Tendon Transfers for Median and Ulnar Nerve Palsy

Eight Fundamental Principles

Every successful tendon transfer must satisfy these criteria:

Patient Selection and Evaluation

History:

• Mechanism and timing of nerve injury
• Previous surgery or repair attempts
• Hand dominance and occupation
• Patient goals and expectations
• Compliance with rehabilitation

Examination:

• Full motor assessment (Medical Research Council grade)
• Sensory examination (two-point discrimination)
• Passive ROM of all joints
• Joint stability (ligament integrity)
• Soft tissue condition (scars, coverage)
• Check all potential donor muscles (M4+ required)

Investigations:

• EMG/NCS: Confirm irreversible nerve damage
• Radiographs: Rule out joint arthritis or contracture
• MRI: Not routine, but useful if muscle quality uncertain

General Operative Principles

Tensioning:

• Most critical and difficult aspect
• Too tight: swan neck or boutonniere deformity
• Too loose: inadequate function
• Use intraoperative passive wrist motion to assess

Standard Tensioning Formulas:

• Opponensplasty: Thumb opposes base of small finger with wrist neutral
• FPL reconstruction: IP joint flexed 20-30 degrees with wrist neutral
• Intrinsic reconstruction: MCP flexion 70 degrees, IP extension full

Juncture Techniques:

• Weave technique: Strongest (Pulvertaft)
• End-to-end: Use for tendon-to-tendon of similar size
• Side-to-side: Use for static tenodesis
• Minimum 3 weaves for Pulvertaft (some recommend 4-6)

Postoperative Protocol:

• Week 0-3: Immobilization in splint (position varies by transfer)
• Week 3-6: Gentle active motion, protected
• Week 6-8: Progressive strengthening
• Week 8-12: Full activity as tolerated
• Final outcome: 3-6 months

Tendon Transfer Biomechanical Principles

Strength Loss After Transfer:

• Transferred muscle loses ONE grade of strength
• M5 donor becomes M4 after transfer
• M4 donor becomes M3 (acceptable functional level)
• M3 donor becomes M2 (unacceptable - insufficient)

Excursion Requirements:

• Opponensplasty: 3-5cm excursion needed
• FPL reconstruction: 5cm excursion
• Intrinsic transfers: 2-3cm excursion
• Wrist motors: 3cm excursion (insufficient for finger work)

Donor Excursion Available:

• FDS: 7cm (excellent for most transfers)
• EDC/EIP: 5cm (good for opposition, intrinsics)
• ECRL/ECRB: 3cm (limited use without graft)
• Wrist flexors: 3cm (need graft for finger work)

Moment Arm Considerations:

• Preserve or improve moment arm at insertion
• Pulley systems maintain moment arm
• Direct insertion may need bone tunnel placement

Work Capacity:

• Work = Force × Distance
• Transferred tendon must perform equivalent work
• Cannot expect full strength restoration
• Realistic goal: M3-M4 functional strength

Postoperative Therapy Protocol

Successful tendon transfer requires excellent patient compliance with therapy.

Phase 1: Protection (Weeks 0-3)

• Splint in position specific to transfer
• NO active motion
• Edema control, finger ROM of uninvolved digits
• Patient education

Phase 2: Early Active Motion (Weeks 3-6)

• Remove splint for therapy sessions
• Gentle active motion of transferred tendon
• Re-education: patient learns new motor pattern
• Splint between sessions

Phase 3: Strengthening (Weeks 6-12)

• Progressive resistance exercises
• Functional activities
• Discontinue splint (gradual weaning)
• Return to work planning

Phase 4: Maturation (Months 3-6)

• Continued strengthening
• Refinement of motor control
• Final outcome assessment

Brand EIP Transfer - Gold Standard Technique

Indications:

• Irreversible low median palsy with loss of opposition
• Failed nerve repair (6+ months, no recovery)
• Patient motivated for rehabilitation
• Full passive thumb ROM

Contraindications:

• Inadequate passive ROM (correct first)
• Active infection or poor soft tissue coverage
• Patient non-compliance anticipated
• Ongoing nerve recovery (wait)

