Development and Preliminary Trajectory Verification of the Electromotor-Driven Parallel External Fixator for Deformity Correction

Abstract

External fixators are widely used in deformity correction based on distraction osteogenesis. Traditionally, the rods are manually operated by patients several times a day, which will ensure the patient’s compliance, accumulative adjustment error, and trajectory deviation. To reduce the patients’ compliance and the complexity of adjustment, an electromotor-driven parallel external fixator is developed to gradually correct the deformity, which allows the fixator to be automatically adjusted and can correct any three-dimensional deformity with continuous stability. Two adjustment strategies are proposed through different trajectory control methods based on the inverse kinematics solution, and the trajectory and bone shape are generated to investigate the characteristics of the new bone more intuitively. The range of motion is performed utilizing the numerical searching method to assess the fixator’s correction capability. Finally, the trajectory verification experiment is carried out using the artificial bone model to perform the two adjustment strategies. The results show that the developed external fixator has high correction accuracy with 0.0172 mm, and can accurately and safely realize the preset correction trajectory. The developed fixator system can also be used as a teaching tool for medical training for clinicians to learn deformity correction technology.