Optimization of deformity correction modes and their control methods for hexapod robot based external fixator

In terms of deformity correction with hexapod robot based external fixators, there were complex types of correction modes under existing criterions which could create redundant modes and selection confusion in clinic environment. This study proposed two original deformity correction modes under optimized criterions that can help doctors choose the proper mode and get their corresponding control methods much easier. We provided the kinematics analysis for hexapod robot based external fixator. And based on that, three traditional deformity correction modes and their respective control methods were introduced. In addition, we came up with the new correction modes classification criterion which just related execution sequence of fixators fixation and parameters measurement. Then we proposed two modes including measurement first mode and operation first mode with their corresponding control methods. At the same time, a robot orthopedic simulator for bone deformities simulations was built and a computer aided tool which provide control methods with electronic prescriptions using digital twin technology was designed. Combining these tools, deformity correction simulations were finally carried out in fifteen cases under two new modes to verify their correction effectiveness. After the simulating deformity correction with hexapod external fixators under measurement first and operation first modes, deformities in all cases were corrected and bones mechanical axis were recovered as expected. The new criterion for modes selection according to the execution sequence was more in line with actual clinical demand and operation. Deformities could be corrected effectively under measurement first mode and operation first mode. Meanwhile, measurement of deformity parameters could be reduced under the operation first mode which could weaken the influence of artificial measurement error on prescription accuracy and deformity correction effect.