Basic Instrument Use Course Notes: Scissors

Introduction to Scissors Blades Surgical scissors are instruments that can be used Scissors have two blades: the inner blade and the outer for both cutting and dissection. The three main blade. The inner blade is the side of the blade that faces applications for scissors include: the opposing blade and is visible when the instrument is open. The outer blade is the side of the blade that can 1. Sharply cutting soft tissues be seen when the scissors are in the closed position. 2. Bluntly spreading soft tissues during dissection The cutting edge of the blade is located along the inner 3. Cutting suture or bandage materials. side of the blade.

Scissors offer several advantages over scalpel blades, The spine of the blade is the thickest part, and it is such as the ability to precisely cut loose soft tissues, located opposite the cutting edge. Finally, the end of especially deeper tissues that cannot be held under the blade region is called the tip or point of the scissor, tension. Another advantage is that scissors allow for and is the area that tends to receive the most wear. superior depth control during dissection. However, Scissor tips vary in configuration and they can be blunt, scissors have one significant limitation; they require an sharp, or a combination of sharp and blunt. opening in the tissue to insert the lower blade. Scalpels, on the other hand, can be used to incise through an Types of Scissors intact tissue surface. Despite this limitation, scissors Scissors come in many shapes and sizes, most are important surgical instruments and are frequently bearing the name of the surgeon that developed the used during surgery. instrument. Some names are descriptive, like the sharp-blunt scissors. Others are named for the type In this module we will examine the common types of of procedure they are often used in, such as tenotomy scissors used in veterinary surgery; how to properly scissors or bandage scissors. In this topic, we will focus grip, use, and pass scissors; the four cutting and on the main classes of scissors used most commonly dissection techniques for scissors; and the surgical in veterinary surgery. Learn more about each type of applications for scissors. scissor shown here below.

