Automatic Planning Method of Reduction Trajectory for Parallel Fracture Surgery Robot

Parallel fracture surgery robot and its computer-aided diagnosis and treatment technology solve the risk of trauma and secondary infection in fracture reduction surgery. However, the existing fracture reduction trajectory planning methods have some problems, such as low collision detection efficiency, long reduction path and excessive muscle tension, which make it difficult to achieve accurate and safe reduction treatment. To solve this problem, an automatic planning method is proposed, which combines collision detection, muscle force analysis and shortest path search. Firstly, three-dimensional bone model is reconstructed based on CT images of patients, and the target of fracture reduction is obtained by taking the healthy side bone model of patients as reduction reference. Secondly, the collision detection threshold is defined, and the closest pair of points between broken bones is quickly found based on the octree search algorithm, so as to realize the collision detection of broken bones. Then, a personalized fracture muscle model is established by the standard model of OpenSim through scaling features, and the muscle force in the reduction process is obtained in real time. Finally, the trajectory search node and evaluation function of A* algorithm are designed to realize trajectory planning with the constraints of no collision of bones, minimum muscle tension and shortest path. Compared with the interactive trajectory planning method, the reduction trajectory planning experiment of 9 groups of tibia and fibula fractures is carried out. The average planning time of this method is only 3.2s, which is two orders of magnitude less than that of the interactive method. The average reduction path length is 24.3 mm, which is 36.7%, and the average muscle force is 96.4 N, which is 16.2%. The results show that this method has short time-consuming trajectory planning, high reduction efficiency and high trajectory safety, which provides a new idea for accurate and safe fracture reduction treatment. © 2022 Journal of Mechanical Engineering.