O.T. Instrumentation for the Medical Student: A Detailed Guide
Purpose: These notes are designed to provide you, the medical student, with a foundational understanding of the general instruments you will encounter in the Operating Theatre (O.T.). Knowing these tools is crucial for understanding the procedure, anticipating the surgeon’s needs, and being a helpful member of the team.
Core Concept: Instruments are extensions of the surgeon’s hands. Your goal is to learn their language—each instrument has a specific name and function.
I. The Four Major Categories of Instruments
Instruments are classified by their primary function. This is the most useful way to learn and remember them.
1. Cutting & Dissecting Instruments
Used to cut tissue, suture, and dissect anatomical planes.
| Instrument & Image | Description & Key Features | Primary Use & Clinical Tip |
|---|---|---|
| Scalpel | – Handle (#3 is most common): The grip. – Blade (size #10, #11, #15, #20): The sharp, disposable component. | – #10: Large incisions (e.g., laparotomy). – #15: Fine precision work (e.g., plastic surgery). – #11: Stabbing incisions (e.g., abscess drainage, cardiac cases). Tip: The scrub nurse loads the blade onto the handle using a needle holder for safety. |
| Mayo Scissors | – STRAIGHT: Thick, strong blades with rounded tips. – CURVED: Same strength, but curved. | – Straight: Cutting suture (“suture scissors”) or tough structures like fascia. – Curved: Dissecting and cutting dense tissue. Tip: “Mayo’s are for Mayo.” They cut things that are tough. |
| Metzenbaum Scissors | – CURVED: Long, thin, and delicate shafts. Rounded tips. | – Dissecting and cutting delicate tissues (e.g., fat, muscle, vessels). Tip: “Metz’s are for metz.” They cut things that are soft and delicate. |
| Operative Scissors | – Lister Bandage Scissors: Have a blunt, flat lower blade to slide under bandages safely. | – Cutting bandages, drapes, and dressings. Never used on tissue. |
| Rongeur | – Looks like a powerful nibbler or punch. Cup-shaped, sharp jaws. | – Biting away pieces of bone (e.g., in spinal laminectomy or cranial procedures). Tip: You will hear a distinct “crunch” when it’s used. |
| Osteotome | – A bone chisel. | – Used with a mallet to cut bone (e.g., in orthopaedic procedures). |
2. Grasping & Holding Instruments
Used to grasp tissue, suture, needles, or dressings. The key distinction is traumatic vs. atraumatic.
| Instrument & Image | Description & Key Features | Primary Use & Clinical Tip |
|---|---|---|
| Tissue Forceps (With Teeth) | – Have 1+ teeth at the tip that interdigitate. – e.g., Adson’s: Small, with fine teeth. | – Grasping skin and tough tissue (e.g., fascia). The teeth provide grip but cause trauma. Tip: “If it has teeth, it’s for the skin.” |
| Thumb Forceps (Without Teeth) | – Have serrated tips, but no teeth. – e.g., DeBakey: Long, smooth, atraumatic tips. | – Atraumatically handling delicate tissues (e.g., bowel, blood vessels, heart). Tip: Hold these like a pencil. Never use them to grasp skin. |
| Sponge Holding Forceps (e.g., Rampley’s) | – Long, circular, and fenestrated tips that lock. | – Primarily used to hold a gauze swab (“peanut”) for blunt dissection or mopping blood. – Sometimes used to hold the cervix. |
| Haemostatic Forceps (“Clamps” or “Artery Forceps”) | – Scissor-like handles with a locking ratchet (first click, second click). Jaws are longitudinal serrations. | – Clamping blood vessels to stop bleeding (hence “haemostatic”). – Blunt dissection. – Tagging sutures or structures. |
| – Mosquito (Halstead): Small, fine, full serrations. | – For tiny, delicate vessels. | |
| – Kelly (Crile): Medium-sized, often curved. Partial serrations. | – The general-purpose clamp for small to medium vessels. | |
| – Rochester-Péan (Ochsner): Large, heavy, and long. | – For clamping large tissue pedicles or bundles. | |
| Needle Holder | – Short, thick jaws, often with cross-hatching or tungsten carbide inserts for grip. | – Holding the suture needle for driving it through tissue. – Mayo-Hegar: Standard. – Olsen-Hegar: Has built-in scissors (be careful, you can cut the suture accidentally). Tip: The needle is gripped at the junction of its posterior 1/3 and anterior 2/3. |
3. Retracting & Exposing Instruments
Used to hold back tissue to create and maintain exposure of the surgical field.
