WRIST ARTHRODESIS
Total vs Four-Corner | SLAC/SNAC Staging | Radiolunate Critical | Position Matters
WRIST ARTHRODESIS TYPES
Critical Must-Knows
- Total fusion: Pan-carpal arthritis, SLAC/SNAC Stage IV, eliminates all wrist motion
- Four-corner fusion: SLAC/SNAC Stage II-III with INTACT radiolunate joint, preserves 50% motion
- Radiolunate joint assessment critical - any arthritis contraindicates four-corner
- Fusion position: Neutral to 15-20° extension for optimal function
- Complete cartilage removal to bleeding bone is most important technical factor
Examiner's Pearls
- "SLAC staging guides treatment: Stage II-III = four-corner or PRC, Stage IV = total fusion
- "Radiolunate joint must be intact for four-corner - assess on X-ray and CT
- "Scaphoidectomy and radial styloidectomy required for four-corner fusion
- "Nonunion most common complication - complete cartilage removal prevents it
Critical Wrist Arthrodesis Exam Points
Total vs Four-Corner Decision
Total fusion for pan-carpal arthritis or SLAC/SNAC Stage IV. Four-corner fusion for SLAC/SNAC Stage II-III with INTACT radiolunate joint. Radiolunate arthritis is absolute contraindication to four-corner - must do total fusion. Assess radiolunate joint on X-ray and CT before deciding.
Radiolunate Joint Critical
Radiolunate joint must be intact for four-corner fusion. Any arthritis on imaging (X-ray, CT) contraindicates four-corner - patient needs total fusion. This is the most common error: performing four-corner when radiolunate is arthritic, leading to persistent pain and need for revision.
Complete Cartilage Removal
Complete cartilage removal to bleeding subchondral bone is the most important technical factor. Inadequate removal is the leading cause of nonunion. Use rongeur, curette, and burr systematically. Bleeding bone confirms adequate preparation.
Fusion Position
Optimal position: Neutral to 15-20° extension, neutral radial/ulnar deviation. This functional position allows hand-to-mouth, perineal care, and writing. Excessive flexion or extension limits function. Position cannot be revised after fusion - get it right first time.
Quick Decision Guide - Wrist Arthrodesis
| Patient Scenario | SLAC Stage | Treatment | Key Consideration |
|---|---|---|---|
| SLAC Stage II-III, intact radiolunate joint | Stage II-III | Four-corner fusion or PRC | Preserves 50% motion at radiolunate joint |
| SLAC Stage IV, radiolunate arthritis | Stage IV | Total wrist fusion | All motion eliminated but reliable pain relief |
| Pan-carpal arthritis, RA, post-traumatic | Pan-carpal | Total wrist fusion | Gold standard for end-stage disease |
| Severe instability, paralytic wrist | Instability | Total wrist fusion | Provides stable pain-free platform |
RSCLSLAC Wrist Staging
Memory Hook:RSCL progression: Radial styloid → Scaphoid fossa → Capitolunate → Lunate fossa. Stage IV requires total fusion.
CLEARFour-Corner Fusion Requirements
Memory Hook:CLEAR requirements for four-corner: Cartilage intact, Lunate preserved, Excise scaphoid, Assess preop, Radial styloidectomy.
NEUTRALFusion Position
Memory Hook:NEUTRAL position: Neutral extension, test right first time, immobilize until fusion - position is permanent.
Overview and Epidemiology
Definition: Wrist arthrodesis is a salvage procedure that fuses wrist joints to eliminate motion and provide pain relief. Total wrist fusion eliminates all wrist motion, while four-corner (partial) fusion preserves radiolunate motion. The choice depends on disease extent and radiolunate joint status.
Historical Context: Wrist arthrodesis has evolved from simple pin fixation to modern dorsal plating systems with improved fusion rates. Recognition that radiolunate joint can be preserved in SLAC Stage II-III has made four-corner fusion a motion-preserving alternative to total fusion.
