MCP Joint Arthritis

History

Rheumatoid Arthritis:

• Bilateral symmetric hand pain and stiffness
• Morning stiffness greater than 1 hour (classic, improves with activity)
• Progressive ulnar drift and visible deformity
• Difficulty with power grip (holding objects) and precision pinch
• Known RA diagnosis with systemic involvement (other joints, lungs, heart)
• DMARD treatment history (methotrexate, biologics)
• Duration of hand symptoms (months to years)

Post-Traumatic:

• History of MCP trauma (fracture, dislocation, ligament injury)
• Unilateral, single digit pain and stiffness
• Reduced ROM compared to contralateral side
• Pain with gripping activities
• Delayed onset (months to years after injury)

Primary OA:

• Insidious onset, gradual progression
• Usually older age (greater than 60 years)
• Occupational history (manual labor, repetitive gripping)
• Less systemic symptoms than RA

Examination

Inspection:

• Ulnar drift: Fingers deviate ulnarly at MCPs (pathognomonic for rheumatoid)
• Volar subluxation: Proximal phalanx displaced volarly, dorsal step-off at MCP
• Swelling: Boggy synovitis at MCP joints (active RA), fusiform swelling
• Deformity: Swan-neck (MCP flexion, PIP hyperextension, DIP flexion) or boutonniere at IP joints
• Extensor tendon position: Displaced ulnarly into valleys between MCP heads
• Skin: Rheumatoid nodules (extensor surface, olecranon, MCP), thinning, fragility
• Z-collapse: Wrist radial deviation with MCP ulnar drift

Palpation:

• MCP joint line tenderness (dorsal palpation)
• Synovial thickening (boggy, compressible, warm in active inflammation)
• Collateral ligament stability (radial and ulnar stress testing at MCP)
• Volar plate (test for hyperextension laxity)

Range of Motion:

• Active MCP flexion-extension: Normal 0-90 degrees, reduced in arthritis
• Passive ROM: Compare to active (capsular tightness vs extensor lag)
• Extensor lag: Inability to fully extend MCP actively (extensor displacement/weakness)
• Compare to contralateral hand

Special Tests:

• Intrinsic tightness test: With MCP extended, attempt PIP flexion. If intrinsics tight, PIP flexion is limited. With MCP flexed (relaxes intrinsics), PIP flexion should improve.
• Extensor lag: Active extension deficit compared to passive extension (indicates extensor tendon pathology)
• Collateral ligament stability: Radial and ulnar stress at MCP in flexion (normally tight) and extension (normally lax). Excessive laxity suggests ligament attenuation.
• Grip strength: Dynamometer testing (compare to contralateral, age-matched norms)
• Pinch strength: Key pinch and pulp pinch (assess thumb MCP stability)

Functional Assessment:

• Power grip: Holding objects, jar opening
• Precision pinch: Writing, buttoning
• ADLs: Dressing, eating, hygiene
• Work demands: Manual labor vs sedentary

Examination findings guide surgical planning and inform patient expectations.

Radiographic Assessment

Standard Views:

• PA (posteroanterior) hand x-ray: Evaluate joint space, erosions, ulnar drift
• Lateral hand x-ray: Assess volar subluxation of proximal phalanx
• Oblique views: Additional detail of MCP joint surfaces
• Bilateral hands: Compare symmetry (rheumatoid is bilateral and symmetric)

Rheumatoid Arthritis Radiographic Progression

Early Findings:

• Periarticular osteopenia (juxta-articular bone loss)
• Soft tissue swelling (fusiform MCP)
• Maintained joint space initially
• No erosions yet

Moderate Findings:

• Joint space narrowing (less than 50% loss)
• Marginal erosions at MCP (bare areas not covered by cartilage)
• Subchondral cysts
• Volar subluxation of proximal phalanx (lateral view)
• Ulnar deviation (PA view)

Late Findings:

• Severe joint space narrowing (greater than 50% loss or complete loss)
• Large erosions (central and marginal)
• Volar and ulnar subluxation
• Metacarpal head destruction
• Ankylosis (rare, usually fibrous)
• Mutilating arthropathy (opera glass hand, telescoping digits)

Larsen Radiographic Grading (Rheumatoid MCP)

Grade III-V typically require surgical intervention if symptomatic and failed medical management.

