5 Review of Studies on Graft Hair Survival
Summary
Keywords: hair transplant graft survival hair follicles storage solutions hair survival density follicular unit grafts hydrogen peroxide
Key Points
•Multifollicular grafts have higher survival rates than follicular unit grafts.
• “Chubby” grafts fare better than skeletonized grafts in survival studies.
•Surprisingly, there are very few studies comparing follicular unit transplantation and follicular unit extraction harvested grafts.
5.1 Introduction
Meeting a patient’s expectations of density is one of the most important goals in hair transplantation. Since achieving density is directly related to graft survival, understanding the factors that can increase or decrease survival is extremely important to the field of hair restoration surgery.
Performing survival studies that are accurate, clinically significant, and easy to interpret is difficult for numerous reasons. Some of the most significant difficulties are as follows:
•Decreased survival is not the result of just one factor, but the cumulative effect of multiple factors that push the follicle over a certain “survival threshold.” This can make interpreting the significance of a study on an individual factor difficult. For example, if we are studying the effect of incisional density on survival, we do not know if the results are due directly to the variation in blood flow from different incisional densities versus variation in difficulty in planting at high densities.
•Another issue is that hair counts in a given area of the scalp are not “static” over time. Van Ness showed that snapshots taken of the same 1-cm area of the scalp regularly over a year exhibited significant differences in hair counts as follicles went in and out of anagen and telogen. Obviously, this would introduce error if a study was done in an area that was not totally alopecic.1
•Finally, even with digital macrophotography, hair counts are very difficult to perform with complete accuracy. Anyone who has performed hair counts knows there is a strong subjective component. Distinguishing between a single hair and two hairs stuck together, or between a small hair and a shadow, can be difficult. Since many studies are done with small numbers, even the inclusion or exclusion of a few FU can significantly alter the results.
In spite of the aforementioned difficulties, these studies are important and useful, as they accumulate valid answers to our questions that over time. .
This chapter will focus primarily on studies that evaluated intraoperative factors that influence survival using hair counts (Fig. 5.1). Due to space limitations, only brief summaries and discussion of these studies are presented.
Fig. 5.1 Six study boxes outlined with corner tattoo dots and a narrow 2-mm bald “moat” around each box, with recently placed grafts.
5.2 Follicular Unit Graft Survival
In 2011, the authors summarized 21 separate studies in which the FUs were planted as controls and were not subjected to any stress factors. A total of 7,362 FU grafts were analyzed. The grafts included one-, two-, and three-hair grafts in various ratios with a variety of recipient-site types. Planting densities ranged from 20 to 50 FUs/cm2. The results of the meta-analysis showed that the survival percentage for the 7,362 FU grafts was 89.7%.2
5.3 Multifollicular Unit Graft Survival
Only a few studies have looked at MFU (multifollicular unit or mini graft) survival.
•In 1999, Beehner studied the survival in 65 “minigrafts,” containing a total of 493 hairs, placed into round recipient sites. The results at 7 months showed a survival of 493/521 follicles for a survival rate of 94.6%.3
•In 2000, Unger studied survival of minigrafts in three patients for a total of 229 hairs. At 8 to 9 months, 241 hairs were found to be growing, for an overall survival rate of 105.2% (241/229).4
•In 2005, Beehner conducted another study in which 12 “round” MFU grafts were compared with 12 “slit” MFU grafts. The growth rate for the 78 hairs in the “round” graft was 101% (79/78) and 100% (66/66) for the slit grafts.5
Editor’s/Author’s Interpretation
Survival of MFU grafts appears to be between 95 and 105%, which is slightly higher than FU survival (which is closer to 90%). A few theories about why MFU grafts have a slightly higher survival (and sometimes over 100%) include the following:
•Greater protection of the follicles by the surrounding tissue.
•Unseen early catagen or exogen hairs, not seen in the original hair count, that grew out later.
5.4 “Skinny” versus “Chubby” FU Graft Survival
•In 1997, Seager sought to see if there was a difference in survival between “skinny” and “chubby” FU grafts. The follicular survival rate of 88 “skinny” FU grafts was 89%, compared with 113% for the “chubby” grafts (Fig. 5.2a, b). Fig. 5.2a, b).6
•In 1999, Beehner repeated Seager’s study. He left a little more tissue around the bulb than Seeger did in his “skinny grafts.” The follicular survival at 1 year was 103% for the skinny grafts and 133% for the chubby ones.7
•In 2010, Beehner published a third study in which he compared the survival of one- and two-hair FU grafts (410 follicles) that were trimmed: “skeletonized,” “medium,” or “chubby.” The follicular survival rates at 19 months were 68.7% (skeletonized), 80% (medium), and 88% (chubby). The survival rates for one-hair FUE grafts were 48% (skeletonized) and 98% (medium).8
Fig. 5.2 Grafts planted in Seager’s 1997 study of (a) “chubby” grafts and (b) “skeletonized” follicular unit (FU) grafts.