Current Indications:
Total Wrist Fusion:
- Pan-carpal arthritis (post-traumatic, inflammatory, degenerative)
- SLAC/SNAC Stage IV (radiolunate arthritis)
- Severe instability (RA, post-traumatic)
- Failed prior salvage procedures
- Paralytic/spastic wrist requiring stable platform
Four-Corner Fusion:
- SLAC/SNAC Stage II-III with intact radiolunate joint
- Scaphoid non-union advanced collapse (SNAC)
- Preserves 50% wrist motion at radiolunate joint
Epidemiology:
- Frequency: Common in hand surgery (1-2 per month in hand centers)
- Age: Peak 40-60 years (post-traumatic), older for RA
- Gender: Equal distribution (trauma-related), female predominance in RA
- Trend: Four-corner fusion increasing for SLAC Stage II-III
Why Wrist Arthrodesis Exists
Wrist arthrodesis provides reliable pain relief for end-stage wrist pathology when motion-preserving procedures are not possible or have failed. Total fusion eliminates all motion but provides pain-free stable platform. Four-corner fusion preserves radiolunate motion (~50%) but requires intact radiolunate joint - this is the critical decision point.
Pathophysiology and Mechanisms
Wrist Joint Anatomy:
Radiocarpal Joint:
- Radioscaphoid fossa: Articulates with scaphoid
- Radiolunate fossa: Articulates with lunate
- Sigmoid notch: Articulates with ulna (DRUJ)
Midcarpal Joint:
- Scaphocapitate: Scaphoid-capitate articulation
- Capitolunate: Capitate-lunate articulation
- Triquetrohamate: Triquetrum-hamate articulation
Carpal Bones:
- Proximal row: Scaphoid, lunate, triquetrum, pisiform
- Distal row: Trapezium, trapezoid, capitate, hamate
- Carpal height: Critical for four-corner fusion
Ligamentous Anatomy:
Extrinsic Ligaments:
- Radioscaphocapitate: Primary scaphoid stabilizer
- Radiolunate: Stabilizes lunate
- Dorsal radiocarpal: Dorsal stability
Intrinsic Ligaments:
- Scapholunate: Critical for carpal stability
- Lunotriquetral: Ulnar carpal stability
Nerve Anatomy:
Superficial Radial Nerve:
- Branches cross dorsal radial wrist
- Injury causes numbness (10% incidence)
- Must protect during approach
Dorsal Ulnar Sensory Branch:
- Ulnar side of incision
- Must protect
Biomechanics:
After Total Fusion:
- All wrist motion eliminated
- Compensatory motion at elbow, shoulder
- Grip strength improves (pain relief)
- Functional adaptation required
After Four-Corner Fusion:
- 50% wrist motion preserved (radiolunate joint)
- Carpal height maintained
- Better function than total fusion
- Risk of radiolunate arthritis progression
Classification Systems
Scapholunate Advanced Collapse
Stage I:
- Arthritis between radial styloid and scaphoid
- Early disease
- Treatment: Radial styloidectomy, debridement
Stage II:
- Entire radioscaphoid joint involved
- Scaphoid fossa arthritis
- Treatment: Four-corner fusion or PRC (if radiolunate intact)
Stage III:
- Capitolunate arthritis
- Capitate migrates proximally
- Treatment: Four-corner fusion or PRC (if radiolunate intact)
Stage IV:
- Radiolunate arthritis
- Pan-carpal involvement
- Treatment: Total wrist fusion (four-corner contraindicated)
SLAC staging guides surgical decision-making and predicts outcomes.
