Inflammatory Arthritis of the Foot

Rheumatoid Arthritis

Epidemiology

• Presents in middle age
  
• More common in women

Aetiology

• Symmetric inflammatory polyarthropathy
  
• Affects smaller joints more → forefoot > hindfoot

Pathoanatomy

• Synovitis is the hallmark and is caused by:
  • Infiltration with Macrophages, B Lymphocytes & Monocytes
    
  • Inflammatory cytokines released – TNF-α, IL-6, IL-7
    
• RANKL activates osteoclasts → biologic bone erosions
  
• Pannus (fibrotic granulation tissue) causes mechanical erosions
  
• Rheumatoid factor positive in 2/3 of patients

Markers of Severity

• Presence of Rheumatoid factor
  
• Extraarticular manifestations
  • Most common are Rheumatoid nodules

Foot and Ankle Problems

Forefoot

• Most affected in RA
  
• Common pathologies:
  • Hindfoot arthritis
    
  • Posterior Tibial Tendon arthritis
    
  • Ankle arthritis
    
• Disease primarily affects lesser toe MTPJs
  
• Synovitis causes capsular and collateral ligament destruction
  
• Hyperextension → MTPJ subluxation & dislocation
  
• Valgus deviation at MTPJs
  
• Plantar plates pulled distally → atrophy of plantar fat pad
  
• Exposure of metatarsal heads causes metatarsalgia
  
• Clawing of the toes → overpowering by FDL and intrinsic muscles
  
• Hallux Valgus (HV) is common
  • HV is severe due to deviation of lesser toes
    
  • Splayfoot with bunionette deformity may also occur

Hindfoot and TP Tendinopathy

• Occurs in about 25% of RA patients (usually after forefoot deformities)
  
• Typical deformity: Pes Planovalgus
  
• Caused by:
  • Subtalar erosions and eversion
    
  • Unlocked and synovitic Mid-Tarsal Joints
    
  • Synovitic Spring ligament
    
  • Arch collapse → Talar head plantar, navicular subluxates laterally
    
  • Tibialis Posterior Tendon prone to synovitis, attenuation, and rupture

Ankle

• Severe erosions occur, though ankle is not usually unstable
  
• When deformity occurs, it is valgus
  • Due to subtalar joint valgus and pes planus deformity

Medical Management

Disease-Modifying Anti-Rheumatic Drugs (DMARDs)

• Methotrexate
  • Most commonly used as the ‘anchor’ drug
    
• Prednisolone
  
• Hydroxychloroquine
  
• Cyclosporin

TNF-α Antagonists (Biologic DMARDs)

• Etanercept – Best tolerated
  
• Infliximab
  
• Adalimumab – Best disease suppression

DMARDs and Surgery

• DMARDs reduce joint disease → less surgical intervention required
  
• Perioperative DMARD Use:
  • Stopping DMARDs increases risk of RA exacerbation
    
  • Continuing DMARDs increases risk of infection & delayed healing
    
  • General recommendation: Stop TNF-α antagonists for 1-5 half-lives (5-15 days) before surgery

Surgical Management

Forefoot

1st MTPJ Options

• Fusion – Gold standard for HV in RA
  
• Keller procedure (excision arthroplasty & soft tissue repair)
  • Option for older patients (quicker results, lower morbidity)
    
• Arthroplasty
  
• Joint-preserving osteotomy likely to fail due to soft tissue incompetence

Lesser Toes Options

• MT head excision arthroplasty
  • Plantar or dorsal transverse incision or multiple longitudinal dorsal incisions
    
• PIPJ fusion or excision arthroplasty with temporary wire stabilization
  
• Stainsby procedure
  • Unstable toes, unsightly appearance

Hindfoot

• Triple fusion – Gold standard treatment
  
• Higher rate of non-union and malunion than OA
  
• Good symptom relief
  
• Some surgeons treat pes planovalgus like non-rheumatoids using isolated fusions, soft tissue reconstruction, or osteotomy
  
• Risk: Progressive arthritis in other joints → deformity recurrence

Ankle

Synovectomy

• 80% 10-year success rate across all joints
  
• Good option for young patients, early disease, no deformity
  
• Less common now due to DMARDs

Ankle Fusion

• Gold standard treatment with long-term success
  
• Arthroscopic fusion with percutaneous screws preferred
  • Shorter surgery time
    
  • Quicker fusion
    
  • Fewer soft tissue complications
    
• Traditionally, deformity & equinus were contraindications for arthroscopic fusion
  
• Current thinking:
  • Mild deformity & non-plantigrade foot may still be suitable
    
  • Bone resection required arthroscopically – technically difficult

Open Fusion

• Very effective operation with good results
  
• Approaches: Anterior, posterior, lateral, or combined
  
• Screw Configuration
  • 3 screws more stable than 2
    
  • Cross screws more stable in lab studies

Ankle Replacement

• Newer-generation replacements have longer survivorship
  
• Survival rates:
  • Swedish Registry: 70% at 10 years
    
  • Wrightington: 93% at 5 years, 80% at 10 years
    
• Good option for older, low-demand RA patients
  • Improved ROM
    
  • More normal gait pattern
    
  • Possible reduced adjacent joint arthritis (not proven)
    
• Best option for pantalar arthritis – triple fusion + ankle replacement
  
• Much better than pantalar fusion for patients