When follicular unit excision (formerly know as follicular unit extraction) was first established, physicians performed the procedure exclusively with manual sharp punch tools. The idea behind the sharp punch made sense: the tool needed to be sharp enough to puncture the skin and allow full tissue dissection down to the level of the follicle (roughly 4-5 mm). However, because the direction of the hair follicles above and beneath the surface of the skin didn't often match, hair restoration physicians noted increased transection rates and less viable grafts for transplanting. Those that were transplanted wouldn't produce any new hairs.
The solution to this problem, first advocated by Dr. James Harris, was the invention of a blunt (unsharpened/dull) tipped punch device. Unlike a sharp punch, the blunt tip is able to separate the follicular unit from its surrounding tissue without causing follicle transection. Even if the direction of the follicle below and above the surface doesn’t match, the unsharpened, dull tip will not slice the follicle during extraction.
Because a blunt punch could not easily puncture the scalp, Dr. Harris proposed a multiple step extraction process.
Multi-Step Extraction Process
There are a two variations of the multiple step extraction process.
The Three Step Extraction Process:
The 3 step process utilizes both a sharp and a blunt punch. First, a small sharp punch scores the skin around a follicular unit. Then, a small blunt punch is used to go deeper into the soft tissue surrounding the follicular unit for extraction. Finally, the follicular unit is removed with forceps.
The Two Step Extraction Process:
The 2 step process utilizes only a sharp punch. First, a sharp punch is used to score the skin and separate the follicular unit from the scalp. In order to avoid transection, the sharp punch is not inserted as deeply as the blunt punch is during the three step process. However, the punch enters the skin deeply enough to loosen the graft and allow for removal. Finally, the loosened graft is removed with forceps. Graft removal sometimes requires more force and work than during the three step technique.
Manual and Motorized Extraction Devices
Sharp and blunt punches were made available to manual extraction tools and to motorized devices once invented. This includes Dr. Harris' Powered SAFE Scribe - the motorized version of his original manual SAFE system. Because of the ability to apply a fast initial rotation speed, the motorized blunt tip is able to penetrate the scalp without prior sharp scoring of the skin. However, because the tip is blunted, it reduces overall follicular transection.
Over time, FUE physicians applied a variety of sharp and blunt punches to other motorized devices and offered patients the ability to undergo FUE via sharp punch motorized extraction, blunt punch motorized extraction, sharp or blunt manual extraction, and a combination of both.
The above gets confusing when considering all the options. Thus, below includes a summary of the potential advantages and disadvantages of each device and punch along with a description of some of the more popular extraction devices.
Advantages and Disadvantages of Sharp and Blunt Punches
Advantages of the sharp punch include the ability to easily penetrate through the scalp and a reduced number of rotations/oscillations to remove the follicular unit.
Disadvantages of the sharp punch include increased risks of transection during extraction and a tendency to dull quickly, requiring surgeons to use multiple punches per procedure.
Advantages of the blunt punch include greatly reduced transection of the follicular units and reduced trauma to tissue surrounding the follicle during extraction.
Disadvantages of the blunt punch include an increased number of oscillations/rotations required to penetrate the scalp and reach appropriate depth during extraction. Some experts believe this creates excessive heat, tension, friction and torsion on the grafts and surrounding tissue. Moreover, use of the manual blunt punch requires an additional step when combined with sharp punch.
Size (Diameter) of the FUE Punch Tool
The diameter (size) of the FUE punch tool varies from around 0.6 mm all the way up to 1.2 mm with 0.75 to 0.9 mm being fairly standard. Because the size of the follicular units differ, most hair restoration physicians now use a variety of different sized punches during an FUE procedure. For example, a 0.75 mm FUE punch may be used to remove a small, 1 hair follicular unit because it will decrease transection and prevent unnecessary scarring. However, a 0.75 mm punch would be too narrow for a 3-4 hair graft, and would cause transection during removal. For a graft of this size, a 0.9 mm punch would likely be more appropriate.
In general, smaller punches are ideal for reducing the circular scarring associated with FUE procedures, but are not effective for removing larger grafts. Conversely, larger punches are best suited for removing bigger follicular units, but also create a greater amount of scarring. Normally, physicians strike an appropriate balance between scarring and transection rate by using a variety of different diameter punch tools for different sized follicular units.
Also, learn more about "Automated and Robotic Assisted FUE Extraction Devices.