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

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, August 1, 2012 1:17 pm