Pelvic Fracture Closed Reduction Planning Of Robot-Assisted And Mechanical Study Of Its Clamp

The robot-assisted pelvic fracture closed reduction technology is in its infancy.Currently,automatic fracture fragment reduction planning is only limited to linear planning,and complex fracture reduction still requires the surgeon’s planning,which affects the timeliness of surgery and the thoroughness of obstacle avoidance,and the surgeon’s planning does not consider the influence of path length and muscle resistance on the safety of surgery.Therefore,how to solve the above problems has become an important research direction for robot-assisted pelvic fracture closed reduction.This study aims to develop an intelligent path planning algorithm for robot-assisted pelvic fracture closed reduction: to complete robot-assisted pelvic fracture closed reduction surgery under the constraint of collision-free of soft and hard tissues with minimum muscle resistance,and to improve the safety of the surgical system.The main contents and innovations of the paper are as follows:(1)To address the problems of low versatility and stiffness of the pelvic traction clamp,a 5-degree-of-freedom pelvic traction clamp was designed,which can be adjusted for the amount of extension or rotation of each joint to clamp different sizes of the pelvis.The stress-strain of the clamp system at the conventional and ultimate positions was analyzed,and the clamp configuration and material to meet the strength of pelvic fracture reduction surgery were explored.The results showed that the 12-mm stainless steel supra-acetabular transverse pin clamp combination performed optimally in five aspects: bone surface stress,traction pin stress,clamp stress,maximum displacement,and ultimate traction force.(2)To address the problem of secondary collision in traditional pelvic fracture reduction planning,a collision detection method combining spatial overlap detection and cross-bounding box technology is proposed.The method is based on the spatial partitioning theory of octree to grid static objects,and collision detection can be performed by using the intersection test of pointsrectangles and rectangles-rectangles.The experimental results of in vitro simulated pelvic reduction show that the proposed collision detection method can effectively avoid the occurrence of secondary collisions and can be extended and applied to other fracture reduction planning algorithms for collision detection.(3)To address the problem of steep increase in muscle force before and after orientation reduction of pelvic fractures,an Orientation Planning Strategy(OPS)for fracture bone fragments was proposed,which allows the fracture fragments to gradually adjust their orientation according to the set orientation variables and solves the drawback of steep increase in muscle resistance due to one-time orientation reduction of fracture fragments in traditional reduction planning.The results show that the OPS-based path planning method can reduce the muscle resistance by 49.4% compared with the conventional method.(4)To address the lack of muscle force constraints on the pelvic fracture reduction path,a dynamic muscle resistance calculation method is proposed.The method builds a musculoskeletal model file of pelvic fracture based on OpemSim 4.0 platform,which can be used for secondary development to calculate the muscle force in a specific muscle stretch state,and finally incorporates the muscle force value as an influencing factor in the heuristic function of the path search algorithm to search for the fracture reduction path with the least muscle resistance.The results show that the reduction path based on this muscle force constraint method can further reduce the muscle resistance by 12.8%.