3.4 Scissors & Other Cutting Instruments

Reading a Scissor

Every pair of surgical scissors can be described with four attributes, and the exam relies on all four: blade-to-shank ratio, blade tip (blunt/blunt, sharp/blunt, sharp/sharp), curvature, and overall length.

The blade-to-shank ratio is the fastest cue. A Mayo has a comparatively short shank and a substantial blade — a stubby, heavy look. A Metzenbaum has long slender shanks and a short, fine blade — an elegant, long-legged look. Once you see the proportion, you rarely confuse them again.

---

The Core Scissors

Straight Mayo = suture; curved Mayo = tissue. That single sentence answers a large share of scissor questions. In practice, straight Mayos are the workhorses that dull fastest because they cut suture, drain tubing, and packing.

---

Supercut and Tungsten Carbide Scissors

• Supercut: one blade is razor-honed, giving a much finer cut. Traditionally identified by black ring handles (sometimes black-and-gold). Supercut edges cannot be resharpened by ordinary methods and require the manufacturer's process.
• Tungsten carbide scissors: identified by gold ring handles with TC insert edges that hold sharpness far longer and can be re-inserted rather than scrapped.

Both are premium instruments and both attract misuse. A supercut Metzenbaum used on suture is destroyed in a single case.

---

Scalpel Handles and Blade Pairing

Blade-and-handle mismatch is a frequent assembly error and a frequent exam item.

Blade shapes: #10 curved belly (general skin), #11 straight pointed stab blade, #12 curved hook (sinus/tonsil), #15 small curved belly (precise short incisions), #20–#23 larger versions of #10 for the #4 handle.

Inspection point: scalpel handles are checked so the blade seat is not burred or spread — a worn seat lets a blade rock or detach, which is both a sharps injury risk and a retained-fragment risk.

---

Other Cutting and Dissecting Instruments

• Rongeurs (Kerrison, Leksell, Stille-Luer): spring-loaded, bite bone or disc. The Kerrison has a footplate and an up-biting punch and comes in stated widths and angles.
• Osteotomes and chisels: an osteotome is bevelled on both sides, a chisel on one. This is a classic exam discrimination.
• Curettes (Volkmann, bone, uterine): looped or cupped scraping ends, sized by number.
• Bone cutters and pin cutters: heavy dual-action cutting forceps.
• Elevators / periosteal elevators (Key, Cobb, Freer, Langenbeck): lift periosteum or tissue planes.
• Meniscotome, Beaver blade, dermatome: specialty cutting devices.

---

Cutting-Instrument Abuse

Using a tissue scissor on wire, suture, drapes, or tubing is the definitive example of instrument abuse in the Ethics content area. It flattens or notches the edge in one use, and the damage is usually visible as a nick partway down the blade — the exact point where the wire was cut. A specialist who sees a repeating pattern of notched Metzenbaums is looking at a practice problem in the OR, and the correct action is to document and escalate, not simply to keep replacing scissors.

Why Scissors Are Deliberately Set-Specific

Nothing destroys a scissor faster than using it on the wrong material, which is why departments maintain separate lines on the count sheet for scissors that look broadly similar.

Tissue scissors — Metzenbaum, Mayo (tissue pattern), Potts-Smith, iris — cut only living tissue. Suture scissors, typically a straight Mayo, cut suture material and nothing else. Dressing or bandage scissors, such as the Lister with its blunt flattened lower tip, cut dressings and are never used on tissue. Wire scissors carry a notch and hardened blades for cutting surgical wire; using a tissue scissor on wire will notch the edge permanently in a single cut.

The exam frames this as both an identification question and an ethics question. If a set arrives with the suture scissors visibly notched, the specialist's obligation is to remove it and report the pattern, because a notched edge means the instrument has been used outside its indication somewhere upstream.

Curved, Straight, and the Rule of Thumb That Follows

The conventional teaching is straightforward and testable: curved scissors for tissue, straight scissors for suture. Curvature lets the surgeon see past the blade and follow tissue planes; straight blades give a clean, controlled cut on a suture end. A Mayo scissor exists in both forms, and the count sheet will distinguish "Mayo curved" from "Mayo straight" as separate items.

Length follows depth, exactly as with clamps. The Metzenbaum is available from roughly 5 to 11 inches, and the long versions serve deep pelvic and thoracic work. The scissors that arrive with the finest, most delicate blades — iris, tenotomy, Westcott — are microsurgical or ophthalmic items and require tip protectors during assembly.

Dissectors, Elevators and Osteotomes

The blueprint groups cutting with dissecting, so know the non-scissor cutters too. A Freer elevator is a double-ended, flat, semi-sharp instrument for lifting periosteum and mucoperichondrium. A Key or Cobb elevator performs the same lifting function on bone at a larger scale. Osteotomes have a bevel on both faces and are driven with a mallet to cut bone; chisels are bevelled on one face only; gouges carry a curved, trough-shaped blade for scooping bone. These three are constantly confused, and the single-versus-double bevel is the discriminator.

Curettes are looped or cupped scrapers, rongeurs bite away bone with cupped jaws, and Kerrison rongeurs punch upward through bone with a footplate and are inspected for a clean, unnicked cutting rim.