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Rheumatoid Hindfoot

- See: Rheumatoid Arthritis

- Epidemiology:
    - forefoot is involved twice as often as the hindfoot;
    - initially, RA involves the forefoot, then the midtarsal joints, and finally the hindfoot;
    - sites of involvement:
          - ankle joint is frequently spared;
          - talonavicular joint is affected most frequently;
          - calcaneocuboid joint is involved least often;
          - use differential injections to figure out which joints are tender;
    - subtalar joint is often the most severely affected joint;
          - among RA pts with subtalar disease, a valgus deformity develops in 25% and varus deformity will develop in 2%;
          - valgus deformity may develop due to soft tissue laxity;
          - valgus deformity in pts w/ RA is most likely caused by pronation forces on weakened & inflamed talonavicular & subtalar joints;
          - as general rule, valgus deformity in RA foot is not the result of posterior tibial tendon dysfunction;
          - structures stabilizing talocancaneo-navicular joint eversion are ligaments (cervical, calcaneofibular, deltoid, medial talocalcaneal), 
                 tendons (tibialis posterior, FDL), & bony surfaces (lateral talar process against calcaneus against sinus tarsi);
          - differential dx of hindfoot valgus:
                 - rupture of tibialis posterior:
                 - neuroarthropathic (Charcot) involvement of the midfoot or hindfoot
                 - tarsometatarsal degenerative arthitis
                 - relaxed pes planus
                 - old Lisfranc fracture dislocation
                 - idiopathic degenerative osteoarthritis of the tarsometatarsal joint

- Radiographs:
    - in pts w/ RA, talonavicular joint narrowing is usually first finding in hindfoot arthritis;
    - bone scans can also be used to help determine sites of arthritic involvement (TN vs CC vs subtalar);

- Non Operative Treatment:
    - Orthotics for the Foot:

- Surgical Treatment:
    - isolated fusions of the talonavicular joint is suggested for older pts;
    - in younger, more active pts, a double arthrodesis (calcaneocuboid, talonavicular) may be performed;
    - talonavicular arthrodesis:
        - w/ early hindfoot dz (pes planovalgus & forefoot abduction), consider early talonavicular arthrodesis if hindfoot is passively 
              correctable to neutral;
        - following talonavicular fusion, minimal motion occurs in subtalar joint because for subtalar motion to occur, navicular must rotate 
              around the head of the talus;
    - triple arthrodesis:
         - if significant involvement of subtalar joint has failed to respond to nonoperative treatment (inserts & short leg braces) & if ankle 
              joint is only minimally involved, triple arthrodesis is indicated;
         - if ankle joint is involved (& pt has pan talar arthritis) or if pt has the dry, stiff type of of RA, then triple arthrodesis will intolerable 
              stress on joints proximal and distal to the site of fusion;
              - in such a patient consider talectomy

Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis.