Surgical positioning and nerve injuries — structured oral station (12 minutes)

Opening prompt — "Tell me what you would do."

Model response — say it in this order: ^[2][3]

• "I would document the deficit immediately — the time of detection, the limb tested, the motor and sensory findings using the MRC scale for power and dermatomal mapping for sensation, and the reflexes."
• "I would name the most likely diagnosis: brachial plexus injury, upper trunk C5-C6 distribution, due to prolonged steep Trendelenburg with shoulder abduction >90 degrees — a stretch injury of the plexus against the humeral head."
• "I would reposition the patient — return to supine, ensure padding, re-examine in 15-30 minutes. I would counsel the patient about the cause, the prognosis, and the recovery curve." ^[3]

Examiner is listening for: the documentation standard, the named nerve and mechanism, the immediate repositioning, and the patient communication.

Probe 1 — "What is your differential diagnosis?"

• "Brachial plexus injury from positioning is the most likely diagnosis given the procedure and the distribution."
• "Differential: central cause — stroke, spinal cord compression — would typically have upper motor neuron signs and bilateral or non-dermatomal distribution; MRI brain/spine if suspected."
• "Shoulder injury — dislocation, glenohumeral, clavicular fracture — particularly after steep Trendelenburg with cephalad sliding; check the shoulder clinically."
• "Compartment syndrome — the lower extremities can be affected by prolonged lithotomy, but here the deficit is upper limb." ^[2]

Probe 2 — "When do you refer for further investigation?"

• "Any motor deficit at 48 hours warrants neurology referral. Any deficit at 7 days also warrants referral."
• "EMG and nerve conduction studies at 3-6 weeks localise the lesion (axon vs myelin) and quantify severity (neurapraxia vs axonotmesis vs neurotmesis)."
• "Repeat at 3-6 months for prognosis — axonal regrowth is approximately 1 mm/day." ^[2]

Probe 3 — "How do you communicate this to the patient?"

This is a scored domain, not a courtesy. Demonstrate it out loud: ^[1]

• Move to her eye level, use her name, brief plainly: "You have a weakness in your arm after the operation. We believe it is from the position we used during surgery. It is most likely temporary, but we will need to monitor your recovery over the next few weeks."
• Acknowledge fear, name the team supports, commit to follow-up with named clinician, schedule neurology referral if persistent.
• Document the conversation contemporaneously with named witness.
• Duty of candour — disclose the event, commit to the investigation and follow-up, do not minimise, do not speculate on cause.

Probe 4 — "How would you prevent this next time?"

• "Tuck both arms at the patient's side with foam padding; avoid shoulder abduction >90 degrees; avoid external rotation; limit Trendelenburg to under 45 degrees; reverse the position every 2-3 hours." ^[4]
• "Document the position, time of placement, padding used, planned time of removal, intra-op reassessment every 30-60 minutes." ^[4]
• "Standardise the team brief and debrief on positioning. The ASA Practice Advisory 2018 is the standard of care — padded arm boards, neutral position, head rotation under 30 degrees, eye protection, documentation." ^[4]