| Objective:To provide practical anatomy and radiographic data about the lumbosacral area for developing L5/S1 anterior approach internal fixation by measuring the related data of L5/S1 area.Methods:Dozens of anatomic and radiographic specimens in lumbosacral region were selected in the study to measure the parameters as follow:the width,height of L5/S1 vertebrae and pedicles,the length of bone-crew routeway from pedicles to anterior vertebrae,The transverse screw angle(TSA),the sagital screw angle(SSA)and lumbosacral joint angle(LJA)etc.Other index were observed in 20 normal adult specimens in the study,which included aortic bifurcation(AB),confluence of the common iliac veins(CCIV),middle sacral arteries and veins and the location of lumbosacral sympathetic nerve.Both the data were taken for statistics analysis.Results:The height of the vertebra was 30.27±2.52mm in L5 and 31.57±3.37mm in S1;The width of vertebra was 51.03±3.20mm in L5 and 34.03±3.14mm in S1;The height of the pedicles was 11.88±2.35mm in L5 and 16.25±1.90mm in S1;The width of the pedicles was 14.53±2.20mm in L5 and 11.17±2.15ram in S1;The length of bone-screw passageway was 49.16±3.36mm in L5 and 43.94±4.60mm in S1.The lumbosacral joint angle is 137.4±6.7°,and the thickness of L5/S1 disc is 7.23±3.21mm.The entry location of screw was 12±2mm to the upper level of the lower edge of L5 vertebra and to the lower level of the upper edge of S1 vertebra.They were located 6mm away from the middle line.The transverse screw angle is 7.2±1.9°in L5 and9.0±1.1°in S1;The sagital screw angle is25.5±3.0°in L5 and 26.6±2.3°in S1.The screw to develop is considered to be no longer than 50mm in L5 and 40mm in S1,the diameter is no longer than 8mm.The lumbosacral joint angle is 137.4±6.7°.The distance from aortic bifurcation(AB)to low edge of L5 vertebra is 43.86±12.24mm in male and 36.81±12.93mm in female.The aortic bifurcation was most frequently situated at L4/5 disc.The distance from confluence of the common iliac veins(CCⅣ)to low edge of L5 vertebra is 26.85±14.72mm in male and 24.77±12.33mm in female.The CCⅣmostly locate at the level of upper part of the L5 vertebrate,no case was found to be superior to the level of middle third of L4 vertebrate.There was no great variation of the initial point or the numbers of the middle sacral artery,whereas we can see a lot of variations of the confluent point and numbers of the middle sacral vein which origined from left common iliac vein by 82.8%.The distance from ureter striding iliac artery to AB is 53.35±7.48mm at right,and 45.95±2.41mm at left.About 85%of superior hypogastric plexus(SHP)situated in the left lumbosacral area and multitruck was common.There is no significant statistical difference between the anatomic measure and radiographic measure.Conclusion:1 The related data of L5/S1 vertebrate such as LJA,SSA,TSA,BSPL etc are important to develop to the internal fixation.2 The longest distance of L5S1 bone-screw passageway is from back part of pedicle to anterior vertebrate 6 mm side to the middle line.3 There is a relative safe operative area to imbed the internal fixation which is like double- trapezoid and 18.60cm~2 in area.
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