NERVE TRANSFERS
Robbing Peter to Pay Paul
Transfer Types
Critical Must-Knows
- Converts a high-level injury (long regeneration time) to a low-level injury (short time).
- Requires a viable motor end plate (must be done generally within 12 months).
- Donor nerve must be expendable or redundant.
- Donor and Recipient must be synergistic for easier retraining (e.g., wrist flexor to finger extensor).
Examiner's Pearls
- "Oberlin Transfer restores Elbow Flexion (Ulnar fascicle to Biceps).
- "Somsak Transfer restores Triceps (Intercostal to Radial).
- "AIN to Ulnar reduces the risk of Claw Hand in high unar palsy.
The Clock is Ticking
Time is Muscle
12-18 Months After this, motor end plates degenerate irreversibly. Nerve transfers must be performing BEFORE this window closes.
Distance Matters
Regeneration Rate 1mm/day. If the injury is 30cm from the muscle, it takes ~300 days to reach. Transferring distally cuts this distance to under 5cm (50 days).
| Feature | Nerve Graft | Nerve Transfer |
|---|---|---|
| Source | Sural (Sensory only) | Expendable Motor Branch |
| Coaptation | Two (Proximal & Distal) | One (Distal) |
| Distance | Long (entire length) | Short (close to target) |
| Outcome | Good for sensation, variable for motor | Excellent for specific motor targets |
| Donor Morbidity | Numbness | Weakness (minor) |
PERFECTFeatures of Ideal Donor
Memory Hook:The Perfect Donor.
SAMSDonor Nerves
Memory Hook:SAMS nerves.
TIMEIndications for Transfer
Memory Hook:When to transfer.
Overview
Nerve Transfer (Neurotization): The surgical coaptation of a healthy, expendable donor nerve (proximal to the injury) to a denervated recipient nerve (distal to the injury) to restore function.
It has revolutionized the management of Brachial Plexus Injuries (BPI) and high peripheral nerve injuries.
Pathophysiology and Mechanisms
Shoulder Reanimation (Suprascapular Nerve)
- Target: Supraspinatus / Infraspinatus (Abduction/ER).
- Donor: Spinal Accessory Nerve (CN XI).
- Technique: Posterior approach. CN XI is distal to Trapezius innervation.
Accessory to Suprascapular is the "Workhorse" of shoulder reanimation.
Classification
Intra-plexus Transfers
- Source: Roots or Trunks adjacent to the injury.
- Example: C5 rupture, C6 avulsion to Use C5 stump (if available) or Medial Pectoral Nerve.
- Pros: Same limb integration.
Requires exploring the supraclavicular plexus (danger zone).
Clinical Assessment
Pre-operative Planning
- Power: Donor muscle must be at least MRC Grade 4 (preferably 5).
- Expendability: Ensure taking the donor won't cause unacceptable deficit (e.g. existing weakness in other muscles).
- Synergy: Check if patient can activate the donor easily.
Examination
- Deltoid/RC: Assess for Axillary/SSN targets.
- Biceps: Assess for MC target.
- Hand: Assess intrinsics.
Investigations
EMG / NCS
- Role: Confirm donor viability.
- Signs: Motor Unit Potentials (MUPs) in donor muscle confirm healthy axons.
- Denervation: Fibs/Sharps in recipient muscle confirm need for target.
Crucial to verify the "Expendable" donor is actually working properly.
Treatment
Diagnosis (Day 0-3 weeks)
- Confirm injury level.
- Rule out penetrating trauma (explore early).
- Closed injury: Wait and watch?
Mechanism is key: High velocity traction usually means avulsion.
Surgical Technique
Oberlin Transfer (Ulnar to Biceps)
- Approach: Medial arm.
- Identifcation: Musculocutaneous nerve (MCN) to Biceps. Ulnar nerve nearby.
- Stimulation: Identify a fascicle in Ulnar nerve that supplies FCU (expendable-ish redundancy).
- Transfer: Cut FCU fascicle distally, Cut MCN proximally. Coapt tension-free.
