Module 4 · Intraoperative Procedures I: The Sterile Team
Lesson 4.3 — Surgical Instruments
Instrument identification is one of the most consistently tested content areas on the CST exam. The exam uses descriptive language to test recognition — not photographs. A student who understands what makes each instrument distinct can answer identification questions they have never seen before. That is the goal of this lesson.
📋 NBSTSA Blueprint: Domain I-B · Intraoperative Procedures · Tasks: Identify instruments by function, application, and classification · Pass instruments and supplies · Assemble and maintain retractors
🎯 High-Yield Topics — What Gets Tested
Eight instrument classifications and what belongs in each · Mayo vs. Metzenbaum scissors — when each is used · Scalpel blade numbers 10, 11, 15, 20 and their handles · Halsted mosquito vs. Kelly vs. Crile vs. Kocher — what makes each distinct · Allis vs. Babcock — which touches bowel · DeBakey vs. Russian vs. Adson forceps · Self-retaining vs. hand-held retractors · Passing in functional position — every instrument type · Suture cutting rule — avoid the knot · Gold ring handles = tungsten carbide · Needle loading — middle third rule · Instrument care on the sterile field · Ratcheted instruments stored open during sterilization
1. The Classification System — Eight Categories
The NBSTSA content outline requires candidates to “identify instruments by function, application, and classification.” Classification is the organizational framework — knowing which category an instrument belongs to tells you its purpose even if you have never seen that specific instrument before.
| Classification | Function & Key Instruments |
|---|---|
| 1. Cutting & Dissecting | Incise or separate tissue. Scalpels, scissors (Mayo, Metzenbaum, iris, bandage), osteotomes, rongeurs, curettes, dermatomes, saws |
| 2. Clamping & Occluding | Control bleeding or occlude a vessel/structure. Hemostats (Halsted, Crile, Kelly), vascular clamps (Satinsky, bulldog), Kocher, right-angle (Mixter) |
| 3. Grasping & Holding | Hold tissue or objects. Tissue forceps (DeBakey, Russian, Adson), ratcheted graspers (Allis, Babcock), towel clamps, tenaculum, Foerster ring |
| 4. Retracting & Exposing | Hold tissue away to expose the operative field. Hand-held: Richardson, Deaver, Army-Navy, Senn. Self-retaining: Weitlaner, Gelpi, Balfour, Bookwalter, O’Connor-O’Sullivan |
| 5. Suturing & Stapling | Place sutures or staples for wound closure. Needle holders (Mayo-Hegar, Crile-Wood, Castroviejo), skin staplers, GIA/TA/EEA stapling devices |
| 6. Suctioning & Aspirating | Remove fluid and debris from the operative field. Yankauer (tonsil tip), Poole, Frazier, Baron |
| 7. Probing & Dilating | Explore cavities or expand lumens. Sounds, dilators (Hegar, Bakes), probes, grooved directors |
| 8. Viewing & Specialty | Instruments that don’t fit neatly above. Endoscopes, specula, laparoscopic instruments, bone-specific instruments (periosteal elevators, curettes, rongeurs) |
2. Cutting and Dissecting Instruments
📝 Knowledge Check 1: The surgeon has just placed a heavy absorbable suture and asks for scissors to cut it. Which scissors should the scrub tech pass?
A. Curved Metzenbaum — they are the most common scissors on the field
B. Straight Mayo — straight Mayo scissors are used for cutting suture
C. Iris scissors — for precise suture cutting
D. Curved Mayo — for cutting heavy tissue and suture
Reveal Answer
✅ Correct Answer: B
Straight Mayo scissors are used for cutting suture. This is one of the most tested scissors questions on the CST exam. Metzenbaum scissors are for delicate tissue dissection only — using them to cut suture immediately dulls the blades, making them ineffective for tissue work. Curved Mayo scissors are for cutting dense tissue like fascia and muscle. Option D is a trap: curved Mayo scissors are used for heavy tissue, not specifically for suture. The straight configuration is what designates a scissors for suture-cutting duty.
