Abstract:

BACKGROUND: Traditional fixation device for femoral neck fracture can cause screw loosening, extraction and higher failure rate when fixation device on bone-screw interface with insufficient grasping force or bearing load too large.
OBJECTIVE: To develop and evaluate biomechanical characteristics of the trigeminal form expansion hollow compression screw.
METHODS: Based on the special biomechanical characteristics of the femoral neck fracture, the trigeminal form expansion hollow compression screw was designed, which was composed of two parts: hollow nail and inside plug which could be screwed into the channel of the hollow nail. Within the bolt screwed through the nail produced pressure effect. Then AO cannulated screw by anti-axial compression was made as control. Axial compression test, three-point bending test and maximal axial pullout strength test were detected respectively.
RESULTS AND CONCLUSION: Under 300 N axial or bending external force, axial compression stiffness and bending stiffness in the experimental group were higher than those of the control group (P < 0.05), but axial displacement and radial degree in the experimental group were lower than those of the control group (P < 0.05). The maximal axial pullout strength of the experimental group was higher than that of the control group (P < 0.05). It is indicated that trigeminal form expansive hollow compression screw is significantly superior to AO cannulated screw in fixation firmly and biomechanical properties. Trigeminal form expansive hollow compression screw has good performance in anti-axial compression, anti-bend, anti-torsion and anti-pullout which is the advantage that AO cannulated screw does not have.