Extensor Tendon Repair (Zones I-VIII)

Surgical Exposure and Zone Identification

Initial Assessment and Planning

Examine wound under tourniquet control after proper preparation and draping. Assess wound characteristics: sharp laceration vs crush injury, clean vs contaminated, time since injury (primary repair <24 hours ideal, up to 7-10 days acceptable), associated injuries (nerve, artery, bone, joint).

Identify injured zone using Kleinert-Verdan classification:

• Zone I: Over DIP joint (mallet finger)
• Zone II: Over middle phalanx (simple repair)
• Zone III: Over PIP joint (central slip - boutonniere risk)
• Zone IV: Over proximal phalanx (straightforward repair)
• Zone V: Over MCP joint (sagittal band injury risk)
• Zone VI: Over dorsal hand under extensor retinaculum (worst prognosis)
• Zone VII: Over dorsal wrist (multiple tendons at risk)
• Zone VIII: Distal forearm musculotendinous (good prognosis)

Wound Extension Technique

Extend laceration longitudinally to expose tendon ends (typically 3-5 cm total length). For digital zones (I-IV), use Bruner zigzag incisions if extensive exposure needed - preserves neurovascular structures and prevents longitudinal scar contracture. Mid-axial incisions acceptable alternative.

For Zones V-VIII, straight longitudinal incisions over dorsal hand/wrist/forearm are safe and provide excellent exposure. Avoid transverse incisions over joints (cause scar contracture and limit ROM).

Identify and protect dorsal sensory nerves:

• Radial sensory nerve: Superficial at Zone VI-VII level
• DBUN (Dorsal Branch Ulnar Nerve): Ulnar dorsal hand
• DBRUN (Dorsal Branch Radial Ulnar Nerve): Dorsal digits

Tendon Retrieval

Retracted tendons must be retrieved before repair. Use blunt probe or dedicated tendon retriever. Retraction patterns:

• EPL: Retracts all the way to forearm (Zone VIII)
• EDC: Retracts to dorsal hand (juncturae may limit)
• Digital extensors: Usually retract to hand level

May need separate proximal window if tendon retracted beyond primary incision. Gentle handling prevents further trauma. Keep retrieved tendons moist with saline-soaked gauze.

Tendon Repair Fundamentals

Tendon End Preparation

Inspect tendon ends carefully. Sharp lacerations typically have clean edges requiring minimal trimming (1-2 mm maximum). Crush injuries may have frayed, devitalized tissue requiring debridement to healthy tendon - but preserve length as much as possible.

Assess gap after minimal trimming. Extensor tendons have less excursion than flexors (approximately 5 cm total excursion vs 7 cm for FDP). Gaps greater than 1 cm difficult to close without undue tension. Consider advancement techniques or reconstruction if gap excessive.

Core Suture Techniques

Zones II-VIII (standard repair):

Figure-of-Eight Technique (most common for extensors):

• Use 3-0 or 4-0 braided non-absorbable suture (Ethibond, FiberWire)
• Pass suture transversely through tendon 5-7 mm from cut end
• Cross to opposite side and pass transversely again 5-7 mm from edge
• Return to starting side creating figure-8 pattern
• Tie knot on dorsal surface (less irritation)
• Achieves 2-4 mm purchase on each side

Modified Kessler Alternative:

• Horizontal mattress with locking loops
• Similar strength to figure-of-eight
• May be preferred in thicker tendons (ECRL/ECRB, Zone VII-VIII)

Zone I (mallet finger - special considerations):

• Tendon substance tear: Horizontal mattress or figure-of-eight with 4-0 suture
• Bony avulsion: Extension block K-wire pinning across DIP (0.035-0.045 inch wire)
• Pull-out wire suture technique: Through tendon and out dorsal nail/skin, tied over button
• Large fragment (>30% articular surface): ORIF with lag screw or tension band

Epitendinous Suture (Critical Step)

Running epitendinous suture around entire tendon circumference using 5-0 or 6-0 monofilament (nylon, Prolene). Cross-stitch or simple running technique.

Benefits of epitendinous suture:

• Adds 10-20% repair strength (more critical in extensors than flexors)
• Prevents gapping at repair site during motion
• Smooths repair bulk (prevents triggering)
• Approximates paratenon for gliding

Start at knot location from core suture, run circumferentially with small bites (1-2 mm), cross-stitch pattern provides maximum smoothness. Tie at completion, bury knot.