Patient Position:

• Supine, arm on hand table
• Shoulder abducted 90 degrees
• Tourniquet on upper arm

Surgical Steps:

Step 1: Harvest EIP Tendon

Incision:

• Longitudinal incision over dorsal 2nd metacarpal (6-8cm)
• Centered over index MCP joint
• Extend proximally to mid-metacarpal

Dissection:

• Incise skin and subcutaneous tissue
• Protect dorsal sensory nerves (radial nerve branches)
• Identify extensor tendons over index finger

EIP Identification:

• EIP lies ULNAR to EDC-index
• Both insert on index proximal phalanx
• Test: independent index extension with MP joints flexed

Harvest:

• Divide EIP at insertion on proximal phalanx
• Confirm EDC-index still provides full extension
• Free EIP proximally with blunt dissection

Step 2: Route EIP Around Ulnar Border of Wrist

The EIP is retrieved proximally and routed subcutaneously around the ulnar border of the distal forearm/wrist. This recreates the line of pull of abductor pollicis brevis, which originates from the radial side but pulls the thumb out of the plane of the palm toward the pisiform - so the transfer must approach the thumb obliquely from the ulnar/proximal direction to provide true opposition (palmar abduction + pronation), not just radial abduction.

Forearm Incision:

• Transverse or short oblique incision at the distal forearm/wrist (3-4cm)
• Positioned to retrieve the EIP and direct it toward the ulnar wrist

Create Subcutaneous Tunnel:

• Retrieve EIP proximally through the wrist incision
• Create a wide, superficial subcutaneous tunnel sweeping around the ulnar border of the wrist toward the pisiform, then volar across the palm to the thumb
• Avoid the dorsal sensory branch of the ulnar nerve in this route
• Keep the line of pull straight - the pisiform acts as the functional "pulley" for opposition

Step 3: Insert into APB Insertion

Thumb Incision:

• Volar-radial incision over thumb MCP joint (2-3cm)
• Along thenar crease
• Protect radial digital nerve

Identify APB Insertion:

• APB inserts on radial base proximal phalanx
• Also into extensor hood (variably)
• May be atrophied - identify remnant

Pass EIP:

• Create subcutaneous tunnel from wrist to thumb
• Pass EIP to thumb MCP area
• Ensure no twisting or kinking

Weave Technique:

• Pulvertaft weave into APB remnant OR
• Bone tunnel in proximal phalanx if APB absent
• 3-4 passes minimum
• Use 3-0 non-absorbable suture (Ethibond, Fiberwire)

Step 4: Tensioning - CRITICAL STEP

Proper Tension:

• Thumb should oppose to BASE of small finger
• NOT to tip of small finger (too tight)
• Wrist in neutral position
• Thumb MCP slightly flexed (30-40 degrees)

Assess:

• Thumb should reach small finger base comfortably
• Should be able to adduct thumb back to palm
• No excessive force required

Complete Weave:

• Secure weave with multiple interrupted sutures
• Test tension by passive wrist motion
• Trim excess EIP tendon

Step 5: Closure and Splinting

Wound Closure:

• Close all incisions with absorbable subcuticular sutures
• Steri-strips, sterile dressing
• Soft dressing

Splint:

• Thumb spica splint
• Thumb in full opposition (to small finger)
• Wrist neutral
• Forearm included for stability

Postoperative Care:

• Elevate for 48 hours
• Keep splint dry and intact
• Immobilize 3 weeks strict
• Remove sutures 2 weeks

Step 6: Rehabilitation Protocol

Weeks 0-3:

• Immobilization in thumb spica
• No active motion
• Edema control

Weeks 3-6:

• Remove splint for therapy
• Begin active opposition exercises
• Re-education (learn to activate EIP for opposition)
• Splint between sessions

Weeks 6-12:

• Progressive strengthening
• Functional activities
• Wean splint
• Return to light work

Months 3-6:

• Full strengthening
• Return to full duty work
• Final outcome assessment

Expected Outcome:

