer releases the graft, and it sits about one-half to three-quarters of the way into the incision, he/she can easily re-grip the graft at the point where it exits the skin and can adjust it downward so that it is either flush with or slightly elevated above the epithelium. In this technique, the placer never has to insert the forceps more than approximately one-half way into the incision, thus decreasing the amount of popping in difficult cases.

TWO PEOPLE PER GRAFT INSERTION IN PRE MADE INCISIONS

BUDDY TECHNIQUE

Most techniques employ a single person to insert grafts throughout the entire placing process. Less commonly, two people, “buddies,” divide the insertion. With this approach:

1. The first assistant finds and opens the incision site;
2. The second assistant partially inserts the graft;
3. And finally, the first assistant adjusts the graft to the proper depth and then locates and opens the next site.

Placers can use this approach when making all of the incisions first or when employing the stick and place technique. When they use the stick and place technique, the first assistant makes the incision, rather than simply finding and opening the existing incisions. The benefits of this approach are:

1. Opening the incision site permits gentler placing and less popping;
2. The first assistant never has to take his/her eyes off the recipient site, so there is less chance of losing his/her place, of piggybacking, or of missing sites;
3. Opening the site makes the mechanics of insertion easier, decreasing the possibility of trauma or popping;
4. Continuous minimizing of bleeding after every incision improves visibility;
5. Stick and Place is a good method when training a new assistant without losing quality control;
6. Although it is not necessary in all situations, “stick and place” is a good technique to have in reserve for difficult cases prone to bleeding and popping.

The disadvantages of this technique are:

1. It requires more staff;
2. Usually only one area of the head can be placed at a time, and total placement time depends on the difficulty of the case with respect to bleeding and popping. In cases where bleeding and popping are problematic, it is faster and more effective to have two people work together in one area than to have two people struggle separately in different areas. When bleeding and popping are not problems, however, it is more efficient to have two people placing grafts separately in different areas.

“STICK AND PLACE” TECHNIQUE

Stick and Place is the general placing approach of making an incision and inserting the graft immediately afterward.

1. Potential Advantages of the Stick and Place Technique
   1. The ability to control homeostasis, since the incision houses a graft immediately after it is made. There is less bleeding and more visibility.
   2. No “missed” incisions when grafts are being inserted.
   3. No piggybacking.
   4. Inserting a graft immediately after making an incision takes advantage of the initial dilation of the incision by the needle or blade. The latter makes insertion of the graft easier and less traumatic and results in less popping.
2. Potential Disadvantage of the Stick and Place Technique
   1. The risk of “painting yourself into a corner.” When the placer sticks and places, he/she works in a small area and sometimes misses the big picture. It is possible, therefore, to run out of grafts before obtaining the desired distribution or to cover an area unevenly.
   2. If the physician’s State Medical Board (or other local authority) requires that the surgeon make all the incisions, then he/she has to be in the room for the complete stick and placing process and the procedure must stop if the physician leaves the operating room for any reason.
   3. If the physician’s State Medical Board (or other local authority) allows him/her to delegate in the process of making incisions, then he/she can delegate part or all of the placing process tasks. However, the more the physician delegates, the greater loss of control he/she has over the distribution, pattern angle and direction of graft placement, which means the physician must trust the skill and judgment of his/her assistants. This is particularly important when delegating the responsibility of the hairline area or when using less experienced assistants. Supervision and methods of quality control are especially crucial in these situations.

EXPERIENCE AND QUALITY CONTROL

Experience and skill are more important than the use of a particular technique to place grafts successfully. While experienced placers achieve good results with a variety of techniques, inexperienced placers can create poor results no matter which technique they use. In many practices, assistants place all grafts, and, therefore, it is important for the surgeon to maintain quality control. In the past, when placers inserted only a few hundred grafts at a time, it was easier for the physician to oversee the placing process and to maintain quality control. Grafts were larger, less susceptible to trauma, and easily adjustable by the physician at the end of surgery. Maintaining quality control and using experienced assistants is more difficult today for a variety of reasons:

1. Placing has become more complex and, therefore, more prone to problems. It is no longer possible simply to check the grafts at the end of a procedure. A high level of skill must be maintained throughout the entire placing process.
2. Many physicians today do not know how to place grafts and are totally dependent on their assistants.
3. In small medical practices, it is hard for assistants to perform cases on a regular enough basis to increase their skill levels.
4. In larger practices, the combination of a high staff turnover rate and the need for more assistants exposes patients to new and inexperienced assistants.

It is important for the physician to implement quality control and not to delude himsel/herself that the staff naturally places grafts well.

CONCLUSION

We want to develop placing techniques that will insure both the maximum yield and the greatest degree of naturalness. To insure maximum yield, grafts must be placed gently and promptly, thereby limiting the potential for physical trauma, dehydration, and extended time out of the body. To insure the highest degree of naturalness, grafts must be placed at the desired depth and direction. Many factors that influence the success of placing have been covered in this discussion. The most important, however, always remains experience and skill.