The Relationship Between Ulnar Styloid Fracture Internal Fixation And Distal Radioulnar Joint Stability:a Finite Element Analysis

Currently there is controversy about the role of additional internal fixation of the ulnar styloid fracture when distal radius fracture combined with ulnar styloid fracture. The main cause of this problem is shortage of biomechanical research and varied the reported surgical methods about the internal fixation of the ulnar styloid fracture. For the past few years, the finite element analysis has been used in biomechanical research of tooth, spine, hip joint and shoulder joint, and developed relevant model until now. But there is no report about the finite element model of internal fixation of the ulnar styloid fracture.Objective:1. To establish the three-dimension finite element model of distal radius fracture combined with ulnar styloid base fracture; to establish the three-dimension finite element model of the oblique "T" type locking plate and ulnar styloid micro screw. On this basis, to establish the three-dimension finite element model of both oblique "T" type locking plate for treatment of distal radius fractures and micro screw for the treatment of fractures of the ulnar styloid.2To analyze the stress distribution and displacement of the distal radioulnar joint under the model of oblique "T" type locking plate for treatment of distal radius fractures and micro screw for the treatment of ulnar styloid base fra-cture, and assess the relationship between ulnar styloid fracture internal fixation and distal radioulnar joint stability, which can provide the biomechanical basic research for clinical application.Materials and Methods:1. In the basis of the normal radioulnar joint three-dimensional finite element model[4], we firstly took a fracture line on the ulnar styloid base and distal radius, and established the three-dimension finite element model of distal radius fractures (AO:23C) combined with ulnar styloid fracture. Secondly, we measured the accurate data of oblique "T" type locking plate and micro screw, and established these three-dimension finite element models using pretreatment procedures of ANSYS10.0. Lastly, we acquired the three-dimension finite element model of both oblique "T" type locking plate for treatment of distal radius fractures and micro screw for the treatment of fractures of the ulnar styloid using Boolean operations.2. Under the established model, we defined the boundary conditions to force loading. So we gave an axial compression of100N, a bend load of2.5N.m, a prone load of22N.m and a supine load of22N.m respectively in the neutral position, then analyzed the stress distribution and displaeementResult: After the internal fixation of ulnar styloid base fracture, the displacement and maximum pressure of interosseous membrane, extensor maximum pressure value was significantly reduced.Conclusion: When distal radius fractures combined with ulnar styloid base fracture, should be held. the additional internal fixation for treatment of ulnar styloid base fracture should be held.The innovation in this study:1. During the finite element analysis and biomechanical study in internal fixation and external fixation of distal radius fracture, most of them did not simulate the stress distribution and stress displacement under the buckling condition. In this study, we simulated flexion, pronation and supination conditions, as well as compression, which was In accordance with the real force conditions of distal radioulnar joint.2. It is the first finite element analysis of internal fixation of using oblique "T" type locking plate for treatment of distal radius fractures and micro screw for the treatment of fractures of the ulnar styloid at the same time. It can provide the biomechanical theory for clinical application.