Flexor digitorum longus transfer with medial displacement calcaneal osteotomy. Biomechanical rationale.

The rationale behind combining a medical displacement calcaneal osteotomy with a flexor digitorum longus (FDL) transfer is to realign the valgus heel under the mechanical axis of the leg and to reduce the deforming valgus moment of the gastrocnemius soleus muscle group on the hindfoot. This reduces the antagonistic force on the relatively weak FDL transfer. This combination has a potential for producing a more mechanically balanced foot and acts as a double tendon transfer in which the Achilles tendon is transferred medially in addition to the FDL transfer, which substitutes for the degenerative posterior tibial tendon.