3. Clamping and Occluding Instruments — Know Each Distinction
The exam uses descriptive language to distinguish hemostatic clamps. Key descriptors: size, presence or absence of teeth, serration pattern (full vs. partial), and intended tissue type (delicate vs. heavy, tissue to be preserved vs. tissue to be removed).
| Instrument | Also Known As | Key Distinguishing Features & Use |
|---|---|---|
| Halsted Mosquito | Mosquito hemostat | Smallest hemostat; fully serrated jaws; no teeth. Used to clamp small, delicate vessels — capillaries, small bleeding points. Available straight or curved. |
| Crile Hemostat | Snap, stat | Medium-sized; fully serrated jaws; no teeth (atraumatic). Clamps vessels that will be tied off; also used for blunt dissection. One of the most versatile hemostats. |
| Kelly Clamp | Kelly hemostat | Larger than Crile; partially serrated jaws (serrations on distal half only); no teeth. Clamps larger vessels. The partial serration distinguishes it from the fully serrated Crile. |
| Kocher Clamp | Ochsner clamp | Traumatic — has interdigitating teeth at the tip (one tooth on one jaw, two on the other). Used to grasp tissue that will be removed (specimen, bowel for resection). Never used on tissue to be preserved. |
| Right-Angle Clamp | Mixter, Gemini | Jaws are perpendicular (90°) to the handle — used to pass ties, suture, or drain tubing around vessels or ducts in tight spaces where a standard clamp cannot reach. |
| Satinsky Clamp | Vascular clamp | C-shaped jaw for partial occlusion of a vessel wall — allows blood flow to continue while the wall is repaired. Atraumatic longitudinal serrations. Used in vascular surgery. |
| Bulldog Clamp | Spring clamp | Small, spring-loaded (no ratchet); atraumatic. Temporary occlusion of small vessels. Used in vascular and cardiac surgery. Released by squeezing the handles. |
💡 The Kocher vs. Kelly Distinction: Both are medium-to-large clamps. The Kocher has teeth (traumatic) — it grips tissue that is being resected. The Kelly has no teeth but partial serration (atraumatic) — it clamps vessels that will be tied. The exam describes the Kocher as having “interlocking teeth at the tip” — that phrase = Kocher every time.
4. Grasping and Holding Instruments
📝 Knowledge Check 2: During a common bile duct exploration, the surgeon requests an instrument to retrieve a stone. Which of the following is correct?
A. Fogarty clamp — to occlude the duct
B. Randall stone forceps — curved fenestrated jaws for stone retrieval
C. Pennington clamp — to grasp the duct wall
D. Mixter right-angle — to pass a tie around the duct
Reveal Answer
✅ Correct Answer: B
Randall stone forceps have curved, fenestrated jaws specifically designed to grasp and retrieve calculi (stones) from the common bile duct. They appear by name on the actual NBSTSA practice exam. The Fogarty is a balloon catheter used to extract stones or embolus from vessels — not a grasping forceps. The Pennington is for colorectal tissue. The Mixter right-angle is for passing ties around structures. Knowing instrument-to-procedure pairings is exactly how the CST exam tests this category.
5. Retractors — Hand-Held vs. Self-Retaining
Hand-Held Retractors
Require a person (assistant or first assistant) to hold them throughout the procedure. Passed handle-first to the surgeon or assistant; handle is placed in the palm.
Richardson (Rich)
Curved blade; retracts deep tissue and abdominal wall. Baby Rich = smaller version.
Deaver
Long, curved blade shaped like a question mark; retracts deep abdominal structures and liver. Wide blade for maximum exposure.
Army-Navy (US Army)
Double-ended with a small blade each side; used for skin and subcutaneous tissue retraction during superficial incisions.
Senn
Double-ended: one end is a rake (sharp or blunt prongs), one end is a small right-angle blade. Superficial wound retraction.