• 85-95% achieve functional opposition
• Pulp-to-pulp pinch restored
• Strength 60-80% of normal side
• High patient satisfaction

Royle-Thompson FDS Transfer

Donor: FDS ring finger

Advantages:

• Strong donor (M5 typically)
• Good excursion (7cm)
• Excellent outcomes

Disadvantages:

• Loses ring finger independent PIP flexion
• More complex harvest than EIP

Technique:

• Harvest FDS-ring through volar approach
• Route subcutaneously around ulnar wrist
• Insert into APB or bone tunnel
• Tension same as Brand (base of small finger)

Phalen-Miller APL Transfer

Donor: Abductor pollicis longus

Advantages:

• Local donor (thumb area)
• Simple surgery
• No distant harvest

Disadvantages:

• Short amplitude (may need tendon graft)
• Removes thumb abduction power
• Less reliable outcomes

Technique:

• Expose APL at radial wrist
• Divide at insertion on 1st metacarpal base
• May need palmaris longus graft for length
• Route to APB insertion
• Tension as per Brand

Camitz Palmaris Longus Transfer

Donor: Palmaris longus with volar fascia extension

Advantages:

• Simple, low morbidity
• Can be done during carpal tunnel release
• Good for elderly, low demand

Disadvantages:

• Weak motor (PL is a weak tendon)
• Restores palmar abduction more than true opposition (no pulley unless modified) - a pulley modification improves the opposition vector
• Not durable for young, high-demand patients
• Palmaris longus congenitally absent in roughly 10-15% (population-variable, up to ~25% in some series)

Technique:

• Harvest PL in continuity with a strip of palmar aponeurosis for length
• Route subcutaneously to thumb
• Insert into APB
• Best reserved for low-demand patients, often combined with carpal tunnel release

Reconstruction for High Median Nerve Lesions

High median palsy affects nerve proximal to forearm. Additional deficits beyond opposition:

Brachioradialis-to-FPL Transfer

Indications: High median palsy with lost thumb IP flexion

Technique:

• Expose brachioradialis in distal forearm
• Divide at insertion (radial styloid)
• Route deep in forearm to FPL
• Pulvertaft weave into FPL
• Tension: Thumb IP flexed 20-30 degrees, wrist neutral
• Immobilize 3 weeks

Outcomes: Good restoration of thumb IP flexion, key pinch strength

FDP Index/Middle Reconstruction

Options:

1. Side-to-side to ring/small FDP: Simple, allows mass flexion
2. ECRL-to-FDP: Independent flexion maintained
3. Accept deficit: If patient has mild symptoms only

Most patients do well with side-to-side tenodesis to ulnar-innervated FDP tendons.

Median Palsy Transfer Complications

Intraoperative:

• PIN injury: Devastating - prevent by staying superficial during proximal EIP harvest
• Superficial radial / dorsal ulnar sensory nerve injury: Painful neuroma, bury or repair
• EDC division instead of EIP: Repair EDC, abort or revise plan
• Dorsal sensory branch of ulnar nerve injury: In the ulnar-border routing tunnel - protect during tunnelling

Early Postoperative (0-6 weeks):

• Juncture rupture (2-5%): Sudden loss of opposition, needs reoperation
• Infection (less than 1%): Antibiotics, possible washout
• Hematoma: Drain if symptomatic

Late Complications (6+ weeks):

• Inadequate opposition: Under-tensioning - may need revision
• Swan neck deformity: Over-tensioning - release transfer
• Adhesions: Tenolysis may be needed
• Persistent thenar atrophy: Cosmetic concern only if function good

Zancolli FDP Lasso Procedure - Simplest Claw Correction

Indications:

• Low ulnar palsy with claw deformity
• MCP hyperextension, PIP/DIP flexion (ring/small fingers)
• Low-demand or elderly patients
• Failed conservative management (splinting)

Contraindications:

• Fixed MCP contracture (release first)
• High ulnar palsy (FDP also paralyzed)
• High-demand patients wanting physiologic reconstruction

Principle:

