A 4-DOF Parallel External fixator for Foot-Ankle Deformity Correction

Foot-ankle deformity is one of the common complaints in orthopaedic surgery. The external fixator has been selected as the medical apparatus to help with gradual correction, and the configuration may affect the final correction results. It is meaningful to design novel parallel external fixator with deformity-targeting property. Taking the main foot-ankle deformities with four corrective degree-of-freedom (c-DOF) as research object, a 4-DOF parallel configuration is proposed in this paper. Considering several applicable conditions, lower-mobility kinematic struts are selected to provide desired constraints. Then, inverse kinematic model and Jacobian matrix are derived. Finally, after the structural design, clinical case is simulated to prove the applicability of the parallel external fixator.