Deltoid ligament strain after correction of acquired flatfoot deformity bytriple arthrodesis

Deltoid insufficiency represents a difficult surgical challenge. We have wi tnessed patients who have developed a valgus tibiotalar deformity following a properly positioned triple arthrodesis, To investigate whether the tripl e arthrodesis itself, by creating a rigid triple joint complex below the an kle, leads to increased strain of the deltoid complex, a flatfoot model was created in 8 fresh-frozen below-knee amputation specimens. Each specimen w as loaded in three gait cycle (GC) positions: Heel strike (0% GC), midstanc e (10% GC), and heel rise (40% GC). The three components of the ground reac tion force (GRF) and the tendon forces consistent with those respective pos itions were applied. To simulate a posterior tibial tendon insufficient sta te the posterior tibial tendon was not loaded. Strain at the tibiocalcaneal fibers of the superficial deltoid ligament complex was determined at each of the three foot positions. A triple arthrodesis was performed and the del toid strains were again recorded for each position, A significant increase in the strain of the deltoid ligament was observed for only the heel rise p osition (p=0.007) in our cadaver model following triple arthrodesis, The re sults favor medializing the calcaneus following arthrodesis to protect the deltoid complex.