Post-Traumatic OA Findings

• Joint space narrowing (usually focal, asymmetric)
• Subchondral sclerosis (increased bone density)
• Subchondral cysts
• Osteophyte formation (dorsal MCP prominence)
• Post-traumatic deformity (malunion, articular step-off)
• Usually unilateral, single digit

Advanced Imaging (Rarely Needed)

MRI:

• Indications: Assess synovitis extent, erosions not visible on x-ray, tendon integrity, rule out occult fracture
• Findings: Synovial enhancement (active inflammation), erosions (T1 dark, bone destruction), marrow edema (T2 bright, pre-erosive changes), tendon rupture or displacement
• Not routine: Plain x-rays sufficient for most cases

Ultrasound:

• Indications: Assess synovial thickening, power Doppler for active inflammation (guide injection or medical therapy)
• Advantages: Dynamic assessment, real-time, lower cost than MRI
• Findings: Synovial hypertrophy, joint effusion, power Doppler signal (active synovitis), erosions
• Use: Rheumatology follow-up, not routine orthopaedic assessment

Plain radiographs are the primary imaging modality for diagnosis and surgical planning.

Laboratory Tests

Rheumatoid Arthritis Workup:

• Rheumatoid factor (RF): Positive in 70-80% of RA patients (IgM antibody against Fc portion of IgG)
  • Not specific: Can be positive in other conditions (hepatitis C, cryoglobulinemia, elderly)
• Anti-CCP (anti-cyclic citrullinated peptide) antibodies: Positive in 70% of RA, more specific than RF
  • High specificity (greater than 95%) for RA
  • Prognostic: Predicts erosive disease
• ESR (erythrocyte sedimentation rate): Elevated in active inflammation (guides DMARD therapy)
• CRP (C-reactive protein): More specific than ESR for acute inflammation, tracks disease activity
• ANA (antinuclear antibody): May be positive in RA (20-30%), consider overlap syndromes (SLE, Sjogren)
• CBC: Anemia of chronic disease (normocytic, normochromic), thrombocytosis (active inflammation)

Seronegative Spondyloarthropathies:

• RF and anti-CCP: Negative (hence "seronegative")
• HLA-B27: Positive in ankylosing spondylitis (90%), reactive arthritis (60-80%), psoriatic arthritis (20%)
• ESR/CRP: May be elevated
• Clinical diagnosis: Psoriasis (skin, nail changes), axial involvement, DIP joint arthritis

Psoriatic Arthritis:

• RF negative, anti-CCP negative
• May have elevated ESR/CRP
• Diagnosis: Clinical (psoriasis, nail pitting, oil spots, DIP and MCP involvement, sausage digits)
• X-ray: "Pencil-in-cup" deformity at DIP, erosions, osteolysis

Crystalline Arthropathy (Gout, Pseudogout):

• Serum uric acid: Elevated in gout (greater than 6.8 mg/dL), but may be normal during acute attack
• Joint aspiration (arthrocentesis):
  • Gout: Negatively birefringent needle-shaped monosodium urate crystals (yellow when parallel to polarizer)
  • Pseudogout: Positively birefringent rhomboid-shaped calcium pyrophosphate crystals (blue when parallel)
  • Synovial fluid: Inflammatory (WBC greater than 2000, often greater than 50,000 in acute)
• X-ray: Chondrocalcinosis (pseudogout, CPPD), tophi (gout, soft tissue masses)

Pre-operative Labs (if surgery planned):

• CBC, CMP (comprehensive metabolic panel): Baseline
• ESR/CRP: Assess disease activity (defer surgery if active flare)
• Nutrition: Albumin, prealbumin (wound healing)
• Coordination with rheumatology: DMARD perioperative management (methotrexate often held 1-2 weeks pre-op, biologics held per half-life)

Laboratory tests confirm diagnosis and guide medical management, but imaging and clinical examination determine surgical candidacy.

Disease-Modifying Therapy (Rheumatoid)

DMARDs (Disease-Modifying Anti-Rheumatic Drugs):

First-Line:

• Methotrexate (MTX): 10-25mg weekly (oral or subcutaneous)
  • Mechanism: Folate antagonist, anti-inflammatory
  • Efficacy: 60-70% response rate
  • Monitoring: CBC, LFTs, renal function (every 8-12 weeks)
  • Side effects: Nausea, hepatotoxicity, bone marrow suppression, teratogenic
  • Supplement: Folic acid 1mg daily (reduces side effects)

Alternative/Combination:

• Sulfasalazine: 2-3g daily (divided doses)
  • Efficacy: Moderate (less than MTX)
  • Use: Combination with MTX or if MTX intolerant
• Hydroxychloroquine: 200-400mg daily
  • Efficacy: Mild disease
  • Monitoring: Ophthalmology (retinal toxicity, rare)
• Leflunomide: 10-20mg daily
  • Efficacy: Similar to MTX
  • Use: MTX alternative

Triple Therapy: MTX + sulfasalazine + hydroxychloroquine (moderate-severe RA, as effective as some biologics)

