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Position of Fusion: Subtalar Fusion

- Discussion:
    - traditionally, subtalar arthrodesis has been performed w/ ankle in neutral dorsiflexion / plantarflexion & neutral or slight valgus;
    - by placing calcaneus in 5 degrees of valgus, transverse tarsal joint remains supple and provides mobility to the forefoot;
    - in presence of fixed forefoot equinus, however, which often occurs following trauma, subtalar fusion may need to be placed in relative dorsiflexion to accommodate for the forefoot position;
    - fusion in slight plantarflexion is necessary only in the presence of quadriceps weakness;
           - it never should be done to accommodate for heel ht in female pts;

- Excessive Varus:
    - if subtalar joint is placed into varus, transverse tarsal joint is locked & forefoot is rigid, resulting in vaulting type of gait;
    - any degree of varus is poorly tolerated and excessive varus can lead to painful callosities under 5th MT head;

- Excessive Valgus:
    - excessive hindfoot valgus will cause too much pronation in forefoot and may lead to calcaneo-fibular impingement;
    - most common problem following fusion of subtalar joint w/ excessive pronation is hallux valgus deformity;
    - patient may develop stress along medial side of ankle or knee joint.
    - patient also may note arch pain