Anatomy of Scissors Mayo Scissors Handle Mayo scissors are characterized by a smaller blade- All scissors feature a handle, where the scissors are to-handle length ratio. These stout scissors are often held during cutting or dissection. The handle has used for cutting tough tissue or suture. Mayo scissors two rings, called the finger hole and the thumb hole. are available in both straight-bladed and curved- Scissors are made to work most effectively for a bladed styles. The straight-bladed Mayo scissors are specified right- or left-handed surgeon. Many left- designed for cutting tough tissues near the surface of handed individuals learn to use right-handed scissors the body. Curved-bladed Mayo scissors allow for better with their left hands, but this can be ineffective and visualization during deep tissue awkward. Left-handed scissors are available for left- dissection. handed surgeons who prefer them. Metzenbaum Scissors Shanks Metzenbaum scissors are characterized by distinctive, Scissors have a set of articulating blades, each of which long, slender handles and shorter blades. These are attached to the handle by the shank. The shanks scissors come in a variety of lengths and are used to can either be of equal length or be unequal in length cut and dissect delicate soft tissues. Metzenbaum by an amount known as an “offset.” Surgical scissors scissors should never be used for cutting sutures or usually have shanks of equal length. The shanks and tough tissues. Because of their specific function, they the blades meet at the pivot screw. The pivot screw is sometimes are called Metzenbaum dissecting scissors. responsible for holding the blades together at a specific tension. 1 Tenotomy and Iris Scissors tough tissue. In addition, straight scissors can provide Tenotomy and iris scissors are very small dissecting a more precise straight cut compared to their curved scissors. Iris scissors have a fine, pointed tip and are counterparts. These characteristics explain the normally reserved for the most meticulous work. common practice of using straight, stout, Mayo scissors Tenotomy scissors are similar in size and purpose, but to open the tough linea alba in midline abdominal have blunt tips that push tissues aside rather than approaches, where it is important to avoid straying piercing and damaging them. These scissors are used to paramedian into the rectus muscles. dissect around delicate neurovascular bundles, and for purposeful cutting of vital smaller structures, such as Blunt-tipped scissors are favored over sharp- the ureter or urethra. tipped scissors in situations where dissection is being performed around important structures. Wire Cutting Scissors The advantage of the blunt tip is that it is less likely Wire cutting scissors are characterized by short, stout to get caught in tissue. Additionally, blunt-tipped blades with a sharp, angled tip. One side has a serrated scissors separate tissue without damaging nearby blade, while the other side has a smooth blade. On the neurovascular structures, especially when probing or serrated side, the blade often has a small notch at the bluntly separating connective tissue layers. base to help hold wire in the blades during cutting. Some scissors possess a serrated edge. These edges Lister Bandage Scissors have fine notches, like teeth on a metal saw, which help Lister bandage scissors have angled, serrated or prevent tissue from slipping out of the blades. Serrated unserrated blades and an angled, blunt tip. Bandage scissors are useful for cutting slippery tissue, or for scissors are often found in first aid kits and have firm, tough tissue such as the ear canal, which tends numerous uses that make them valuable. Their three to slide out of the blades during scissor cuts. Plastic mains functions include: trimming bandages to custom surgeons often choose serrated curved scissors in size, cutting through gauze, and helping to remove order to create accurate and conforming skin incisions. patient bandages. For this last purpose, the angled blades are extremely important, since they angle away Some scissors, like the Super Cut™, Microsharp, and from anything beneath the cutting surface. This helps SureCut scissors, possess specialized blade edges. keep the scissors away from the skin, preventing injury These scissors have uniquely ground edges where during bandage removal. The blunt tips also minimize one edge has microserrations and the opposing edge the risk of piercing the skin, which might occur with is honed sharp. This combination ensures precise, sharp tipped scissors. fine, and non-crushing cuts that minimize trauma. The Super Cut™ patterns also cut efficiently when used Selecting Scissors in most angles without changing hands or turning the scissors over. Metzenbaum, Mayo, and iris scissors are In addition to main families, scissors are classified all usually supplied with Super Cut™ blades. Keep in according to a number of other differentiating mind that although Super Cut™ scissors cut soft tissues characteristics. Features such as straight shanks, very well, they dull easily, especially when used to cut curved shanks, or serrated edges greatly impact the tough tissue or sutures. Super Cut™ scissors are readily suitability of the instrument for cutting and dissection identified by their black ring handles. purposes. In this topic, we will explore a range of scissor variations and the surgical applications for which they Some scissors have tungsten carbide inserts on are best suited. the blade edges. Carbide is a very hard metal that maintains a sharp edge much longer than stainless Curved scissors are often chosen when the tissues steel, reducing the frequency of sharpening. However, need to be cut in a smooth curve. Another advantage unlike carbide tipped needle holders, the carbide of scissors with curved blades is that they offer 30–40 inserts in scissors cannot be replaced. Carbide-tipped degrees more directional mobility than straight scissors are readily identified by their gold ring handles. scissors. When working in remote recesses where horizontal cutting is needed, curved scissors also Gripping, Using, and Passing Scissors allow for better visibility of the tissues being cut, when compared to straight scissors. The most common manner of gripping scissors is to insert the tip of your thumb on your dominant hand Straight scissors provide better mechanical advantage, into one ring and the tip of your ring finger into the making them superior to curved scissors for cutting other. The rings should rest between P2 and P3, 2 but do not insert your fingers further than the last How Scissors Work knuckle. Inserting the fingers more proximally reduces Most surgeons favor scissors over scalpels when the motion and action, and handling becomes awkward cutting flaccid tissue or when dissecting close throughout the range of motion of the wrist. The index to important structures. The reason behind this finger is placed on the shanks, close to the hinge, and preference is that scissors are good at stabilizing tissue, provides stability by supporting the sides of the shank. allowing for a more accurate cut. To understand why In the scissors grip, the positions of the thumb, index, this is so, let’s take a closer look at the physics behind and ring fingers form a triangle, giving rise to the term how scissors work. “tripod grip.” The greater the distance between these fingers, the better control the surgeon has with the Scissors are designed so that three force vectors scissors. are simultaneously used in cutting. The three forces include closing, shearing, and torque. The forces are As with all ringed instruments, scissors should not be transferred from the surgeon’s hand to the shanks, held using a grasp like a “bear claw” or mitten. Instead, then through the fulcrum (or hinge) to the cutting insert your fingertips into the rings for more dexterous edges of the blades. The closing force is the force that handling. However, for optimal stability and direction brings the blades together. The shearing force pushes control, and to achieve the shear and torque necessary the one blade flat against the other while closing. for accurate and clean tissue cutting, avoid using your Torque is the force that rolls the leading edge of each index or middle fingers. blade inward to touch the other. It is the shear and torque between the scissor blades that allow clean With the scissors in the tripod grip, you are ready to effective cutting. perform a cutting maneuver. If you are right-handed, you can now comfortably cut from right to left, with the Right-handed scissors are constructed to maximize palm and inner forearm aligned and facing you. When shear and torque. With the palm down, the thumb cutting left to right however, dorsoflex the carpal joint ring is hinged beneath the finger ring. This blade and rest the shanks on the middle of the more out- arrangement allows the natural pushing with the stretched index finger. This grip is preferable to turning thumb and pulling with the finger, analogous to the the scissors around and cutting “backward.” This type gripping motion of the right hand, and directs maximal of “backward” cutting does not provide adequate shear and torque through the blades. As most surgical stability to ensure cutting accuracy. standard packs contain only right-handed instruments, surgeons recommend that left-handed individuals While cutting with scissors, your hand and arm position consider learning to use scissors with their less are also important. When cutting in a horizontal plane, dominant, right hands. To use right-handed scissors the most common cutting plane, try to hold the scissors in the left hand, pull with the left thumb and push with with the palm facing down. The hand in pronation the left ring finger in their respective finger rings. Such remains mobile and can be supinated 180 degrees motion will achieve shear and torque between the without any change in body position. blades. At first, it is awkward to learn this technique; however, it can be mastered with practice. When passing scissors, hold the closed blades with the rings exposed towards the receiver. Firmly place When scissors are used for cutting, both direction the scissors in the palm of the surgeon’s dominant control and accuracy depend upon the stability of the outstretched hand. The blades should be angled off tissue between the scissor blades and the operator’s the palm, in the direction between the thumb and index grip. Tissue stability is related to how far the scissors fingers. As with all curved instruments, the curve of are opened during cutting. When scissors are opened the blades or tines is passed so that the curve points widely, tissue is closer to the hinge and the blades consistently AWAY from the receiver’s palm. That tend to push the tissue away, bunching it ahead of the way, the surgeon does not have to look at the curved shearing action of the blades. Although the closing instrument as it is passed to know its orientation. An force does tend to be greater in this state, as the blades alert surgeon knows the orientation of the instrument are opened more widely, the scissors lose shearing and is planning the next move even before the force and are less effective in stabilizing the tissue and particular site is exposed. therefore cut less accurately. Cutting closer to the tips of the scissors provides less closing force on the tissue,