| Instrument & Image | Description & Key Features | Primary Use & Clinical Tip |
|---|---|---|
| Hand-Held Retractors | – Require an assistant (or the surgeon) to hold them. | – Allows for dynamic retraction, adjusting pressure as needed. |
| – Langenbeck: Broad, flat blade, often with one sharp hook. | – Retracting abdominal incisions or muscle. | |
| – Army-Navy: Shallow, double-ended. | – Retracting superficial wounds. Very common. | |
| – Morris: Deeper and broader than Langenbeck. | – For deep abdominal retraction. | |
| – Skin Rakes / Hooks (e.g., Gillies): Small, sharp prongs. | – Retracting skin edges. | |
| Self-Retaining Retractors | – Mechanical devices that hold their position, freeing the assistants’ hands. | – Provide constant, static retraction. |
| – Gelpi: Two sharp, single-pronged ends that separate. | – Used in orthopaedic, spinal, and deep plastic surgery cases. | |
| – Weitlaner: A “clicking” retractor with multiple blunt or sharp prongs. | – For superficial wounds and smaller incisions. | |
| – Balfour: A large frame with a central and two lateral blades. | – The standard retractor for major abdominal procedures (e.g., laparotomy). |
4. Accessory & Miscellaneous Instruments
Essential tools that don’t fit neatly into the other categories.
| Instrument & Image | Description & Key Features | Primary Use & Clinical Tip |
|---|---|---|
| Suction Tips & Tubing | – Yankauer (Poole): A wide-bore tip with a hollow handle and multiple holes to prevent tissue from being sucked in. | – General suction for fluids and smoke from diathermy. The workhorse of O.T. suction. |
| – Frazier: A long, thin, angled tip with a stylet to clear blockages. | – For delicate, deep-field suction (e.g., neurosurgery, spinal surgery). | |
| Probes & Dilators | – Probe: A slender, blunt rod. – Dilator: Tapered instrument. | – Probe: Exploring fistulas or ducts (e.g., lacrimal duct). – Dilator: Gradually enlarging an orifice (e.g., urethral dilators). |
II. Practical Tips for the Medical Student in the O.T.
- The “Mayo Stand”: This is the large, movable stainless-steel tray that holds the primary instruments for the case. Never lean on or touch the Mayo stand. It is sterile.
- The “Back Table”: This is where the scrub nurse keeps all other instruments and supplies not immediately in use.
- How to Watch a Case:
- Don’t just watch the surgeon’s hands. Watch the scrub nurse. They are preparing the next 2-3 instruments. This teaches you the sequence of the operation.
- Listen to the surgeon’s requests. They will call for instruments by name.
- How to Be Helpful:
- Ask the Circulating Nurse (the non-sterile nurse) if you can help with tasks like fetching supplies.
- If you are asked to hold a retractor, HOLD IT STILL. The field you provide is crucial. Ask for clarification: “Like this? Is this the right amount of tension?”
- Never touch anything sterile (blue drapes, instruments on the Mayo stand) if you are not scrubbed in.
- Safety:
- Be aware of sharp instruments. The scrub nurse will announce “Sharp!” when passing a scalpel or needle.
- Know where the kick bucket (for waste) is located so you don’t trip over it.
- If in doubt, ask. The O.T. team would much rather you ask a question than make an assumption that compromises sterility or safety.
Final Note: Proficiency comes with time and repetition. Focus first on learning the names and functions of the most common instruments (Scalpel, Mayo Scissors, Metzenbaum Scissors, Forceps, Kelly Clamps, Needle Holder, Army-Navy Retractor). This knowledge will dramatically increase your confidence and value in the operating theatre.