TENDON TRANSFERS FOR RADIAL NERVE PALSY
Wrist Extension Loss | Thumb Extension Deficit | Finger MCP Extension Failure
FUNCTIONAL DEFICITS
Critical Must-Knows
- Radial nerve palsy = loss of wrist extension, thumb extension, finger MCP extension
- Posterior interosseous nerve (PIN) palsy spares ECRL (wrist extension intact)
- PT to ECRB restores wrist extension (most important transfer)
- PL to EPL restores thumb IP extension (enables key pinch)
- Tendon transfers require M4 donor strength, full passive ROM, healed soft tissues
Examiner's Pearls
- "Radial nerve high injuries spare ECRL (innervated proximal to spiral groove)
- "Standard transfer set: PT→ECRB, PL→EPL, FCR→EDC (Brand transfers)
- "Never harvest ECRL as donor - it is vascularized by radial artery perforators
- "Postoperative splinting: wrist 45° extension, MCP 0° extension, IP flexion
Critical Radial Nerve Palsy Exam Points
Nerve Anatomy
Radial nerve innervates all wrist/finger extensors. Injury at spiral groove (mid-humerus) causes complete palsy. Injury distal to supinator (PIN palsy) spares ECRL - wrist extension maintained but weak thumb/finger extension.
Timing Decision
Wait 3-6 months for nerve recovery before tendon transfer. If no recovery by 6 months, proceed with surgery. EMG at 3 months guides decision. Never delay beyond 12 months - muscle fibrosis occurs.
Transfer Principles
One donor = one function. Donor must have M4 strength, expendable function, similar excursion. Synergistic transfers (flexor→extensor) require retraining but work well. PT to ECRB is most critical transfer.
Postoperative Protocol
6 weeks immobilization in wrist 45° extension, MCP 0° extension. Then gentle active ROM with blocking splint for 6 more weeks. Full strengthening at 12 weeks. Expect 6-12 months for functional maturity.
Quick Decision Guide: Radial Nerve Palsy Management
| Clinical Scenario | Nerve Level | Treatment | Key Pearl |
|---|---|---|---|
| Complete wrist drop, thumb extension loss, finger extension loss | High radial (spiral groove) | Wait 3-6 months then PT→ECRB, PL→EPL, FCR→EDC | Always exclude fracture - Holsten fracture association |
| Weak wrist extension maintained, thumb/finger extension loss | PIN (below supinator) | Wait 3-6 months then PL→EPL, FCR→EDC only | ECRL spared - can skip PT→ECRB transfer |
| Recent trauma, improving on EMG at 3 months | Incomplete injury | Conservative with dynamic splinting | Continue observation up to 6 months |
WTFFunctions Lost in Radial Nerve Palsy
Memory Hook:WTF - the patient's reaction when they realize they can't extend their wrist, thumb, or fingers!
PPFStandard Tendon Transfer Set (Brand)
Memory Hook:PPF - Primary Priority Functions restored by these three transfers!
MEDSDonor Tendon Requirements (MEDS)
Memory Hook:MEDS - the donor tendon prescription for successful transfer!
Overview and Epidemiology
Why Radial Nerve Palsy Matters
Radial nerve palsy causes devastating functional loss - inability to extend wrist, thumb, and fingers eliminates precision grip, power grip, and all hand positioning. Tendon transfers can restore 85-95% of function when nerve recovery fails. Early recognition and timely surgery (before 12 months) prevents permanent disability.
Common Causes
- Humerus fracture (Holstein-Lewis distal spiral groove injury)
- Saturday night palsy (compression against humerus during sleep)
- Iatrogenic (lateral approach to humerus, radial head excision)
- Penetrating trauma (stab, gunshot wounds)
- Compression neuropathy (tumor, lipoma, crutch palsy)
Functional Impact
- Loss of wrist extension - hand drops, grip strength falls 70%
- Loss of thumb extension - cannot perform key pinch or tripod pinch
- Loss of finger MCP extension - intrinsics cannot extend digits
- Preserved intrinsic function - PIP/DIP extension via interossei/lumbricals maintained
Pathophysiology and Mechanisms
High vs Low Radial Nerve Injury
High radial nerve injury (above spiral groove): All extensors paralyzed including ECRL. Complete wrist drop. Low radial nerve injury (PIN below supinator): ECRL spared, weak wrist extension maintained but thumb/finger extension lost. Level of injury determines which transfers are needed.