Critical Zone-Specific Techniques

Zone I - Mallet Finger Management

Classification (Doyle):

• Type I: Closed injury
• Type II: Open injury (laceration)
• Type III: Open with skin loss (>1cm)
• Type IV: Pediatric (physeal injury)

Decision Making:

Non-operative (extension splinting 6-8 weeks continuous):

• Closed injury (Type I)
• Articular involvement <30% of joint surface
• DIP subluxation <1mm
• Compliant patient

Operative indications:

• Open injury (Types II-III)
• Articular fragment >30% joint surface
• DIP subluxation >1mm
• Failed conservative treatment (rare indication)

Surgical Techniques:

Extension Block Pinning:

• Reduce DIP joint to neutral or slight hyperextension
• Place 0.035-0.045 inch K-wire from dorsal distal phalanx, across DIP joint into middle phalanx
• Leave in place 6 weeks
• Prevents DIP flexion while allowing early protected motion if desired

Pull-Out Wire Suture:

• Place horizontal mattress suture through terminal extensor tendon
• Pass suture through drill hole in distal phalanx
• Exit through dorsal nail or skin
• Tie over button on dorsal surface
• Remove 6 weeks

ORIF for Large Fragments:

• 1.3mm lag screw if fragment large enough
• Tension band construct (small K-wires + figure-8 wire)
• Low profile plate rarely needed

Zone III - Central Slip and Boutonniere Prevention

Anatomy Review: Central slip is the continuation of extensor digitorum communis inserting onto dorsal base middle phalanx. Extends PIP joint. Lateral bands pass volar to PIP axis and dorsal to DIP axis - extend DIP when central slip intact.

Boutonniere Mechanism: Central slip rupture → lateral bands sublux volar to PIP axis → become PIP flexors instead of extensors → unopposed pull on DIP by terminal extensor → PIP flexion + DIP hyperextension deformity

Diagnosis:

• Elson Test: PIP flexed to 90° over table edge, patient extends PIP against resistance. If central slip ruptured, weak PIP extension + rigid DIP (lateral bands pull entirely on terminal extensor). If central slip intact, strong PIP extension + DIP flexible.

Acute Repair Technique:

• Identify central slip tear
• Repair with figure-of-eight 3-0 or 4-0 non-absorbable suture
• May need drill holes in middle phalanx if bony avulsion
• Assess lateral band position - should be dorsal to PIP axis after repair
• Test intraoperatively: passive DIP flexion should not cause PIP extension lag

Post-operative Protocol:

• PIP extended in splint or cast
• DIP MUST BE FREE (prevents extensor lag by maintaining lateral band length)
• 6 weeks strict PIP extension
• Then gradual ROM with dynamic extension splinting for 2-4 weeks

Chronic Boutonniere (>3 weeks old):

• Trial closed treatment with serial static or dynamic splinting
• If failed conservative: reconstruction options include:
  • Terminal extensor tendon turndown (Fowler technique)
  • Lateral band mobilization and centralization
  • FDS slip transfer (Snow-Littler)

Zone V - Sagittal Band Injury

Anatomy: Sagittal bands are transverse fibers extending from extensor hood to volar plate and proximal phalanx at MCP level. Function: stabilize extensor tendon centrally over MCP joint dorsum.

Injury Patterns:

• Traumatic (laceration, forced flexion against resistance)
• Radial sagittal band injury: less common
• Ulnar sagittal band injury: MORE common (extensor subluxes ulnarly)
• Most common in long and ring fingers

Clinical Presentation:

• Painful snap or clunk with MCP flexion-extension
• Visible/palpable subluxation of extensor tendon
• Weak MCP extension (not absent - lateral bands still function)
• Extensor lag 20-40 degrees common

Acute Surgical Management:

• Identify sagittal band tear
• Centralize extensor tendon over MCP
• Repair sagittal band with 3-0 or 4-0 non-absorbable suture
• May need pants-over-vest repair if tissue quality poor
• If tendon also lacerated, repair both

Post-operative:

• MCP extension splint (0-10 degrees)
• IP joints FREE (prevent stiffness)
• 4 weeks immobilization
• Then dynamic extension splinting 2 weeks
• Gradual strengthening 6-8 weeks

Chronic Management:

• Trial of extension splinting 6-8 weeks
• If failed: surgical options include:
  • Sagittal band reconstruction (juncturae, slip of EDC)
  • Extensor tendon centralization with retinacular sling
  • Cross-over EDC transfers if multiple finger involvement

Zone VI - Retinaculum and Adhesion Prevention

Why Zone VI is Worst:

