Basilar Thumb Arthritis

Introduction

Arthritis of the carpal-metacarpal (CMC) joint
Epidemiology
- race
  - thumb CMC arthritis is more common in Caucasians
  - hand OA is more common in native Americans than Caucasians/African Americans
- common arthritis of the hand
  - 2nd only to DIP arthritis
  - DIP > thumb CMC > PIP > MCP
  - OA in 1 joint in a row (proximal row) predicts for OA in other joints in same row
Pathoanatomy
- theorized to be due to attenuation of anterior oblique ligament (Beak ligament)
  - leading to instability, subluxation, and arthritis of CMC joint
Associated conditions
- MCP hyperextension deformity

Anatomy

Trapezial metacarpal joint is a biconcave saddle joint
Trapezium has a palmar groove for flexor carpi radialis (FCR) tendon
Ligaments
- anterior oblique ligament (Beak ligament)
  - primary stabilizing restraint to subluxation of CMC joint
- intermetacarpal ligaments
- posterior oblique ligament
- dorsal-radial capsule (injured in dorsal CMC dislocation)
Biomechanics
- CMC joint reactive force is 13X applied pinch force

Classification

Eaton and Littler Classification of Basilar Thumb Arthritis
Stage I	slight joint space widening (pre-arthritis)
Stage II	slight narrowing of CMC joint with sclerosis, osteophytes <2mm
Stage III	marked narrowing of CMC joint with osteophytes, osteophytes >2mm
Stage IV	pantrapezial arthritis (STT involved)

Presentation

Symptoms
- pain at base of thumb
- difficulty pinching and grasping
- concomitant carpal tunnel syndrome
  - up to 50% incidence
Physical exam
- painful CMC grind test
  - combined axial compression and circumduction
- swelling and crepitus
- metacarpal adduction and web space contractures
  - are later findings
- may have adjacent MCP fixed hyperextension (zig-zag or "Z" deformity)
  - occurs during pinch as a sequlae of CMC arthritis

Imaging

Radiographs
- technique
  - X-ray beam is centered on trapezium and metacarpal with thumb flat on cassette and thumb hyperpronated
- findings
  - joint space narrowing
  - osteophytes
  - may show MCP hyperextension

Differential Diagnosis

de Quervains tenosynovitis
STT arthritis
scaphoid nonunion/SNAC
radioscaphoid arthritis

Treatment

Nonoperative
- NSAIDS, thumb spica bracing, symptomatic treatment, steroid injections
  - indications
    - indicated as first line of treatment for mild symptoms
- hyaluronic acid injections
  - show no difference for the relief of pain and improvement in function when compared to placebo and corticosteroids
Operative
- closing wedge dorsal extension osteotomy of 1st metacarpal
  - indications
    - for early Stage I disease
  - technique
    - redirects the force to the dorsal, more uninvolved portion of the first carpometacarpal joint
  - outcomes
    - gained in popularity
    - 93% have symptom improvement at 7 years
- ligament reconstruction with FCR
  - indications
    - Stage I disease when joint is hypermobile and unstable (pain with varus valgus stress)
- trapeziectomy + LRTI (ligament reconstruction and tendon interposition)
  - indications
    - Stage II-IV disease
    - most common procedure and favored in most patients
  - technique
    - there are many different surgical options available
      - trapezial excision is most important, regardless of other specifics of CMC arthroplasty
      - FCR tendon most commonly used in reconstruction to suspend metacarpal
        
        alternatively, ECRL or APL may be used for suspension
        
        or PL around FCR to correct subluxation
  - outcomes
    - can expect ~25% subsidence postoperatively
      postoperatively
      - with no change in outcomes
    - results in improved grip and pinch strengths
- hematoma arthroplasty (trapezial resection alone without LRTI)
  - indications
    - Stage II-IV disease
  - technique
    - trapezium resection and pinning of thumb metacarpal without LRTI
  - outcomes
    - comparable outcomes to trapeziectomy + LRTI
- excision of proximal third of trapezioid
  - indications
    - concomitant scaphotrapezioid arthritis (present in 62%), especially in Eaton-Littler stage IV
- CMC arthroscopy and debridement
  - indications
    - early stages of disease
- trapeziometacarpal (CMC) arthrodesis
  - indications
    - Stage II-III disease in young male heavy laborers
      - preserves grip strength
  - contraindications
    - scaphotrapeiotrapezoidal (STT) arthritis
  - technique
    - CMC joint fused in
      - 35° radial abduction
      - 30° palmar abduction
      - 15° pronation
  - outcomes
    - good pain relief, stability, and length preservation
    - decreased ROM; inability to put hand down flat
    - nonunion rate of 12%
- volar capsulodesis, EPB tendon transfer, sesamoid fusion, or MCP fusion
  - indications
    - thumb MCP hyperextension instability (hyperextension > 30°) otherwise a Swan neck deformity will arise
    - see below (Complications) for algorithm
- silicone replacements
  - indications
    - not recommended
    - complications of prosthesis fracture, subluxation, or silicone synovitis

Complications

1st metacarpal subsidence and narrowing of trapezial space height
- after trapeziectomy ± tendon suspension
- salvage treatment
  - LRTI with ECRL tendon or APL tendon
  - if FCR is already used /ruptured
MCP hyperextension deformity
- treatment depends on degree of hyperextension
  - <10° - no surgical intervention
  - 10-20° - percutaneous pinning of MCP in 25-35° flexion x 4wk ± EPB tendon transfer
  - 20-40° - volar capsulodesis or sesamoidesis
  - >40° - MCP fusion

Basal joint arthritis (C1185)