A reconfigurable seven-link multi-mode external-fixation system for improving emergency limb fracture stabilization efficiency

Abstract. The traditional external fixation has problems such as a single fixed dimension, limited application range, long fixation time, and heavy weight. A single-function external fixation is unable to meet the various needs of fracture fixation in scenarios involving a large number of injured patients. This paper proposes a reconfigurable-configuration comprehensive method based on a seven-link mechanism. A new type of reconfigurable external-fixation frame with multi-dimensional, multi-posture, and multi-fracture scenario applicability is formed, able to achieve rapid and stable external fixation for fractures in the femur, tibia, elbow joint, knee joint, and ankle joint. A reconfigurable mechanism configuration design is proposed based on the comprehensive configuration of the seven-link mechanism and the analysis of the working space. Human–fixator coupled biomechanical model is established, and the mechanical and stability performance of fractures under five reconfigurable configurations are analysed based on finite-element analysis. Compared with the corresponding single-function external-fixation frame in terms of performance, mechanics, and fixation time, a comparative experiment was finally conducted based on the cross-knee joint of dogs for verification. The results confirmed that the external fixation has the advantages of light weight, stable structure, multiple dimensions, multiple postures, and applicability to various fracture scenarios in addition to the fact that it shortens the fixation time significantly (< 10 min). Compared with other unilateral external fixation, the new external fixation is lighter in weight (weighing 950 g), with a fracture displacement of 3 mm, and the load is 274.2 N, the stiffness is 95.2 N mm−1, and the stability is higher than that of the unilateral external fixator (237.63 N, 72.4 N mm−1). When the relative rotation angle of the fracture end reaches 30°, the torque is 14.66 N m. This external fixation can be widely used in temporary fracture fixation in emergency medical scenarios.