Self-Retaining Retractors
Hold themselves in place — lock open once positioned, freeing the assistant’s hands. Passed to surgeon and placed; scrub tech does not hold them.
Weitlaner
Hinged, ratchet-lock with multiple sharp or blunt prongs; spreads tissue apart. Superficial and moderate-depth wounds.
Gelpi
Two single sharp prongs that lock apart on a ratchet. Smaller than Weitlaner; orthopedic and spinal procedures.
Balfour
Large abdominal self-retaining retractor with lateral blades and a center bladder blade. Standard for open abdominal cases.
Bookwalter
Table-mounted ring system with interchangeable blades; maximum retraction for deep pelvic and abdominal procedures.
O’Connor-O’Sullivan
Self-retaining retractor for pelvic/vaginal procedures; has a center blade for bladder retraction.
💡 Weitlaner vs. Gelpi: Both are self-retaining with prongs. The Weitlaner has multiple prongs on each arm and is wider; the Gelpi has single sharp prongs and is smaller. The exam describes the Weitlaner as used “in a larger or more superficial wound” and the Gelpi in “orthopedic or spinal cases.” Balfour is the answer whenever the exam says “large open abdominal case needing a self-retaining retractor.”
6. Suction Tips — Match to the Field
| Suction Tip | Description & Primary Use |
|---|---|
| Yankauer (Tonsil) | Large, rigid, curved tip with vent holes; pharyngeal and surface suction; oral and general surgery |
| Poole | Outer sheath with multiple holes; removes large volumes of fluid rapidly from the abdominal cavity (irrigation, blood pooling) |
| Frazier | Small, angled tip with thumb-controlled vent; ENT, neurosurgery, spinal — any small or confined field where fine suction is needed |
| Baron | Very small angled tip; ear (tympanic membrane procedures) and microlaryngeal surgery |
7. Passing Instruments — Functional Position and Technique
The CST exam tests how instruments are passed — not just what they are. Every instrument is passed in the functional position: the position in which the surgeon can use it immediately upon receipt, without repositioning.
Ring-Handled Instruments (Scissors, Hemostats, Needle Holders, Clamps)
Held by the box lock (the hinge area); the shanks of the instrument are placed firmly into the surgeon’s palm with a snap — the surgeon should feel it arrive. The rings are oriented so the surgeon’s thumb and ring finger can immediately slip in. Instruments are passed closed (ratcheted at first position) unless the surgeon specifically requests open. The scrub tech’s fingers grip the box lock — not the rings.
Scalpel
Preferred method: neutral zone (basin or designated area on the Mayo stand — see Lesson 4.1). If passed hand-to-hand (when neutral zone cannot be used), the scalpel handle is held in the scrub tech’s palm with the blade facing away from the hand and pointing downward, and placed firmly into the surgeon’s palm — never handed blade-first. The surgeon’s dominant hand is the receiving hand.
Thumb Forceps (Pick-Ups)
Held at the midpoint of the shaft and placed in the surgeon’s non-dominant hand in the closed position; tips facing the operative site. The surgeon grasps it like a pencil.
Needle Holder (Loaded with Suture)
The needle is loaded onto the needle holder in the middle third of the needle’s curve — not at the tip (dulls it) and not at the swaged end (can release the suture or bend the needle). The needle is positioned at approximately 90° to the needle holder jaws.
The loaded needle holder is passed with the needle pointing away from the surgeon’s hand; the suture tail is draped over the back of the scrub tech’s passing hand so it does not tangle or enter the surgeon’s palm with the instrument.
Retractors
Hand-held retractors are placed handle-first into the palm of the surgeon or assistant. Self-retaining retractors are handed assembled and ready for placement — the scrub tech presents them by the central body.
⚠️ Suture Cutting Rule — Avoid the Knot: When cutting suture after the surgeon has tied a knot, the scrub tech cuts with the scissors angled slightly away from the knot — never through it. Cutting through a knot weakens it. The standard suture tail left after cutting is approximately ¼ inch (3–4 mm) unless the surgeon specifies otherwise. The most tested suture cutting question: “What is the most important consideration when cutting suture?” Answer: avoid the knot.