Biologic DMARDs (Moderate-Severe RA)

Anti-TNF Agents:

• Adalimumab (Humira): 40mg subcutaneous every 2 weeks
• Etanercept (Enbrel): 50mg subcutaneous weekly
• Infliximab (Remicade): 3-10mg/kg IV every 8 weeks (with MTX)
• Mechanism: Inhibit TNF-alpha (key inflammatory cytokine)
• Efficacy: 60-70% ACR20 response (20% improvement)
• Risks: Infections (TB reactivation, screen PPD), malignancy (lymphoma, skin cancer)

IL-6 Inhibitors:

• Tocilizumab (Actemra): 8mg/kg IV every 4 weeks or 162mg subcutaneous weekly
• Sarilumab (Kevzara): 200mg subcutaneous every 2 weeks
• Mechanism: Block IL-6 receptor
• Efficacy: Similar to anti-TNF

JAK Inhibitors (Newer):

• Tofacitinib (Xeljanz): 5mg oral twice daily
• Baricitinib (Olumiant): 2mg oral daily
• Mechanism: Inhibit Janus kinase (intracellular signaling)
• Efficacy: Similar to biologics, oral administration (advantage)
• Risks: Infections, thrombosis (black box warning)

B-Cell Depletion:

• Rituximab (Rituxan): 1000mg IV x2 (day 0 and 14), repeat every 6 months
• Mechanism: Depletes CD20+ B cells
• Use: Failed anti-TNF

T-Cell Costimulation Blockade:

• Abatacept (Orencia): IV or subcutaneous
• Mechanism: Blocks T-cell activation

Indication for Biologics: Moderate-severe RA uncontrolled on MTX monotherapy, high disease activity, erosive disease.

Perioperative Management: Hold anti-TNF for 1-2 half-lives pre-op (e.g., adalimumab hold 2-4 weeks), restart when wound healed (2 weeks post-op). Coordinate with rheumatology.

Anti-Inflammatory Medications

NSAIDs:

• Ibuprofen: 400-800mg three times daily
• Naproxen: 500mg twice daily
• Celecoxib (COX-2 selective): 200mg daily or twice daily
• Mechanism: Inhibit cyclooxygenase, reduce prostaglandin synthesis
• Efficacy: Symptomatic relief (pain, stiffness), do NOT modify disease progression
• Risks: GI bleeding (PPI co-prescription if high risk), renal impairment, cardiovascular events (especially COX-2 inhibitors)
• Monitoring: Renal function, CBC

Corticosteroids:

• Low-dose oral prednisone: 5-10mg daily
  • Use: Acute flares, bridge therapy while starting DMARDs (takes 8-12 weeks for DMARD effect)
  • Minimize long-term use: Osteoporosis, infection risk, glucose intolerance, Cushing syndrome
  • Taper: Gradual taper when DMARDs effective
• Intra-articular corticosteroid injections: See next tab

Medical management is first-line for rheumatoid MCP arthritis. Surgery reserved for failed medical management with persistent symptoms and functional impairment.

Corticosteroid Injections

Indications:

• Active synovitis with pain and swelling
• MCP joint effusion
• Failed oral medications (NSAIDs, DMARDs optimized)
• Temporary relief while awaiting DMARD effect
• Patient refuses or cannot tolerate surgery

Technique:

• Approach: Dorsal, between extensor tendon and collateral ligament
• Needle: 25-27 gauge, 1 inch
• Medication:
  • Triamcinolone acetonide: 20mg (0.5-1ml)
  • Methylprednisolone: 20-40mg (0.5-1ml)
  • Betamethasone: 3-6mg
• Local anesthetic: Optional (lidocaine 1%, 0.5ml) to confirm intra-articular placement (immediate pain relief)
• Sterile technique: Alcohol prep, no-touch technique

Post-Injection:

• Rest hand for 24-48 hours
• Ice for 15 minutes (reduce post-injection flare)
• Avoid heavy gripping for 1 week

Efficacy:

• Pain relief: 50-70% of patients
• Duration: 3-6 months (less than larger joints like knee)
• Less effective in small joints compared to knee, shoulder

Risks:

• Cartilage damage: Limit to 3 injections per year, avoid frequent injections
• Tendon weakening/rupture: Avoid injecting into extensor tendon
• Infection: Rare (less than 1 in 10,000), strict aseptic technique
• Subcutaneous atrophy: Fat atrophy, skin depigmentation (improper technique, superficial injection)
• Hyperglycemia: Diabetic patients (monitor glucose)

Contraindications:

• Active infection
• Overlying cellulitis
• Coagulopathy (relative)

Splinting

MCP Ulnar Drift Orthosis:

