Transmission efficiency of Ilizarov external fixator orthopedic force based on coordinate transformation theory / 中国组织工程研究

ABSTRACT

BACKGROUND: The study on the mechanism of force conduction of Ilizarov bone external fixator is of great significance for clinical orthodontics of the knee varus, the knee valgus and the tibial fracture. OBJECTIVE: To explore the force conduction mechanism of Ilizarov bone external fixator and the force changes of each orthopedic force in the process of tibia correction, and to objectively evaluate the overall use effect of the external fixator. METHODS: According to the structure of the external fixator, the coordinate transformation matrix relations were established, and the mathematical transformation relationship between the holding force and the pulling tension was obtained. A special laboratory bench was set. The experiment of tibia correction was conducted. The load on the external fixator and the variation of the orthotic force were measured. The theoretical value of the tension at the broken bone is calculated and compared with the actual value of the tension measured by the six-dimensional force sensor. The curve of efficiency of force transmission during correction was obtained. RESULTS AND CONCLUSION: (1) During the correction, the structure of the Ilizarov bone external fixator resulted in the interaction and restriction of its adjustment rod and support rod. When one adjustment force increased, the other adjustment force would decrease. (2) The efficiency of force transmission was increased greatly in the early stage, and then stabilized at about 50%. The experimental results could evaluate the overall correction effect of the external fixator. (3) Theoretical calculation and experiment of the tension at the broken bone due to the loss during the force transmission process were different in the result curves, but from the experimental results, it could be indicated that the overall force change trend of the adjustment force, supporting force, the theoretical value of the tension and the actual value of the tension was basically the same, indicating the validity of the theoretical calculations and experimental results. The evaluation results can provide a reference for the optimal design of Ilizarov’s external fixation architecture and the precise control of tibial orthopedic surgery.