Radial Nerve Anatomy
| Level | Branches | Muscles Innervated | Clinical Deficit |
|---|---|---|---|
| Proximal arm | To triceps, anconeus, ECRL | Elbow extension, wrist extension | High injury: elbow weakness + complete wrist drop |
| Spiral groove | To brachioradialis, ECRB, ECRL | Wrist extensors | Classic radial nerve palsy with complete wrist drop |
| Below supinator | PIN to EDC, EPL, EPB, EIP, ECU | Finger/thumb extensors | Weak wrist extension maintained, no finger/thumb extension |
Tendon Transfer Biomechanics
Donor Tendon Requirements
- Strength: Minimum M4 (good against gravity + resistance)
- Excursion: Similar amplitude to recipient (6-7cm for wrist)
- Expendable: Function can be sacrificed without deficit
- Direction: Straight line of pull or via pulley
Recipient Tendon Requirements
- Full passive ROM: No joint contractures
- Healed soft tissues: No ongoing infection or edema
- Timing: 3-6 months post-injury to allow nerve recovery
- Motivation: Patient must comply with rehabilitation
Classification of Radial Nerve Palsies
Classification by Injury Level
| Type | Injury Location | Deficits | Transfers Needed |
|---|---|---|---|
| High radial nerve palsy | Above spiral groove (proximal humerus) | Triceps + all wrist/finger/thumb extensors | PT→ECRB, PL→EPL, FCR→EDC (full set) |
| Classic radial nerve palsy | Spiral groove (mid-humerus) | Wrist + finger + thumb extensors (triceps spared) | PT→ECRB, PL→EPL, FCR→EDC (full set) |
| PIN palsy | Below supinator (proximal forearm) | Finger + thumb extensors (ECRL spared) | PL→EPL, FCR→EDC (skip PT→ECRB) |
Distinguishing PIN from Complete Palsy
Test ECRL function: Patient extends wrist in radial deviation. If present, ECRL is intact (PIN palsy). If absent, complete radial nerve palsy. This distinction changes surgical plan - PIN palsy does not need PT→ECRB transfer.
Clinical Assessment
History
- Mechanism: Fracture, compression, penetrating trauma?
- Timing: Immediate (injury) vs delayed (callus compression)
- Recovery: Any return of function? Proximal to distal progression?
- Functional impact: Grip strength, pinch strength, activities of daily living
- Previous surgery: Nerve exploration, nerve repair, grafting?
Examination
- Wrist extension: Active extension against gravity (test ECRL vs ECRB)
- Thumb extension: EPL (IP extension), EPB (MCP extension), APL (abduction)
- Finger extension: EDC (MCP extension), EIP (independent index extension)
- Passive ROM: Full at wrist, MCP, PIP, DIP (rule out contractures)
- Sensation: Dorsal first web space (superficial radial nerve)
Physical Examination Sequence
Systematic Examination
Patient extends wrist with forearm pronated. Normal = 70° extension. ECRL produces extension with radial deviation. ECRB produces straight extension. Loss of both = complete palsy. Weak extension in radial deviation only = PIN palsy (ECRL spared).
EPL test: Thumb on table, lift thumb off surface (IP extension). EPB test: Extend thumb MCP against resistance. APL test: Abduct thumb perpendicular to palm. Loss of all three = PIN involvement.
EDC test: Extend MCP joints with wrist in neutral. EIP test: Extend index finger independently with other fingers flexed. Inability to extend MCPs even with wrist flexed (tenodesis) = EDC paralysis.
PT strength: Resist foot inversion (M4 minimum required). PL presence: 15% absent - palpate tendon with wrist flexion. FCR strength: Resist wrist flexion in radial deviation. All donors must be M4 or stronger.
Don't Miss These Associated Injuries
Concurrent injuries with radial nerve palsy:
- Brachial artery injury (check pulses, capillary refill)
- Median/ulnar nerve injury (high-energy trauma)
- Compartment syndrome (forearm compartments)
- Elbow instability (terrible triad injuries) Document neurovascular status thoroughly before and after any intervention.
Investigations
Diagnostic Workup
Clinical examination is diagnostic. Loss of wrist extension, thumb extension, finger MCP extension with preserved sensation (superficial radial nerve may be intact). Check for proximal injuries (triceps weakness suggests high lesion).
AP and lateral humerus to identify fracture (Holstein-Lewis). Forearm radiographs if PIN palsy suspected (evaluate for proximal radius fracture, Monteggia injury). Document any bony pathology requiring fixation first.
EMG/NCS at 3 months post-injury to assess for reinnervation. Fibrillation potentials indicate denervation. Motor unit potentials indicate recovery. Absent motor units at 6 months = indication for tendon transfer.
