Punch Designs

54 Punch Designs

Ken Williams

Summary

Circular round punches have been used for harvesting grafts with both the punch grafting technique described in the early literature by Okuda and Orentriech and the contemporary follicular unit excision (FUE) techniques of today. They varied greatly with respect to size, cutting-edge sharpness, and design. For far too long punches were manufactured with little documentation about their specific design. In addition, very often, manufactures did not use high-grade materials now available that extend the life of FUE punches. In 2013, a committee formed by the International Society of Hair Restoration Surgery (ISHRS) to standardize the language used in FUE published its findings on various FUE devices, terminology, and punch designs and shapes. FUE punches were described and categorized by various characteristics including the specific diameters, the location of cutting edge, the punch size determined by to the diameter of its cutting edge, and whether the cutting edge was sharp or blunt. Recently, a variety of new punch designs and systems were introduced to the FUE community that broaden the hair restoration surgeon’s options when selecting punches for FUE harvesting. Because of the newer punch designs, the ISHRS and FUE community will need to expand or revise to some degree the current categories of FUE punches. Some of the newer punch designs and systems will be described in this chapter and in Chapter 67.

Keywords: sharp punch blunt punch trumpet punch open punch flared punch Hex punch DrUPunch Curl Punch hybrid punch

Key Points

•Traditionally, follicular unit excision (FUE) donor harvesting has used sharp and blunted punches for harvesting.

•Several novel FUE punch designs that allow the hair restoration surgeon to increase harvesting rates and decrease graft transection rate are discussed.

•The improvement of graft quality is critical to successful harvesting and cosmetic outcomes.

54.1 Introduction

A fundamental component of the follicular unit excision (FUE) technique is the punch. It is important for the surgeon to fully understand the composition of the punches, various designs, the nature and location of the cutting edge, accurate determination of punch diameter, and the advantages and disadvantages of different punch designs. Although the basic principles of preforming an FUE procedure are the same, variation in punch design and properties can influence technical and procedural details as well the success of the procedure. For far too long punches were manufactured with little documentation about their specific design. In addition, very often, manufactures did not use high-grade materials now available that extend the life and wear of FUE punches.

In 2013, a committee formed by the International Society of Hair Restoration Surgery (ISHRS) to standardize the language used in FUE published its findings on various FUE devices, terminology, and punch designs and shapes.1 FUE punches were described and categorized by various characteristics including the following:

•Specific diameters: internal lumen, external wall, and cutting edge (Table 54.1).

•Location of the cutting edge: internal bevel with outside cutting edge, external bevel with inside cutting edge, and mid-bevel with cutting edge in the middle (Table 54.2).

•Punch size: determined by the diameter of its cutting edge (Table 54.3).

•Sharpness of the cutting edge: sharp versus blunted (Table 54.4).

Table 54.1 Classification of punch by diameters

External diameter of the punch	Diameter of the external surface on one side of the punch to the external surface on the opposite side of the punch
Internal diameter of the punch	Diameter of the internal surface on one side of the punch to the internal surface on the opposite side of the punch
Cutting-edge diameter of the punch	Diameter from the cutting part of the punch on one side of the punch to the cutting part on the opposite side of the punch

Table 54.2 Classification of punch by the location of the cutting edge

Outside diameter punch (inside bevel punch)	The cutting edge is located on the external surface of the punch
Middle diameter punch (middle bevel punch)	The cutting edge is in the middle of the wall of the punch^a
Inside diameter punch (outside bevel punch)	The cutting edge is located on the internal surface or wall of the punch
^a The cutting edge may not be exactly in the middle wall portion of the punch.

Table 54.3 Classification of punch by the diameter of the cutting edge

Small	Cutting-edge diameter that is ≤0.8 mm
Medium	Cutting-edge diameter is >0.8 mm and <1.0 mm
Large	Cutting-edge diameter that is ≥1.0 mm

Table 54.4 Classification of punch by the sharpness of the cutting edge

Sharp	Punch possesses a sharpened cutting edge
Dull blunted	Punch does not have a sharpened cutting edge

Although not universally agreed upon, another way to broadly categorize punch types is as follows:

•First came traditional sharp punches which had as a main characteristic, a forward-directed sharp cutting edge formed by the junction of the inner and outer walls.

•Then came the original blunt punch which had a thick, rounded, forward-facing surface and used blunt dissection to separate tissue.(i.e Harris SAFE punch).