Result: Flex elbow by thinking "Flex Wrist".
Specific Transfers Details
Spinal Accessory to Suprascapular:
- Dorsal approach.
- Locate XI.
- Locate SSN in suprascapular notch (release ligament).
- Direct repair.
Radial to Axillary:
- Posterior/Axillary approach.
- Long Head Triceps branch (Radial) to Anterior division of Axillary nerve (Deltoid).
- Restores abduction.
Intercostal to Musculocutaneous:
- Use 3rd, 4th, 5th intercostals.
- Motor branch is the lower one in the rib space.
- Requires nerve graft usually (or direct if dissected far anteriorly).
Contralateral C7:
- For total plexus avulsion.
- The entire C7 root from the healthy side is cut.
- Routed across the neck (retropharyngeal or subcutaneous).
- Bridged with vascularized Ulnar nerve graft.
- Connect to Median nerve for wrist/finger flexion.
Complications
Key Complications
Donor Morbidity: Weakness in donor distribution (e.g. traps weakness) is usually transient or well compensated.
Failure: No reinnervation despite surgery.
Co-contraction: Difficulty isolating movement.
Sensory Loss: If using sensory transfers.
Sensory re-education is vital to overcome cortical confusion. This is a long-term commitment.
Patients must learn that activating the donor now produces the recipient action.
Therefore, motivation is a key selection criterion.
This is not a quick fix.
Postoperative Care
- Sling/Splint: Protect repair. No tension.
- Donor Activation: "Breathe" for intercostals, "Flex Wrist" for Oberlin.
- Biofeedback: Visual cues to link donor action to recipient effect.
This phase requires intense physiotherapy and patient motivation.
- Brain adapts. Movement becomes natural.
Plasticity allows the patient to eventually just "Flex Elbow" without thinking "Flex Wrist".
Prognosis
-
Upper Trunk (Erb's): Good prognosis. Shoulder and Elbow usually recoverable.
- Abduction recovery is generally 80-90% of normal ROM.
- Elbow flexion (Oberlin) is very reliable (greater than 90% success).
-
Total Plexus: Poor prognosis. Goal is "Helper Hand" or just Elbow Flexion.
- Hand function is unlikely to be significantly restored.
- Pain relief is a major goal (DREZ lesions for avulsion pain).
-
Time: Earlier is better. Results degrade significantly after 6-9 months.
- The "Goldilocks" period is 3-6 months.
- After 12 months, free functioning muscle transfer (Gracilis) is the only option for motor recovery.
- Tendon transfers are an alternative if local muscles are available.
Always have a Plan B (Salavage) if the transfer fails.
Pre-operative counselling is crucial to manage expectations.
Evidence Base
Oberlin Transfer
- Described Ulnar to Biceps transfer
- 24/30 patients achieved M3 or M4 power
- No permanent deficit in ulnar function
Double Fascicular Transfer
- Added Median to Brachialis transfer to the Oberlin
- Superior elbow flexion strength compared to single transfer
- Synergistic reinnervation
Nerve Transfers vs Grafts
- Systematic Review
- Nerve transfers showed superior results for shoulder and elbow
- Fewer complications than long grafts
Somsak Transfer
- Intercostal to Musculocutaneous nerve transfer
- Restoration of elbow flexion in C5-C7 avulsion
- Achieved M3 or better in 90% of patients
AIN to Ulnar
- Distal AIN to Ulnar Motor branch
- Prevents clawing and restores pinch
- Does not compromise pronation significantly
Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: The Erb's Palsy
"A 25-year-old male motorcyclist presents with a C5/C6 avulsion injury 4 months post-accident. No recovery. Examination shows deltoid/biceps paralysis. Hand is normal."
Scenario 2: High Ulnar Nerve
"Patient with a high ulnar nerve transection at the axilla. 6 months post-injury. Primary repair was done but prognosis is guarded."
Scenario 3: Total Plexus Avulsion
"A 22-year-old male sustained a motorcycle accident with complete C5-T1 avulsion injury. MRI shows pseudomeningoceles at all levels. He presents at 5 months with a flail arm."