• Design: Custom-molded thermoplastic or prefabricated splint
• Function: Holds MCPs in neutral alignment (0 degrees radial-ulnar deviation)
• Wear schedule: During activities (gripping, writing) or at night
• Efficacy: Does NOT reverse deformity, only slows progression
• Duration: Long-term use (years)

Resting Hand Splint:

• Design: Full hand splint
• Position: Wrist 20-30 degrees extension, MCPs 30-45 degrees flexion, IPs extended (intrinsic plus position)
• Indication: Acute rheumatoid flares (painful synovitis)
• Function: Reduces pain, prevents deformity during inflammation
• Wear: Night splinting during flares, remove during day for function

Dynamic Extension Splint:

• Use: Post-operative (after silicone arthroplasty)
• Design: Outrigger with elastic bands pulling MCPs into extension and radial deviation
• Function: Maintains MCP extension, prevents ulnar drift recurrence
• Critical: 6 weeks full-time, then night splinting for 3 months

Splinting is adjunctive, not curative. Primary management is medical (DMARDs, biologics).

Occupational Therapy and Hand Therapy

Goals:

• Preserve ROM and strength
• Protect joints from deforming forces
• Improve function with ADLs
• Educate patient on joint protection

Joint Protection Education:

• Avoid ulnar-deviating forces: Use jar openers, twist with radial deviation (not ulnar)
• Use larger joints: Carry bags on forearm (not fingers), push doors with body (not hand)
• Reduce grip force: Use built-up utensils (larger diameter reduces grip force), adaptive equipment
• Rest during flares: Avoid heavy activities during active synovitis
• Proper ergonomics: Workstation setup, keyboard/mouse positioning

ROM Exercises:

• Active MCP flexion-extension: Fist making, finger extension exercises (maintain ROM)
• Passive ROM: Gentle passive stretching (therapist or self)
• Frequency: Daily, multiple sessions (10 reps each)
• Avoid aggressive stretching: Can worsen inflammation

Strengthening:

• Gentle grip strengthening: Therapy putty (soft to medium resistance), foam ball squeezes
• Avoid heavy resistance in active disease (worsens synovitis)
• Progression: Once inflammation controlled (DMARD effect), gradually increase resistance

Adaptive Equipment:

• Built-up utensils: Larger diameter handles (forks, spoons, pens)
• Key turners: Leverage devices for key turning (avoid ulnar deviation)
• Jar openers: Reduce grip force
• Button hooks, zipper pulls: Assistive dressing devices
• Electric can openers: Reduce repetitive gripping

Splinting: As above (MCP ulnar drift orthosis, resting splints)

Functional Training:

• ADL practice: Dressing, eating, hygiene with adaptive equipment
• Work simulation: Task-specific training
• Energy conservation: Pacing, rest breaks

Hand therapy is essential non-operative management and critical post-operative for arthroplasty success (dynamic splinting).

Non-operative management should be optimized for 3-6 months before considering surgery.

Silicone MCP Arthroplasty

Historical Context:

• Introduced by Alfred Swanson in 1960s-1970s
• Revolutionized rheumatoid hand surgery
• Flexible spacer concept (not load-bearing hinge)
• Fibrous encapsulation provides stability

Indications:

• Rheumatoid MCP arthritis with ulnar drift and/or volar subluxation
• Post-traumatic MCP arthritis (digits 2-5)
• Failed conservative management (DMARDs, splinting, injections for greater than 3-6 months)
• Desire to preserve motion (vs arthrodesis)
• Larsen Grade III-V radiographic changes
• Functional impairment (difficulty with grip, ADLs)

Contraindications:

• Active infection (absolute)
• Inadequate soft tissue coverage (exposed bone, compromised skin)
• Severe bone loss (insufficient bone stock for implant stems)
• Thumb MCP (arthrodesis preferred)
• Active rheumatoid flare (defer until controlled)
• Non-compliant patient (will not adhere to post-op splinting protocol)

Implant Types:

• Swanson silicone implant: Original design, hinge with stems
• Sutter silicone implant: Similar to Swanson
• NeuFlex: Newer silicone design with titanium grommets (reinforced)
• Pyrocarbon (surface replacement): Not silicone, requires intact bone stock, higher revision rate, NOT standard
• Silicone is standard: Flexible elastomer, NOT load-bearing, acts as spacer

Silicone Implant Mechanism:

• NOT a true joint replacement: Does not replicate normal joint biomechanics
• Acts as flexible spacer maintaining joint space
• Fibrous capsule forms around implant (encapsulation) - provides stability
• Allows motion through implant flexion (elastomer property)
• Not load-bearing: Cannot withstand high compressive loads (hence thumb MCP contraindication)