3 but this stabilizes the tissue more securely between the fashion the curve pointing toward you when cutting. scissor blades, resulting in a more accurate cut. The push cut is useful for midline or linea approaches. Here, you can more easily follow the grain of the Scissor Methods rectus muscle, with fewer tendencies to stray into the paramedian muscle tissue if the blade is held against Scissor Cuts the midline fascia. The scissor cut is the typical cutting pattern used by surgeons. All three force vectors (closing, shearing, Suture Cutting and torque) are utilized in the scissor cut, helping Scissors are also used to cut suture. To perform a to produce a cut that is precise in both depth and suture cut, begin by opening the scissors just wide direction. To perform the scissor cut correctly, fully enough to get the blades on either side of the suture. insert the scissors into the tissue before beginning This forces the surgeon to only use the tips of the the cut. Then close the blades and sever the tissue. scissors for suture cutting. If scissors are opened more Only after the tissue has been cut should the blades be widely, and sutures are cut in the middle of the blade, opened and advanced, and the cutting action repeated. the operator might inadvertently damage tissue at the When positioning the tissue between the blades, it is tips of the blade because the tip is outside of his or her best to cut the tissue closer to the blade tips, rather direct visual field during the cut. To determine where than near the hinge. Cutting near the tips helps prevent to cut the suture in relation to the knot, look from the tissue from being “pushed” away from the cutting above for the knot between the slightly spread blades, blades as the jaws are closed. However, use enough rather than “stooping” down to visualize the knot blade length to complete the desired cut. To cut thicker underneath the blades. At this juncture, light pressure tissue, take several bites initiated with the tips, rather should be applied through the scissor handles to secure than one large bite starting near the hinge area. the suture in the blades. As the suture is secured, the blades are rotated 45–90 degrees to reveal the Tip: location of the scissor blades relative to the knot. Always remember to insert the scissors into the Once the appropriate suture tag length is verified, the tissue first, and then start the scissors cut. It is equally scissors are then closed to complete the cut. important not to pull back on the scissors until the complete cut has been made. Novice surgeons tend to When cutting suture in the deep recesses of a wound, insert and cut at the same time, often pulling back while it is acceptable to steady the scissor blades by using cutting, much like the motion used with a two-handled your non-dominant hand or a fixed part of the wound manual hedge trimmer. This “snipping” method of as a fulcrum. Once the knot has been located, and your cutting is uncontrolled and should be avoided. hand is steady, close the blades and cut the suture as described above. When cutting wire or pins with Push Cuts special scissors, always hold what will become the With push cutting, only two force vectors are severed end of the wire or pin with a clamp, to avoid important. The scissors are held with the blades launching a sharp, metallic projectile into someone’s slightly open and maximum shear and torque forces eye or a sterile gloved hand. Once the ends of the wire are exerted as the instrument is advanced through or suture are cut, discard them onto the floor, making a sheet of tissue. This is the same motion used when sure that they are clear of the table. pushing sharp, partially open scissors through thin wrapping paper. At the beginning of a push cut, you will Blunt Dissection find greater resistance to tissue cutting. To overcome In addition to sharp cutting, scissors with appropriate this resistance, start the push cut with a short scissors tips also make excellent instruments for blunt cut. However, stop the closing action before the blades dissection. Although other instruments can be used to meet at the tips, and then continue into the cut by bluntly dissect, scissors are best since they can be used pushing the scissors forward through the tissue while during both blunt (via use of the tips with a spreading simultaneously applying a lifting force to the scissors. out motion) and sharp (via use of the blades that cut You can also end the push cut with a short scissors cut. tissue when closed) dissection without changing This will provide greater control of the length of the instruments. Blunt dissection is most often performed cut, helping avoid the possibility of slipping and going when separating natural divisions between muscle further than intended. planes, or separating tissue layers by bluntly spreading within and parallel to the layer with the least tensile When using curved instruments for push cuts, use the strength. curved tips to your advantage. It is less awkward to 4 To perform appropriate blunt dissection, the surgeon There are several factors to keep in mind when alternates between inserting the closed scissor considering whether to use blunt dissection. First, blades into the tissue and spreading the blades open the spreading and probing motions associated with to divide or establish tissue dissection planes. It is blunt dissection do cause more tissue trauma than very important to avoid closing the scissor blades sharp dissection. Therefore, the use of blunt dissection when they are inserted in tissues. The scissor blades is often restricted to situations where important should ALWAYS be withdrawn from tissues in the open structures that must be protected are in close position, and closed only when fully retracted from proximity to the cutting field. Second, blunt dissection the target tissue. Closing the blades when they are not is contraindicated when working around scar tissue. It visible can lead to serious surgical errors. is dangerous to bluntly dissect old scars that traverse natural planes or when dense scar tissue is stronger When using curved dissection scissors, such as than the structures that it binds. For example, bluntly Metzenbaums, for blunt dissection, it is important dissecting a strong adhesion to the intestine from the to keep in mind that the scissors should be used with abdominal wall might tear the more friable intestinal the tips of the scissors facing away from the palm, or wall rather than the stronger scar region. Lastly, towards the patient. Note that this is the opposite whenever possible, blunt dissection should only of how curved clamps are normally applied, with the be performed under direct view. Therefore, when tips facing “up,” or away from the patient. In this video dissecting through structures, do not dissect too deeply demonstration, notice that the blade tips are facing into one area. If the area cannot be fully exposed, blunt downward, allowing the surgeon to visualize the tissue dissection should only be performed when the surgeon planes that are being dissected, and minimizing the risk is confident that there are no important structures in of inadvertent dissection errors. the area: for example, when a subcutaneous tunnel is created to insert a thoracostomy tube or Penrose drain.