📝 Knowledge Check 3: The surgeon is about to perform skin closure. She asks for tissue forceps. Which of the following should the scrub tech pass?
A. DeBakey forceps — the most common forceps in surgery
B. Adson forceps (with teeth) — fine, delicate forceps for skin closure
C. Babcock clamp — for atraumatic tissue handling
D. Russian forceps — strongest grip for skin closure
Reveal Answer
✅ Correct Answer: B
Adson forceps with teeth are the standard choice for skin closure — they are small and lightweight, and their fine teeth provide adequate grip on skin without excessive trauma. DeBakey forceps are atraumatic (no teeth) and designed for delicate structures like vessels and bowel — not ideal for skin. Russian forceps are heavy and would be used for fascia, not skin. Babcock is a ratcheted grasping clamp — not a thumb forceps for suturing. The exam regularly tests forceps selection by tissue type: skin → Adson with teeth; vessels/bowel → DeBakey; fascia → Russian or Bonney.
8. Instrument Care on the Sterile Field
Wipe instruments after every use. Blood, tissue, and debris are wiped from instrument jaws with a moist sponge immediately after return to the scrub tech. Dried blood makes instruments harder to clean and can interfere with sterilization later. Never allow instruments to sit in pools of fluid on the field.
Ratcheted instruments are stored OPEN during sterilization. Hinged and ratcheted instruments (hemostats, scissors, needle holders) must be in the open position when sterilized so steam can penetrate all surfaces and joints. They are placed on the tray open. The instrument count sheet accompanies the tray from SPD.
Inspect every instrument before and during use. Check for proper function (ratchets lock and release cleanly, scissors cut smoothly, clamp jaws align). A malfunctioning instrument found mid-case is reported to the surgeon and replaced — never silently continued with a broken instrument.
Never soak instruments in saline on the sterile field. Prolonged saline exposure corrodes stainless steel. Saline solution basins on the sterile field are for sponge moistening and irrigation — not instrument storage. Instruments are kept dry between uses on the Mayo stand.
Curved instruments are grouped with curves facing the same direction on the Mayo stand. This allows the scrub tech to pick up a curved clamp or retractor quickly without reorienting. Ring handles are placed over a rolled towel or holder — not hanging off the edge of the Mayo stand.
📝 Knowledge Check 4: The scrub tech notices a ratcheted hemostat on the sterile tray is not locking properly — the ratchet slips open immediately after being closed. The surgeon has not yet begun the case. What should the scrub tech do?
A. Continue with the instrument — minor equipment issues are normal
B. Remove the instrument from the sterile field, inform the circulator, and request a replacement
C. Tell the surgeon when they arrive so the surgeon can decide whether to proceed
D. Attempt to fix the ratchet using a hemostat to bend the mechanism back into position
Reveal Answer
✅ Correct Answer: B
A malfunctioning instrument is identified before the case and removed from the sterile field immediately. The scrub tech notifies the circulator, who can retrieve a replacement from sterile supply. A hemostat that will not maintain its ratchet cannot reliably occlude a bleeding vessel — using it could result in an uncontrolled hemorrhage. Never attempt to repair an instrument on the sterile field (Option D), and never leave the decision to the surgeon when the malfunction is already identified (Option C — the scrub tech acts now, not later). The NBSTSA content outline specifically tasks the CST with inspecting, testing, and assembling instruments — identifying a defect is the expected outcome of that task.
⚡ Rapid Review — Instrument High-Yield Facts
Lesson 4.3 Complete
Instrument questions appear throughout the entire CST exam — not just in the instrumentation section. Every specialty procedure module will test whether you know the instruments specific to that specialty. Use the classification framework to reason through any instrument you encounter, and the specific instruments in this lesson to anchor your knowledge of the most-tested names.
Next: Lesson 4.4 — Wound Closure