Surgical Technique

Pre-operative Planning:

• Bilateral hand x-rays (PA, lateral, oblique)
• Assess bone stock (degree of erosion, metacarpal head destruction)
• Measure implant size from x-ray (templating)
• Coordinate with rheumatology (DMARD perioperative management)
• Optimize medical management (control active synovitis)
• Educate patient on post-op splinting commitment (6 weeks full-time)

Patient Position:

• Supine, arm on radiolucent hand table
• Pneumatic tourniquet (upper arm, 250mmHg)
• Exsanguination with Esmarch or elevation

Incision:

• Longitudinal dorsal incision centered over MCP joint
• 3-4cm length
• Multiple MCPs: Can use single longitudinal incision (index through small) or separate incisions for each digit
• Avoid excessive skin undermining (preserve venous drainage)

Exposure:

1. Subcutaneous dissection: Preserve dorsal veins and cutaneous nerves
2. Identify extensor tendon: Extensor digitorum communis (EDC) overlying MCP
3. Develop plane between extensor and joint capsule
4. Elevate extensor mechanism radially: Preserves sagittal bands if intact, or elevate as a flap if ruptured
5. Longitudinal capsulotomy: Open capsule to expose MCP joint

Synovectomy (if rheumatoid):

• Complete synovectomy: Remove all hypertrophic, inflamed synovium from MCP joint
• Use rongeur, curette, or electrocautery
• Critical to remove as much pannus as possible (reduces recurrent synovitis)

Bone Preparation:

1. Resect metacarpal head: Oscillating saw, perpendicular cut to metacarpal shaft
   • Amount: Resect minimal bone (approximately 5-10mm), preserve length
   • Angle: Perpendicular to shaft (not angled)
   • Remove osteophytes, smooth edges
2. Ream intramedullary canals:
   • Metacarpal canal (hand reamers or burr)
   • Proximal phalanx canal
   • Goal: Snug fit for implant stems (avoid over-reaming)
3. Trial implant sizing: Insert trial implant, assess fit (should be snug, not loose)
4. Select definitive implant size: Match to trial size
5. Insert silicone implant: Stems into metacarpal and proximal phalanx canals
   • Avoid over-stuffing: Too large implant causes stiffness, implant fracture
   • Avoid under-sizing: Too small implant allows recurrent deformity

Soft Tissue Balancing (CRITICAL):

1. Extensor Tendon Centralization:

• Rationale: Extensor tendon has displaced ulnarly into valley, acts as ulnar deviator
• Technique: Reposition extensor tendon over center of MCP
• Suture to radial capsule: 3-0 non-absorbable suture (Ethibond, Ti-Cron), secure extensor to radial side
• Alternative: Radial sagittal band reconstruction (if sagittal band ruptured)

2. Radial Collateral Ligament Reconstruction:

• Rationale: Radial collateral ligament is stretched/incompetent, allows ulnar drift
• Technique: Reef (plicate) radial collateral ligament, or
• Reconstruct: Use radial capsule, suture to metacarpal neck (radial side)
• Goal: Tighten radial structures, resist ulnar drift

3. Intrinsic Release (if tight):

• Test intrinsic tightness: With MCP extended, attempt PIP flexion (limited if intrinsics tight)
• Release ulnar intrinsics: Release ulnar interosseous from proximal phalanx (ulnar side)
• Preservation: Preserve radial intrinsics (counteract ulnar drift)

4. Crossed Intrinsic Transfer (advanced, selective):

• Indication: Severe recurrent ulnar drift despite ligament reconstruction
• Technique: Transfer ulnar intrinsic to radial side (e.g., transfer ulnar lateral band to radial side)
• Rarely performed: Reserve for severe, recurrent cases

Without soft tissue balancing, arthroplasty WILL fail (recurrent ulnar drift).

Closure:

• Capsule: Close capsule over implant (2-0 absorbable suture, Vicryl)
• Extensor mechanism: Ensure extensor centralized, close sagittal bands if opened
• Subcutaneous: 3-0 absorbable
• Skin: 4-0 or 5-0 nylon, running or interrupted

Dressing:

• Non-adherent dressing (Xeroform), gauze
• Immediate application of dynamic MCP extension splint (see post-op protocol)

Post-operative Protocol

Immobilization:

• Dynamic MCP extension outrigger splint:
  • Custom-fabricated by certified hand therapist
  • Wrist in 20-30 degrees extension, MCPs in extension (0 degrees) with radial deviation
  • Elastic bands pull MCPs into extension and radial deviation
  • Allows controlled passive flexion, blocks ulnar deviation
• Wear schedule:
  • Weeks 0-6: Full-time (23 hours/day, remove for hygiene only)
  • Weeks 6-12: Night-time only
  • Months 3-6: Night-time as needed

