Design And Invention Of A New Internal Fixator For Hoffa Fracture

Objective: At present,the fixation methods of Hoffa fractures are mainly screw fixation through articular cartilage surface or superposition fixation of multiple reconstruction plates.This fixation method has the disadvantages of iatrogenic irreversible damage to articular cartilage,large surgical trauma,unreliable fixation,and inability to overcome the shear force during early rehabilitation,which leads to fracture internal fixation failure.It is more likely to occur when combined with osteoporosis.It eventually leads to fracture complications and joint dysfunction in the long term after surgery.With the rapid development of transportation industry and altitude industry in China,the incidence of comminuted and complex knee fractures caused by high-energy injuries is increasing,including Hoffa fractures.Hoffa fractures are intra-articular unstable fractures,and it is difficult to achieve good prognosis by conservative treatment.The treatment follows the principles of open anatomical reduction,strong internal fixation,reduction of soft tissue injury and early functional activity of the knee joint.However,the internal fixators in current clinical practice can not meet the current surgical fixation of Hoffa fractures.Therefore,it is of great clinical significance to develop a new type of internal fixation device with the above performance.Methods: Firstly,we observed the morphological characteristics of the steel plate through the cadaveric specimen,and traced the general structure of the designed steel plate on the surface of the femoral condyle specimen based on the medical theory and internal fixation science we had learned.After repeated observation and copy,modification and elaboration to determine the structure of the steel plate.Then,according to the three-dimensional reconstruction image of the first medical image database in Tianshui City,the approximate ellipse shape of the lateral surface of the femoral condyle was drawn by the method of fitting and drawing a circle on the side of the femoral condyle.The long axis and short axis of the ellipse were measured by the three-dimensional reconstruction image to provide the required data for the quantitative analysis of the steel plate.The patent was applied,and the mechanical manufacturing company was sought for cooperation.According to the structural characteristics of the sample and the three-dimensional data of the knee joint medical image,the Mimics software was used for modeling,and then the Soli Dworks software was used for virtual fracture reduction and internal fixation.Finally,the finite element analysis method of ANSYS software was used to compare the biomechanics of the traditional screw internal fixation and the new anatomical plate fixation,and the conclusion was drawn.Results: A steel plate is developed and has the following functions;1.Avoid iatrogenic injury of articular surface cartilage;2.With the rear anti-shear barrier plate function;3.The internal fixator is closer to the load interface,so as to obtain greater load and better fixed strength.Conclusion: The new anatomical plate has a good fit with the cadaver specimen.The finite element analysis shows that the new anatomical plate does not damage the cartilage of the femoral and tibial articular surface,but also increases the reliability of fixation,and can overcome the shear force on the fracture block during early rehabilitation.The structure and function of the plate give proper consideration to the stability and flexibility of the knee joint fracture,and can prevent the possible re-displacement of the fracture,so as to reduce the incidence of postoperative complications and promote the rapid recovery of joint function after operation.