Surgical Instrumentation

Chapter 7

Surgical Instrumentation

Instrument Categories

Each type of surgical instrument is designed for a particular use and should be used only for that purpose. Using instruments for procedures for which they are not designed (e.g., using Metzenbaum scissors to cut suture or tissue forceps to hold bone) may dull or break them.


Scalpels are the primary cutting instruments used to incise tissue (Fig. 7-1). Reusable scalpel handles (Nos. 3 and 4) with detachable blades are most commonly used in veterinary medicine; however, disposable handles and blades are available. Disposable scalpels with a locking retractable shield are designed to minimize the risk of surgical blade injuries while passing blades between procedural steps and during disposal (BD Bard-Parker, Franklin Lakes, NJ). Blades are available in various sizes and shapes, depending on the intended task. A No. 10 blade is most commonly used in small animal surgery for incision and excision of tissues. A No. 15 blade is a smaller version of a No. 10 and is used for precise incisions in smaller tissues. A No. 11 blade is ideal for stab incisions into fluid-filled structures or organs. The curved angle of the No. 12 blade limits its applicability, but it is most often used in cats for elective dissection onychectomy (declawing).

Scalpels usually are used in a “slide cutting” fashion, which means that the direction of pressure applied to the knife blade is at a right angle to the direction of scalpel pressure. When incising skin, the scalpel blade should be kept perpendicular to the skin surface. Scalpels can be held with a pencil grip, a fingertip grip, or a palmed grip. The pencil grip allows shorter, finer, and more precise incisions than the other grips because the scalpel is at a 30- to 40-degree greater angle to the tissue (Fig. 7-2). However, this angle reduces cutting edge contact, making this grip less useful for long incisions. The fingertip grip offers the best accuracy and stability for long incisions. The palmed grip is the strongest hold on the scalpel and allows exertion of great pressure on the tissue, but this is often unnecessary in surgical situations.


Scissors come in a variety of shapes, sizes, and weights and generally are classified according to the type of point (e.g., blunt-blunt, sharp-sharp, sharp-blunt), the blade shape (e.g., straight, curved), or the cutting edge (e.g., plain, serrated) (Fig. 7-3). Curved scissors offer greater maneuverability and visibility, whereas straight scissors provide the greatest mechanical advantage when cutting tough or thick tissue. Metzenbaum (also called Metz, Nelson, delicate, or tissue scissors) or Mayo scissors are most commonly used in small animal surgery. Metzenbaum scissors are more delicate than Mayo scissors and are designed for sharp and blunt dissection or incision of finer tissues; Mayo scissors are used for cutting dense, heavy tissue, such as fascia. Heavy scissors are used to cut suture, but these are separate instruments from those used to cut tissue. Suture scissors used in the operating room are different from suture removal scissors. The latter have a concavity on one blade to gently hook the suture away from the skin and facilitate easy removal. Delicate scissors (e.g., tenotomy scissors, iris scissors) are often used in ophthalmic procedures and other meticulous surgeries, such as perineal urethrostomy, that require fine, precise cuts. Bandage scissors have a blunt tip, which reduces the risk of cutting skin when the scissors are introduced under the bandage. Scissors should be utilized only for their specific purpose and should be regularly maintained to keep them sharp.

Scissors may be used for sharp cutting or blunt dissection. They are held with the tips of the thumb and ring finger through the finger rings and with the index finger resting on the shanks near the fulcrum. The ring finger or thumb should not be allowed to “fall through” the handle; the rings should be kept near the distal finger joint. This is referred to as a wide-based tripod grip. Most scissors are designed for use with a right-handed grip, so the natural pushing of the thumb and pulling of the fingers in a gripping motion applies maximal shear and torque to the blades. When used in the left hand, loss of shear and torque forces results in less precision and increased tissue trauma. Therefore, left-handed surgeons should learn to cut with scissors with their right hand or should invest in specifically designed left-handed scissors.

