The effect of tibio-talar arthrodesis on foot kinematics and ground reaction force progression during walking

Degenerative osteoarthritis in the subtalar and mid-tarsal joints occurring after tibio-talar arthrodesis is thought to be a consequence of abnormal foot dynamics. We hypothesized that the forward tilt of the tibia during stance induces early heel-off and alteration of the progression of ground reaction force (GRF) after ankle arthrodesis. Three-dimensional gait analysis was performed on nine patients who had an ankle arthrodesis fused in a neutral position and on ten control subjects. Patients walking barefoot were compared to controls. The GRF progression was shifted forward during mid-stance, heel-off occurred earlier and was associated with less anterior tilt of the tibia and a more posterior position of the GRF with reference to the metatarsal heads. The GRF progression, heel-off and tibial tilt were not significantly different between patients and controls when walking in shoes but the GRF was still more posterior at heel-off. Increasing the walking speed worsened the anomalies of foot dynamics. These alterations of foot dynamics are thought to be associated with pathogenic stresses applied to the mid-foot.