Clinical Assessment
History:
- Pain location (dorsal, radial, ulnar)
- Instability symptoms (giving way, clunking)
- Previous trauma (fractures, ligament injuries)
- Functional limitations (grip, activities)
- Occupation and hand dominance
Physical Examination:
Inspection:
- Swelling, deformity
- Carpal collapse (SLAC wrist)
- Muscle atrophy
Palpation:
- Joint line tenderness
- Scapholunate gap (Watson test)
- Instability (ballottement)
Range of Motion:
- Flexion-extension: Normal 70-80° each direction
- Radial-ulnar deviation: Normal 20-30° each direction
- Pronation-supination: Normal 80° each direction
Special Tests:
- Watson test: Scapholunate instability
- Midcarpal shift: Midcarpal instability
- Grip strength: Compare with contralateral
Radiographic Assessment:
- PA view: Carpal alignment, joint spaces, SLAC stage
- Lateral view: Carpal collapse, DISI/VISI deformity
- CT scan: Cartilage assessment, radiolunate joint evaluation
Investigations
Plain Radiographs:
- PA wrist: Carpal alignment, joint spaces, SLAC staging
- Lateral wrist: Carpal collapse, DISI/VISI deformity
- Oblique views: Better visualization of specific joints
- Stress views: Instability assessment
CT Scan:
- 3D reconstruction: Essential for planning
- Cartilage assessment: Radiolunate joint evaluation (critical for four-corner)
- Bone stock: Quality for fixation
- Deformity quantification: Carpal collapse, alignment
MRI:
- Cartilage evaluation: Early changes, radiolunate status
- Ligament integrity: Scapholunate, lunotriquetral
- Avascular necrosis: Scaphoid, lunate
Arthroscopy:
- Diagnostic: Direct cartilage visualization
- Therapeutic: Debridement, limited procedures
Management Algorithm
Decision Framework
The key decision is total vs four-corner fusion. Total fusion for pan-carpal arthritis or Stage IV. Four-corner for Stage II-III with intact radiolunate. Radiolunate joint assessment is critical - any arthritis contraindicates four-corner.
Decision Tree
Step 1: Assess Disease Extent
- SLAC/SNAC staging (I-IV)
- Radiolunate joint status (critical)
- Pan-carpal vs localized
Step 2: Evaluate Radiolunate Joint
- X-ray: Joint space, alignment
- CT: Cartilage status, subchondral changes
- Any arthritis? → Total fusion
- Intact? → Consider four-corner
Step 3: Patient Factors
- Age, demand, occupation
- Hand dominance
- Functional requirements
Step 4: Surgical Decision
- Stage IV or radiolunate arthritis → Total fusion
- Stage II-III with intact radiolunate → Four-corner or PRC
- Stage I → Joint-sparing procedures
The goal is pain relief with optimal function preservation.
Surgical Technique
Pre-operative Planning Steps
1. Disease Assessment:
- SLAC/SNAC staging
- Radiolunate joint evaluation (critical)
- Bone quality assessment
2. Decision Making:
- Total vs four-corner fusion
- Radiolunate status determines choice
3. Equipment:
- Dorsal wrist fusion plate (total)
- Four-corner fusion plate (spider/circular)
- Bone graft (iliac crest or local)
- Fluoroscopy
4. Patient Preparation:
- Smoking cessation mandatory
- Medical optimization
- Hand dominance consideration
Proper planning ensures correct procedure selection and optimal outcomes.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Nonunion | 5-10% total, 10-20% four-corner | Inadequate cartilage removal, poor fixation, smoking, insufficient graft | Revision with better preparation, rigid fixation, bone graft |
| Hardware prominence | 10% | Dorsal plate location, thin skin | Removal once fused (18-24 months) if symptomatic |
| Persistent pain | 10-15% | Nonunion, adjacent joint arthritis, hardware irritation | Identify cause, treat accordingly |
| Radiolunate arthritis | 10-20% (four-corner) | Progressive disease, altered biomechanics | Conversion to total fusion if symptomatic |
| Nerve injury | 10% superficial radial | Dorsal approach, nerve branches | Observation, most recover |
| Carpal collapse | 5-10% (four-corner) | Inadequate fixation, bone loss | Revision with better fixation |
| Infection | 2-5% | Hardware present, diabetes, smoking | Debridement, antibiotics, may need hardware removal |
Most Common Complication: Nonunion
Nonunion is the most common complication: 5-10% for total fusion with plate, 10-20% for four-corner fusion. Leading cause is inadequate cartilage removal. Prevention requires complete denudation to bleeding subchondral bone using rongeur, curette, and burr systematically. Treatment requires revision with better preparation, rigid fixation, and bone graft.