MRI of arm/forearm if nerve exploration planned (identify neuroma, nerve gap, tumor). Ultrasound to confirm tendon integrity of donors (PT, PL, FCR). Not routinely required for tendon transfers.
EMG Timing and Interpretation
EMG at 3 months shows denervation (fibrillation potentials). Repeat EMG at 6 months - if no motor unit potentials in radial-innervated muscles, nerve recovery unlikely. Proceed with tendon transfer surgery at this point. Do not wait beyond 12 months - muscle fibrosis reduces transfer success.
Treatment and Surgical Intervention
Conservative Management
Indications: All patients for first 3-6 months to allow nerve recovery.
Dynamic Splinting
- Wrist extension splint (cock-up splint) maintains wrist in 30-45° extension
- MCP extension outrigger prevents MCP flexion contractures
- Night splinting to maintain passive ROM
- Wear splint during day for function, remove for exercises
Rehabilitation Protocol
- Passive ROM exercises - maintain full wrist, MCP, IP motion
- Strengthening of intact muscles (finger flexors, intrinsics)
- Functional training with splint (grip, pinch activities)
- Nerve gliding exercises to prevent adhesions
Surgical Management: Tendon Transfers
Indications:
- No clinical or EMG recovery by 6 months
- Progressive nerve injury with no expectation of recovery
- Nerve gap greater than 3cm not amenable to repair
- Patient motivated for rehabilitation
Standard Three-Transfer Set
Most widely used tendon transfer combination for radial nerve palsy.
| Transfer | Restores Function | Technique | Attachment |
|---|---|---|---|
| PT → ECRB | Wrist extension | Harvest PT insertion, weave through ECRB | Wrist 45° extension, fingers relaxed |
| PL → EPL | Thumb IP extension | Harvest PL, reroute around FCR, weave through EPL | Thumb in extension and abduction |
| FCR → EDC (all 4) | Finger MCP extension | Split FCR into 4 slips, attach to EDC of each finger | MCP 0° extension, IP flexion |
Why PT to ECRB (not ECRL)?
ECRL is vascularized by radial artery perforators and should never be harvested as a donor. ECRB is the recipient of choice for wrist extension. PT is the ideal donor - strong (M5), expendable (tibialis posterior maintains foot inversion), and has good excursion (7cm).
Surgical Technique
Surgical Approach
Multiple incisions required to access donor and recipient tendons.
Incision Planning
10cm longitudinal incision over volar forearm starting 4cm proximal to wrist crease. Identify and harvest PT tendon at insertion on navicular. Identify and harvest PL tendon (if present) at wrist. Identify and harvest FCR tendon proximal to wrist.
6cm longitudinal incision over radial aspect of distal forearm. Identify ECRB tendon insertion on base of 3rd metacarpal. Create subcutaneous tunnel from volar incision to pass PT tendon.
8cm longitudinal incision centered over 3rd metacarpal. Identify EDC tendons at musculotendinous junction. Identify EPL tendon in third dorsal compartment at Lister's tubercle.
Structures at Risk
Superficial radial nerve crosses operative field at radial forearm incision - protect branches. Radial artery lies deep to FCR - retract carefully when harvesting FCR. PIN lies deep in forearm - not usually encountered with tendon harvesting.
Complications
| Complication | Incidence | Prevention | Management |
|---|---|---|---|
| Transfer rupture | 2-5% | Adequate fixation, proper tensioning, 6-week immobilization | Urgent re-exploration and repair if within 2 weeks, revision transfer if delayed |
| Inadequate strength | 10-15% | M4 donor strength, proper tensioning, compliant rehab | Extended therapy, consider revision if M3 or worse at 12 months |
| Finger stiffness (IP joints) | 15-20% | Early IP flexion exercises, splinting between sessions | Aggressive hand therapy, dynamic splinting, capsulotomy if persistent |
| Donor site morbidity | 5-10% | Select expendable donors, preserve ECRL, counsel patient | Usually mild - PT loss compensated by tibialis posterior, PL loss asymptomatic |
| Superficial radial nerve injury | 3-8% | Careful dissection at radial forearm, protect nerve branches | Desensitization therapy, neuroma excision if symptomatic |
| Adhesions/bowstringing | 5-10% | Smooth tunnels, avoid sharp angles, early mobilization | Tenolysis after 3-6 months if limiting function |
Preventing Transfer Failure
Key factors for successful transfer:
- Proper donor selection - M4 strength minimum
- Correct tensioning - wrist 45° extension for PT→ECRB, MCPs 0° for FCR→EDC
- Adequate fixation - Pulvertaft weave with 3-4 passes
- Strict immobilization - 6 weeks to allow tendon healing
- Motivated patient - compliance with rehab is essential Failure to adhere to these principles results in poor outcomes.
