| Objective:Femoral intertrochanteric fracture is a fracture type common in the elderly. Evans I C intertrochanteric fracture is an unstable fracture, its features are:the fracture displacement, lesser trochanter fracture after reduction, medial cortical bone is not attached, fracture instability. In the clinical work of common fractures. According to statistics, the average age of the patients was 70 years old. The femoral intertrochanteric fractures after the rich blood supply, a rare occurrence of nonunion postoperative complications, but fracture is common in hip varus, and cause long-term bedridden elderly patients had more complications, mortality rate was 15%-20%. In clinical practice, see more unstable intertrochanteric fractures, because the elderly osteoporosis, fixation control force difference, after internal fixation easily screw loosening, fracture displacement, internal fixation failure consequence. In recent years, emerge in an endless stream fixation device and operation method for the treatment of this fracture fixation, also is not, in short, there are still many problems unsolved. The commonly used internal fixation devices, PFNA has a good biomechanical stability, compressive and anti rotation ability, has become the treatment of intertrochanteric fracture of the femur in particular is the preferred method of fracture of unstable intertrochanteric. And the dynamic hip screw used with static and dynamic pressure effect, also frequently used in clinic, but the experiment results show that the anti rotation effect of dynamic hip screw for the poor, often caused by the failure of internal fixation. Therefore, it is suggested with an anti rotation screw to increase the anti rotation effect of the whole device in dynamic hip screw nail. This experiment aimed to biomechanical research, comparison of PFNA and dynamic hip screw and the nail screw fixation of Evans I C intertrochanteric fracture fixation stability, provide a theoretical basis for clinical treatment.Methods:The experiment was carried out with 8 after old embalmed. Specimens, including male 5, female 3, age 51-82 years old, average 76 years old. To make the experimental model:the anatomy of the muscles around the shaft and carefully remove the soft tissue, proximal to the retention of femoral head, neck and tuberosity femur, distal femur from the truncation, before the experiment by X ray film out of bone tumor, deformity, trauma, pathology, dual energy X-ray absorptiometry for bone density measurement, no statistically significant difference in the results. The double plastic bag sealed storage at -20℃ for use in refrigerator handle specimens specimens,6 hours prior to the experiment at room temperature and thawing, with physiological saline infiltration to keep fresh in the experiment specimens. In 8 cadavers with oscillating saw made intertrochanteric fracture model of Evans I C, pay attention to the medial cortex cut into triangular pieces of bone. The same specimens were fixed with PFNA about pairing, one side, the other side by dynamic hip screw fixation, each of the 8 specimens.Group PFAN:with trochanteric tip as entry point, through the opening, reaming after insertion of guide pin, and then choose the appropriate PFNA nail insertion, connecting extramedullary sight the sleeve in the lateral femoral cortex, the insertion of the femoral neck pin, C C-arm fluoroscopy is located close to the lower part of femur cortical distance, length of femoral head in 5-7mm, the lateral femoral neck slightly at the rear, selection of the spiral blade in the unlocked state hammer into locking blade. According to a screw in the distal locking screw, installation of the tail cap.Dynamic hip screw nail group:in the greater trochanter of femur using the 135°guide keep the direction of femoral neck anteversion, femoral neck cannulated screws to enter, the installation of 4 hole plate on proximal femoral, guarantee the dynamic hip screw fixation of the tip apex distance< 25mm. Then, in the 1cm above the main nail, parallel to the main direction of screw screw in 17.3mm cannulated screw, the screw tip from the femoral head vertex 6-7mm.Will make a good measuring specimens distal embedding, using the type of denture base resin and stable fixed mounted on the distal proximal fixture, vertical pressure and cyclic compression experiments by pressurized module Biomechanical Experimental machine. To eliminate the influence of creep specimens, in each experiment before in longitudinal pressure pre 100N contained 3 experimental specimens, intact without damage. For compression is completed, in the vertical compression experiment, increase rate of 20N/S, the vertical downward to the femoral head load pressure, recorded in the 500N and 700N fracture displacement corresponding numerical. Cyclic pressure before the experiment give the pre compression, and then to the frequency of 2Hz to femoral head loading of 1500N peak alternating stress, loading a sine wave, periodic loading cycle recording fracture shift more than 5mm number.SPSS 17.0 statistical software was used for statistical analysis, using the paired t test methods, P< 0.05 with significant difference.Results:1 the detection results of X-ray absorptiometry showed, the bone density of the selected samples of left femur intertrochanteric region was 0.791±0.181g/cm2 to 0.809 ± 0.105 g/cm2, right side, left, right, no statistically significant differences on both sides of specimens (P= 0.427, 0.05).2 vertical compression experiment:through the vertical pressure data measured in the experiment, when the pressure is 500N, the displacement of the PFNA group was 0.128 ± 0.093mm, dynamic hip screw and the displacement of the nail screw group was 0.531 ± 0.289mm, two groups of data, the results were statistically significant (P< 0.05). The pressure is 700N, the displacement of the PFNA group was 0.203 ± 0.118mm, dynamic hip displacements and the nail screw group was 0.709 ± 0.281mm, two groups of data, the results were statistically significant (P< 0.05).circular pressurization test:at the end of the experiment cycle of the PFNA group was 1957.637 ± 83.735, cycle dynamic hip and the nail screw group was 823.333 ± 56.468, two groups of data, the results were statistically significant (P< 0.05).Conclusion:For Evans I c intertrochanteric fracture, in terms of compression of biomechanical stability, PFNA is better than the dynamic hip screw with anti-rotation screw. |
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