- 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