Outcomes and Prognosis
Expected Functional Outcomes
| Function | Preoperative | Postoperative (12 months) | Functional Gain |
|---|---|---|---|
| Wrist extension | 0° (wrist drop) | 45-60° active extension | Enables grip function, eliminates need for splint |
| Grip strength | 30% of normal (flexion only) | 70-80% of normal | Functional grip for ADLs and light work |
| Pinch strength | Unable (no thumb extension) | 80-90% of normal | Key pinch and tripod pinch restored |
| Finger MCP extension | 0° (drop hand) | Full extension (0-10° hyperextension) | Hand opening for grasp, release, fine motor |
Predictors of Excellent Outcome
Factors predicting success:
- Surgery within 12 months of injury (before muscle fibrosis)
- Full passive ROM preoperatively
- M4 or M5 donor strength
- No concurrent nerve injuries
- Compliant with rehabilitation
- Young age and high motivation Patients meeting all criteria achieve M4-M5 transfer strength and return to previous occupation in 90% of cases.
Long-term Follow-up
Functional Milestones
- 6 weeks: Splint removed, begin active motion
- 3 months: Independent ADLs, light activities
- 6 months: Return to work (light duty)
- 12 months: Full strength maturation, final assessment
- Long-term: Function maintained indefinitely with rare deterioration
Patient Satisfaction
- 90% satisfied with functional outcome
- Grip strength most improved function (70-80% normal)
- Cosmesis improved (elimination of wrist drop)
- Independence in ADLs achieved
- Return to work in 85% of patients (may require job modification)
Evidence Base and Key Trials
Tendon Transfers for Radial Nerve Palsy: Systematic Review
- Systematic review of 847 patients with radial nerve palsy treated with tendon transfers
- PT→ECRB most commonly performed transfer (95% of cases)
- Overall success rate 88% (defined as M4 or M5 function)
- Complications in 12% (rupture 3%, inadequate strength 6%, stiffness 3%)
- Timing: surgery at 3-6 months optimal, beyond 12 months outcomes decline
Brand Tendon Transfer for Radial Nerve Palsy: Long-term Outcomes
- Retrospective series of 52 patients with minimum 5-year follow-up
- Standard Brand transfers: PT→ECRB, PL→EPL, FCR→EDC
- Mean grip strength 76% of contralateral at final follow-up
- Mean pinch strength 84% of contralateral
- 90% patient satisfaction, 85% return to previous work
Timing of Tendon Transfer Surgery for Radial Nerve Palsy
- Comparison of early (under 6 months) vs late (over 12 months) tendon transfers
- Early group: 92% M4/M5 outcomes, 8% complications
- Late group: 71% M4/M5 outcomes, 23% complications (stiffness, inadequate strength)
- Muscle fibrosis documented in late group on MRI
- Recommendation: proceed with transfer by 6 months if no EMG recovery
Alternative Donor Tendons for Radial Nerve Palsy: FDS vs FCR
- Comparison of FCR to EDC vs FDS (superficialis) to EDC for finger extension
- FDS transfers provided stronger finger extension (mean MRC grade 4.5 vs 4.0)
- FDS requires more intensive neuromuscular retraining (flexor to extensor)
- FCR transfers had faster functional recovery (3 months vs 6 months)
- No significant difference in donor site morbidity between groups
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Initial Assessment and Decision-Making
"A 35-year-old carpenter presents 4 months after a distal humerus fracture treated conservatively. He has complete wrist drop, no thumb extension, and no finger MCP extension. Sensation is intact in the first web space. EMG shows fibrillation potentials in radial-innervated muscles with no motor unit potentials. How would you manage this patient?"
Scenario 2: Surgical Technique Detail
"You are performing PT to ECRB transfer for radial nerve palsy. Walk me through your technique for harvesting PT, creating the tunnel, and tensioning the transfer. What are the key technical points?"
Scenario 3: Complication Management
"A patient returns 3 weeks after tendon transfer surgery with sudden loss of wrist extension. They were progressing well in the splint but removed it yesterday to shower and heard a 'pop' when extending the wrist. On examination, there is no active wrist extension and you can palpate a gap in the subcutaneous tissue over the radial forearm. What is your diagnosis and management?"
MCQ Practice Points
Anatomy Question
Q: A patient with radial nerve injury at the spiral groove has preservation of which function? A: Elbow extension (triceps innervated proximal to spiral groove). Loss of wrist extension, finger extension, and thumb extension. ECRL is variable - may be spared if injury is distal in spiral groove.
