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Objective: With the social development and the improvement of people's average life expectancy, incidence of femoral neck fracture gradually increased. Femoral neck fracture in the femoral neck is in a special anatomical location, has been a huge challenge for orthopedic surgeons. So far, its treatment and results still left many unresolved issues. Most major problems faced in the treatment of femoral neck fracture nonunion and avascular necrosis. Study found the biomechanical properties of the femoral head ischemic necrosis and nonunion incidence with internal fixation of femoral neck fracture is closely related to the internal fixation screw Steinmann pin, cannulated screws, power hip screw and so on. In order to protect the blood supply of the femoral head as much as possible to reduce surgical trauma, through hollow compression screw fixation of femoral neck fracture is the most commonly used method of fixing. Trauma, fixed Indeed, low-cost derived from widely used. Three cannulated compression screws into the femoral neck to the triangle, and the bone tissue structure together form a three-dimensional framework structure, higher shear forces, bending and anti-torsion force, more in line with the principles of biomechanics have been many scholars The study confirmed and accepted by the majority of clinicians. However, the same kind of equipment placed space layout or location of different compressive and tensile role and stability are not the same. The purpose of this experiment is mechanical experiments, explore the application the cortex support (cortical support) theory \screw the best choice of the needle position to provide a theoretical basis. Methods: eight anti-corrosion the adult femur cadavers (antiseptic treatment 1 year or so), five men and three women, aged 30 to 65 years, with an average age of 41 years. Removing the muscles and soft tissue, bone destruction excluded by the naked eye, and dual-energy X-ray absorptiometry check, tuberculosis, cancer and degenerative osteoarthritis changes. The femur is removed from each corpse specimens, stripping the soft tissue attached to the femur, amputated in the lower 1/3 of the femur at the junction of experiments, taking on segment femur. Femoral neck were with a hacksaw in accordance with the most common human fractures Pauwels 70 ° angle sawing, causing a femoral neck fracture model. Eight bodies were randomly divided into two groups, each group of four. Anatomy reset fractures after the second gold close below the left side of specimens cortical support with three 7.3mm hollow compression screw fixation, specific methods: the first one at the top front of the femoral neck close before the top of the cortex; cortex; third gold close to the posterior cortex. All the right side of the specimen is fixed, non-cortical support: the first one at the top front of the femoral neck, close to the upper front cortex; second gold in the femoral neck below, from the bottom of the cortex 1.0cm third gold in the femoral neck the rear, away from the posterior cortex 1.0cm. The two groups of three screws are parallel into the front end of the screw from the femoral cortex, 5-10mm. Experimental simulation of the human body with one foot standing femoral shaft and the body was a 15 ° angle. The first set of specimens in the torsion test. Reverse the direction to take femoral head forward to reverse, reverse the speed of 0.2 ° / S, a continuous record of the femoral head torsion angle and torsional moment to fixation failure. Fail criteria: specimen fractures, femoral neck or femoral head rupture, torsion angle - torque curve remains flat or falling. Record its reverse torque at 2 °, 4 ° and 6 °. The second group were the vertical load experiments, 20N / S speed vertical load, load up to 800N. Record 100N, 200N, 400N, 600N, 800N when the femoral head sinking of displacement set. Maximum vertical load measured real then, until the failure of internal fixation. Fail criteria: the specimens rupture, fractures, femoral neck or femoral head force-displacement curve remains flat or falling. The record limit load. Application SPSS13.0 statistical software for statistical analysis, t-test, P lt; the 0.05 difference significant concluded. Results: no significant difference in BMD absorptiometry testing experimental group and control group. To reverse experiment, reversing the cortex support groups and non-cortex support group torque average 2 ° of 5.127 ± 0.627NM and 2.270 ± 0.104NM, reversing the 4 ° for a 10.406 ± 1.515NM and 6.628 ± 1.163NM, reversing the 6 ° for 15.328 ± 1.471 NM 9.072 ± 1.570NM groups against torsion significant differences (P lt; 0.01). The vertical load experiments 100N, 200N, 400N, 600N, 800N load cortex support group femoral head sinking average displacement, respectively: 0.132 ± 0.048mm, 0.231 ± 0.070mm, 0.457 ± 0.106mm, 0.677 ± 0.135 mm, 0.907 ± 0.132mm, the cortex support group average displacement: 0.359 ± 0.038mm, 0.506 ± 0.046mm, 0.674 ± 0.130mm, 0.899 ± 0.160mm, 1.202 ± 0.152mm. 100N-800N compressive, the experimental group and the control group showed a significant difference (P lt; 0.05). At maximum load, the average maximum load of the cortical support group 2782 ± 228N, Non-cortical supported Group average 1950 ± 281N groups had significant difference (P LT; 0.01). Conclusion: This study biomechanics investigate the cortex supporting theory Biomechanical Analysis 3 cannulated screw fixation for femoral neck fracture and non-cortical support three cannulated screw fixation of femoral neck fractures. The following conclusions: Based on the findings in the area of ??anti-torsion: cortex of support group torsional rigidity was significantly better than the the cortex support group; compression and maximum load: biomechanical effects of cortical support group also significantly better than non-cortical support group . The experimental results for the femoral neck fracture clinical hollow screw the best choice of the needle position to provide a theoretical basis. Support applications cortex support (cortical support) theory with three cannulated screw fixation of femoral neck fracture, biomechanics effect is better.
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