Rigid Flatfoot

Aka: Rigid Flatfoot, Tarsal Coalition, Calcaneonavicular coalition, Talocalcaneal coalition, Subtalar coalition

1. Epidemiology
   1. Prevalence: <1% of U.S. population
   2. Gradual onset in adolescence
2. Etiology
   1. Tarsal Coalition
      1. Congenital cartilaginous, fibrous or bony bridges
      2. Bridges form between Calcaneus, talus, and navicular
   2. Hindfoot Arthritis
3. Pathophysiology
   1. Tarsal Coalition results in range of motion loss
      1. Local irritation
      2. Protective spasm of the peroneal muscles
4. Types
   1. Fusion or bridge type
      1. Fibrous fusion (Syndesmosis)
      2. Cartilaginous fusion (Synchondrosis)
      3. Osseous fusion (Synostosis)
   2. Distribution of fusion
      1. Calcaneonavicular coalition (53% of cases)
      2. Talocalcaneal coalition or Subtalar coalition (37%)
5. Symptoms
   1. Bilateral involvement in 50% of cases
   2. Foot stiffness
   3. Painful limp
6. Signs
   1. Tenderness over peroneal tendons or hindfoot
   2. Heel everted
   3. Subtalar joint (midtarsal) range of motion
      1. Limited and painful
   4. Provocative maneuvers
      1. Passive Stretching of peroneal tendons
      2. Forefoot Adduction and Inversion
   5. Swelling suggests other comorbid condition
      1. Rheumatoid Arthritis
7. Radiology: Foot XRay
   1. Associated findings: Hindfoot Arthritis
   2. Calcaneonavicular coalition (best visualized on oblique AP film)
   3. Talocalcaneal coalition (observe for secondary signs on lateral film)
      1. Talar beaking (talar head with superior margin flaring)
      2. Lateral talar process with flattening and broadening
      3. Posterior talocalcaneal joint narrowing
      4. C-Sign (Medial outline of talar dome and posteroinferior outline of substentaculum tali)
      5. Absent middle facet sign (Subtalar joint middle facet is obscured on standing lateral view)
8. Management
   1. Symptomatic
      1. Rest
      2. Heat
      3. NSAIDs
      4. Short Leg Walking Cast intermittently as needed
   2. Surgery often necessary
      1. Arthritis
         1. Arthrodesis of hindfoot and Tarsal Navicular
      2. Tarsal Coalition
         1. Bony and cartilaginous bar resection
         2. Arthrodesis of hindfoot and Tarsal Navicular
            1. Indicated for failed resection