Increasing shoe instep improves gait dynamics in patients with a tibiotalar arthrodesis

Degenerative osteoarthritis in subtalar and midtarsal joints occurring after tibiotalar arthrodesis may be related to biomechanical factors. For patients with tibiotalar arthrodesis walking with their everyday shoes, the ground reaction force is posterior at heel-off and the maximal foot-tibia dorsiflexion is at its upper limit. We hypothesized that increasing the instep of the shoes would improve these abnormalities. Three-dimensional gait analysis was done in nine patients with ankle arthrodesis fused in the neutral position and for 10 control subjects. Four conditions of walking were tested: barefoot, wearing everyday shoes, wearing everyday shoes with the instep increased by 1 cm, and wearing everyday shoes with the instep increased by 2 cm. In the arthrodesis group, the two modified delayed heel-off shoe conditions shifted the ground reaction force closer to the metatarsal heads at heel-off to a normal range, and reduced the maximal foot and tibia dorsiflexion angle. Based on these results, patients with a tibiotalar arthrodesis in the neutral sagittal position may be advised to choose shoes with an instep of approximately 25 mm.