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Chopart Amputation


- See:
      - Syme's Amputation
      - Transmetatarsal Amputation

- Discussion:
    - Francis Chopart first described disarticulation thru midtarsal joint;
    - Chopart amputation removes the forefoot and midfoot, saving talus and calcaneus;
    - Chopart amptutations should not performed for ischemia;
    - this is a very unstable amputation, noting that most of the tendons which act around the ankle joint have lost their insertion into foot and 
           the heel remains unstable;
    - has a pronounced tendency to go into equinus and must usually be fitted with a prosthesis that extends upto the patellar tendon level;
    - if the ankle joint is in a neutral position and good ankle motion is present, AFO derivatives or boot type prostheses may be required;
    - technical considerations:
          - rebalancing is required to prevent equinus and varus deformities, and can be accomplished by Achilles tenotomy, anterior tibialis or
                 extensor digitorum transfer to the talus, and post op casting;
          - transfer of the tibialis anterior to the talar neck is necessary to control the deformity of the hindfoot;
                 - tendon of the tibialis anterior is detached from its insertion and is passed thru a hole drilled in the neck of the talus;
                 - tendon is then sutured upon itself and the extensor tendons are carefully sutured to the fascia and soft tissues of the
                        sole of the foot;
                 - note that rupture of the transposed tibialis anterior tendon is common after many years of use;
          - some say the ankle joint should be fused;
    - complications:
         - Robert Jones believed that Chopart's procedure invariably failed because of progressive equinovarus deformity - as was Lisfranc's 
                  amputation;
         - in the chopart amputation, the stump goes into equinus, so that the  preserved heel cushion is not used and the pressure is on the
                 anterior end of the os calcis;
                 - transfer of the anterior tibial tendon has an insufficient moment arm to prevent this;
                 - initial release of the tendo achilles may reduce this problem;
         - with all amputations of the foot, there will be some loss of normal arch of the foot