Module 3 · Operating Room Environment and Preparation
Lesson 3.4 — Surgical Patient Positioning
Positioning is where OR setup meets patient safety. An anesthetized patient cannot report pain, protect their own nerves, or reposition themselves. Every decision the surgical team makes — which position, which accessories, which padding, how fast to move — either protects the patient or puts them at risk of nerve injury, pressure injury, or cardiovascular compromise. The CST is an active participant in all of it.
📋 NBSTSA Blueprint: Perioperative Care — Preoperative Preparation · Tasks: Transfer patient to OR table · Apply patient safety devices · Participate in positioning · Coordinate positioning devices
🎯 High-Yield Topics — What Gets Tested
Which position is used for which procedure · Safety strap placement (2 inches above the knees) · Arm abduction limit (never exceed 90°) · Common peroneal nerve — where it is and how it gets injured · Ulnar nerve — the most commonly injured nerve overall · Brachial plexus — Trendelenburg and arm abduction risks · Axillary roll in lateral position · Log-roll technique for prone and lateral · Lithotomy: both legs up and down simultaneously · Pressure points by position · Compartment syndrome risk in lithotomy · Pregnant patient: left lateral tilt after 20 weeks
1. Positioning Principles — Before Any Position Is Applied
These universal rules govern every position on every patient. The CST exam tests these as baseline knowledge — if you miss them, you miss points across multiple position-specific questions.
Positioning is a team effort under the surgeon’s direction. The surgeon is responsible for positioning. The anesthesia provider protects the airway and endotracheal tube throughout any position change. The CST assists — never moves the patient independently.
All bony prominences must be padded. Anesthesia suppresses the patient’s ability to sense ischemia. Pressure over bony prominences without padding → ischemic pressure injury within minutes of surgery duration.
Arms are never abducted more than 90°. Beyond 90° stretches the brachial plexus. Arms on armboards must be checked — palm up (supinated) to protect the ulnar nerve at the elbow.
Safety strap placed 2 inches above the knees. Snug but not occlusive — must not impair circulation. Applied after the patient is transferred to the OR table, before positioning accessories are added.
Position changes are made slowly and in controlled coordination. Rapid position changes in an anesthetized patient → blood pressure drops, cardiovascular compromise, and uncontrolled limb movement.
Skin cannot tolerate metal contact. No part of the patient’s body touches metal table components without padding. This also applies to the ESU return electrode placement rule — never over a bony prominence.
2. The Eight Surgical Positions — What You Must Know for Each
For each position the exam tests: the description, the procedures it is used for, the accessories required, and the primary injury risks. Learn all three layers for each one.
📝 Knowledge Check 1: A patient is placed in lithotomy position for a laparoscopic hysterectomy. Thirty minutes into the case, the circulator notes that the patient’s right leg is resting against the metal post of the candy-cane stirrup at the knee. What is the primary concern?
A. Ulnar nerve compression from contact with the metal post
B. Common peroneal nerve compression at the fibular head — risk of foot drop
C. Sciatic nerve traction from hip hyperflexion
D. Obturator nerve injury from abduction of the hip
Reveal Answer
✅ Correct Answer: B
The common peroneal nerve wraps around the head of the fibula (the lateral aspect of the knee) and is highly vulnerable to compression there — especially in lithotomy position where the leg contacts the stirrup post at that exact level. The result is foot drop — the patient wakes up unable to dorsiflex the foot. This is the most frequently tested nerve injury in lithotomy position and one of Jerry’s standing content priorities. The circulator must immediately reposition and pad the leg. Boot-type stirrups significantly reduce this risk over candy-cane stirrups because they distribute pressure along the calf rather than concentrating it at the fibular head.
3. Nerve Injuries — The Exam’s Most-Tested Positioning Topic
Positioning-related nerve injuries account for a significant percentage of perioperative malpractice claims. The CST exam tests both the mechanism of injury and the prevention. Know where each nerve is vulnerable and why.
Nerve Injury Master Table
| Nerve | Vulnerable Position(s) | Mechanism | Result & Prevention |
|---|---|---|---|
| Ulnar (Most common overall) |
Supine, prone, lateral | Compression at medial epicondyle (elbow); forearm pronated against table | Weakness/numbness in 4th and 5th digits. Prevention: pad elbows, supinate forearm (palm up) |
| Brachial Plexus (2nd most common) |
Supine, Trendelenburg, lateral | Arm abduction >90° (stretch); shoulder brace misplacement in Trendelenburg; down-side shoulder in lateral without axillary roll | Shoulder, arm, hand weakness/numbness. Prevention: arms <90°, padded shoulder braces on outer shoulder only, axillary roll in lateral |
| Common Peroneal | Lithotomy, lateral | Compression at fibular head (lateral knee) by stirrup post or table surface | Foot drop (inability to dorsiflex foot). Prevention: boot stirrups, pad lateral knee in lateral position |
| Radial | Supine, lateral | Compression in spiral groove of humerus against table or arm support | Wrist drop. Prevention: pad upper arm, avoid prolonged pressure on humerus |
| Obturator | Lithotomy | Hyperabduction of the hips in stirrups | Weakness of hip adductors. Prevention: avoid extreme hip abduction |
| Sciatic | Lithotomy, prone | Hip hyperflexion or excessive external rotation in lithotomy; prolonged pressure in prone | Leg and foot weakness and numbness. Prevention: avoid extreme hip positions; limit procedure duration where possible |
| Femoral | Lithotomy | Compression under the inguinal ligament with extreme hip flexion | Weakness of hip flexion and knee extension. Prevention: avoid excessive hip flexion |
📝 Knowledge Check 2: A patient is to be placed in lateral position for a left nephrectomy. The operative side is the left. The patient is placed with their right side down. An axillary roll is being placed. Where exactly should it be positioned, and what does it protect?