•Next, flat punches evolved from the blunt punch, having as a primary characteristic, a “flat” surface sandwiched between a smoothed inner edge and sharp outer edge that is directed perpendicular to the axis of the punch. (i.e. Harris’ hex punch, Devroyes’ hybrid-Trumpet & Tornado punch, Duas’ tube punch). These flat punches were the first to officially be called a hybrid punch because they combined the properties of both sharp and blunt punches. Like a sharp punch, the external cutting edge easily cut the epidermis; while, like a blunt punch the flat surface is protective against graft transection upon deeper dissection.

• More recently, newer sharp punch designs have developed which have as a main feature a more laterally directed sharp cutting edge (i.e. Trivellini edgeout and flared punch, Umar intelligent punch). Similar to hybrid-flat punches, these newly designed sharp punches had the benefits of penetrating the epithelium easily, while at the same time being more protective against graft transection than traditional sharp punches. For this reason, some have also refereed to these newly designed sharp punches as hybrid punches.

Both hybrid-flat punches and laterally directed sharp punches offer significant improvements over the original forward-facing sharp punches. However, sharp punches and flat punches have differing physical properties and mechanisms of action. In addition, from a historical perspective, the term hybrid first originated to describe hybrid-flat punches. Therefore, there is currently some controversy about lumping them both under the same general term `hybrid’ without qualifiers. One possible solution is to use the more specific terminology `hybrid-flat punch’ or `hybrid-sharp punch’ when discussing specific punches.

It should be mentioned that a specific FUE technique is much more than just the punch used. It is also a function of multiple other factors such as; the properties of the motor used; type of rotation, the presence of suction, irrigation, depth control, etc.

These variables are just as important and work hand in hand with punch design to create the total system. Although there is some crossover in content, this chapter will focus more on punch design, while other chapters will focus more on the other factors.

54.2 Punch Composition

For the hair surgeon assessing FUE punches, the characteristics of type of stainless steel, wear, toughness, heat treatment, passivation, and surface treatment of the punch are important. These factors determine the quality and resistance to dulling. Resistance to dulling does impact follicular transection and harvesting rates. Punches ideally should be hard, have good tensile strength, and be resistant to wear and tear. They need to withstand abrasion and corrosion. They need to be able to withstand chipping and cracking during stress or pressure. This is determined by the manufacturing process, content of alloying elements, amount of carbon, level of impurities, etc.

The types of steels potentially used for the manufacturing of FUE punches are categorized into four groups based on their chemical compositions:

•Tool steels: Containing tungsten, molybdenum, cobalt, and vanadium.

•Stainless steel types: Austenitic, ferritic, and martensitic.

•Carbon steel content: Low, medium, and high carbon.

•Alloy steel content: Manganese, silicon, nickel, titanium, copper, chromium, and aluminum.

Stainless steel is the most common material used for punches. There are over 3,500 different grades of steel with unique physical, chemical, and environmental characteristics per the World Steel Association. Stainless steel in the 400 series is considered by the author an excellent heat treatable steel for use in FUE punches and medical devices. The 400 series is known to be highly resistant to corrosion and heat exposure.

Heat treatment or tempering of punches is standard during the manufacturing process and known to increase the strength of the material. If a punch is not heat treated, it probably will be deformed and cannot be used on subsequent FUE procedures. Not all stainless steels are able to be heat treated. Heat treating steel requires proper controlled heating and/or cooling of metals to alter their physical and mechanical properties.

Passivation is an essential step to reduce the potential corrosion effects of stainless steels upon human tissue. Passivation is a process where the punches are put into an acid bath to remove a thin film of oxide from the surface. The chemical process results in the elimination of “free iron” particles from the punch surface and reduces the potential for corrosion. Electropolishing has the same effect and is used by some punch manufacturers as an alternative.

Surface treatment of the punch with titanium nitride (TiN) or titanium carbonitride increases the life of the punch when applied as a coating to the external surface. TiN is inert, nontoxic, and exceptionally hard ceramic material. Applying a coat of TiN to a punch hardens and protects the punches’ cutting surfaces. The application of TiN coatings typically extends the tool life by five to seven times and does not corrode.

54.3 General Punch Characteristics

In general, most punches are hollow cylinders with an inner and outer wall. They have a shaft and distal tip that contains a cutting edge (Fig. 54.1). The design and distal tip of punches can vary with respect to many factors, including inner and outer wall diameter; bevel direction, modifications to tip shape (flared, serrated, slotted, etc.), modifications of inside wall (textured, curved etc.), etc. Different punch designs confer different cutting properties as well as the ability to produce quality grafts with minimal trauma or transection. In the following sections, we will discuss some of the more common and important punch designs and their properties.