5 Course Credits Course Authors

Daniel Smeak, DVM, Dipl. ACVS Professor Emeritus, The Ohio State University, College of Veterinary Medicine Professor, Chief of Small Animal Surgery College of Veterinary Medicine and Biomedical Sciences Colorado State University

Lawrence N. Hill, DVM, Diplomate ABVP (Canine and Feline) Associate Professor - Clinical Department of Veterinary Clinical Sciences Hospital for Companion Animals College of Veterinary Medicine The Ohio State University

Texas A&M University Course Development Team

Jodi A. Korich, DVM Clinical Assistant Professor Director of Educational Technologies College of Veterinary Medicine & Biomedical Sciences Texas A&M University

Scott A. Birch Creative Director Center for Educational Technologies College of Veterinary Medicine & Biomedical Sciences Texas A&M University

Tonya A. Miles Assistant Director Center for Educational Technologies College of Veterinary Medicine & Biomedical Sciences Texas A&M University

References Anderson RM, Romfh RF. Technique in the Use of Surgical Tools. Appleton-Century-Crofts, New York, 1980.

Knecht CD, Allen AR, Williams DJ, Johnson JH. Fundamentals in Veterinary Surgery. 3rd ed. WB Saunders, Philadelphia, 1987.

Nealon TF. Fundamental Skills in Surgery 2nd ed. WB Saunders, Philadelphia, 1971.

Toombs JP, Clarke KM. Basic Operative Techniques. In Slatter editor, 3rd ed. Textbook of Small Animal Surgery, 199-222, 2002.

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