Rehabilitation:

• Immediate (Day 1-2): Passive ROM with dynamic splint (flexion allowed, extension assisted by splint)
• Week 1: Hand therapy begins, passive ROM exercises (therapist-guided)
• Weeks 2-6: Progressive passive ROM, gentle active ROM within splint
• Week 6: Remove dynamic splint during day, begin active ROM exercises
• Weeks 6-12: Progressive active ROM, strengthening begins (gentle resistance)
• Week 12: Progress to full strengthening (power grip, resistance training)

Critical: Patient compliance with dynamic splinting is key to preventing recurrent ulnar drift.

Outcomes

Range of Motion:

• Expected: 30-40 degrees MCP flexion arc (0-40 degrees typical)
• Not normal: Silicone does not restore full ROM (normal 0-90 degrees)
• Functional: 30-40 degrees sufficient for most ADLs and grip

Alignment:

• Ulnar drift correction: 80-85% maintain correction long-term (if soft tissue balanced)
• Volar subluxation correction: 85-90% maintain reduction

Pain Relief:

• Significant improvement: 80-90% of patients
• Mechanism: Removes painful synovium, stabilizes joint, improves alignment

Survivorship:

• 10 years: 80-90% survival (implant in situ, functioning)
• 15 years: 60-70% survival
• Failure modes: Implant fracture (5-10%), subsidence (5%), recurrent deformity (10-15%)

Patient Satisfaction:

• High: 85-90% satisfied with pain relief and alignment
• Expectations: Counsel that this is spacer, not normal joint (limited ROM)

Complications:

• Implant fracture: 5-10% (see Complications section)
• Recurrent ulnar drift: 10-15% (inadequate soft tissue balancing)
• Stiffness: 20-30% (less than expected ROM, adhesions)
• Subsidence: 5% (implant sinks into bone)
• Infection: Less than 2%
• Squeaking: Occasional patient complaint (silicone friction)

Silicone MCP arthroplasty is highly successful for rheumatoid MCP arthritis when combined with meticulous soft tissue balancing and post-operative dynamic splinting.

MCP Joint Arthrodesis (Fusion)

Indications:

• Thumb MCP arthritis (post-traumatic or rheumatoid) - PREFERRED over arthroplasty
• Post-traumatic arthritis with significant bone loss (insufficient bone stock for arthroplasty)
• Failed MCP arthroplasty (implant fracture, subsidence, infection)
• Young, high-demand patients (manual labor, high grip forces)
• Severe MCP instability (collateral ligament incompetence)
• Patient preference for stability over motion

Contraindications:

• Stiff IP joints (if IP joints fused or stiff, need MCP motion to compensate)
• Bilateral multiple digit fusion (would eliminate all grip function)
• Index-small fingers in low-demand patients (arthroplasty preferred)

Rationale for Thumb MCP Arthrodesis:

• Thumb MCP requires stability for pinch (lateral key pinch, pulp pinch)
• High loads during pinch (5-10x pinch force)
• Arthroplasty risks instability, recurrent pain, implant failure
• Fusion provides pain-free stable pinch - gold standard for thumb MCP

Fusion Position (CRITICAL)

Cascading Flexion Principle:

• Ulnar digits progressively more flexed (mimics normal hand cascade)
• Allows all digits to contact palm during grip

Rotation: Neutral (digit points toward scaphoid when flexed)

Confirm intraoperatively: Test pinch (thumb) or grip (digits 2-5) with trial position before fixation.

Surgical Technique (Thumb MCP Arthrodesis)

Patient Position:

• Supine, arm on hand table
• Tourniquet (upper arm, 250mmHg)

Incision:

• Dorsal longitudinal over thumb MCP joint
• 3-4cm length
• Centered over MCP joint line

Exposure:

1. Subcutaneous dissection, preserve dorsal veins
2. Identify EPL tendon (radial to incision)
3. Protect EPL: Retract radially
4. Open joint capsule longitudinally (ulnar side of EPL)
5. Expose MCP joint

Synovectomy (if rheumatoid):

• Complete synovectomy if synovitis present

Joint Preparation:

1. Resect articular cartilage:
   • Metacarpal head: Saw or rongeur, remove cartilage down to subchondral bone
   • Proximal phalanx base: Remove cartilage
2. Shape surfaces:
   • Cup-and-cone: Metacarpal head conical, phalanx base concave (maximize contact)
   • OR Flat cuts: Perpendicular cuts on both surfaces (simpler, adequate contact)
3. Decortication: Burr or curette to create bleeding bone (promotes fusion)
4. Trial position:
   • Flex thumb MCP 10-15 degrees
   • Neutral rotation (thumb pad faces radially)
   • Test pinch: Simulate key pinch and pulp pinch (confirm good position)
5. Provisional fixation: K-wires (0.045 or 0.062 inch, 2-3 wires crossed)