Postoperative Care and Rehabilitation
Total Wrist Fusion Rehabilitation
Immobilization (0-12 weeks):
- Short arm cast or splint
- Immobilize 6-12 weeks until radiographic fusion
- X-rays at 6, 12 weeks assess fusion
- Bridging bone on 3+ cortices indicates fusion
After Fusion (12+ weeks):
- Remove cast/splint once fused
- Gentle finger ROM exercises
- Strengthening
- NO wrist motion (fused - this is expected)
Functional Adaptation:
- Compensatory motion at elbow and shoulder
- Occupational therapy for adaptive techniques
- Most patients adapt well
Return to Activities:
- Light activities: 3-4 months
- Full activities: 6 months
- Hardware removal: 18-24 months if symptomatic
Total fusion rehabilitation focuses on finger function and adaptation.
Outcomes and Prognosis
Total Wrist Fusion Outcomes:
- Pain relief: 80-90% achieve good to excellent relief
- Motion: 0° wrist motion (expected and desired)
- Grip strength: 60-80% of opposite side
- Satisfaction: 80-85% satisfied despite motion loss
- Nonunion: 5-10% with plate fixation
Four-Corner Fusion Outcomes:
- Pain relief: 70-80% achieve good relief
- Motion: ~50% preserved (average 30° arc)
- Grip strength: 75-80% of opposite side
- Satisfaction: 85-90% satisfied
- Nonunion: 10-20% (higher than total)
Long-term Considerations:
- Radiolunate arthritis: 10-20% develop over 5-10 years (four-corner)
- Hardware removal: 20-30% require removal for prominence
- Revision: 10-15% require revision (nonunion, complications)
- Adjacent joints: CMC, DRUJ may develop issues
Predictors of Success
Good outcomes are associated with: complete cartilage removal, rigid fixation (plates), adequate bone graft, proper alignment, smoking cessation, and dedicated therapy. Poor outcomes are associated with: inadequate cartilage removal, poor fixation, smoking, non-compliance, and complications.
Evidence Base and Key Trials
Wrist Arthrodesis Outcomes
- Total fusion: 80-90% pain relief, 0° motion, 60-80% grip strength
- Nonunion rate 5-10% with plate fixation
- Hardware prominence in 10% requiring removal
Four-Corner Fusion
- Four-corner fusion preserves 50% motion at radiolunate joint
- Nonunion rate 10-20% (higher than total)
- Radiolunate arthritis develops in 10-20% over 5-10 years
SLAC Wrist Staging
- SLAC staging guides treatment decisions
- Stage II-III: four-corner or PRC
- Stage IV: total fusion required
Cartilage Removal and Nonunion
- Inadequate cartilage removal is leading cause of nonunion
- Complete denudation to bleeding bone critical
- Bone graft enhances fusion rates
Fusion Position
- Neutral to 15-20° extension optimal for function
- Allows hand-to-mouth, perineal care, writing
- Position cannot be revised after fusion
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Total vs Four-Corner Decision (~3-4 min)
"A 55-year-old patient presents with SLAC wrist. X-rays show Stage III disease with capitolunate arthritis but radiolunate joint appears preserved. Walk me through your decision-making for total vs four-corner fusion, including how you assess the radiolunate joint and what factors influence your choice."
Scenario 2: Surgical Technique (~3-4 min)
"Walk me through the surgical technique for four-corner fusion, including approach, scaphoidectomy, cartilage removal, and fixation."
Scenario 3: Nonunion Management (~2-3 min)
"A patient presents 6 months after four-corner fusion with persistent pain. X-rays show no bridging bone and lucency at fusion interfaces. How do you manage this nonunion?"
