RESUMO
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.
RESUMO
BACKGROUND: Through clinical research, we found that in the treatment of distal radius fracture combined with ulnar styloid process fracture, the proportion of complications of ulnar column after manual reduction and splint fixation was smaller than that of patients who only received open reduction and internal fixation of distal radius. We deemed that the wrist joint was treated as a whole in the treatment cycle, the splint as elastic fixation could provide the relative stability of the ulnar column and reconstruct the stability of the three columns of the wrist. OBJECTIVE: To explore the biomechanical mechanism of splint intervention on the ulnar column after type Frykman VIII fracture of the distal radius by finite element analysis. 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. Two kinds of finite element models of type Frykman VIII fracture of the distal radius with ulnar styloid type I and type II fractures were established by using finite element software to divide the mesh, cut and mold. On this basis, four wrist joint finite element models with splint fixation and steel plate fixation for type Frykman VIII fracture of the distal radius were established. Under axial compression, lateral extension, pronation and supination working conditions, stress distribution and relative displacement of the distal radioulnar joint, displacement and direction of the ulnar styloid fracture broken end were analyzed. RESULTS AND CONCLUSION: (1) The stress values of the ulnolunate ligament, ulnotriquetral ligament, and the palmar dorsal radioulnar ligament in the model of type Frykman VIII fracture of the distal radius with ulnar styloid type I fracture after splint intervention were lower than those in the model after plate intervention in the lateral tension, pronation and supination conditions. (2) In the pronation and supination conditions, the relative displacement values of the distal radioulnar joints in type Frykman VIII fracture of the distal radius models with ulnar styloid type I and type II fractures after splint intervention were smaller than those in the models after plate intervention. (3) In the lateral tension, pronation and supination conditions, the relative displacement values of the ulnar styloid fracture broken end in type Frykman VIII fracture of the distal radius models with ulnar styloid type I and type II fractures after splint intervention were smaller than those in the models after plate intervention. (4) The finite element study shows that distal radioulnar joint stability becomes worse after type Frykman VIII fracture of the distal radius, which is more obvious in the model with ulnar styloid type II fracture. In the treatment of this kind of fracture, compared with the simple internal fixation of distal radius fracture, the splint as elastic fixation takes the wrist joint as a whole in the treatment cycle and provides the relative stability of the ulnar column, thus further revealing the advantages of the splint elastic fixation.