Surgical positioning and nerve injuries — structured SAQ (15 marks)

(a) Most likely nerve injury and mechanism (3 marks)

One mark per element, maximum three. ^[3]

• Nerve: brachial plexus injury, upper trunk (C5-C6) distribution. The pattern of weakness (shoulder abduction, external rotation, elbow flexion) and the dermatomal distribution point to upper trunk involvement.
• Mechanism: prolonged steep Trendelenburg with shoulder abduction >90 degrees and external rotation stretches the brachial plexus against the humeral head; the operative time of 4 hours exceeds the safe threshold for position without reassessment.
• Predisposing factors: diabetes, low BMI, alcohol excess, vitamin deficiency, previous nerve injury; time in steep Trendelenburg; arm position in relation to the patient's anatomy.^[3]

Bands: name the nerve; name the mechanism; name the risk factors.

(b) Bedside assessment and documentation (4 marks)

One mark per aspect, marked for completeness. ^[1][2]

• Motor examination: MRC power scale 0-5 for shoulder abduction, external rotation, elbow flexion, wrist extension, finger abduction, hip flexion, knee extension, ankle dorsiflexion (screening the contralateral side for comparison).
• Sensory examination: dermatomal mapping C4-T1 for upper limb; document light touch, pinprick, proprioception in the affected distribution.
• Reflexes: biceps (C5-C6), triceps (C7), brachioradialis (C5-C6); compare with the contralateral side.
• Documentation: time of detection, name of assessor, limb tested, position used (Trendelenburg angle, arm position, padding, duration), intervention (repositioning, padding added), subsequent examination findings; allocate blame is NOT documented.^[1]

(c) Management plan, differential diagnosis and indications for further investigation (5 marks)

One mark per element, marked for specificity. ^[2][6]

• Immediate repositioning: recheck the patient's position, remove the Trendelenburg, return to supine, ensure padding; reassess the deficit at 15-30 minutes.
• Counsel the patient: explain the cause, the likely prognosis (neurapraxia recovers in days to 6 weeks, axonotmesis in months), and the recovery curve; commit to follow-up.
• Differential diagnosis: exclude central cause (stroke, spinal cord compression — MRI brain/spine if bilateral or upper motor neuron signs); exclude shoulder dislocation, glenohumeral injury, clavicular fracture; exclude compartment syndrome (lower extremity, the reverse Trendelenburg repositioning could precipitate it).
• Indications for neurology referral: any motor deficit at 48 hours; any deficit at 7 days; EMG/nerve conduction studies at 3-6 weeks to localise the lesion and quantify severity; repeat at 3-6 months for prognosis.
• Multidisciplinary engagement: physiotherapy, occupational therapy, pain service (gabapentin, pregabalin, duloxetine for neuropathic pain); incident report, MOPS review, root cause analysis; notify medical indemnity.^[1]

(d) Prevention strategy (3 marks)

One mark per element. ^[4][5]

• Arm position: tuck both arms at the patient's side with foam padding; avoid shoulder abduction >90 degrees; avoid external rotation.
• Trendelenburg angle: limit to under 45 degrees; reverse every 2-3 hours; consider lower extremity compression devices.
• Positioning standardisation: team brief and debrief; document the position, time of placement, padding used, planned time of removal; intra-op reassessment every 30-60 minutes; ASA Practice Advisory 2018 standard of care (padded arm boards, neutral position, head rotation under 30 degrees, eye protection, documentation).^[4][5]