MCQ Practice Points
Indications Question
Q: What is the primary indication for four-corner fusion? A: SLAC/SNAC Stage II-III with INTACT radiolunate joint. The radiolunate joint must have no arthritis on X-ray or CT - any arthritis contraindicates four-corner and requires total fusion.
Surgical Technique Question
Q: What is the most important technical factor for successful wrist fusion? A: Complete cartilage removal to bleeding subchondral bone. Inadequate removal is the leading cause of nonunion. Use rongeur, curette, and burr systematically to denude all fusion surfaces.
Complications Question
Q: What is the nonunion rate for four-corner fusion versus total wrist fusion? A: Four-corner fusion has higher nonunion rate (10-20%) compared to total fusion (5-10%). This is due to more fusion interfaces, smaller contact areas, and technically more difficult cartilage removal.
Position Question
Q: What is the optimal fusion position for total wrist arthrodesis? A: Neutral to 15-20° extension, neutral radial/ulnar deviation. This functional position allows hand-to-mouth, perineal care, and writing. Position cannot be revised after fusion - must be correct initially.
Staging Question
Q: How does SLAC staging guide surgical treatment? A: Stage I: Radial styloidectomy. Stage II-III: Four-corner fusion or PRC (if radiolunate intact). Stage IV: Total wrist fusion (radiolunate arthritis requires total fusion).
Australian Context and Medicolegal Considerations
Australian Practice Patterns
Wrist arthrodesis common in hand surgery centers (1-2 per month), Four-corner fusion increasing for SLAC Stage II-III, Total fusion remains gold standard for Stage IV, Modern plating systems preferred over pins
Medicolegal Considerations
Informed consent: Must discuss motion loss extensively, Radiolunate assessment: Must document evaluation before four-corner, Position errors: Cannot be revised - must document position confirmation, Alternatives: Must discuss PRC and total fusion options
Medicolegal Risk Factors
Key documentation requirements:
- Preoperative radiolunate joint assessment (X-ray, CT)
- Discussion of motion loss and functional implications
- Fusion position confirmation on fluoroscopy
- Alternative procedures discussed (PRC, total fusion)
- Informed consent for permanent motion loss
Common litigation issues:
- Performing four-corner when radiolunate is arthritic
- Nonunion due to inadequate cartilage removal
- Malposition causing functional impairment
- Failure to discuss alternatives
Proper documentation and systematic approach minimize medicolegal risk.
Wrist Arthrodesis
High-Yield Exam Summary
Key Indications
- •Total fusion: pan-carpal arthritis, SLAC/SNAC Stage IV, severe instability
- •Four-corner: SLAC/SNAC Stage II-III with intact radiolunate joint
- •Radiolunate assessment critical - any arthritis contraindicates four-corner
- •Scaphoid non-union advanced collapse (SNAC) similar to SLAC
Surgical Technique
- •Dorsal approach: protect superficial radial and dorsal ulnar nerves
- •Scaphoidectomy: complete removal, radial styloidectomy 4-6mm
- •Cartilage removal: complete to bleeding bone (most important factor)
- •Fixation: dorsal plate (total) or four-corner plate (partial)
- •Bone graft: iliac crest or local (scaphoid for four-corner)
Fusion Position
- •Neutral to 15-20° extension: functional position
- •Neutral radial/ulnar deviation
- •Test position on fluoro before fixing
- •Position cannot be revised after fusion
Complications
- •Nonunion: 5-10% total, 10-20% four-corner (most common)
- •Hardware prominence: 10% requiring removal
- •Radiolunate arthritis: 10-20% over 5-10 years (four-corner)
- •Nerve injury: 10% superficial radial (numbness)
Outcomes
- •Total fusion: 0° motion, 80-90% pain relief, 60-80% grip
- •Four-corner: 50% motion preserved, 70-80% pain relief, 75-80% grip
- •Satisfaction: 80-85% total, 85-90% four-corner
- •Hardware removal: 20-30% for prominence