The Influence of Ankle Joint Arthrodesis on Hind Foot Motion

Objective To explore the characteristics of hind foot motion,and its changes when ankle joint is fused.Methods Eight fresh frozen adult shrank-foot specimens were placed in a Cartesian coordinate system with skin removed and calcaneal marked.The displaycements of the marked points in the coordinate system were recorded with ankle joint locked,subtalar joint locked,and none joint locked,respectively.Through matrix translation and Euler equation,the angles of the calcaneals rotation were obtained,which represented the range of motion(ROM) of the ankle joint in different situation.Results Three dimensional(3D) motion was observed in hind foot as well as in ankle joint.Before arthrodeses,ROMs of hingdfoot were: 22.62° dorsiflextion,40.88° plantarflextion,18.87° inversion,8.87° eversion,17.48° adduction and 11.47° abduction.When ankle joint was locked,they were 3.70°,5.87°,15.99°,8.62°,7.64° and 3.99° respectively.Arthrodeses of the ankle joint would change the hindfoot motion significantly (P0.001).Conclusion The subtalar and ankle joint contribute to the 3D movement of the hind foot.For their affinity,the function of ankle joint should be reserved instead of being fused in clinical practice.