• Repair occurs within extensor retinaculum compartments
• Limited space for tendon excursion
• Scar formation between tendon and retinaculum = adhesions
• 30-40% patients have significant adhesions limiting motion

Retinaculum Anatomy (6 compartments):

1. APL, EPB
2. ECRL, ECRB
3. EPL (unique oblique course)
4. EDC, EIP
5. EDM
6. ECU

Surgical Strategy:

Compartment Release:

• Release ONLY the involved compartment
• Preserve adjacent compartments to prevent bowstringing of other tendons
• Wide release of injured compartment for exposure

Repair Technique:

• Standard core + epitendinous as other zones
• Ensure smooth repair (any irregularity increases adhesions)

Retinaculum Reconstruction Controversy:

Traditional (reconstruct):

• Prevents bowstringing
• Risk of adhesions from retinaculum repair

Modern (leave open):

• Less adhesions
• Risk of bowstringing (usually minimal, cosmetic only)

Compromise (recommended):

• Loose reconstruction allowing tendon gliding
• Create window in retinaculum
• Use absorbable suture for less inflammation

EPL Unique Considerations:

• Third compartment - oblique course around Lister's tubercle
• Juncturae from EDC index allow some thumb extension even with complete EPL laceration
• Test EPL specifically (thumb IP extension against resistance with wrist neutral)
• Retraction to forearm common - need proximal retrieval

Zones VII-VIII - Wrist and Forearm

Good Prognosis (85-95% excellent outcomes):

• Proximal to retinaculum (less adhesions)
• Robust tendons allowing strong repair
• Good soft tissue coverage
• Early motion well tolerated

Multiple Tendon Injuries Common: Identify each injured tendon:

• ECRL (radial wrist extension, strong)
• ECRB (central wrist extension, stronger)
• EPL (thumb extension, oblique course)
• EDC (finger extension, may have multiple slips)
• EIP (index extension, independent)
• ECU (ulnar wrist extension)

Surgical Technique:

• Generous exposure (do not underestimate extent of injury)
• Standard core suture (3-0 or 4-0) + epitendinous (5-0)
• Repair each tendon individually
• Test each repaired tendon (passive motion, independent function)

Post-operative:

• Wrist extension 30-40 degrees
• 4-6 weeks immobilization
• Earlier ROM possible with strong repair (3-4 weeks)

Quality Control and Wound Closure

Intraoperative Repair Testing

Before closure, comprehensive testing ensures repair integrity:

Gap Testing:

• Release tourniquet temporarily (check perfusion simultaneously)
• Passively flex wrist to neutral
• Passively flex and extend digits through full ROM
• Observe repair site - should have NO gapping (>1-2mm gap requires revision)

Smooth Gliding:

• Ensure tendon glides smoothly without catching
• Palpate repair site during passive motion
• Any triggering sensation indicates bulky repair (needs smoothing or slight advancement)

Tension Assessment:

• Not too tight: should allow full passive flexion of wrist/digits
• Not too loose: should not gap with passive motion
• "Goldilocks zone" - snug but not restricting passive ROM

Independent Function (if multiple tendons repaired):

• Extend each digit passively - should move independently
• Verify no inadvertent suturing of adjacent tendons together
• Check juncturae - should be intact but not incorporating repair

Active Testing (WALANT cases only):

• Patient performs gentle active extension
• Ultimate test of repair strength and excursion
• Allows real-time adjustment of technique

Retinaculum Management (Zone VI)

Decision Algorithm:

Reconstruct if:

• Significant bowstringing anticipated (young patient, strong tendons)
• Multiple compartments released (need stability)
• Surgeon preference for traditional approach

Leave Open if:

• Single compartment injury
• Concern for adhesions high (crush injury, contamination)
• Surgeon preference for modern approach

Compromise Technique (author's preference):

• Loose reconstruction with 4-0 or 5-0 absorbable suture
• Leave gaps/windows in reconstruction
• Allows gliding while preventing significant bowstringing
• Best of both approaches

Skin Closure

Techniques:

• 4-0 or 5-0 absorbable subcuticular preferred (no suture removal trauma)
• Skin adhesive (Dermabond) over subcuticular for reinforcement
• Avoid deep dermal sutures if possible (increase bulk, potential infection nidus)

Closure Principles:

• NO tension on skin edges (causes necrosis over swollen repair)
• Evert wound edges slightly (prevents depressed scar)
• In digital zones, ensure closure does not constrict (allow for swelling)