Definitive Fixation Options:

1. Plate and Screws (Preferred):

• Dorsal locking plate: 2.0mm or 2.4mm hand plate
• Screws: 2-3 screws in metacarpal, 2-3 in proximal phalanx
• Advantage: Rigid fixation, allows earlier mobilization, higher fusion rate
• Technique: Apply plate dorsally, compress joint if possible, lock screws

2. K-wires (Alternative):

• Two or three crossed K-wires: 0.045 or 0.062 inch
• Configuration: Oblique wires crossing fusion site
• Advantage: Simple, low profile
• Disadvantage: Less rigid, requires longer immobilization (6 weeks), wire removal needed

3. Headless Compression Screw:

• Single screw (e.g., Herbert screw, Acutrak screw) across fusion site
• Technique: Lag screw from metacarpal head into proximal phalanx
• Advantage: Low profile, compression, no hardware removal
• Disadvantage: Requires good bone quality

4. Tension Band Wiring (Rare):

• Figure-of-8 wire dorsally with K-wires
• Rarely used for MCP fusion

Plate fixation is preferred (most rigid, highest fusion rate, allows earlier ROM of IP joint).

Bone Grafting:

• Usually NOT needed if good bone contact
• Indications: Significant bone loss, poor bone quality, revision fusion
• Source: Iliac crest (cancellous), distal radius (local)

Closure:

• Capsule (2-0 absorbable)
• Subcutaneous (3-0 absorbable)
• Skin (4-0 or 5-0 nylon)

Dressing:

• Non-adherent, gauze
• Thumb spica splint (immobilizes wrist, thumb MCP, allows thumb IP motion)

Post-operative Protocol

Immobilization:

• If plate fixation: Thumb spica splint 2 weeks (protective), then removable splint, allow thumb IP ROM
• If K-wire fixation: Thumb spica cast 6 weeks (rigid immobilization until fusion), then remove K-wires

Rehabilitation:

• Weeks 0-2 (plate) or 0-6 (K-wires): Immobilization, no ROM
• Week 2 (plate): Begin thumb IP ROM, keep MCP immobilized in removable splint
• Week 6: X-ray to assess fusion
  • If fusing: Discontinue splint, progressive ROM and strengthening
  • If not fusing: Continue immobilization 2-4 more weeks, repeat x-ray
• Week 8-12: Progressive strengthening (grip, pinch)

Outcomes

Fusion Rate:

• 90-95% union rate (plate fixation)
• Time to fusion: 8-12 weeks radiographically
• Nonunion: 5-10% (risk factors: smoking, poor bone quality, rheumatoid)

Pain Relief:

• Excellent: 95%+ near-complete pain relief
• Mechanism: Eliminates painful arthritic joint motion

Function:

• Stable pinch: Key advantage (lateral key pinch, pulp pinch)
• Loss of MCP motion: Accept for stability (IP joint compensates)
• Grip strength: Preserved or improved (stable thumb post)

Patient Satisfaction:

• High: 90%+ satisfaction for thumb MCP fusion
• Preferred over arthroplasty for thumb

Complications:

• Nonunion: 5-10% (see below)
• Malposition: Fused in wrong angle (too much/little flexion, rotation) - avoid by testing intraoperatively
• Hardware prominence: Plate or screw prominence dorsally (rare, remove if symptomatic)
• Infection: Less than 2%
• Stiffness of IP joint: Secondary stiffness (hand therapy)

Thumb MCP arthrodesis is the gold standard for thumb MCP arthritis, providing pain-free stable pinch.

MCP Synovectomy

Historical Context:

• Performed in pre-DMARD era for rheumatoid MCP synovitis
• Goal: Remove inflamed synovium, prevent joint destruction
• Largely supplanted by DMARDs/biologics (medical management more effective systemically)

Indication (Rare):

• Early rheumatoid MCP arthritis (Larsen Grade I-II) with persistent synovitis DESPITE optimized DMARD therapy
• BEFORE significant erosions or deformity
• Isolated MCP synovitis (not systemic flare)

Contraindication:

• Larsen Grade III-V (significant erosions, deformity) - need arthroplasty/arthrodesis, not synovectomy
• Active systemic rheumatoid flare (optimize medical management)
• Poor medical optimization (DMARD not tried or insufficient duration)

Surgical Technique:

