ABSTRACT
BACKGROUND: Generally, the treatment of distal radius fractures or joint dislocations is generally valued in clinical practice, but little attention is paid to the ulnar styloid fracture, and whether the ulnar styloid fracture needs to be fixed is controversial. In the study of orthopedic biomechanics, the selection of cadaver model may encounter some problems, such as different selection criteria of cadaver model and different mechanical measurement methods. OBJECTIVE: Based on Mimics software, the finite element simulation model of type Frykman VIII fracture of the distal radius fixed by plate and screw was constructed using finite element analysis. The working condition and load were set for mechanical analysis. It is hoped to provide a reference for the choice of the repair plan of this kind of fracture. METHODS: A three-dimensional finite element model of normal wrist joint was established based on the forearm and wrist CT images of a healthy volunteer. After debugging the model, Von Mises stress of the distal radius was obtained by loading the 100 N stress in the axial direction, and the validity of the model was verified by comparing with the experimental data in the literature. Two kinds of finite element models of Frykman VIII fracture with ulnar styloid type I and type II fractures were established by using finite element software to divide the mesh, cut and mold, and the model of plate and screw fixation of distal radius was assembled. Setting load under rotating working conditions, we analyzed the changes of the stress distribution of the steel plate unit in two models, and the relative displacement of the distal radioulnar joint as well as the ulnar styloid fracture broken end. RESULTS AND CONCLUSION: (1) A three-dimensional finite element model of normal wrist joint was established and validated, and the other two models of type Frykman VIII fracture of the distal radius with ulnar styloid type I and type II fractures fixed by plate and screw were established based on this model. (2) Under the same rotating load, this study showed that the stress and stress distribution of the steel plate unit in the steel plate fixation model of Frykman VIII fracture of the distal radius combined with ulnar styloid type I fracture were smaller than those of the fracture model combined with type II fracture of styloid process of ulna; the relative displacement values of the distal radioulnar joint and the ulnar styloid fracture broken end were smaller than the latter too. (3) The three-dimensional finite element model of wrist joint constructed in this study can be used to analyze the mechanical mechanism of wrist fracture. The results of finite element analysis showed that the fracture of styloid process of ulna in Frykman VIII fracture of the distal radius would affect the stability of the distal radioulnar joint, especially in the case of ulnar styloid type II fracture, which can provide a certain clinical reference for the selection of operation scheme of such fracture.
ABSTRACT
BACKGROUND: Distal radius fractures are often accompanied by the ulna styloid process fractures, and the treatment of the ulna styloid process fracture is disputed in clinic. Manipulative reduction and splint fixation is a common method to treat such diseases. The mechanism of intervention on ulnar styloid process is difficult to obtain in the corpse mechanics experiments. In recent years, the finite element analysis method has been widely used in the field of orthopedics, which has opened up a way for the study of orthopedic disease. OBJECTIVE: To explore the biomechanical mechanism of splint intervention on ulnar styloid fracture by finite element analysis, and to provide the basis for clinical treatment choice. METHODS: A three-dimensional finite element model of normal wrist joint was established based on the forearm and wrist CT images of a healthy volunteer. The validity of the model was verified by comparing with the experimental data in the literature. On this basis, four wrist joint finite element models with and without splint fixation for ulnar styloid type I and type II fractures were established. Under axial compression, lateral extension, pronation and supination working conditions, the changes of the relative displacement of the distal radioulnar joint and the ulnar styloid fracture broken end were analyzed. RESULTS AND CONCLUSION: (1) A three-dimensional finite element model of normal wrist joint was established and validated, and the other four models were established based on this model. (2) In pronation and supination conditions, the relative displacement values of the ulnar and radial joints in the ulnar styloid type I and II fracture models were greater than those in the normal wrist joint model, and the displacement was smaller in the type I fracture model than in the type II fracture model; the displacement was significantly reduced after the intervention on the two fracture models by the splint. (3) In the lateral tension, pronation and supination conditions, the displacement values of the ulnar styloid fracture end in the ulnar styloid type I fracture model were smaller than in the type II fracture model, and the displacement values were significantly reduced after the intervention by the splint. Under the remaining conditions, the change of the above values was not obvious. (4) In conclusion, the stability of distal radioulnar joint became worse after ulnar styloid fracture, and the stability of distal radioulnar joint after type I fracture was less than that after type II fracture. As an elastic fixation method, splint can increase the stability of the wrist ulnar column during the treatment.