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Purpose of femoral neck fracture is common in the elderly bone injury, accounting for 3.6% of body fractures. Due to the special nature of the blood supply of the femoral head, femoral neck fracture easily damage the head and neck of the blood supply to the femoral head blood supply decreases, not only difficult to heal the fractures, and prone to avascular necrosis. Experimental methods to study the impact of the cannulated screws an important factor of stability in the femoral head, hollow screw in the clinical treatment of femoral neck fractures to choose the ideal surgical options provide a theoretical basis. MATERIALS AND METHODS Materials and specifications Jiangsu production imitation AO7.3mm hollow compression screw, nail diameter 4.5mm thread diameter 7.3mm, thread length 18mm, total length of 75mm, stainless steel material; cannulated screw fixation of surgical instruments: 7.3mm wire-tapping, 2.8mm Kirschner, 4.5mm hollow drill, medical electric drill, hollow screwdriver; cooler of the two the ice several vernier caliper, compasses. Experimental instrument WDW microcomputer controlled electronic universal testing machine; dual-energy X-ray absorptiometry Lunar DXP-L; U.S. General Electric Company production of C-arm X-ray machine; homemade fixed femoral head holder, screw top cap holder; Statistics SPSS11.5 software package with 31 adults in low-temperature refrigeration preservation of the femoral head specimens, cannulated screws in accordance with the axial direction of the femoral head, femoral neck fractures implantation of the femoral head (two locations, at different depths). Record the patient's age, vernier caliper to measure the diameter of the femoral head, dual energy X-ray absorptiometry measurements of femoral head anteroposterior bone density, distance measuring screw tip to the femoral head articular surface cartilage; fixed the femoral head and the screw cap, through the WDW microcomputer control electronic universal testing machine the cannulated screws pull the experiment, the stress - strain curve measured screw pull, to record the maximum pullout load. Stepwise multiple regression analysis of the experimental data (Table 1) using SPSS11.5 software package. Maximum pull results femoral head bone density and cannulated screws implanted in the femoral head depth different, leading to the screw pull-out force, the higher the bone density, the deeper the hollow screw implanted femoral head, corresponding to the stress - strain curve The greater the load, that is, the better the stability of the screw in the femoral head. Stepwise multiple regression analysis showed: the bone mineral density of the femoral head and screw tip to the distance of the femoral head articular cartilage maximum pullout load, the former showed a positive correlation (P = 0.002), while the latter was negatively correlated (P = 0.000 ). Screw tip to the articular surface of the femoral head is greater than the maximum pullout load 8mm group and less than 8mm group between a significant difference (P = 0.004 lt; 0.05). Conclusion cannulated screws prognosis of femoral neck fractures and femoral head bone density, screw depth is closely related to the implantation of the femoral head. Higher in patients with femoral head bone density, screw implanted in a certain range, the deeper and more conducive to the stability of internal fixation and fracture healing. Osteoporosis patients with femoral neck fractures using cannulated screw fixation treatment might not be appropriate, and should take into account the hip replacement treatment.
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