• Dorsal approach to MCP (as for arthroplasty)
• Open capsule longitudinally
• Complete synovectomy: Remove all hypertrophic, inflamed synovium with rongeur, curette
• Inspect extensor tendons (centralize if displaced)
• Repair radial collateral ligament if lax
• Close capsule, skin

Adjunct Procedures (Combine with Synovectomy):

• Extensor tendon centralization: If extensor displaced ulnarly
• Radial collateral ligament repair: If radial laxity present
• Intrinsic release: If tight ulnar intrinsics

Post-operative:

• Splint in MCP extension, radial deviation for 2 weeks
• Then hand therapy (ROM, strengthening)

Outcomes:

• Temporary relief: 3-5 years average (synovitis recurs)
• Pain improvement: 70-80% short-term
• Does NOT reverse deformity, only slows progression
• Does NOT prevent erosions long-term (synovitis recurs)

Current Role:

• Very limited: DMARDs/biologics more effective at controlling synovitis systemically
• Synovectomy occasionally combined with arthroplasty (remove synovium during joint replacement)
• Rarely performed as isolated procedure

Soft Tissue Adjunct Procedures

These are performed in combination with arthroplasty, not as isolated procedures:

1. Extensor Tendon Centralization:

• Reposition extensor tendon over MCP center (from ulnar displaced position)
• Suture to radial capsule or reconstruct radial sagittal band
• Essential for preventing recurrent ulnar drift after arthroplasty

2. Radial Collateral Ligament Reconstruction:

• Reef (plicate) stretched radial collateral ligament
• Suture radial capsule to metacarpal neck (tighten radial structures)
• Resists ulnar drift forces post-operatively

3. Ulnar Intrinsic Release:

• Release tight ulnar interosseous muscle from proximal phalanx
• Indicated if intrinsic tightness test positive
• Reduces ulnar deviating force

4. Crossed Intrinsic Transfer:

• Transfer ulnar lateral band to radial side
• Creates active radial deviation force
• Rarely performed, reserved for severe recurrent ulnar drift

Critical Point: Arthroplasty without soft tissue balancing has high failure rate (recurrent ulnar drift). Soft tissue procedures are NOT optional.

Synovectomy alone is rarely performed. Soft tissue balancing is integral to arthroplasty success.

Failed MCP Arthroplasty: Revision Options

Causes of Failure:

Presentation:

• Return of pain (indicates implant fracture, subsidence, or recurrent synovitis)
• Loss of motion (stiffness from adhesions)
• Recurrent deformity (ulnar drift, volar subluxation)
• Palpable implant fracture (crepitus, instability)
• Swelling, erythema (infection)

Imaging:

• X-ray (PA, lateral):
  • Implant fracture (visible break in silicone)
  • Subsidence (implant sinking into bone, loss of joint space height)
  • Bone resorption around implant
  • Recurrent ulnar drift, volar subluxation

Management Algorithm:

Revision Arthroplasty Technique:

1. Remove fractured implant:

   • Dorsal approach (may be scarred from prior surgery)
   • Identify and remove all implant fragments
   • Curette fibrous capsule (encapsulation)

2. Assess bone stock:

   • Evaluate metacarpal and phalanx canals (bone resorption from subsidence?)
   • If adequate bone: Proceed with revision arthroplasty
   • If poor bone: Arthrodesis

3. Insert larger implant if bone loss:

   • If canals enlarged from subsidence, use larger implant size
   • Avoid over-stuffing (causes stiffness)

4. Aggressive soft tissue balancing (CRITICAL):

   • Extensor tendon centralization (more aggressive than primary)
   • Radial collateral ligament reconstruction (reef radial structures tightly)
   • Release ulnar intrinsics
   • Consider crossed intrinsic transfer (transfer ulnar lateral band to radial side) to actively resist ulnar drift

5. Post-operative dynamic splinting:

   • Even more critical than primary (6 weeks full-time, then night splinting 6 months)

Outcomes of Revision Arthroplasty:

• Less predictable than primary surgery
• Satisfactory outcome: 70-80% (vs 85-90% primary)
• Higher recurrent deformity rate: 20-30%
• Counsel realistic expectations

Salvage Arthrodesis:

• Indication: Failed arthroplasty with poor bone stock, infection, patient preference for stability
• Technique:
  • Remove implant and all fibrous tissue
  • Prepare metacarpal and phalanx for fusion (as in primary arthrodesis)
  • Bone grafting often needed (iliac crest or distal radius) due to bone loss
  • Plate fixation preferred
• Fusion position: As per primary arthrodesis (cascading flexion)
• Outcomes: 80-90% fusion rate, excellent pain relief, loss of motion (accept)

Revision surgery is challenging. Emphasize soft tissue balancing and patient compliance with splinting.