• Use FDP itself as donor (no separate donor needed)
• Create lasso around A1 pulley
• FDP pull flexes MCP joint (corrects hyperextension)
• Passive IP extension follows (intrinsic cascade)

Patient Position:

• Supine, arm on hand table
• Tourniquet on upper arm

Surgical Steps:

Step 1: Incision and Exposure

Incisions:

• Bruner zigzag incisions over A1 pulleys
• Ring and small fingers (can do middle if also involved)
• Center over proximal digital crease

Dissection:

• Incise skin carefully (avoid neurovascular bundles)
• Identify A1 pulley (transverse fibers at MCP level)
• Identify FDP tendon (deeper than FDS)

Step 2: Create FDP Lasso

Split FDP Longitudinally:

• Split FDP into two equal slips
• Split length: 2-3cm proximal to A1 pulley
• Use sharp knife or scissors

Create Lasso Around A1:

• Pass one FDP slip volar to A1 pulley
• Pass other FDP slip dorsal to A1 pulley
• Creates "lasso" configuration around A1
• A1 acts as pulley for FDP

Preserve A2/A4 Pulleys:

• DO NOT release A2 or A4 pulleys
• Only A1 is used for lasso
• A2/A4 prevent bowstringing

Step 3: Tensioning - CRITICAL

Proper Tension:

• MCP flexion 70 degrees with wrist neutral
• IP joints should extend fully passively
• NO forced flexion or extension

Test Tension:

• Passively extend wrist - MCP should flex more
• Passively flex wrist - MCP should extend slightly
• Tenodesis effect confirms proper tension

Suture FDP Slips:

• Suture two FDP slips to each other
• Use 3-0 non-absorbable suture
• Multiple interrupted sutures
• Secure knots

Step 4: Closure and Splinting

Closure:

• Close skin with absorbable sutures
• Steri-strips, sterile dressing

Splint:

• Hand-based splint
• MCP flexed 70 degrees
• IP joints extended
• Wrist neutral
• Immobilize 3 weeks

Step 5: Rehabilitation

Weeks 0-3:

• Immobilization strict
• Edema control
• Uninvolved finger ROM

Weeks 3-6:

• Remove splint for therapy
• Active MCP flexion exercises
• Passive IP extension
• Splint between sessions

Weeks 6-12:

• Progressive strengthening
• Functional grip activities
• Wean splint
• Return to work

Expected Outcomes:

• Corrects MCP hyperextension in 85-90%
• Some loss of DIP flexion (10-20 degrees)
• Patient satisfaction high
• Simple, low morbidity

Brand Four-Tail FDS Transfer - Most Physiologic

Indications:

• Low ulnar palsy with claw deformity
• Young, high-demand patients
• Desire for physiologic intrinsic reconstruction
• Inadequate results from Zancolli lasso

Advantages Over Zancolli:

• Active motor (FDS donor)
• Restores both MCP flexion AND IP extension
• No DIP flexion loss
• More physiologic function

Disadvantages:

• More complex surgery
• Longer operative time
• Requires FDS sacrifice (loses independent PIP flexion one finger)

Donor Selection:

• Usually FDS middle or ring finger
• Choose based on patient preference
• Requires M4+ strength

Surgical Steps:

Step 1: Harvest FDS Donor

Incision:

• Volar zigzag incision over donor finger (middle or ring)
• Expose FDS tendon in palm and digit

Harvest:

• Divide FDS at insertion (middle phalanx)
• Free FDS from vincula
• Retrieve proximally into palm
• Confirm FDP still functional

Step 2: Split FDS Into Four Tails

Split Technique:

• Split FDS longitudinally into 4 equal slips
• Each tail for one lateral band (index, middle, ring, small)
• Equal thickness important

Step 3: Route Through Lumbrical Canals

Route Each Tail:

• Pass each FDS tail through lumbrical canal
• Radial side of each finger
• Volar to transverse metacarpal ligament
• To lateral band of each finger

Step 4: Insert Into Lateral Bands

Weave Technique:

• Pulvertaft weave each tail into lateral band
• At proximal phalanx level
• 2-3 passes per tail
• Use 4-0 non-absorbable suture

Tensioning:

• MCP flexed 70 degrees
• IP extended fully
• Equal tension all four tails
• Test by passive wrist motion

Step 5: Rehabilitation

Same as Zancolli - 3 weeks immobilization, then gradual mobilization.