Dressing:

• Non-adherent layer over incision
• Fluffed gauze for padding and edema control
• Apply zone-specific splint immediately

Post-operative Management and Return to Function

Zone-Specific Splinting Protocols

Zone I (DIP):

• DIP extension 0-5 degrees
• PIP and MCP FREE
• Duration: 6-8 weeks continuous, then night splinting 2-4 weeks
• May use stack splint, aluminum foam splint, or custom thermoplastic

Zones II-IV (Digit):

• Wrist extension 30-40 degrees
• MCP slight flexion (20-30 degrees) or neutral
• IP joints extended
• Duration: 4-6 weeks

Zone III (Central Slip) - SPECIAL:

• PIP extension (0 degrees or slight hyperextension 5-10 degrees)
• DIP MUST BE FREE (maintain lateral band length)
• Duration: 6 weeks strict, then dynamic extension splinting 2-4 weeks

Zone V (Sagittal Band):

• MCP extension (0-10 degrees flexion)
• IP joints FREE
• Duration: 4 weeks, then dynamic extension splinting 2 weeks

Zones VI-VIII (Wrist/Forearm):

• Wrist extension 30-40 degrees
• Digits in composite extension or intrinsic plus
• Duration: 4-6 weeks (may shorten to 3-4 weeks if strong repair)

Mobilization Strategies

Static Immobilization (traditional):

• 3-4 weeks strict immobilization
• Then gradual active ROM
• Transition to dynamic splinting 4-6 weeks
• Strengthening 6-8 weeks
• Pros: Safe, 1-2% rupture rate
• Cons: More stiffness (especially Zone VI), slower recovery

Early Protected Motion (modern trend):

• Relative motion protocols
• Synergistic motion (wrist extension with digit flexion relaxes repair)
• Early active short arc motion
• Pros: Less adhesions, faster recovery, better outcomes in Zone VI
• Cons: Higher rupture risk (3-5%), requires compliant patient and experienced therapist

Hybrid Approach (most common):

• Static immobilization 2-3 weeks
• Transition to early protected motion 3-6 weeks
• Dynamic splinting 6-8 weeks
• Balances safety and outcomes

Zone VI Specific:

• Early protected motion MOST beneficial here (combats adhesions)
• Accept slightly higher rupture risk
• Place-and-hold exercises starting week 2-3
• Gentle passive ROM week 3-4
• Active ROM week 4-6

Rehabilitation Timeline

Weeks 0-2:

• Strict immobilization or very gentle protected motion (zone-dependent)
• Edema control (elevation, compression)
• AROM of adjacent non-immobilized joints
• Patient education on splint care and precautions

Weeks 2-4:

• Continue immobilization (static protocol) OR
• Initiate early protected motion (place-and-hold, short arc)
• Begin gentle tendon gliding exercises if allowed
• Monitor for complications (rupture, excessive pain, infection)

Weeks 4-6:

• Transition to active ROM (static protocol) OR
• Progress protected motion (hybrid/early motion protocol)
• Dynamic extension splinting may begin
• Light functional activities (no resistance)

Weeks 6-8:

• Active ROM emphasis
• Discontinue static splinting if zone allows
• Continue dynamic splinting if needed
• Begin light strengthening (putty, foam)
• Progressive functional activities

Weeks 8-12:

• Aggressive strengthening
• Resistance exercises
• Sports-specific training if applicable
• Gradual return to manual labor

Months 3-6:

• Return to full activities
• Unrestricted use for most activities
• May have 10-20 degree extensor lag (common, acceptable if functional)

Expected Outcomes by Zone

Zone I:

• 80-90% achieve functional DIP extension
• 10-20 degree lag acceptable
• 10-15% develop swan-neck if overcorrected

Zones II, IV:

• 85-95% good-excellent outcomes
• Minimal extensor lag (<10 degrees)
• Low complication rate

Zone III:

• 70-80% good outcomes with proper management
• 15-20% develop boutonniere if central slip inadequately repaired
• Chronic cases have guarded prognosis

Zone V:

• 75-85% good outcomes
• 10-20 degree extensor lag common (sagittal band stretching)
• Recurrent subluxation 10-15% if inadequate repair

Zone VI:

• 60-80% good outcomes (worst zone)
• 30-40% develop significant adhesions
• Tenolysis required in 10-20%
• Early protected motion improves outcomes

Zones VII-VIII:

• 85-95% excellent outcomes (best zones)
• Minimal adhesions
• Good excursion
• Early motion well tolerated