The Study On The Biomechanical Mechanism Of Small Splint On The Ulnar Column Of FrykmanⅧ Distal Radius Fractures

1.BackgroundFrykman Ⅷ distal radius fractures(DRFs)are common clinical upper limb fractures,and small splint fixation is a common treatment for such fractures.The injury of the ulnar column will lead to the loss of the stability of the distal radioulnar joint.Through the previous clinical research,we found that,in the treatment of DRFs combined with styloid fracture of ulna,the incidence of complications of ulnar column in the group of manual reduction+splint external fixation was lower than that in the group of open reduction+plate internal fixation,which intervened only for the distal radius.We think that this is due to,in the treatment of Frykman Ⅷ DRFs,small splint elastic external fixation regard the wrist joint as a whole and can provide relative stability for the ulnar column,reconstructing of the stability of the three columns of the wrist joint.The purpose of this study is to investigate the biomechanics of the above hypothesis by using the finite element analysis method,and to deeply explore the application advantages of small splints.2.ObjectiveThrough the finite element analysis method,this study explores the mechanism and advantage of small splint,comparing with the steel plate internal fixation,on ulnar lateral column of Frykman Ⅷ fracture of distal radius and its influence on the stability of distal radioulnar joint so as to further guide the clinical application.3.MethodThe CT images of right forearm and wrist of a healthy volunteer will be collected.Based on the data,a three-dimensional finite element model of normal wrist joint will be constructed by software.The validity of the model will be verified by the data of cadaver research in the literature.According to the characteristics of this kind of fractures,the basic model will be further cut and modeled by the finite element software so that two kinds of finite element models of Frykman Ⅷ distal radius fractures combined with ulna styloid process type Ⅰ and type Ⅱ fractures will be established.On this basis,four kinds of finite element models of small splint and steel plate fixation of this kind of fractures can be constructed respectively.Under the four conditions of transverse stretching,pronation,supination and axial compression,we will analyze the displacement and direction of ulna styloid process fracture,the stress distribution and relative displacement of distal radioulnar joint.4.Result4.1 Stress change of main ligamentAfter small splint intervention,the stress values of palmar radioulnar ligament,ulnolunate ligament,dorsolateral radioulnar ligament and ulnar triangle ligament in Frykman Ⅷ distal radius fractures model(combined with ulnar styloid process type I fracture)are less than those in the corresponding fracture model fixed by steel plate under pronation,supination and transverse stretching conditions.Compared with steel plate fixation model,small splint can help the main ligament of wrist to compensate more force,so its fixation model has better stability of ulnar column.4.2 Relative displacement of the distal radioulnar jointIn the condition of pronation and supination,the relative displacement of the distal radioulnar joint of Frykman Ⅷ DRFs model after splint intervention is less than that of the corresponding plate intervention fracture model.At the same time,in each model,the relative displacement of the distal radioulnar joint of the model combined with type Ⅱ ulna styloid process fracture is bigger than that of the model combined with type Ⅰ fracture4.3 Displacement change in the end of ulna styloid process fractureAfter splint intervention,the displacement value in the end of ulnar styloid process fracture in Frykman Ⅷ DRFs(with ulnar styloid process type I and II fractures)model are smaller than that in corresponding steel plate intervention fracture model in pronation,supination and transverse stretching conditions.At the same time,in each model,the displacement in the end of ulna styloid process fracture combined with type Ⅰ fracture model are smaller than that of the model combined with type Ⅱ fracture4.4 Stress changes in the ulnar side of the distal radiusUnder the same rotating load,the stress distribution in the sigmoid notch of radius are observed,which from the distal ulna direction,but not in the finite element model of plate fixation.At the same time,the peak stress and the area of high peak stress in the model of fixation of Frykman VIII distal radius fractures(combined with type Ⅱ fracture)with splint and steel plate are significantly larger than that in the model combined with type Ⅰ fracture.5.ConclusionThe results of the finite element analysis show that:(1)The stability of the distal radioulnar joint becomes worse after Frykman Ⅷtype distal radius fracture,especially combined with type Ⅱ ulna styloid process fracture.Therefore,the fixation of ulna styloid process fracture in clinical treatment can increase the stability of the distal radioulnar joint and reduce the clinical complications(2)In the treatment of this kind of fractures,compared with the steel plate internal fixtion which only fixed the distal radius fractures,the small splint ring elastic external fixation can provide the relative stability for the ulnar column and reconstruct the stability of the three columns of the wrist joint,which highlighting the advantages of the small splint external fixation.