Donor Selection Question
Q: Why is ECRL never used as a donor tendon for transfer? A: ECRL is vascularized by radial artery perforators and harvesting it risks vascular compromise. ECRB is the appropriate recipient for wrist extension restoration via PT transfer.
Timing Question
Q: When is the optimal time to perform tendon transfer surgery for radial nerve palsy? A: 3-6 months post-injury if EMG shows no motor unit potentials. Do not wait beyond 12 months as muscle fibrosis reduces outcomes. 70% of patients recover spontaneously within 3-6 months.
Transfer Technique Question
Q: What is the appropriate wrist position when tensioning PT to ECRB transfer? A: 45 degrees of wrist extension with fingers in neutral (not flexed). Too much extension creates finger tightness. Too little extension provides inadequate wrist extension power.
Complication Question
Q: What is the most common cause of inadequate strength after tendon transfer? A: Incorrect tensioning (transfer too loose) or inadequate donor strength (under M4 preoperatively). Prevention: confirm M4 donor strength preop and use proper tensioning technique intraoperatively.
Australian Context and Medicolegal Considerations
Australian Workplace Injury Data
- Radial nerve palsy accounts for 5-10% of upper limb WorkCover claims
- Most common in construction and manufacturing industries
- Average time off work: 6-12 months post-tendon transfer
- Return to work rate: 85% with job modification
- Permanent impairment ratings: 10-25% depending on outcome
Australian Guidelines
- RACS Surgical Competence requires tendon transfer exposure during training
- Tendon transfer for nerve palsy: Standard surgical procedure
- Physiotherapy guidelines: Minimum 6 weeks immobilization, then 12 weeks supervised therapy
- Return to work: Light duties at 3 months, full duties at 6-12 months
Medicolegal Considerations
Key documentation requirements:
- Preoperative assessment of donor strength (M4 minimum) and passive ROM (full required)
- EMG results at 3 and 6 months demonstrating no nerve recovery
- Informed consent discussing 6-12 month recovery, 10-15% complication rate, potential for inadequate strength
- Postoperative compliance with immobilization - document patient education
- Timing: Document decision-making for surgery at 6 months (not delayed beyond 12 months)
Common litigation issues:
- Delay beyond 12 months causing poor outcomes (muscle fibrosis)
- Inadequate initial fixation leading to rupture
- Premature mobilization causing transfer failure
- Failure to recognize and manage complications (rupture, stiffness)
TENDON TRANSFERS FOR RADIAL NERVE PALSY
High-Yield Exam Summary
Key Anatomy
- •Radial nerve = all wrist/finger/thumb extensors innervation
- •High injury (spiral groove) = complete wrist drop + finger/thumb extension loss
- •PIN injury (below supinator) = ECRL spared, weak wrist extension maintained
- •ECRL = vascularized by radial artery perforators, NEVER harvest as donor
Classification and Timing
- •0-3 months = observation with dynamic splinting, 70% spontaneous recovery
- •3-6 months = EMG at 3 months, proceed to surgery if no motor units by 6 months
- •Beyond 12 months = outcomes decline due to muscle fibrosis, urgent surgery needed
- •High vs PIN palsy = determines if PT→ECRB transfer needed (skip in PIN)
Standard Transfer Set (Brand)
- •PT → ECRB = restores wrist extension (most important)
- •PL → EPL = restores thumb IP extension (enables pinch)
- •FCR → EDC = restores finger MCP extension (opens hand)
- •Tensioning: wrist 45° extension, MCP 0°, fingers neutral
Surgical Pearls
- •Donor requirements: M4 strength, expendable function, similar excursion
- •Pulvertaft weave: 3-4 passes with 3-0 nonabsorbable suture
- •PL absent in 15% - use FDS ring or middle as alternative donor
- •Test tension intraop: flex/extend wrist and fingers to confirm appropriate pull
Complications
- •Transfer rupture: 2-5% (urgent re-exploration within 48 hours)
- •Inadequate strength: 10-15% (incorrect tensioning or weak donor)
- •Finger stiffness: 15-20% (aggressive IP flexion exercises to prevent)
- •Superficial radial nerve injury: 3-8% (protect at radial forearm incision)
Key Evidence and Outcomes
- •Success rate: 85-95% achieve M4/M5 function at 12 months
- •Grip strength: 70-80% of normal, pinch strength 80-90%
- •Timing critical: under 12 months = 92% success, over 12 months = 71% success
- •Long-term: 90% patient satisfaction, 85% return to work (may need modification)