Biomechanical Comparison Of Locking Plate Internal Fixation For Periprosthetic Femoral Fractures Of Vancouver Type C

Objective: With total hip arthroplasty(THA)surgery gradually carrying out in the clinic and its postoperative complications continuing to occur,periprosthetic femoral fracture(PFF)is an extremely serious complication of total hip replacement.Vancouver type C periprosthetic femoral fractures occur far from the tip of the prosthesis.This type of fracture is currently dealt with locking compression plate(LCP).In this paper,biomechanical comparisons of four locking plate internal fixation methods for Vancouver C type periprosthetic femoral fractures were performed by axial ballast test,torsion test,four-point bend test inside and outside,and four-point bend test front and behind.Exploring different stiffness of the different distances between the locking plate and the tip of the femoral prosthesis and stress concentration helps to make the plan of the clinical treatment.Methods: Ten pairs of fresh adult cadaver femurs were grouped and all specimens were replaced with proximal prostheses.The distal tip of the prosthesis is fixed in four different ways: Structure A,the most proximal bicortical locking screw is one bone diameter from the tip of prosthesis.Structure B,the most proximal bicortical locking screw is flush with the tip of the prosthesis.Structure C,the most proximal single cortical screw overlaps one bone diameter with the tip of prosthetic.Structure D,the most proximal single cortical screw overlaps two bone diameters with the tip of prosthetic.All of the models are fixed with eight cortical bones in proximal and distal ends.All of the models are performed by axial ballast test,torsion test,four-point bend test inside and outside,and four-point bend test front and behind,collecting data records in computer folders at the same time.Then,we calculate the stiffness of all tests and conduct statistical analysis by SPSS software.Finally,all the specimens were tested to a cyclic pressing test until they were destroyed.We analysis the stress concentrations with comparing the positions of the fracture lines in different groups.Results: In axial ballast test,torsion test,four-point bend test inside and outside,and four-point bend test front and behind,the stiffness of structure D is higher than other structures.The stiffness of structure C and structure D with the single cortical locking screws are higher than structure A and structure B without the single cortical locking screws.In the cyclic load test,the fracture line of structure D appears at the tip of the prosthesis and the proximal and distal screws of the plate.The fracture lines of structure A and structure C appear between the tip of the prosthesis and the most proximal screw.The fracture lines of structure B appear at the tip of the prosthesis.Structure D not only has the highest stiffness but also has a relatively dispersed stress concentration.Conclusion: The longer length of the steel plate,the greater stiffness the structure shows in locking plate internal fixation for periprosthetic femoral fractures of Vancouver type C.