Direction, control, and accuracy in cutting depend on the stability of the tissue between the blades of the scissors and the stability of the scissors in the operator’s grip. The larger the angle between the blades when cutting, the less the scissors stabilize the tissue and the less accurate the cut. Using the end of the blade stabilizes tissue more securely and allows a more precise cut. Scissors should not be completely closed if the incision is to be continued because the result is a ragged incision; scissors should be nearly closed, advanced, and nearly closed again. Blunt dissection (i.e., separation of tissue by inserting the points and opening the handle) may be used to separate loosely bound tissues, such as muscle or fat, or to undermine skin edges for wound closure. Blunt dissection should not be used in tougher tissue or where precise cuts are possible.

Needle Holders

Needle holders grasp and manipulate curved needles (Fig. 7-4). Size and type of needle holder are determined by characteristics of the needle to be held and location of tissue to be sutured. Larger needles require wider, heavier jawed needle holders. If needle holders are used to hold suture, the jaws should be finely serrated or smooth to prevent damaging the suture by fraying or cutting it. Long needle holders facilitate working in deep wounds. High-quality needle holders are made of noncorrosive, high-strength alloy and have a glare-free finish. The tips are hardened by coating them with a diamond surface or by fusing tungsten carbide to the face. Tungsten carbide inserts may be replaced when they become damaged or fail to hold suture adequately.

Most needle holders (e.g., Mayo-Hegar, Olsen-Hegar types) have a ratchet lock just distal to the thumb, but some (e.g., Castroviejo type) have a spring and latch mechanism for locking. Mayo-Hegar needle holders are commonly used in veterinary medicine for manipulating medium to coarse needles. Olsen-Hegar needle holders are used similarly, but have scissor blades that allow suture to be tied and cut with the same instrument. The disadvantage of Olsen-Hegar needle holders is that expertise is required to prevent cutting the suture during knot tying. Mathieu needle holders have a ratchet lock at the proximal end of the handles of the needle holder, which permits locking and unlocking simply by progressively squeezing the handles together.

Needles generally should be placed perpendicular to the needle holder because this allows greatest maneuverability. When needles are placed at an angle, the handles must move through a wide arc during suturing. A needle generally is grasped near its center to allow it to be advanced through tissue with greater force and less risk of breakage. When the needle is grasped near the eye or swage, maximum needle length is available for suturing and risk of needle slippage is reduced; however, the needle is more likely to bend or break unless delicate tissue is being sutured. Conversely, holding the needle near the pointed end allows the greatest driving force when suturing tough tissue, but extracting the needle is difficult.

Needle holders may be held using a palmed grip (no fingers are placed in the rings, and the upper ring rests against the ball of the thumb [Fig. 7-5]), a thenar grip (the upper ring rests on the ball of the thumb, and the ring finger is inserted through the lower ring [Fig. 7-6]), a thumb-ring finger grip (thumb is placed through the upper ring and the ring finger through the lower ring [Fig. 7-7]), or a pencil grip (index finger and thumb rest on the shafts of the needle holder [Fig. 7-8]), which is used with Castroviejo needle holders. The palmed grip is most advantageous for suturing tough tissue that requires a strong needle-driving force; however, the needle cannot be easily released and regrasped after a stitch without changing to another grip, making suturing less precise.

The thenar grip allows the needle to be released and regrasped for extraction without changing grips. Although it allows mobility, releasing the needle holder by exerting pressure on the upper ring with the ball of the thumb causes the needle holder handles to “pop” apart, and some needle movement occurs during this process. The greatest advantage of a thumb-ring finger grip is that it allows precision when releasing a needle. Although slower than the palmed or thenar grip, it is preferred when tissue is delicate or when precise suturing is required.

Tissue Forceps

Tissue (thumb) forceps are tweezer-like, nonlocking instruments used to grasp tissue (Fig. 7-9). The proximal ends are bonded together to allow the grasping ends to spring open or be squeezed shut. They are available in various shapes and sizes; tips (grasping ends) may be pointed, flat, round, smooth, or serrated with small or large teeth. Tissue forceps with large teeth should not be used to handle tissue that is easily traumatized. Tissue forceps with smooth tips, such as DeBakey forceps, are recommended for manipulation of delicate tissue, such as viscera or blood vessels. The most commonly used tissue forceps (i.e., Brown-Adson forceps) have small serrations on the tips that minimize trauma but facilitate holding tissue securely.

Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Surgical Instrumentation
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