A. Directly in the right axilla to cushion the shoulder joint from the table
B. Under the right thorax just below the axilla, to lift the chest wall and relieve brachial plexus compression on the down-side arm
C. Under the left hip to prevent the operative side from being compressed against the table
D. Under the right knee to prevent common peroneal nerve compression
Reveal Answer
✅ Correct Answer: B
The axillary roll goes under the thorax — specifically just below the axilla (armpit) of the down-side arm, not in the axilla itself. Its function is to elevate the rib cage and take weight off the down-side shoulder, protecting the brachial plexus from compressive injury. Placing it directly in the axilla would actually increase axillary pressure and cause injury. Option A is the classic wrong answer — “axillary roll” sounds like it goes in the axilla, but it does not. The down-side knee (common peroneal) is protected with padding there, addressed separately.
4. Bony Prominences — Pressure Points by Position
Pressure injuries (formerly pressure ulcers) develop when bony prominences compress soft tissue against the OR table, reducing blood flow. Duration is a key factor — the longer the procedure, the greater the risk. The CST must ensure all contact points are padded before draping.
5. Special Populations — Positioning Modifications
Pregnant Patients (after 20 weeks)
The gravid uterus compresses the inferior vena cava in the supine position → aortocaval compression syndrome → decreased venous return → hypotension → fetal hypoxia. The OR table must be tilted approximately 15° to the left (or a wedge placed under the right hip) to displace the uterus off the vena cava. This is a direct exam question.
Obese / Bariatric Patients
OR table weight capacity must be verified before the patient is transferred. Bariatric table extensions and positioning accessories are required. Extra personnel needed for safe transfer. Respiratory compromise is increased in Trendelenburg — avoid prolonged steep angles.
Pediatric Patients
Age-appropriate padding and positioning devices required. Temperature regulation is critical — a small body surface area relative to weight means children lose heat rapidly on a cold OR table. Warming mattress or forced-air warming blanket is essential.
Patients with Joint Disease / Implants
Preoperative range-of-motion limitations must be noted. Never force a joint beyond its documented range of motion under anesthesia — the patient cannot report pain. Metal implants (hip prostheses, spinal hardware) must be factored into ESU grounding pad placement and image intensifier positioning.
📝 Knowledge Check 3: A patient at 28 weeks gestation is brought to the OR for an emergency appendectomy. She is placed supine on the OR table. Almost immediately, the anesthesia provider notes a drop in blood pressure. What is the most likely cause and the immediate corrective action?
A. Anaphylaxis from anesthetic agents — administer epinephrine
B. Aortocaval compression by the uterus — tilt the table or place a wedge under the right hip to rotate the patient to the left
C. Cardiac depression from the supine position — raise her legs to Trendelenburg
D. Normal blood pressure variation — observe and continue positioning
Reveal Answer
✅ Correct Answer: B
After 20 weeks of gestation, the enlarging uterus can compress the inferior vena cava when the patient lies flat, reducing venous return to the heart and causing supine hypotensive syndrome. The immediate fix is a 15° left lateral tilt — either by tilting the OR table or placing a wedge under the right hip — which displaces the uterus to the left and off the vena cava. This is a predictable, preventable event that should be anticipated for any pregnant patient beyond 20 weeks placed in the supine position.
📝 Knowledge Check 4: After a 4-hour procedure in lithotomy position, the patient reports calf pain and the calf feels firm and tense on exam. What positioning-related complication should be suspected?
A. Common peroneal nerve injury from stirrup compression
B. Deep vein thrombosis secondary to prolonged immobility
C. Compartment syndrome from elevated intracompartmental pressure in the calf
D. Sciatic nerve injury from hip hyperflexion
Reveal Answer
✅ Correct Answer: C
Prolonged lithotomy position increases intracompartmental pressure in the lower leg — especially the calf compartment — due to the elevated leg position reducing arterial inflow while venous drainage is impaired. The hallmark presentation is a firm, tense, painful calf muscle postoperatively, often accompanied by pain with passive stretch. This is compartment syndrome, a surgical emergency requiring fasciotomy. DVT (option B) is also a risk in lithotomy but typically presents with swelling and erythema without the firmness indicating elevated compartment pressure. The distinction matters — compartment syndrome requires immediate intervention; DVT management is different.
⚡ Rapid Review — Position, Procedure, and Risk at a Glance
Module 3 Complete
You have now covered the full OR Environment and Preparation workflow: setup → documentation → sterile technique → positioning. These four lessons account for a substantial portion of the Preoperative Preparation domain on the CST exam.
Next: Module 4 · Preoperative Patient Preparation