A 28-year-old carpenter presents to the emergency department following a glass laceration across the volar aspect of his dominant wrist. He has complete anesthesia in the thumb, index, and middle finger, and loss of opposition. You are assessing him in the clinic. What are your immediate priorities for clinical evaluation, and what is your interpretation of this nerve injury?
Candidate: I would perform a thorough motor and sensory exam using the MRC scale and two-point discrimination. This patient has a high-grade median nerve injury given the sensory and motor loss to the thenar muscles. I would check vascularity, clean the wound, and plan for urgent primary repair.
Candidates often focus exclusively on the nerve and forget to mention the "Rule of Three": Check for associated tendon injuries (flexor digitorum superficialis/profundus) and vascular compromise (radial/ulnar arteries). Failing to document the status of the palmar cutaneous branch or simply saying "nerve repair" without acknowledging the importance of microsurgical magnification is a significant oversight.
A structured approach is required: 1. Exclusion of associated injuries: Assess FDS/FDP function, ulnar nerve integrity, and radial/ulnar arterial perfusion (Allen's test). 2. Neurological Mapping: Document sensory loss specifically (is the radial palm spared? This indicates a injury distal to the palmar cutaneous branch). 3. Surgical Planning: Propose urgent primary repair within 72 hours. Emphasize the need for microsurgical magnification (microscope), tension-free epineurial coaptation, and a bespoke postoperative hand therapy protocol to prevent joint stiffness and ensure nerve gliding.
During your exploration of the volar wrist, you find a significant gap between the nerve ends due to the nature of the injury (crush/avulsion). You cannot perform a primary tension-free repair. How do you approach the decision-making for nerve reconstruction?
Candidate: If a tension-free repair isn't possible, I would use a nerve graft. I would harvest the sural nerve, place it as a cable graft, and suture it with 9-0 nylon. If it's a very short gap, maybe a conduit would work.
Failing to mention the biological principles of the graft. A common mistake is not "reversing" the graft or failing to acknowledge that the gold standard is an autograft, not a conduit, for major nerves like the median or ulnar. Candidates also often forget to mention the morbidity of the donor site.
I would categorize the strategy by gap size: 1. Direct Tension-Free Repair: Always the first choice; utilize wrist positioning (slight flexion) if necessary. 2. Autograft (Gold Standard): For gaps >1cm. I would use the sural nerve or medial antebrachial cutaneous nerve. I would emphasize the need to reverse the graft to prevent axonal leakage. 3. Conduits/Allografts: Only for very small sensory gaps (<5-10mm). 4. Nerve Transfers: If the gap is massive or the proximal stump is poor, consider distal nerve transfers (e.g., AIN to ulnar motor) to optimize functional outcomes, acknowledging that the clock is ticking on end-organ viability.
You have successfully repaired the nerve. The patient returns at 6 months complaining of cold intolerance and minimal sensory recovery. What is your management plan?
Candidate: I would refer the patient for desensitization therapy. I’d explain that nerve recovery is slow, roughly 1mm per day, and tell them to continue their hand therapy.
Accepting "1mm/day" as a universal truth and failing to investigate the cause of the poor recovery. A borderline candidate ignores the possibility of failure—such as a neuroma or mechanical entrapment—and dismisses the patient's concerns as expected recovery time.
I would perform a structured reassessment: 1. Clinical Review: Track Tinel's sign progression; use Semmes-Weinstein monofilament testing to quantify sensation. 2. Investigations: Request NCV/EMG to assess for reinnervation potentials. 3. Rule out Mechanical Failure: Use high-resolution ultrasound or MRI to check for neuroma-in-continuity or proximal nerve entrapment. 4. Multidisciplinary Care: Optimize hand therapy for cold intolerance (protective gear, desensitization). If investigations show no reinnervation, I would discuss secondary surgical options, including neurolysis, further grafting, or potential tendon transfers if motor function remains absent.
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