MCQ Practice Points
Anatomy
Q: Which fascicle of the Ulnar nerve is used in the Oberlin transfer? A: The fascicle supplying the Flexor Carpi Ulnaris (FCU).
Physiology
Q: What is the maximum time window for successful motor nerve transfer? A: Generally 12-18 months before motor end plate fibrosis.
Complications
Q: What is the risk of using the Phrenic nerve as a donor? A: Hemidiaphragm paralysis (Reduced Vital Capacity).
Oberlin Transfer
Q: What is the Oberlin transfer and what does it restore? A: Transfer of Ulnar FCU fascicle to Biceps motor branch. Restores elbow flexion in C5/C6 injuries.
AIN Transfer
Q: What is the purpose of AIN to Ulnar motor transfer? A: Prevents clawing and restores pinch in high ulnar nerve injuries. Reinnervates intrinsic muscles before motor end plate fibrosis.
Regeneration Rate
Q: What is the rate of nerve regeneration after repair? A: Approximately 1mm per day (1 inch per month). This determines the urgency of distal transfers for long injuries.
Australian Context
Major Brachial Plexus Centres:
- New South Wales: Royal North Shore Hospital (Sydney) - Professor Michael Tonkin established Australia's first comprehensive brachial plexus service. Receives referrals from across NSW and interstate.
- Victoria: The Alfred Hospital (Melbourne) - Provides comprehensive plexus reconstruction with microsurgery and hand surgery expertise.
- Queensland: Princess Alexandra Hospital (Brisbane) - Major trauma centre with peripheral nerve capabilities.
Referral Pathways:
- Any closed brachial plexus injury with no clinical or EMG recovery at 3 months MUST be referred urgently.
- Penetrating injuries (knife, glass) should be explored within 72 hours if nerve injury suspected.
- Complete flail arm warrants immediate referral regardless of mechanism.
- The HealthPathways system facilitates rapid referral in most metropolitan areas.
WorkCover and Insurance Considerations:
- Most adult brachial plexus injuries in Australia result from motorcycle accidents or industrial trauma.
- WorkCover (state-based schemes) and Motor Accident schemes fund surgery, rehabilitation, and long-term support.
- DVA provides comprehensive coverage for veteran populations.
- Private insurance may require pre-approval for complex reconstructive procedures.
- CTP (Compulsory Third Party) covers most motor vehicle trauma cases.
Rehabilitation Services:
- Intensive hand therapy is essential for 12-24 months post-surgery.
- Biofeedback-assisted therapy is available at major centres.
- Psychological support addresses the significant adjustment required for brachial plexus injuries.
- Return-to-work programs require coordination with rehabilitation physicians.
Antibiotic Prophylaxis (eTG):
- Open nerve injuries: First-generation cephalosporin (Cephalexin 500mg QID for 5 days) or Flucloxacillin if no beta-lactam allergy.
- Contaminated wounds: Add Metronidazole for anaerobic cover.
- Farm/agricultural injuries: Consider tetanus status and broader-spectrum coverage.
Australian Epidemiology:
- Approximately 500 significant brachial plexus injuries occur annually in Australia.
- Male-to-female ratio is approximately 4:1.
- Peak incidence is in the 18-35 year age group.
- Motorcycle accidents account for approximately 50% of adult traumatic plexus injuries.
High-Yield Exam Summary
Principles
- •Donor Expendability
- •Recipient Viability
- •Proximity (Distal target)
- •Synergy (Easier rehab)
Common Transfers
- •Oberlin: Ulnar to Biceps (Elbow flexion)
- •Somsak: Intercostal to MC (Elbow flexion)
- •XI to SSN: Shoulder reanimation
- •AIN to Ulnar: Intrinsic salvage
Timing
- •Early: 3-6 months (ideal)
- •Late: Greater than 12 months (Muscle transfer required)
- •Motor end plate fibrosis by 18 months
- •Regeneration: 1mm/day