Editor’s/Author’s Interpretation
All the three studies seemed to show that graft survival decreased as tissue trimming increased. Chubbier grafts consistently had the highest growth and skeletonized grafts were consistently the worse. The effect was greater for one-hair grafts than for two-hair grafts. The most common theory for this observation is, once again, the loss of protective tissue around the bulb or bulge that occurs with trimming, or the initial presence of unseen catagen/exogen hairs in chubbier grafts.
5.5 Incisional Density and Survival
•In 2004, Beehner performed 1-cm box survival studies on two-hair FU grafts placed at densities of 20, 30, 40, and 50 incisions per box. At 13 months, the survival rates of grafts at different densities were as follows: 20 grafts/cm2 (91%), 30 grafts/cm2 (96%), 40 grafts/cm2 (89%), and 50 grafts/cm2 (91%).9
•In 2005, Mayer et al placed two-hair FU grafts into four separate 1 cm2 study boxes at densities of 20, 30, 40, and 50 grafts/cm2. A 19-gauge needle was utilized to make the recipient sites, and the grafts were placed with the stick-and-place technique (Table 5.1). The follicular survival rates at 1 year from two persons were 20 grafts/cm2 box (97%), 30 grafts/cm2 box (99%), 40 grafts/cm2 box (92%), and 50 grafts/cm2 box (89%).10
Table 5.1 Planting density study by Mayer et al10 with four different densities
2-hair FU/cm2 | 20 FU/cm2 | 30 FU/cm2 | 40 FU/cm2 | 50 FU/cm2 |
Survival at 1 y | 97% | 99% | 92% | 89% |
Abbreviation: FU, follicular unit. | ||||
In both the aforementioned studies, the grafts planted at 30/cm2 survived the best, but survival was generally good at all four planting densities.
•Nakatsui et al and Tilosani performed 1-cm box studies that showed that good survival “could” be achieved at higher densities of 72 and 100 graft/cm2.11,12
Editor’s/Author’s Interpretation
Most studies demonstrated a slight but consistent trend toward decreased survival as incisional density increased from 20 to 50 FU/cm2, with the best survival typically occurring between 30 and 40 FU/cm. However, survival was fairly good (>85%) at all these densities. Nakatsui et al and Tilosani surprisingly showed that good growth could also be achieved at very high densities of 72 to 100 FU/cm2. The editor feels it is important to point out that one must not interpret the results of Tilosani and Nakatsui et al to say it is “safe” to routinely attempt at very high incisional densities. Although it is of interest that their studies demonstrated that good survival “can” be achieved (under the favorable conditions), it does not mean it “will consistently” be achieved in the less favorable environment of a full surgery. Consistency of good growth is more important than the ability to occasionally achieve good growth. The editor believes that one of the factors that decrease survival at increased densities is greater difficulty and more traumas with placing. The use of implanters could theoretically improve the consistency of survival at higher incisional densities.
5.6 “Time Out of Body” and Survival (Table 5.2)
Table 5.2 Comparison of Limmer’s and Beehner’s study of grafts out of body in sterile saline at 4°C for prolonged periods
Limmer | Beehner | |
2 h | 95% | 74% |
4 h | 90% | 64% |
6 h | 86% | 90% |
8 h | 88% | 90% |
24 h | 79% | 74% |
48 h | 54% | 68% |
72 h | — | 20% |
96 h | — | 12% |
•Limmer in 1992 recorded the survival rates for grafts left out of the body, in chilled normal saline, for variable amounts of time up to 48 hours. The survival rates at different times were 2 hours (95%), 4 hours (90%), 6 hours (86%), 8 hours (88%), 24 hours (79%), and 48 hours (54%). This corresponded approximately to a loss of 1% of the grafts for each hour out of body.13
•In 2010, Beehner repeated Limmer’s study of grafts stored in chilled saline and left “out of body. He extended the time out of body from 48 to 96 hours. The results were similar and as follows: 2 hours (74%), 4 hours (64%), 6 hours (90%), 8 hours (90%), 24 hours (74%), 48 hours (68%), 72 hours (20%), and 96 hours (12%).14
Editor’s/Author’s Interpretation
Both studies showed similar results with graft survival remaining fairly good up to 6 to 8 hours. However, in both studies, survival continued to decrease and was significantly reduced by 24 to 48 hours, hence the general rule to not let grafts stay out of the body past 6 to 8 hours.
Related posts:
Methods and Techniques to Study Hair Cell Survival
Hair Transplantation: The Promise of Cell Therapy
OSHA, Laboratory Screening, and Office-Based Surgery
The Patient with Minimal Hair Loss: Planning and Decision-Making
The Young Patient: Planning and Decision-Making
Introduction and Definition of Follicular Unit Excision
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
