| Objectives:To develop a package of internal fixation system of L5-S1, which fits the anatomical strcuture of anterior lumbosacral vertebrateMethods:This study investigated 41 china human cadavers,the anterior L5-S1 disc space and great bifurcation were measured.According to the parameters, a package of anterior L5-S1 internal fixation system was developed.Through vitodymatic tests, mechanical stability of vertebrates with internal fixation system , vertebrates of simple interbody fusion, and intact spine were obtained and comparedResults:This study indicates great vessels are present in the anterior space of Lumbosacral vertebrae,which mainly are abdominal artery bifurcation and common iliac vein.The bifurcation level of the ventral aorta was quite variable in human cadavers, the confluence level of the common iliacvein was consistent.In the study, we have discovered that the abdominal aorta bifurcation of all 41 specimens and 87.8% of left and right common iliac vein junctions are above the top of L5 vertebra. The safe operation space of the anterior L5-S1 is determined by the path of left common iliac vein and right iliac artery. The distance from the bifurcation to the top of L5/S1 disc was in the average of 3.8±1.0cm The distance from the confluence of left and right common iliac vein to the top of L5/S1 disc was in the average of 2.2±0.8cm. The distance from the confluence of left common iliac vein and right common iliac artery to the top of L5/S1 disc was in the average of 2.0±0.7cm .The bifurcation angle of the ventralaorta averaged 62.8°,the vonfluence angle averaged 71.5°, the confluence of left and right common iliac vein angle averaged 71.8°.in the level of half of L5, the width of left common iliac vein between right common iliac artery averaged 2.14±0.9cm;in the level of intervertebral space between L5 and S1, the width of left common iliac vein between right common iliac artery averaged 3.36±0.94cm. on the plane of intervertebral disc between L5 and S1, left common iliac vein slightly deviates to the midline, leaving a greateer space on the right.(2)through vitodynamic experiments of intact lumbarsacral vertebra, interbody fusion of L5-S1, interbody fusion with the new type of anterior internal fixation system of L5-S1, we came to the conclusion that: Compared to the intact spine and ALIF, the anterior L5—S1 plate substantially increased the stiff by 52.5% and 41.7% during axial compressed(p<0.01),48.3% and 68.8% during extension(P<0.01);54.2% and 70.6% during axial rotation(P<0.01). The ROM of ALIFspecimen in extension ,axial rotation was larger than that of intact specimen(P<0.01);the ROM of ALIF specimen fixed with anterior plate of L5—S1 was less than that of ALIF specimen or intat spceimen(P<0.01).there is no statistical differnce.The stability of anterior interbody fusion with anterior plate fixation system in lateral bending is better than that of intact one and anterior interbody fusion, and there is statistical difference.Conclusion:(1) there is enough operation space anterior to L5-S1, interbody fusion can be safely performed in 87.8% of crowd.(2)the newly innovated L5-S1 internal fixation system satisfies the local anatomical structure, and fully makes use of the safe space and shape of anterior L5-S1,significantly reducing the intervention of great vessels.(3)the vitodynamic intensity of anterior L5-S1 internal fixation system excels the intensity of intact vertebras.(4)the newly innovated L5-S1 internal fixation system, which is easy to manipulate and is able to be immobilized and locked in only one procedure is an important alternative device in L5-S1 surgery, . |
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