Thumb Base Arthritis

Epidemiology

• 80% of postmenopausal women have XR changes
• XR doesn’t always correlate with symptoms

Anatomy of CMCJ

• Saddle shaped
  • Allows polyaxial motion
• 3 Ligaments
  1. Dorsal
  2. Lateral
  3. Volar Ulnar - Beak (most important)

Aetiology

• Beak ligament attenuation and rupture leads to instability of CMCJ
• Instability leads to arthritis

Presenting Features

• Activity-related pain
• Weak grip
• Pain and weakness opening jars
• Night pain
• Superimposed carpal tunnel syndrome common (40%)

Examination

• Wasted thenar eminence – disuse
• Squaring of thumb base
• Adducted 1st metacarpal
• Compensatory MCPJ hyperextension – increases hand span

Grind Test

• Axial compression and grind
• Less pain on distraction and grinding

Crank Test

• Axial compression and flexion, extension pain

Investigations

• AP hand
• Roberts view (true AP of thumb)
  • Thumb maximally abducted & forearm maximally pronated

Classification (Eaton & Littler)

Stage 1

• Joint space widening
• Synovitis and effusion
• No OA changes

Stage 2

• Osteophytes <2mm in size
• Mild subluxation
• Joint space narrowing

Stage 3

• Osteophytes >2mm in size
• Significant subluxation
• Joint more significantly narrowed

Stage 4

• Widespread arthritis – especially of STT joint

Management

• Treat symptoms and functional impairment – not XR

Non-Operative

• Splinting
• Physio (thenar muscle strengthening)
• Activity modification
• Analgesia
• Corticosteroid injection – in clinic or theatre

Operative Management

• Decision making based on:
  • Pain
  • Functional expectations
  • Degree of arthritis

Trapezium Preservation

• No arthritis
• Instability-related pain

Thumb Metacarpal Stabilisation with Split FCR

• Reconstructs the Beak ligament

Extension Osteotomy

• Unload CMCJ

Trapezium Sacrificing Procedures

• Much more common

Trapeziectomy

• Gold standard for patients overall
• 80-90% good results
• Problems:
  • Thumb will be weaker
  • Instability of Metacarpal

Trapeziectomy plus Ligament Reconstruction and Interposition

• Postulated to have better results
• Not proven in any study

Arthrodesis

• For young manual workers only
• Preserves power
• Clenched fist position:
  • 30° abduction
  • 20° flexion
• Technically difficult and prone to complications

Osteotomy – Abduction, Extension

• Good results described for Stage 1-3

Arthroplasty

• Ball and socket constrained design
• Previous failures
• Still some good series
• Lacks follow-up > 3 years
• Higher complication rate

Outcomes

• In general, all procedures have an 80-90% success with good selection
• Warn regarding long rehab time and time to see full benefit – 3-6 months
• Need for splinting for 3-6 months