| Objective 1.With Iso-3D computerized navigation technology, the imitated double screws were placed in the symphysis pubic of embalming cadavers. The aim of this operation was to determine the optimal angles and maximum screw lengths. Under detailed local dissections performed in cadavers, the security of screw channels was verified.2. The models were produced in all embalming cadavers. And cadavers were randomly divided into 4 groups, including reconstruction plate fixation group, double screws fixation group, single screw fixation group and intact pelvic group. Thus, the purpose of the study was to:(1)verify the reliability of the double screws fixation in treatment of the pubic symphysis diastasis by the Biomechanical experiment;(2) analyse reduction and fixation capabilities of 3 kinds of fixation.Method 1.The embalming adult cadavers were 15, the male 8, female 7. All cadavers were truncated from the L5 and 1/3 of the proximal thigh. Under the Iso-3D navigation system, the process of double screws implantation was imitated in the cadavers. The maximum screw length between the fixed points was achieved by adjusting imitated screw angle. Then the percutaneous screws were implanted in the symphysis pubic. With the detailed local dissection, the important nervusvascularis and spematicfunicle (or round ligament of uterus) were exposed completely. The mean distances from entry and exit points to the important-mentioned structures (femoral arteria and vein, femoral nerve, arteria obturatoria et al) were measured respectively. All soft tissue of specimen was removed completely, but the capsular and ligamentous structures were kept intact. The entry angles between lag screws and the coronal plane, between lag screws and horizontal plane of the human body were measured. After surgery the specimen were checked by post-surgery X-ray and CT.2. 20 cadavers were prepared for biomechanical analysis. The pubic symphyses of 20 cadavers were divided with the wire saw, in order to gain the model of AO type B1-1 injury. All specimens were randomly divided into 4 groups, including single screw fixation group, reconstruction plate fixation group, double screws fixation group and intact pelvis group. Then, a specimen was fixed in the designed apparatus in order to imitate an upright standing position. And a displacement sensor system was installed in the pubic symphysis. After applying an axial load of 0-600N at a rate 2mm/min over the lumbar spine(L5), the maximum displacement(mm) was measured and recorded. The process was reproduced thrice. All data was documented in the table by classification and analyzed by the SPSS 19.0 software.Result 1.The entry point of the first screw was in the trailing egde of one side of pubic tubercle. The mean angle of the first screw with the horizontal plane was 7.7±1.9°in male,8.1±1.7± in female. The male mean angle between the first screw and the coronal plane was 7.8±1.8±, the female 7.7±2.0. The entry point of the second screw was in the same place in the other side of pubic tubercle. The mean angle between the second screw and horizontal plane was 30.6±4.0°in male, 30.8±3.4° in female. The mean angle between the second screw and the coronal plane was 9.1±3.0° in male,9.2±3.3°in female.2. The mean displacement of the intact pelvic group was 0.384±0.817mm, but the mean displacement was 0.390± 0.073mm in the double screws group. There was no statistical difference (P>0.05) by comparison between the intact pelvic group and the double screws group.Conclusion With computerized navigation technology, the bony channels of double screws implanted in the symphysis pubic were achieved and reliable. The percutaneous double screws is feasible to treat the pubic symphysis diastasis. |
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