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Sub Talar Dislocation

- See: Sub-Talar Joint

- Discussion:
    - involves dislocation of distal articulations of talus at both talocalcaneal & talonavicular joints;
    - ankle joint is undisturbed;
    - distinguish between medial and lateral subtalar dislocation;
          - method of reduction is different w/ each type
          - long term prognosis appears to be worse with lateral dislocation;
    - associated injuries:
          - Osteochondral Lesions of Talus;
          - Ankle Frx;
          - Frx Base of 5th Metatarsal;
          - Navicular and Cuboid Fractures;

- Anatomy:
    - lateral dislocation anatomy:
         - less common type of subtalar dislocation (15%);
         - calcaneus is displaced lateral to talus;
         - talar head lies medially, and foot appears pronated;
         - navicular lies lateral to the talar neck;
         - lateral dislocations may be complicated by interposed posterior tibial tendon (or sometimes FDL);

- Anatomy:
    - medial dislocation anatomy:
         - most common sub talar dislocation (85%);
         - foot & calcaneus are displaced medially;
         - head of the talus prominent dorsolaterally;
         - navicular lies medial and sometimes dorsal to talar head & neck;
         - foot is plantar flexed and is supinated;
         - inversion causes this injury;
         - called "basket ball foot" since it is a common mechanism;

- Non Operative Rx:
    - closed reduction is facilitated w/ knee flexion to relax the gastroc;
    - follow up CT scan to rule out osteochondral lesions & to assess reduction;

- Operative Indications and Treatment:
    - medial dislocations:
         - approx of 10% of medial dislocations require open reduction;
         - capsule of talonaviclar joint & EDB blocks reduction, or in some cases the talar head may button hole thru the EDB;
          - medial sub talar dislocations are treated by longitudinal anteromedial incision over prominent head and neck of talus & minipulation and release of interposed tissues;
          - since the joint is stable after reduction there is no need for internal fixation;
          - after reduction, a short leg cast is applied for 3 to 4 wks;
    - lateral dislocations:
          - approx 20% of lateral dislocations require open reduction;
          - interposed posterior tibial tendon blocks reductions;
          - incision over sinus tarsi, and three wks of NWB casting, followed by ROM;
 - references:
Anatomical considerations of irreducible medial subtalar dislocation.
Obstacles to reduction in subtalar dislocations
- Complications:
    - infection:
          - may occur in 30% of patients w/ open dislocations, despite aggressive I and D;
          - w/ total talar extrusion, consider replacement w/ a semi-permanent spacer using antibiotic containing methylmethacrylate;
    - avascular necrosis:
          - see: AVN following talar frx:
          - has been reported rarely after subtalar dislocation;
          - because the talus is not disrupted from the ankle mortise, at least some of its blood supply remains intact

Severe open subtalar dislocations. Long-term results.

Subtalar dislocations of the foot.

Subtalar dislocations: long-term follow-up of 39 cases.  

Injury characteristics and the clinical outcome of subtalar dislocations: a clinical and radiographic analysis of 25 cases.

Open Subtalar Dislocation Treated by Distractional External Fixation.

Isolated Subtalar Dislocation