Outcomes:

• Roughly 85-90% claw correction
• Active IP extension via the lateral bands (more physiologic than the lasso)
• No DIP flexion loss (FDP is preserved)
• High satisfaction in young, high-demand patients
• In a randomized comparison, the FDS 4-tail gave marginally better claw correction than the lasso, while the lasso gave faster recovery and better grip-strength return (Chaudhuri 2025)

Restoring Key Pinch - Eliminate Froment's Sign

Froment's sign indicates weak key pinch from adductor pollicis paralysis. Thumb IP flexes when attempting lateral pinch (FPL compensates).

Clinical Impact:

• Cannot perform strong key pinch
• Writing difficult
• Tool use impaired
• Patient frustration high

Reconstruction Priority:

• Often MORE important than claw correction
• Restores key pinch strength 50-80%
• High patient satisfaction
• Essential for hand function

EIP-to-Adductor Pollicis Transfer

Most Common Technique:

Donor: Extensor indicis proprius

Surgical Steps:

Step 1: First Web Space Release

• ESSENTIAL FIRST STEP
• Chronic ulnar palsy has adduction contracture
• Release contracted first dorsal interosseous
• Release adductor fascia
• Must achieve full thumb abduction passively

Step 2: Harvest EIP

• Same as Brand opponensplasty technique
• Harvest EIP from index finger dorsum
• Divide at insertion, free proximally

Step 3: Route EIP

• Route through the second intermetacarpal space (2nd web) toward the thumb, or subcutaneously across the dorsum
• Goal: reach ulnar base of thumb proximal phalanx (adductor insertion) with a straight line of pull

Step 4: Insert Into Adductor

• Identify adductor pollicis insertion
• Ulnar base of thumb proximal phalanx
• Weave EIP into adductor insertion
• Or bone tunnel if tendon quality poor

Step 5: Tensioning

• Thumb adducted to side of index finger
• Thumb IP extended (NOT flexed)
• Gentle adduction force, not excessive
• Wrist neutral

Rehabilitation:

• Thumb spica 3 weeks
• Active adduction exercises week 3
• Strengthening week 6
• Full function 3-6 months

Outcomes:

• Eliminates Froment's sign in 90%
• Improves key pinch strength 50-80%
• High patient satisfaction
• Essential for writing, tool use

Alternative: ECRL-to-Adductor

When to Use:

• Stronger donor needed (ECRL stronger than EIP)
• Combined nerve palsies
• EIP not available

Technique:

• Harvest ECRL (or use ECRB)
• Requires tendon graft (palmaris or plantaris)
• Route from dorsal forearm through interosseous membrane
• Graft to adductor insertion
• Tension as above

Advantages:

• Stronger donor (M5 typically)
• More power for heavy work

Disadvantages:

• Requires graft (more complex)
• Loses wrist extension strength

Combined FDP and Intrinsic Loss

High ulnar palsy paralyzes both intrinsics AND FDP ring/small fingers.

Clinical Features:

• LESS clawing than low ulnar (paradoxical)
• Lost ring/small finger DIP flexion
• Weak grip strength
• All intrinsic deficits (Froment's, weakness)

Ulnar Paradox Explained:

• Low ulnar: Intrinsics lost, FDP intact → severe clawing
• High ulnar: Intrinsics AND FDP lost → less clawing (no FDP to flex IP)
• Counterintuitive but well-documented

Reconstruction Strategy:

Priority 1: FDP Ring/Small Reconstruction

Option A: Side-to-Side Tenodesis (Most Common)

• Suture FDP ring/small to FDP middle (median-innervated)
• Simple procedure
• Allows mass finger flexion
• Loses independent ring/small flexion (usually acceptable)

Technique:

• Volar wrist/palm incision
• Identify all FDP tendons
• Side-to-side suture FDP ring/small to FDP middle
• Tension: equal resting position
• Non-absorbable suture

Option B: ECRL-to-FDP Transfer

• For patients wanting independent flexion
• Use ECRL as motor
• Tendon graft to FDP ring/small
• More complex but maintains independence

Option C: Accept Deficit

• If minimal functional impact
• Patient can compensate with mass flexion
• Avoid surgery if symptoms mild

Priority 2: Intrinsic Reconstruction

Considerations:

• May not need if FDP also lost (less clawing)
• Evaluate clinically after FDP reconstruction
• If significant clawing persists, proceed with intrinsic transfer

Options:

• Zancolli lasso (if FDP reconstructed and functional)
• Brand 4-tail (if want physiologic reconstruction)
• Static tenodesis (simplest option)

Priority 3: Adductor Pollicis

Always Address:

• Froment's sign present in both high and low ulnar palsy
• EIP-to-adductor or ECRL-to-adductor
• Often highest functional priority
• Restore key pinch essential

Staging Strategy:

Stage 1 (Initial):

• FDP reconstruction (side-to-side)
• First web space release
• Allow soft tissue equilibrium

Stage 2 (3-6 months later):

• Intrinsic reconstruction (if needed)
• Adductor reconstruction
• Assess results from stage 1 first

Benefits of Staging:

• Allows soft tissue healing between procedures
• Can assess need for second stage based on stage 1 results
• Reduces overall surgical time/anesthesia
• Better patient tolerance

Success Rates and Functional Results

Opponensplasty Outcomes:

• 85-95% achieve functional opposition
• Pulp-to-pulp pinch restored in 90%
• Strength 60-80% of normal
• High satisfaction for independence in ADLs

Intrinsic Reconstruction Outcomes:

• Clawing corrected in 85-90% (Zancolli and Brand)
• MCP hyperextension eliminated
• Grip strength improves 30-50%
• Cosmesis improved

Adductor Reconstruction Outcomes:

• Froment's sign eliminated in 90%
• Key pinch strength improves 50-80%
• Essential for writing, tool use
• Very high patient satisfaction

Problems and Management

Intraoperative Complications:

Early Postoperative Complications (0-6 weeks):

• Juncture rupture (2-5%): Too early mobilization, inadequate weave

  • Presents as sudden loss of function
  • Requires reoperation and re-weaving
  • Prevention: 3-week immobilization, minimum 3 weaves

• Infection (less than 1%): Rare with clean surgery

  • Antibiotics, possible washout
  • May compromise tendon healing

• Hematoma: Inadequate hemostasis

  • Drain if symptomatic
  • Risk of adhesions

Late Complications:

When Initial Transfer Fails

Indications for Revision:

• Inadequate function despite optimal therapy (6+ months)
• Juncture rupture within healing period
• Persistent deformity (swan neck, claw)
• Unacceptable donor site morbidity

Revision Options:

1. Re-tensioning:

• If under-tensioned initially
• Identify juncture site
• Re-do Pulvertaft weave with correct tension
• Immobilize again 3 weeks

2. Alternative Donor:

• If initial donor inadequate strength
• Choose stronger donor (e.g., ECRL instead of EIP)
• May require tendon graft for length

3. Tenolysis:

• If adequate transfer but adhesions limit motion
• Free tendon from scar tissue
• Early aggressive therapy postoperatively
• Best results within 6-12 months of primary

4. Salvage Procedures:

• Arthrodesis (e.g., thumb IP for failed FPL transfer)
• MCP capsulodesis for persistent clawing
• Acceptance of deficit with adaptive equipment

Outcomes After Revision:

• Less predictable than primary transfer
• Success rate 60-70% (lower than primary 85-90%)
• Scar tissue limits outcomes
• Set realistic expectations with patient

Prevention Better Than Revision:

• Careful patient selection
• Meticulous surgical technique
• Proper tensioning (most critical)
• Adequate rehabilitation