Biomechanical Applicability Investigation Of Cannulated Screw Fixation For Femoral Neck Fractures

Objects:To investigate the stability of internal fixation for femoral neck fracture (FNF) using two or three cannulated screws directed to different fracture lines. Also, we compared the differences of the two fixation methods to provide a theoretical basis for the clinical decision making.Methods:Fifteen fresh frozen human proximal femur samples were collected and made into three FNF models with Pauwels angle of30°,50°and70°respectively. The models were fixed with two or three cannulated screws, then we evaluated their differences at shear and tensile strength, subsidence or loose displacement and three types of stiffness values of femur to identify their biomechanical stability.Results:With Pauwels angle of30°and50°, no statistical differences at the referenced outcomes were observed between two and three cannulated screw fixation for FNF. With the Pauwels angle of70°, three cannulated screws fixation were significantly superior to two cannulated screws fixation for FNF at enforcing shear and tensile strength, reducing subsidence or loose displacement and enhancing stiffness values of femur (P<0.05). Nevertheless, when compared to two or three cannulated screws fixation applied in other type of fractures, three cannulated screws fixation turned out to be relative instable when Pauwels angle was70°.Conclusion:With Pauwels angle of30°and50°, two cannulated screws fixation was similarly stable as using three cannulated screws for FNF. Three cannulated screws fixation were obviously superior to two cannulated screws fixation when Pauwels angle was70°but the application of three cannulated screws could still be insufficiently stable when only such routine fixations were utilized. Therefore, Angle Stabilizing System or anti-sliding screws were needed to enhance the stability of FNF fixation.